Recycling of collagen from solid tannery waste and prospective utilization as adhesives.

Recycling of collagen from solid tannery waste... | F1000Research "use strict";function _typeof(t){return(_typeof="function"==typeof Symbol&&"symbol"==typeof Symbol.iterator?function(t){return typeof t}:function(t){return t&&"function"==typeof Symbol&&t.constructor===Symbol&&t!==Symbol.prototype?"symbol":typeof t})(t)}!function(){var t=function(){var t,e,o=[],n=window,r=n;for(;r;){try{if(r.frames.__tcfapiLocator){t=r;break}}catch(t){}if(r===n.top)break;r=r.parent}t||(!function t(){var e=n.document,o=!!n.frames.__tcfapiLocator;if(!o)if(e.body){var r=e.createElement("iframe");r.style.cssText="display:none",r.name="__tcfapiLocator",e.body.appendChild(r)}else setTimeout(t,5);return!o}(),n.__tcfapi=function(){for(var t=arguments.length,n=new Array(t),r=0;r 3&&2===parseInt(n[1],10)&&"boolean"==typeof n[3]&&(e=n[3],"function"==typeof n[2]&&n[2]("set",!0)):"ping"===n[0]?"function"==typeof n[2]&&n[2]({gdprApplies:e,cmpLoaded:!1,cmpStatus:"stub"}):o.push(n)},n.addEventListener("message",(function(t){var e="string"==typeof t.data,o={};if(e)try{o=JSON.parse(t.data)}catch(t){}else o=t.data;var n="object"===_typeof(o)&&null!==o?o.__tcfapiCall:null;n&&window.__tcfapi(n.command,n.version,(function(o,r){var a={__tcfapiReturn:{returnValue:o,success:r,callId:n.callId}};t&&t.source&&t.source.postMessage&&t.source.postMessage(e?JSON.stringify(a):a,"*")}),n.parameter)}),!1))};"undefined"!=typeof module?module.exports=t:t()}(); dataLayer = dataLayer || []; // Standard GTM initialization - Google Consent Mode handles consent automatically (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start': new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0], j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src= 'https://www.googletagmanager.com/gtm.js?id='+i+dl+ '>m_auth=hzk0Vc3qFsQYhCrIoHz68A>m_preview=env-1>m_cookies_win=x';f.parentNode.insertBefore(j,f); })(window,document,'script','dataLayer','GTM-MWFK8L5J'); ;window.NREUM||(NREUM={});NREUM.init={distributed_tracing:{enabled:true},privacy:{cookies_enabled:true},ajax:{deny_list:["bam.nr-data.net"]}}; ;NREUM.loader_config={accountID:"438030",trustKey:"438030",agentID:"772317073",licenseKey:"97f8f67f26",applicationID:"772317073"} ;NREUM.info={beacon:"bam.nr-data.net",errorBeacon:"bam.nr-data.net",licenseKey:"97f8f67f26",applicationID:"772317073",sa:1} ;/*! For license information please see nr-loader-spa-1.236.0.min.js.LICENSE.txt */ (()=>{"use strict";var e,t,r={5763:(e,t,r)=>{r.d(t,{P_:()=>l,Mt:()=>g,C5:()=>s,DL:()=>v,OP:()=>T,lF:()=>D,Yu:()=>y,Dg:()=>h,CX:()=>c,GE:()=>b,sU:()=>_});var n=r(8632),i=r(9567);const o={beacon:n.ce.beacon,errorBeacon:n.ce.errorBeacon,licenseKey:void 0,applicationID:void 0,sa:void 0,queueTime:void 0,applicationTime:void 0,ttGuid:void 0,user:void 0,account:void 0,product:void 0,extra:void 0,jsAttributes:{},userAttributes:void 0,atts:void 0,transactionName:void 0,tNamePlain:void 0},a={};function s(e){if(!e)throw new Error("All info objects require an agent identifier!");if(!a[e])throw new Error("Info for ".concat(e," was never set"));return a[e]}function c(e,t){if(!e)throw new Error("All info objects require an agent identifier!");a[e]=(0,i.D)(t,o),(0,n.Qy)(e,a[e],"info")}var u=r(7056);const d=()=>{const e={blockSelector:"[data-nr-block]",maskInputOptions:{password:!0}};return{allow_bfcache:!0,privacy:{cookies_enabled:!0},ajax:{deny_list:void 0,enabled:!0,harvestTimeSeconds:10},distributed_tracing:{enabled:void 0,exclude_newrelic_header:void 0,cors_use_newrelic_header:void 0,cors_use_tracecontext_headers:void 0,allowed_origins:void 0},session:{domain:void 0,expiresMs:u.oD,inactiveMs:u.Hb},ssl:void 0,obfuscate:void 0,jserrors:{enabled:!0,harvestTimeSeconds:10},metrics:{enabled:!0},page_action:{enabled:!0,harvestTimeSeconds:30},page_view_event:{enabled:!0},page_view_timing:{enabled:!0,harvestTimeSeconds:30,long_task:!1},session_trace:{enabled:!0,harvestTimeSeconds:10},harvest:{tooManyRequestsDelay:60},session_replay:{enabled:!1,harvestTimeSeconds:60,sampleRate:.1,errorSampleRate:.1,maskTextSelector:"*",maskAllInputs:!0,get blockClass(){return"nr-block"},get ignoreClass(){return"nr-ignore"},get maskTextClass(){return"nr-mask"},get blockSelector(){return e.blockSelector},set blockSelector(t){e.blockSelector+=",".concat(t)},get maskInputOptions(){return e.maskInputOptions},set maskInputOptions(t){e.maskInputOptions={...t,password:!0}}},spa:{enabled:!0,harvestTimeSeconds:10}}},f={};function l(e){if(!e)throw new Error("All configuration objects require an agent identifier!");if(!f[e])throw new Error("Configuration for ".concat(e," was never set"));return f[e]}function h(e,t){if(!e)throw new Error("All configuration objects require an agent identifier!");f[e]=(0,i.D)(t,d()),(0,n.Qy)(e,f[e],"config")}function g(e,t){if(!e)throw new Error("All configuration objects require an agent identifier!");var r=l(e);if(r){for(var n=t.split("."),i=0;i {r.d(t,{D:()=>i});var n=r(50);function i(e,t){try{if(!e||"object"!=typeof e)return(0,n.Z)("Setting a Configurable requires an object as input");if(!t||"object"!=typeof t)return(0,n.Z)("Setting a Configurable requires a model to set its initial properties");const r=Object.create(Object.getPrototypeOf(t),Object.getOwnPropertyDescriptors(t)),o=0===Object.keys(r).length?e:r;for(let a in o)if(void 0!==e[a])try{"object"==typeof e[a]&&"object"==typeof t[a]?r[a]=i(e[a],t[a]):r[a]=e[a]}catch(e){(0,n.Z)("An error occurred while setting a property of a Configurable",e)}return r}catch(e){(0,n.Z)("An error occured while setting a Configurable",e)}}},6818:(e,t,r)=>{r.d(t,{Re:()=>i,gF:()=>o,q4:()=>n});const n="1.236.0",i="PROD",o="CDN"},385:(e,t,r)=>{r.d(t,{FN:()=>a,IF:()=>u,Nk:()=>f,Tt:()=>s,_A:()=>o,il:()=>n,pL:()=>c,v6:()=>i,w1:()=>d});const n="undefined"!=typeof window&&!!window.document,i="undefined"!=typeof WorkerGlobalScope&&("undefined"!=typeof self&&self instanceof WorkerGlobalScope&&self.navigator instanceof WorkerNavigator||"undefined"!=typeof globalThis&&globalThis instanceof WorkerGlobalScope&&globalThis.navigator instanceof WorkerNavigator),o=n?window:"undefined"!=typeof WorkerGlobalScope&&("undefined"!=typeof self&&self instanceof WorkerGlobalScope&&self||"undefined"!=typeof globalThis&&globalThis instanceof WorkerGlobalScope&&globalThis),a=""+o?.location,s=/iPad|iPhone|iPod/.test(navigator.userAgent),c=s&&"undefined"==typeof SharedWorker,u=(()=>{const e=navigator.userAgent.match(/Firefox[/\s](\d+\.\d+)/);return Array.isArray(e)&&e.length>=2?+e[1]:0})(),d=Boolean(n&&window.document.documentMode),f=!!navigator.sendBeacon},1117:(e,t,r)=>{r.d(t,{w:()=>o});var n=r(50);const i={agentIdentifier:"",ee:void 0};class o{constructor(e){try{if("object"!=typeof e)return(0,n.Z)("shared context requires an object as input");this.sharedContext={},Object.assign(this.sharedContext,i),Object.entries(e).forEach((e=>{let[t,r]=e;Object.keys(i).includes(t)&&(this.sharedContext[t]=r)}))}catch(e){(0,n.Z)("An error occured while setting SharedContext",e)}}}},8e3:(e,t,r)=>{r.d(t,{L:()=>d,R:()=>c});var n=r(2177),i=r(1284),o=r(4322),a=r(3325);const s={};function c(e,t){const r={staged:!1,priority:a.p[t]||0};u(e),s[e].get(t)||s[e].set(t,r)}function u(e){e&&(s[e]||(s[e]=new Map))}function d(){let e=arguments.length>0&&void 0!==arguments[0]?arguments[0]:"",t=arguments.length>1&&void 0!==arguments[1]?arguments[1]:"feature";if(u(e),!e||!s[e].get(t))return a(t);s[e].get(t).staged=!0;const r=[...s[e]];function a(t){const r=e?n.ee.get(e):n.ee,a=o.X.handlers;if(r.backlog&&a){var s=r.backlog[t],c=a[t];if(c){for(var u=0;s&&u {let[t,r]=e;return r.staged}))&&(r.sort(((e,t)=>e[1].priority-t[1].priority)),r.forEach((e=>{let[t]=e;a(t)})))}function f(e,t){var r=e[1];(0,i.D)(t[r],(function(t,r){var n=e[0];if(r[0]===n){var i=r[1],o=e[3],a=e[2];i.apply(o,a)}}))}},2177:(e,t,r)=>{r.d(t,{c:()=>f,ee:()=>u});var n=r(8632),i=r(2210),o=r(1284),a=r(5763),s="nr@context";let c=(0,n.fP)();var u;function d(){}function f(e){return(0,i.X)(e,s,l)}function l(){return new d}function h(){u.aborted=!0,u.backlog={}}c.ee?u=c.ee:(u=function e(t,r){var n={},c={},f={},g=!1;try{g=16===r.length&&(0,a.OP)(r).isolatedBacklog}catch(e){}var p={on:b,addEventListener:b,removeEventListener:y,emit:v,get:x,listeners:w,context:m,buffer:A,abort:h,aborted:!1,isBuffering:E,debugId:r,backlog:g?{}:t&&"object"==typeof t.backlog?t.backlog:{}};return p;function m(e){return e&&e instanceof d?e:e?(0,i.X)(e,s,l):l()}function v(e,r,n,i,o){if(!1!==o&&(o=!0),!u.aborted||i){t&&o&&t.emit(e,r,n);for(var a=m(n),s=w(e),d=s.length,f=0;fn,p:()=>i});var n=r(2177).ee.get("handle");function i(e,t,r,i,o){o?(o.buffer([e],i),o.emit(e,t,r)):(n.buffer([e],i),n.emit(e,t,r))}},4322:(e,t,r)=>{r.d(t,{X:()=>o});var n=r(5546);o.on=a;var i=o.handlers={};function o(e,t,r,o){a(o||n.E,i,e,t,r)}function a(e,t,r,i,o){o||(o="feature"),e||(e=n.E);var a=t[o]=t[o]||{};(a[r]=a[r]||[]).push([e,i])}},3239:(e,t,r)=>{r.d(t,{bP:()=>s,iz:()=>c,m$:()=>a});var n=r(385);let i=!1,o=!1;try{const e={get passive(){return i=!0,!1},get signal(){return o=!0,!1}};n._A.addEventListener("test",null,e),n._A.removeEventListener("test",null,e)}catch(e){}function a(e,t){return i||o?{capture:!!e,passive:i,signal:t}:!!e}function s(e,t){let r=arguments.length>2&&void 0!==arguments[2]&&arguments[2],n=arguments.length>3?arguments[3]:void 0;window.addEventListener(e,t,a(r,n))}function c(e,t){let r=arguments.length>2&&void 0!==arguments[2]&&arguments[2],n=arguments.length>3?arguments[3]:void 0;document.addEventListener(e,t,a(r,n))}},4402:(e,t,r)=>{r.d(t,{Ht:()=>u,M:()=>c,Rl:()=>a,ky:()=>s});var n=r(385);const i="xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx";function o(e,t){return e?15&e[t]:16*Math.random()|0}function a(){const e=n._A?.crypto||n._A?.msCrypto;let t,r=0;return e&&e.getRandomValues&&(t=e.getRandomValues(new Uint8Array(31))),i.split("").map((e=>"x"===e?o(t,++r).toString(16):"y"===e?(3&o()|8).toString(16):e)).join("")}function s(e){const t=n._A?.crypto||n._A?.msCrypto;let r,i=0;t&&t.getRandomValues&&(r=t.getRandomValues(new Uint8Array(31)));const a=[];for(var s=0;s {r.d(t,{Bq:()=>n,Hb:()=>o,oD:()=>i});const n="NRBA",i=144e5,o=18e5},7894:(e,t,r)=>{function n(){return Math.round(performance.now())}r.d(t,{z:()=>n})},7243:(e,t,r)=>{r.d(t,{e:()=>o});var n=r(385),i={};function o(e){if(e in i)return i[e];if(0===(e||"").indexOf("data:"))return{protocol:"data"};let t;var r=n._A?.location,o={};if(n.il)t=document.createElement("a"),t.href=e;else try{t=new URL(e,r.href)}catch(e){return o}o.port=t.port;var a=t.href.split("://");!o.port&&a[1]&&(o.port=a[1].split("/")[0].split("@").pop().split(":")[1]),o.port&&"0"!==o.port||(o.port="https"===a[0]?"443":"80"),o.hostname=t.hostname||r.hostname,o.pathname=t.pathname,o.protocol=a[0],"/"!==o.pathname.charAt(0)&&(o.pathname="/"+o.pathname);var s=!t.protocol||":"===t.protocol||t.protocol===r.protocol,c=t.hostname===r.hostname&&t.port===r.port;return o.sameOrigin=s&&(!t.hostname||c),"/"===o.pathname&&(i[e]=o),o}},50:(e,t,r)=>{function n(e,t){"function"==typeof console.warn&&(console.warn("New Relic: ".concat(e)),t&&console.warn(t))}r.d(t,{Z:()=>n})},2587:(e,t,r)=>{r.d(t,{N:()=>c,T:()=>u});var n=r(2177),i=r(5546),o=r(8e3),a=r(3325);const s={stn:[a.D.sessionTrace],err:[a.D.jserrors,a.D.metrics],ins:[a.D.pageAction],spa:[a.D.spa],sr:[a.D.sessionReplay,a.D.sessionTrace]};function c(e,t){const r=n.ee.get(t);e&&"object"==typeof e&&(Object.entries(e).forEach((e=>{let[t,n]=e;void 0===u[t]&&(s[t]?s[t].forEach((e=>{n?(0,i.p)("feat-"+t,[],void 0,e,r):(0,i.p)("block-"+t,[],void 0,e,r),(0,i.p)("rumresp-"+t,[Boolean(n)],void 0,e,r)})):n&&(0,i.p)("feat-"+t,[],void 0,void 0,r),u[t]=Boolean(n))})),Object.keys(s).forEach((e=>{void 0===u[e]&&(s[e]?.forEach((t=>(0,i.p)("rumresp-"+e,[!1],void 0,t,r))),u[e]=!1)})),(0,o.L)(t,a.D.pageViewEvent))}const u={}},2210:(e,t,r)=>{r.d(t,{X:()=>i});var n=Object.prototype.hasOwnProperty;function i(e,t,r){if(n.call(e,t))return e[t];var i=r();if(Object.defineProperty&&Object.keys)try{return Object.defineProperty(e,t,{value:i,writable:!0,enumerable:!1}),i}catch(e){}return e[t]=i,i}},1284:(e,t,r)=>{r.d(t,{D:()=>n});const n=(e,t)=>Object.entries(e||{}).map((e=>{let[r,n]=e;return t(r,n)}))},4351:(e,t,r)=>{r.d(t,{P:()=>o});var n=r(2177);const i=()=>{const e=new WeakSet;return(t,r)=>{if("object"==typeof r&&null!==r){if(e.has(r))return;e.add(r)}return r}};function o(e){try{return JSON.stringify(e,i())}catch(e){try{n.ee.emit("internal-error",[e])}catch(e){}}}},3960:(e,t,r)=>{r.d(t,{K:()=>a,b:()=>o});var n=r(3239);function i(){return"undefined"==typeof document||"complete"===document.readyState}function o(e,t){if(i())return e();(0,n.bP)("load",e,t)}function a(e){if(i())return e();(0,n.iz)("DOMContentLoaded",e)}},8632:(e,t,r)=>{r.d(t,{EZ:()=>u,Qy:()=>c,ce:()=>o,fP:()=>a,gG:()=>d,mF:()=>s});var n=r(7894),i=r(385);const o={beacon:"bam.nr-data.net",errorBeacon:"bam.nr-data.net"};function a(){return i._A.NREUM||(i._A.NREUM={}),void 0===i._A.newrelic&&(i._A.newrelic=i._A.NREUM),i._A.NREUM}function s(){let e=a();return e.o||(e.o={ST:i._A.setTimeout,SI:i._A.setImmediate,CT:i._A.clearTimeout,XHR:i._A.XMLHttpRequest,REQ:i._A.Request,EV:i._A.Event,PR:i._A.Promise,MO:i._A.MutationObserver,FETCH:i._A.fetch}),e}function c(e,t,r){let i=a();const o=i.initializedAgents||{},s=o[e]||{};return Object.keys(s).length||(s.initializedAt={ms:(0,n.z)(),date:new Date}),i.initializedAgents={...o,[e]:{...s,[r]:t}},i}function u(e,t){a()[e]=t}function d(){return function(){let e=a();const t=e.info||{};e.info={beacon:o.beacon,errorBeacon:o.errorBeacon,...t}}(),function(){let e=a();const t=e.init||{};e.init={...t}}(),s(),function(){let e=a();const t=e.loader_config||{};e.loader_config={...t}}(),a()}},7956:(e,t,r)=>{r.d(t,{N:()=>i});var n=r(3239);function i(e){let t=arguments.length>1&&void 0!==arguments[1]&&arguments[1],r=arguments.length>2?arguments[2]:void 0,i=arguments.length>3?arguments[3]:void 0;return void(0,n.iz)("visibilitychange",(function(){if(t)return void("hidden"==document.visibilityState&&e());e(document.visibilityState)}),r,i)}},1214:(e,t,r)=>{r.d(t,{em:()=>v,u5:()=>N,QU:()=>S,_L:()=>I,Gm:()=>L,Lg:()=>M,gy:()=>U,BV:()=>Q,Kf:()=>ee});var n=r(2177);const i="nr@original";var o=Object.prototype.hasOwnProperty,a=!1;function s(e,t){return e||(e=n.ee),r.inPlace=function(e,t,n,i,o){n||(n="");var a,s,c,u="-"===n.charAt(0);for(c=0;c 2?n-2:0),o=2;o {r(A[T],e,w),r(E[T],e,w)})),r(l._A,"fetch",y),t.on(y+"end",(function(e,r){var n=this;if(r){var i=r.headers.get("content-length");null!==i&&(n.rxSize=i),t.emit(y+"done",[null,r],n)}else t.emit(y+"done",[e],n)})),t}const O={},j=["pushState","replaceState"];function S(e){const t=function(e){return(e||n.ee).get("history")}(e);return!l.il||O[t.debugId]++||(O[t.debugId]=1,s(t).inPlace(window.history,j,"-")),t}var P=r(3239);const C={},R=["appendChild","insertBefore","replaceChild"];function I(e){const t=function(e){return(e||n.ee).get("jsonp")}(e);if(!l.il||C[t.debugId])return t;C[t.debugId]=!0;var r=s(t),i=/[?&](?:callback|cb)=([^&#]+)/,o=/(.*)\.([^.]+)/,a=/^(\w+)(\.|$)(.*)$/;function c(e,t){var r=e.match(a),n=r[1],i=r[3];return i?c(i,t[n]):t[n]}return r.inPlace(Node.prototype,R,"dom-"),t.on("dom-start",(function(e){!function(e){if(!e||"string"!=typeof e.nodeName||"script"!==e.nodeName.toLowerCase())return;if("function"!=typeof e.addEventListener)return;var n=(a=e.src,s=a.match(i),s?s[1]:null);var a,s;if(!n)return;var u=function(e){var t=e.match(o);if(t&&t.length>=3)return{key:t[2],parent:c(t[1],window)};return{key:e,parent:window}}(n);if("function"!=typeof u.parent[u.key])return;var d={};function f(){t.emit("jsonp-end",[],d),e.removeEventListener("load",f,(0,P.m$)(!1)),e.removeEventListener("error",l,(0,P.m$)(!1))}function l(){t.emit("jsonp-error",[],d),t.emit("jsonp-end",[],d),e.removeEventListener("load",f,(0,P.m$)(!1)),e.removeEventListener("error",l,(0,P.m$)(!1))}r.inPlace(u.parent,[u.key],"cb-",d),e.addEventListener("load",f,(0,P.m$)(!1)),e.addEventListener("error",l,(0,P.m$)(!1)),t.emit("new-jsonp",[e.src],d)}(e[0])})),t}var k=r(5763);const H={};function L(e){const t=function(e){return(e||n.ee).get("mutation")}(e);if(!l.il||H[t.debugId])return t;H[t.debugId]=!0;var r=s(t),i=k.Yu.MO;return i&&(window.MutationObserver=function(e){return this instanceof i?new i(r(e,"fn-")):i.apply(this,arguments)},MutationObserver.prototype=i.prototype),t}const z={};function M(e){const t=function(e){return(e||n.ee).get("promise")}(e);if(z[t.debugId])return t;z[t.debugId]=!0;var r=n.c,o=s(t),a=k.Yu.PR;return a&&function(){function e(r){var n=t.context(),i=o(r,"executor-",n,null,!1);const s=Reflect.construct(a,[i],e);return t.context(s).getCtx=function(){return n},s}l._A.Promise=e,Object.defineProperty(e,"name",{value:"Promise"}),e.toString=function(){return a.toString()},Object.setPrototypeOf(e,a),["all","race"].forEach((function(r){const n=a[r];e[r]=function(e){let i=!1;[...e||[]].forEach((e=>{this.resolve(e).then(a("all"===r),a(!1))}));const o=n.apply(this,arguments);return o;function a(e){return function(){t.emit("propagate",[null,!i],o,!1,!1),i=i||!e}}}})),["resolve","reject"].forEach((function(r){const n=a[r];e[r]=function(e){const r=n.apply(this,arguments);return e!==r&&t.emit("propagate",[e,!0],r,!1,!1),r}})),e.prototype=a.prototype;const n=a.prototype.then;a.prototype.then=function(){var e=this,i=r(e);i.promise=e;for(var a=arguments.length,s=new Array(a),c=0;c e())),t};function m(e,t){i.inPlace(t,["onreadystatechange"],"fn-",E)}function b(){var e=this,t=r.context(e);e.readyState>3&&!t.resolved&&(t.resolved=!0,r.emit("xhr-resolved",[],e)),i.inPlace(e,f,"fn-",E)}if(function(e,t){for(var r in e)t[r]=e[r]}(o,p),p.prototype=o.prototype,i.inPlace(p.prototype,J,"-xhr-",E),r.on("send-xhr-start",(function(e,t){m(e,t),function(e){h.push(e),a&&(y?y.then(A):u?u(A):(w=-w,x.data=w))}(t)})),r.on("open-xhr-start",m),a){var y=c&&c.resolve();if(!u&&!c){var w=1,x=document.createTextNode(w);new a(A).observe(x,{characterData:!0})}}else t.on("fn-end",(function(e){e[0]&&e[0].type===d||A()}));function A(){for(var e=0;e {r.d(t,{t:()=>n});const n=r(3325).D.ajax},6660:(e,t,r)=>{r.d(t,{A:()=>i,t:()=>n});const n=r(3325).D.jserrors,i="nr@seenError"},3081:(e,t,r)=>{r.d(t,{gF:()=>o,mY:()=>i,t9:()=>n,vz:()=>s,xS:()=>a});const n=r(3325).D.metrics,i="sm",o="cm",a="storeSupportabilityMetrics",s="storeEventMetrics"},4649:(e,t,r)=>{r.d(t,{t:()=>n});const n=r(3325).D.pageAction},7633:(e,t,r)=>{r.d(t,{Dz:()=>i,OJ:()=>a,qw:()=>o,t9:()=>n});const n=r(3325).D.pageViewEvent,i="firstbyte",o="domcontent",a="windowload"},9251:(e,t,r)=>{r.d(t,{t:()=>n});const n=r(3325).D.pageViewTiming},3614:(e,t,r)=>{r.d(t,{BST_RESOURCE:()=>i,END:()=>s,FEATURE_NAME:()=>n,FN_END:()=>u,FN_START:()=>c,PUSH_STATE:()=>d,RESOURCE:()=>o,START:()=>a});const n=r(3325).D.sessionTrace,i="bstResource",o="resource",a="-start",s="-end",c="fn"+a,u="fn"+s,d="pushState"},7836:(e,t,r)=>{r.d(t,{BODY:()=>A,CB_END:()=>E,CB_START:()=>u,END:()=>x,FEATURE_NAME:()=>i,FETCH:()=>_,FETCH_BODY:()=>v,FETCH_DONE:()=>m,FETCH_START:()=>p,FN_END:()=>c,FN_START:()=>s,INTERACTION:()=>l,INTERACTION_API:()=>d,INTERACTION_EVENTS:()=>o,JSONP_END:()=>b,JSONP_NODE:()=>g,JS_TIME:()=>T,MAX_TIMER_BUDGET:()=>a,REMAINING:()=>f,SPA_NODE:()=>h,START:()=>w,originalSetTimeout:()=>y});var n=r(5763);const i=r(3325).D.spa,o=["click","submit","keypress","keydown","keyup","change"],a=999,s="fn-start",c="fn-end",u="cb-start",d="api-ixn-",f="remaining",l="interaction",h="spaNode",g="jsonpNode",p="fetch-start",m="fetch-done",v="fetch-body-",b="jsonp-end",y=n.Yu.ST,w="-start",x="-end",A="-body",E="cb"+x,T="jsTime",_="fetch"},5938:(e,t,r)=>{r.d(t,{W:()=>o});var n=r(5763),i=r(2177);class o{constructor(e,t,r){this.agentIdentifier=e,this.aggregator=t,this.ee=i.ee.get(e,(0,n.OP)(this.agentIdentifier).isolatedBacklog),this.featureName=r,this.blocked=!1}}},9144:(e,t,r)=>{r.d(t,{j:()=>m});var n=r(3325),i=r(5763),o=r(5546),a=r(2177),s=r(7894),c=r(8e3),u=r(3960),d=r(385),f=r(50),l=r(3081),h=r(8632);function g(){const e=(0,h.gG)();["setErrorHandler","finished","addToTrace","inlineHit","addRelease","addPageAction","setCurrentRouteName","setPageViewName","setCustomAttribute","interaction","noticeError","setUserId"].forEach((t=>{e[t]=function(){for(var r=arguments.length,n=new Array(r),i=0;i 1?r-1:0),i=1;i {e.exposed&&e.api[t]&&o.push(e.api[t](...n))})),o.length>1?o:o[0]}(t,...n)}}))}var p=r(2587);function m(e){let t=arguments.length>1&&void 0!==arguments[1]?arguments[1]:{},m=arguments.length>2?arguments[2]:void 0,v=arguments.length>3?arguments[3]:void 0,{init:b,info:y,loader_config:w,runtime:x={loaderType:m},exposed:A=!0}=t;const E=(0,h.gG)();y||(b=E.init,y=E.info,w=E.loader_config),(0,i.Dg)(e,b||{}),(0,i.GE)(e,w||{}),(0,i.sU)(e,x),y.jsAttributes??={},d.v6&&(y.jsAttributes.isWorker=!0),(0,i.CX)(e,y),g();const T=function(e,t){t||(0,c.R)(e,"api");const h={};var g=a.ee.get(e),p=g.get("tracer"),m="api-",v=m+"ixn-";function b(t,r,n,o){const a=(0,i.C5)(e);return null===r?delete a.jsAttributes[t]:(0,i.CX)(e,{...a,jsAttributes:{...a.jsAttributes,[t]:r}}),x(m,n,!0,o||null===r?"session":void 0)(t,r)}function y(){}["setErrorHandler","finished","addToTrace","inlineHit","addRelease"].forEach((e=>h[e]=x(m,e,!0,"api"))),h.addPageAction=x(m,"addPageAction",!0,n.D.pageAction),h.setCurrentRouteName=x(m,"routeName",!0,n.D.spa),h.setPageViewName=function(t,r){if("string"==typeof t)return"/"!==t.charAt(0)&&(t="/"+t),(0,i.OP)(e).customTransaction=(r||"http://custom.transaction")+t,x(m,"setPageViewName",!0)()},h.setCustomAttribute=function(e,t){let r=arguments.length>2&&void 0!==arguments[2]&&arguments[2];if("string"==typeof e){if(["string","number"].includes(typeof t)||null===t)return b(e,t,"setCustomAttribute",r);(0,f.Z)("Failed to execute setCustomAttribute.\nNon-null value must be a string or number type, but a type of was provided."))}else(0,f.Z)("Failed to execute setCustomAttribute.\nName must be a string type, but a type of was provided."))},h.setUserId=function(e){if("string"==typeof e||null===e)return b("enduser.id",e,"setUserId",!0);(0,f.Z)("Failed to execute setUserId.\nNon-null value must be a string type, but a type of was provided."))},h.interaction=function(){return(new y).get()};var w=y.prototype={createTracer:function(e,t){var r={},i=this,a="function"==typeof t;return(0,o.p)(v+"tracer",[(0,s.z)(),e,r],i,n.D.spa,g),function(){if(p.emit((a?"":"no-")+"fn-start",[(0,s.z)(),i,a],r),a)try{return t.apply(this,arguments)}catch(e){throw p.emit("fn-err",[arguments,this,"string"==typeof e?new Error(e):e],r),e}finally{p.emit("fn-end",[(0,s.z)()],r)}}}};function x(e,t,r,i){return function(){return(0,o.p)(l.xS,["API/"+t+"/called"],void 0,n.D.metrics,g),i&&(0,o.p)(e+t,[(0,s.z)(),...arguments],r?null:this,i,g),r?void 0:this}}function A(){r.e(439).then(r.bind(r,7438)).then((t=>{let{setAPI:r}=t;r(e),(0,c.L)(e,"api")})).catch((()=>(0,f.Z)("Downloading runtime APIs failed...")))}return["actionText","setName","setAttribute","save","ignore","onEnd","getContext","end","get"].forEach((e=>{w[e]=x(v,e,void 0,n.D.spa)})),h.noticeError=function(e,t){"string"==typeof e&&(e=new Error(e)),(0,o.p)(l.xS,["API/noticeError/called"],void 0,n.D.metrics,g),(0,o.p)("err",[e,(0,s.z)(),!1,t],void 0,n.D.jserrors,g)},d.il?(0,u.b)((()=>A()),!0):A(),h}(e,v);return(0,h.Qy)(e,T,"api"),(0,h.Qy)(e,A,"exposed"),(0,h.EZ)("activatedFeatures",p.T),T}},3325:(e,t,r)=>{r.d(t,{D:()=>n,p:()=>i});const n={ajax:"ajax",jserrors:"jserrors",metrics:"metrics",pageAction:"page_action",pageViewEvent:"page_view_event",pageViewTiming:"page_view_timing",sessionReplay:"session_replay",sessionTrace:"session_trace",spa:"spa"},i={[n.pageViewEvent]:1,[n.pageViewTiming]:2,[n.metrics]:3,[n.jserrors]:4,[n.ajax]:5,[n.sessionTrace]:6,[n.pageAction]:7,[n.spa]:8,[n.sessionReplay]:9}}},n={};function i(e){var t=n[e];if(void 0!==t)return t.exports;var o=n[e]={exports:{}};return r[e](o,o.exports,i),o.exports}i.m=r,i.d=(e,t)=>{for(var r in t)i.o(t,r)&&!i.o(e,r)&&Object.defineProperty(e,r,{enumerable:!0,get:t[r]})},i.f={},i.e=e=>Promise.all(Object.keys(i.f).reduce(((t,r)=>(i.f[r](e,t),t)),[])),i.u=e=>(({78:"page_action-aggregate",147:"metrics-aggregate",242:"session-manager",317:"jserrors-aggregate",348:"page_view_timing-aggregate",412:"lazy-feature-loader",439:"async-api",538:"recorder",590:"session_replay-aggregate",675:"compressor",733:"session_trace-aggregate",786:"page_view_event-aggregate",873:"spa-aggregate",898:"ajax-aggregate"}[e]||e)+"."+{78:"ac76d497",147:"3dc53903",148:"1a20d5fe",242:"2a64278a",317:"49e41428",348:"bd6de33a",412:"2f55ce66",439:"30bd804e",538:"1b18459f",590:"cf0efb30",675:"ae9f91a8",733:"83105561",786:"06482edd",860:"03a8b7a5",873:"e6b09d52",898:"998ef92b"}[e]+"-1.236.0.min.js"),i.o=(e,t)=>Object.prototype.hasOwnProperty.call(e,t),e={},t="NRBA:",i.l=(r,n,o,a)=>{if(e[r])e[r].push(n);else{var s,c;if(void 0!==o)for(var u=document.getElementsByTagName("script"),d=0;d {s.onerror=s.onload=null,clearTimeout(h);var i=e[r];if(delete e[r],s.parentNode&&s.parentNode.removeChild(s),i&&i.forEach((e=>e(n))),t)return t(n)},h=setTimeout(l.bind(null,void 0,{type:"timeout",target:s}),12e4);s.onerror=l.bind(null,s.onerror),s.onload=l.bind(null,s.onload),c&&document.head.appendChild(s)}},i.r=e=>{"undefined"!=typeof Symbol&&Symbol.toStringTag&&Object.defineProperty(e,Symbol.toStringTag,{value:"Module"}),Object.defineProperty(e,"__esModule",{value:!0})},i.j=364,i.p="https://js-agent.newrelic.com/",(()=>{var e={364:0,953:0};i.f.j=(t,r)=>{var n=i.o(e,t)?e[t]:void 0;if(0!==n)if(n)r.push(n[2]);else{var o=new Promise(((r,i)=>n=e[t]=[r,i]));r.push(n[2]=o);var a=i.p+i.u(t),s=new Error;i.l(a,(r=>{if(i.o(e,t)&&(0!==(n=e[t])&&(e[t]=void 0),n)){var o=r&&("load"===r.type?"missing":r.type),a=r&&r.target&&r.target.src;s.message="Loading chunk "+t+" failed.\n("+o+": "+a+")",s.name="ChunkLoadError",s.type=o,s.request=a,n[1](s)}}),"chunk-"+t,t)}};var t=(t,r)=>{var n,o,[a,s,c]=r,u=0;if(a.some((t=>0!==e[t]))){for(n in s)i.o(s,n)&&(i.m[n]=s[n]);if(c)c(i)}for(t&&t(r);u {i.r(o);var e=i(3325),t=i(5763);const r=Object.values(e.D);function n(e){const n={};return r.forEach((r=>{n[r]=function(e,r){return!1!==(0,t.Mt)(r,"".concat(e,".enabled"))}(r,e)})),n}var a=i(9144);var s=i(5546),c=i(385),u=i(8e3),d=i(5938),f=i(3960),l=i(50);class h extends d.W{constructor(e,t,r){let n=!(arguments.length>3&&void 0!==arguments[3])||arguments[3];super(e,t,r),this.auto=n,this.abortHandler,this.featAggregate,this.onAggregateImported,n&&(0,u.R)(e,r)}importAggregator(){let e=arguments.length>0&&void 0!==arguments[0]?arguments[0]:{};if(this.featAggregate||!this.auto)return;const r=c.il&&!0===(0,t.Mt)(this.agentIdentifier,"privacy.cookies_enabled");let n;this.onAggregateImported=new Promise((e=>{n=e}));const o=async()=>{let t;try{if(r){const{setupAgentSession:e}=await Promise.all([i.e(860),i.e(242)]).then(i.bind(i,3228));t=e(this.agentIdentifier)}}catch(e){(0,l.Z)("A problem occurred when starting up session manager. This page will not start or extend any session.",e)}try{if(!this.shouldImportAgg(this.featureName,t))return void(0,u.L)(this.agentIdentifier,this.featureName);const{lazyFeatureLoader:r}=await i.e(412).then(i.bind(i,8582)),{Aggregate:o}=await r(this.featureName,"aggregate");this.featAggregate=new o(this.agentIdentifier,this.aggregator,e),n(!0)}catch(e){(0,l.Z)("Downloading and initializing ".concat(this.featureName," failed..."),e),this.abortHandler?.(),n(!1)}};c.il?(0,f.b)((()=>o()),!0):o()}shouldImportAgg(r,n){return r!==e.D.sessionReplay||!1!==(0,t.Mt)(this.agentIdentifier,"session_trace.enabled")&&(!!n?.isNew||!!n?.state.sessionReplay)}}var g=i(7633),p=i(7894);class m extends h{static featureName=g.t9;constructor(r,n){let i=!(arguments.length>2&&void 0!==arguments[2])||arguments[2];if(super(r,n,g.t9,i),("undefined"==typeof PerformanceNavigationTiming||c.Tt)&&"undefined"!=typeof PerformanceTiming){const n=(0,t.OP)(r);n[g.Dz]=Math.max(Date.now()-n.offset,0),(0,f.K)((()=>n[g.qw]=Math.max((0,p.z)()-n[g.Dz],0))),(0,f.b)((()=>{const t=(0,p.z)();n[g.OJ]=Math.max(t-n[g.Dz],0),(0,s.p)("timing",["load",t],void 0,e.D.pageViewTiming,this.ee)}))}this.importAggregator()}}var v=i(1117),b=i(1284);class y extends v.w{constructor(e){super(e),this.aggregatedData={}}store(e,t,r,n,i){var o=this.getBucket(e,t,r,i);return o.metrics=function(e,t){t||(t={count:0});return t.count+=1,(0,b.D)(e,(function(e,r){t[e]=w(r,t[e])})),t}(n,o.metrics),o}merge(e,t,r,n,i){var o=this.getBucket(e,t,n,i);if(o.metrics){var a=o.metrics;a.count+=r.count,(0,b.D)(r,(function(e,t){if("count"!==e){var n=a[e],i=r[e];i&&!i.c?a[e]=w(i.t,n):a[e]=function(e,t){if(!t)return e;t.c||(t=x(t.t));return t.min=Math.min(e.min,t.min),t.max=Math.max(e.max,t.max),t.t+=e.t,t.sos+=e.sos,t.c+=e.c,t}(i,a[e])}}))}else o.metrics=r}storeMetric(e,t,r,n){var i=this.getBucket(e,t,r);return i.stats=w(n,i.stats),i}getBucket(e,t,r,n){this.aggregatedData[e]||(this.aggregatedData[e]={});var i=this.aggregatedData[e][t];return i||(i=this.aggregatedData[e][t]={params:r||{}},n&&(i.custom=n)),i}get(e,t){return t?this.aggregatedData[e]&&this.aggregatedData[e][t]:this.aggregatedData[e]}take(e){for(var t={},r="",n=!1,i=0;i t.max&&(t.max=e),e 2&&void 0!==arguments[2])||arguments[2];super(e,r,j.t,n),c.il&&((0,t.OP)(e).initHidden=Boolean("hidden"===document.visibilityState),(0,N.N)((()=>(0,s.p)("docHidden",[(0,p.z)()],void 0,j.t,this.ee)),!0),(0,O.bP)("pagehide",(()=>(0,s.p)("winPagehide",[(0,p.z)()],void 0,j.t,this.ee))),this.importAggregator())}}var P=i(3081);class C extends h{static featureName=P.t9;constructor(e,t){let r=!(arguments.length>2&&void 0!==arguments[2])||arguments[2];super(e,t,P.t9,r),this.importAggregator()}}var R,I=i(2210),k=i(1214),H=i(2177),L={};try{R=localStorage.getItem("__nr_flags").split(","),console&&"function"==typeof console.log&&(L.console=!0,-1!==R.indexOf("dev")&&(L.dev=!0),-1!==R.indexOf("nr_dev")&&(L.nrDev=!0))}catch(e){}function z(e){try{L.console&&z(e)}catch(e){}}L.nrDev&&H.ee.on("internal-error",(function(e){z(e.stack)})),L.dev&&H.ee.on("fn-err",(function(e,t,r){z(r.stack)})),L.dev&&(z("NR AGENT IN DEVELOPMENT MODE"),z("flags: "+(0,b.D)(L,(function(e,t){return e})).join(", ")));var M=i(6660);class B extends h{static featureName=M.t;constructor(r,n){let i=!(arguments.length>2&&void 0!==arguments[2])||arguments[2];super(r,n,M.t,i),this.skipNext=0;try{this.removeOnAbort=new AbortController}catch(e){}const o=this;o.ee.on("fn-start",(function(e,t,r){o.abortHandler&&(o.skipNext+=1)})),o.ee.on("fn-err",(function(t,r,n){o.abortHandler&&!n[M.A]&&((0,I.X)(n,M.A,(function(){return!0})),this.thrown=!0,(0,s.p)("err",[n,(0,p.z)()],void 0,e.D.jserrors,o.ee))})),o.ee.on("fn-end",(function(){o.abortHandler&&!this.thrown&&o.skipNext>0&&(o.skipNext-=1)})),o.ee.on("internal-error",(function(t){(0,s.p)("ierr",[t,(0,p.z)(),!0],void 0,e.D.jserrors,o.ee)})),this.origOnerror=c._A.onerror,c._A.onerror=this.onerrorHandler.bind(this),c._A.addEventListener("unhandledrejection",(t=>{const r=function(e){let t="Unhandled Promise Rejection: ";if(e instanceof Error)try{return e.message=t+e.message,e}catch(t){return e}if(void 0===e)return new Error(t);try{return new Error(t+(0,D.P)(e))}catch(e){return new Error(t)}}(t.reason);(0,s.p)("err",[r,(0,p.z)(),!1,{unhandledPromiseRejection:1}],void 0,e.D.jserrors,this.ee)}),(0,O.m$)(!1,this.removeOnAbort?.signal)),(0,k.gy)(this.ee),(0,k.BV)(this.ee),(0,k.em)(this.ee),(0,t.OP)(r).xhrWrappable&&(0,k.Kf)(this.ee),this.abortHandler=this.#e,this.importAggregator()}#e(){this.removeOnAbort?.abort(),this.abortHandler=void 0}onerrorHandler(t,r,n,i,o){"function"==typeof this.origOnerror&&this.origOnerror(...arguments);try{this.skipNext?this.skipNext-=1:(0,s.p)("err",[o||new F(t,r,n),(0,p.z)()],void 0,e.D.jserrors,this.ee)}catch(t){try{(0,s.p)("ierr",[t,(0,p.z)(),!0],void 0,e.D.jserrors,this.ee)}catch(e){}}return!1}}function F(e,t,r){this.message=e||"Uncaught error with no additional information",this.sourceURL=t,this.line=r}let U=1;const q="nr@id";function G(e){const t=typeof e;return!e||"object"!==t&&"function"!==t?-1:e===c._A?0:(0,I.X)(e,q,(function(){return U++}))}function V(e){if("string"==typeof e&&e.length)return e.length;if("object"==typeof e){if("undefined"!=typeof ArrayBuffer&&e instanceof ArrayBuffer&&e.byteLength)return e.byteLength;if("undefined"!=typeof Blob&&e instanceof Blob&&e.size)return e.size;if(!("undefined"!=typeof FormData&&e instanceof FormData))try{return(0,D.P)(e).length}catch(e){return}}}var X=i(7243);class W{constructor(e){this.agentIdentifier=e,this.generateTracePayload=this.generateTracePayload.bind(this),this.shouldGenerateTrace=this.shouldGenerateTrace.bind(this)}generateTracePayload(e){if(!this.shouldGenerateTrace(e))return null;var r=(0,t.DL)(this.agentIdentifier);if(!r)return null;var n=(r.accountID||"").toString()||null,i=(r.agentID||"").toString()||null,o=(r.trustKey||"").toString()||null;if(!n||!i)return null;var a=(0,_.M)(),s=(0,_.Ht)(),c=Date.now(),u={spanId:a,traceId:s,timestamp:c};return(e.sameOrigin||this.isAllowedOrigin(e)&&this.useTraceContextHeadersForCors())&&(u.traceContextParentHeader=this.generateTraceContextParentHeader(a,s),u.traceContextStateHeader=this.generateTraceContextStateHeader(a,c,n,i,o)),(e.sameOrigin&&!this.excludeNewrelicHeader()||!e.sameOrigin&&this.isAllowedOrigin(e)&&this.useNewrelicHeaderForCors())&&(u.newrelicHeader=this.generateTraceHeader(a,s,c,n,i,o)),u}generateTraceContextParentHeader(e,t){return"00-"+t+"-"+e+"-01"}generateTraceContextStateHeader(e,t,r,n,i){return i+"@nr=0-1-"+r+"-"+n+"-"+e+"----"+t}generateTraceHeader(e,t,r,n,i,o){if(!("function"==typeof c._A?.btoa))return null;var a={v:[0,1],d:{ty:"Browser",ac:n,ap:i,id:e,tr:t,ti:r}};return o&&n!==o&&(a.d.tk=o),btoa((0,D.P)(a))}shouldGenerateTrace(e){return this.isDtEnabled()&&this.isAllowedOrigin(e)}isAllowedOrigin(e){var r=!1,n={};if((0,t.Mt)(this.agentIdentifier,"distributed_tracing")&&(n=(0,t.P_)(this.agentIdentifier).distributed_tracing),e.sameOrigin)r=!0;else if(n.allowed_origins instanceof Array)for(var i=0;i 2&&void 0!==arguments[2])||arguments[2];super(r,n,Z.t,i),(0,t.OP)(r).xhrWrappable&&(this.dt=new W(r),this.handler=(e,t,r,n)=>(0,s.p)(e,t,r,n,this.ee),(0,k.u5)(this.ee),(0,k.Kf)(this.ee),function(r,n,i,o){function a(e){var t=this;t.totalCbs=0,t.called=0,t.cbTime=0,t.end=E,t.ended=!1,t.xhrGuids={},t.lastSize=null,t.loadCaptureCalled=!1,t.params=this.params||{},t.metrics=this.metrics||{},e.addEventListener("load",(function(r){_(t,e)}),(0,O.m$)(!1)),c.IF||e.addEventListener("progress",(function(e){t.lastSize=e.loaded}),(0,O.m$)(!1))}function s(e){this.params={method:e[0]},T(this,e[1]),this.metrics={}}function u(e,n){var i=(0,t.DL)(r);i.xpid&&this.sameOrigin&&n.setRequestHeader("X-NewRelic-ID",i.xpid);var a=o.generateTracePayload(this.parsedOrigin);if(a){var s=!1;a.newrelicHeader&&(n.setRequestHeader("newrelic",a.newrelicHeader),s=!0),a.traceContextParentHeader&&(n.setRequestHeader("traceparent",a.traceContextParentHeader),a.traceContextStateHeader&&n.setRequestHeader("tracestate",a.traceContextStateHeader),s=!0),s&&(this.dt=a)}}function d(e,t){var r=this.metrics,i=e[0],o=this;if(r&&i){var a=V(i);a&&(r.txSize=a)}this.startTime=(0,p.z)(),this.listener=function(e){try{"abort"!==e.type||o.loadCaptureCalled||(o.params.aborted=!0),("load"!==e.type||o.called===o.totalCbs&&(o.onloadCalled||"function"!=typeof t.onload)&&"function"==typeof o.end)&&o.end(t)}catch(e){try{n.emit("internal-error",[e])}catch(e){}}};for(var s=0;s 1?e[1]=i:e.push(i)}else e[0]&&e[0].headers&&s(e[0].headers,n)&&(this.dt=n);function s(e,t){var r=!1;return t.newrelicHeader&&(e.set("newrelic",t.newrelicHeader),r=!0),t.traceContextParentHeader&&(e.set("traceparent",t.traceContextParentHeader),t.traceContextStateHeader&&e.set("tracestate",t.traceContextStateHeader),r=!0),r}}function x(e,t){this.params={},this.metrics={},this.startTime=(0,p.z)(),this.dt=t,e.length>=1&&(this.target=e[0]),e.length>=2&&(this.opts=e[1]);var r,n=this.opts||{},i=this.target;"string"==typeof i?r=i:"object"==typeof i&&i instanceof Y?r=i.url:c._A?.URL&&"object"==typeof i&&i instanceof URL&&(r=i.href),T(this,r);var o=(""+(i&&i instanceof Y&&i.method||n.method||"GET")).toUpperCase();this.params.method=o,this.txSize=V(n.body)||0}function A(t,r){var n;this.endTime=(0,p.z)(),this.params||(this.params={}),this.params.status=r?r.status:0,"string"==typeof this.rxSize&&this.rxSize.length>0&&(n=+this.rxSize);var o={txSize:this.txSize,rxSize:n,duration:(0,p.z)()-this.startTime};i("xhr",[this.params,o,this.startTime,this.endTime,"fetch"],this,e.D.ajax)}function E(t){var r=this.params,n=this.metrics;if(!this.ended){this.ended=!0;for(var o=0;o 2&&void 0!==arguments[2])||arguments[2];super(e,t,we.t,r),this.importAggregator()}}new class{constructor(e){let t=arguments.length>1&&void 0!==arguments[1]?arguments[1]:(0,_.ky)(16);c._A?(this.agentIdentifier=t,this.sharedAggregator=new y({agentIdentifier:this.agentIdentifier}),this.features={},this.desiredFeatures=new Set(e.features||[]),this.desiredFeatures.add(m),Object.assign(this,(0,a.j)(this.agentIdentifier,e,e.loaderType||"agent")),this.start()):(0,l.Z)("Failed to initial the agent. Could not determine the runtime environment.")}get config(){return{info:(0,t.C5)(this.agentIdentifier),init:(0,t.P_)(this.agentIdentifier),loader_config:(0,t.DL)(this.agentIdentifier),runtime:(0,t.OP)(this.agentIdentifier)}}start(){const t="features";try{const r=n(this.agentIdentifier),i=[...this.desiredFeatures];i.sort(((t,r)=>e.p[t.featureName]-e.p[r.featureName])),i.forEach((t=>{if(r[t.featureName]||t.featureName===e.D.pageViewEvent){const n=function(t){switch(t){case e.D.ajax:return[e.D.jserrors];case e.D.sessionTrace:return[e.D.ajax,e.D.pageViewEvent];case e.D.sessionReplay:return[e.D.sessionTrace];case e.D.pageViewTiming:return[e.D.pageViewEvent];default:return[]}}(t.featureName);n.every((e=>r[e]))||(0,l.Z)("".concat(t.featureName," is enabled but one or more dependent features has been disabled (").concat((0,D.P)(n),"). This may cause unintended consequences or missing data...")),this.features[t.featureName]=new t(this.agentIdentifier,this.sharedAggregator)}})),(0,T.Qy)(this.agentIdentifier,this.features,t)}catch(e){(0,l.Z)("Failed to initialize all enabled instrument classes (agent aborted) -",e);for(const e in this.features)this.features[e].abortHandler?.();const r=(0,T.fP)();return delete r.initializedAgents[this.agentIdentifier]?.api,delete r.initializedAgents[this.agentIdentifier]?.[t],delete this.sharedAggregator,r.ee?.abort(),delete r.ee?.get(this.agentIdentifier),!1}}}({features:[J,m,S,class extends h{static featureName=oe;constructor(t,r){if(super(t,r,oe,!(arguments.length>2&&void 0!==arguments[2])||arguments[2]),!c.il)return;const n=this.ee;let i;(0,k.QU)(n),this.eventsEE=(0,k.em)(n),this.eventsEE.on(se,(function(e,t){this.bstStart=(0,p.z)()})),this.eventsEE.on(ae,(function(t,r){(0,s.p)("bst",[t[0],r,this.bstStart,(0,p.z)()],void 0,e.D.sessionTrace,n)})),n.on(ce+ne,(function(e){this.time=(0,p.z)(),this.startPath=location.pathname+location.hash})),n.on(ce+ie,(function(t){(0,s.p)("bstHist",[location.pathname+location.hash,this.startPath,this.time],void 0,e.D.sessionTrace,n)}));try{i=new PerformanceObserver((t=>{const r=t.getEntries();(0,s.p)(te,[r],void 0,e.D.sessionTrace,n)})),i.observe({type:re,buffered:!0})}catch(e){}this.importAggregator({resourceObserver:i})}},C,xe,B,class extends h{static featureName=de;constructor(e,r){if(super(e,r,de,!(arguments.length>2&&void 0!==arguments[2])||arguments[2]),!c.il)return;if(!(0,t.OP)(e).xhrWrappable)return;try{this.removeOnAbort=new AbortController}catch(e){}let n,i=0;const o=this.ee.get("tracer"),a=(0,k._L)(this.ee),s=(0,k.Lg)(this.ee),u=(0,k.BV)(this.ee),d=(0,k.Kf)(this.ee),f=this.ee.get("events"),l=(0,k.u5)(this.ee),h=(0,k.QU)(this.ee),g=(0,k.Gm)(this.ee);function m(e,t){h.emit("newURL",[""+window.location,t])}function v(){i++,n=window.location.hash,this[ve]=(0,p.z)()}function b(){i--,window.location.hash!==n&&m(0,!0);var e=(0,p.z)();this[pe]=~~this[pe]+e-this[ve],this[ye]=e}function y(e,t){e.on(t,(function(){this[t]=(0,p.z)()}))}this.ee.on(ve,v),s.on(be,v),a.on(be,v),this.ee.on(ye,b),s.on(ge,b),a.on(ge,b),this.ee.buffer([ve,ye,"xhr-resolved"],this.featureName),f.buffer([ve],this.featureName),u.buffer(["setTimeout"+le,"clearTimeout"+fe,ve],this.featureName),d.buffer([ve,"new-xhr","send-xhr"+fe],this.featureName),l.buffer([me+fe,me+"-done",me+he+fe,me+he+le],this.featureName),h.buffer(["newURL"],this.featureName),g.buffer([ve],this.featureName),s.buffer(["propagate",be,ge,"executor-err","resolve"+fe],this.featureName),o.buffer([ve,"no-"+ve],this.featureName),a.buffer(["new-jsonp","cb-start","jsonp-error","jsonp-end"],this.featureName),y(l,me+fe),y(l,me+"-done"),y(a,"new-jsonp"),y(a,"jsonp-end"),y(a,"cb-start"),h.on("pushState-end",m),h.on("replaceState-end",m),window.addEventListener("hashchange",m,(0,O.m$)(!0,this.removeOnAbort?.signal)),window.addEventListener("load",m,(0,O.m$)(!0,this.removeOnAbort?.signal)),window.addEventListener("popstate",(function(){m(0,i>1)}),(0,O.m$)(!0,this.removeOnAbort?.signal)),this.abortHandler=this.#e,this.importAggregator()}#e(){this.removeOnAbort?.abort(),this.abortHandler=void 0}}],loaderType:"spa"})})(),window.NRBA=o})(); window.jQuery || document.write(' ') CKEDITOR_BASEPATH='https://f1000research.com/js/vendor/ckeditor/' window.reactTheme = 'research'; window.MathJax = { CommonHTML: { linebreaks: { automatic: true } }, 'HTML-CSS': { linebreaks: { automatic: true } }, SVG: { linebreaks: { automatic: true } }, AuthorInit: function() { MathJax.Hub.Register.MessageHook('End Process', function () { let timeout = false; // holder for timeout id const delay = 250; // delay after event is "complete" to run callback const reflowMath = function() { const dispFormulas = document.querySelectorAll('.disp-formula.panel'); if (!dispFormulas) { return; } for (const dispFormula of dispFormulas) { const child = dispFormula.querySelector('.MathJax_Preview').nextSibling.firstChild; const isMultiline = MathJax.Hub.getAllJax(dispFormula)[0].root.isMultiline; if (dispFormula.offsetWidth < child.offsetWidth || isMultiline) { MathJax.Hub.Queue(['Rerender', MathJax.Hub, dispFormula]); } } }; window.addEventListener('resize', function() { clearTimeout(timeout); // clear the timeout timeout = setTimeout(reflowMath, delay); // start timing for event "completion" }); }); }, }; if (window.location.hash == '#_=_'){ window.location = window.location.href.split('#')[0] } !function(f,b,e,v,n,t,s){if(f.fbq)return;n=f.fbq=function() {n.callMethod? n.callMethod.apply(n,arguments):n.queue.push(arguments)} ;if(!f._fbq)f._fbq=n; n.push=n;n.loaded=!0;n.version='2.0';n.queue=[];t=b.createElement(e);t.async=!0; t.src=v;s=b.getElementsByTagName(e)[0];s.parentNode.insertBefore(t,s)}(window, document,'script','https://connect.facebook.net/en_US/fbevents.js'); fbq('init', '1641728616063202'); fbq('track', "PixelInitialized", {}); (function(h,o,t,j,a,r){ h.hj=h.hj||function(){(h.hj.q=h.hj.q||[]).push(arguments)}; h._hjSettings={hjid:2318163,hjsv:6}; a=o.getElementsByTagName('head')[0]; r=o.createElement('script');r.async=1; r.src=t+h._hjSettings.hjid+j+h._hjSettings.hjsv; a.appendChild(r); })(window,document,'https://static.hotjar.com/c/hotjar-','.js?sv='); search file_upload Submit your research search menu close search Browse Gateways & Collections How to Publish Submit your Research My Submissions Article Guidelines Article Guidelines (New Versions) Open Data, Software and Code Guidelines Open Data and Accessible Source Materials Guidelines (HSS) Open Data, Software and Code Guidelines (PSE) Prepublication Checks Production Process Posters and Slides Guidelines Document Guidelines Article Processing Charges Peer Review Finding Article Reviewers About How it Works For Reviewers Our Advisors Policies Glossary FAQs For Developers Newsroom Contact My Research Submissions Content and Tracking Alerts My Details Sign In file_upload Submit your research { "@context": "https://schema.org", "@type": "ScholarlyArticle", "mainEntityOfPage": { "@type": "WebPage", "@id": "https://f1000research.com/articles/13-1228" }, "headline": "Recycling of collagen from solid tannery waste and prospective utilization as adhesives.", "datePublished": "2024-10-14T17:19:09", "dateModified": "2025-07-30T16:46:42", "author": [ { "@type": "Person", "name": "Nelly Esther Flores Tapia" }, { "@type": "Person", "name": "Hannibal Brito Moina" }, { "@type": "Person", "name": "Rodny Peñafiel" }, { "@type": "Person", "name": "Lander Vinicio Pérez Aldás" } ], "publisher": { "@type": "Organization", "name": "F1000Research", "logo": { "@type": "ImageObject", "url": "https://f1000research.com/img/AMP/F1000Research_image.png", "height": 480, "width": 60 } }, "image": { "@type": "ImageObject", "url": "https://f1000research.com/img/AMP/F1000Research_image.png", "height": 1200, "width": 150 }, "description": "This study explores the innovative potential of recycled collagen derived from tannery waste for high-performance adhesive formulations. The leather industry generates significant amounts of solid waste, primarily from chromium-tanned leather, which poses substantial environmental challenges. Recent advancements in recycling techniques have opened new avenues for repurposing this waste, particularly through collagen extraction, which comprises about 30-35% of tannery residues. This research systematically reviews the methods and applications of collagen extraction, highlighting the material’s versatility and environmental benefits when used as a bio-adhesive. The review identifies key challenges such as low water resistance, shear strength, and adhesiveness in collagen-based adhesives compared to synthetic counterparts. However, innovative solutions are emerging, including incorporating silane coupling agents and cross-linking technologies that significantly improve adhesive water resistance and mechanical properties. Economic analyses further support using tannery waste-derived collagen in adhesive production, aligning with global sustainability goals and reducing reliance on petrochemical-based adhesives. Despite these advancements, transitioning from laboratory research to commercial applications remains a significant challenge. Current studies primarily focus on small-scale experiments, with limited pilot-scale studies available. Nonetheless, the potential for collagen-based adhesives to replace harmful chemicals in industrial applications is promising, especially in sectors requiring biodegradable and non-toxic materials. This review concludes that while significant progress has been made, further research is necessary to overcome existing limitations and fully realize the commercial potential of collagen-based adhesives derived from tannery waste." } { "@context": "http://schema.org", "@type": "BreadcrumbList", "itemListElement": [ { "@type": "ListItem", "position": "1", "item": { "@id": "https://f1000research.com/", "name": "Home" } }, { "@type": "ListItem", "position": "2", "item": { "@id": "https://f1000research.com/browse/articles", "name": "Browse" } }, { "@type": "ListItem", "position": "3", "item": { "@id": "https://f1000research.com/articles/13-1228", "name": "Recycling of collagen from solid tannery waste and prospective utilization..." } } ] } Home Browse Recycling of collagen from solid tannery waste and prospective utilization... ALL Metrics - Views Downloads Get PDF Get XML Cite How to cite this article Flores Tapia NE, Brito Moina H, Peñafiel R and Pérez Aldás LV. Recycling of collagen from solid tannery waste and prospective utilization as adhesives. [version 2; peer review: 1 approved, 3 approved with reservations] . F1000Research 2025, 13 :1228 ( https://doi.org/10.12688/f1000research.155450.2 ) NOTE: If applicable, it is important to ensure the information in square brackets after the title is included in all citations of this article. Close Copy Citation Details Export Export Citation Sciwheel EndNote Ref. Manager Bibtex ProCite Sente EXPORT Select a format first Track Share ▬ ✚ Review Revised Recycling of collagen from solid tannery waste and prospective utilization as adhesives. [version 2; peer review: 1 approved, 3 approved with reservations] Nelly Esther Flores Tapia https://orcid.org/0000-0002-0851-8117 1 , Hannibal Brito Moina 2 , Rodny Peñafiel 3 , Lander Vinicio Pérez Aldás 3 Nelly Esther Flores Tapia https://orcid.org/0000-0002-0851-8117 1 , Hannibal Brito Moina 2 , Rodny Peñafiel 3 , Lander Vinicio Pérez Aldás 3 PUBLISHED 30 Jul 2025 Author details Author details 1 Research and Development Directorate, Universidad Técnica de Ambato, Ambato, Tungurahua, Ecuador 2 Facultad de Ciencias, Escuela Superior Politecnica de Chimborazo, Riobamba, Chimborazo Province, Chimborazo, Ecuador 3 Food and Biotechnology, Universidad Técnica de Ambato, Ambato, Tungurahua, Ecuador Nelly Esther Flores Tapia Roles: Conceptualization, Formal Analysis, Investigation, Supervision, Writing – Original Draft Preparation, Writing – Review & Editing Hannibal Brito Moina Roles: Conceptualization, Investigation, Methodology, Writing – Original Draft Preparation, Writing – Review & Editing Rodny Peñafiel Roles: Formal Analysis, Investigation, Writing – Original Draft Preparation, Writing – Review & Editing Lander Vinicio Pérez Aldás Roles: Conceptualization, Investigation, Methodology, Writing – Original Draft Preparation, Writing – Review & Editing OPEN PEER REVIEW DETAILS REVIEWER STATUS Abstract This study explores the innovative potential of recycled collagen derived from tannery waste for high-performance adhesive formulations. The leather industry generates significant amounts of solid waste, primarily from chromium-tanned leather, which poses substantial environmental challenges. Recent advancements in recycling techniques have opened new avenues for repurposing this waste, particularly through collagen extraction, which comprises about 30-35% of tannery residues. This research systematically reviews the methods and applications of collagen extraction, highlighting the material’s versatility and environmental benefits when used as a bio-adhesive. The review identifies key challenges such as low water resistance, shear strength, and adhesiveness in collagen-based adhesives compared to synthetic counterparts. However, innovative solutions are emerging, including incorporating silane coupling agents and cross-linking technologies that significantly improve adhesive water resistance and mechanical properties. Economic analyses further support using tannery waste-derived collagen in adhesive production, aligning with global sustainability goals and reducing reliance on petrochemical-based adhesives. Despite these advancements, transitioning from laboratory research to commercial applications remains a significant challenge. Current studies primarily focus on small-scale experiments, with limited pilot-scale studies available. Nonetheless, the potential for collagen-based adhesives to replace harmful chemicals in industrial applications is promising, especially in sectors requiring biodegradable and non-toxic materials. This review concludes that while significant progress has been made, further research is necessary to overcome existing limitations and fully realize the commercial potential of collagen-based adhesives derived from tannery waste. READ ALL READ LESS Keywords collagen; solid tannery wastes; animal glue; collagen adhesives; bio-adhesive, recycled Corresponding Author(s) Nelly Esther Flores Tapia ( [email protected] ) Close Corresponding author: Nelly Esther Flores Tapia Competing interests: No competing interests were disclosed. Grant information: This research was funded by the RESEARCH AND DEVELOPMENT DIRECTORATE and TECHNICAL UNIVERSITY OF AMBATO to support the Investigation. Project Sustainable Polymeric Composites from Agro-Industrial and Wet-Blue Leather Waste for Ecological Applications. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Copyright: © 2025 Flores Tapia NE et al . This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. How to cite: Flores Tapia NE, Brito Moina H, Peñafiel R and Pérez Aldás LV. Recycling of collagen from solid tannery waste and prospective utilization as adhesives. [version 2; peer review: 1 approved, 3 approved with reservations] . F1000Research 2025, 13 :1228 ( https://doi.org/10.12688/f1000research.155450.2 ) First published: 14 Oct 2024, 13 :1228 ( https://doi.org/10.12688/f1000research.155450.1 ) Latest published: 30 Jul 2025, 13 :1228 ( https://doi.org/10.12688/f1000research.155450.2 ) Revised Amendments from Version 1 Compared to the earlier version of the article, this revision includes several substantial improvements. Quantitative data and a comparative table of physicochemical and mechanical properties of collagen-derived adhesives versus conventional synthetic adhesives were added to address prior concerns about the lack of performance data. The discussion of limitations, especially regarding water resistance, durability, and cost of gelatin adhesives, was significantly expanded, incorporating detailed strategies to overcome these issues through hydrophobic additives, enzymatic crosslinking, and other techniques. References to medical adhesives were removed to maintain a clear focus on technical and industrial applications. The Methods section was eliminated in line with conventions for review articles, and repetitive content in the discussion was consolidated to improve clarity and readability. Figure captions were revised to provide more precise and descriptive explanations of all panels. Additionally, statements about the preference for Type I collagen were clarified and supported with appropriate literature citations. Finally, the manuscript underwent comprehensive English language editing to enhance grammar, style, and consistency throughout the text. These revisions collectively aim to strengthen the rigor, clarity, and practical relevance of the work. Compared to the earlier version of the article, this revision includes several substantial improvements. Quantitative data and a comparative table of physicochemical and mechanical properties of collagen-derived adhesives versus conventional synthetic adhesives were added to address prior concerns about the lack of performance data. The discussion of limitations, especially regarding water resistance, durability, and cost of gelatin adhesives, was significantly expanded, incorporating detailed strategies to overcome these issues through hydrophobic additives, enzymatic crosslinking, and other techniques. References to medical adhesives were removed to maintain a clear focus on technical and industrial applications. The Methods section was eliminated in line with conventions for review articles, and repetitive content in the discussion was consolidated to improve clarity and readability. Figure captions were revised to provide more precise and descriptive explanations of all panels. Additionally, statements about the preference for Type I collagen were clarified and supported with appropriate literature citations. Finally, the manuscript underwent comprehensive English language editing to enhance grammar, style, and consistency throughout the text. These revisions collectively aim to strengthen the rigor, clarity, and practical relevance of the work. See the authors' detailed response to the review by Anke Mondschein See the authors' detailed response to the review by Ali Yorgancioglu READ REVIEWER RESPONSES Introduction The leather industry, particularly chromium-based tanning, generates substantial solid waste, including chromium sludge, chrome-tanned leather shavings, and trimmings, with only 20% of raw material converted into leather. 1 – 4 This results in significant collagen-rich waste, which is often discarded in landfills due to the absence of cost-effective recycling programs. 5 – 7 Solid tannery waste, comprising around 25% untreated skin, contains approximately 30% to 35% collagen and 1.5% chromium, underscoring its potential for resource recovery. 8 India alone produces 0.02 million tons of chromium shavings annually (0.8 million tons of chromed leather trimmings per year), indicating a significant potential resource for recycling into valuable products like renewed leather, 9 fertilizers in agriculture, composting, 10 formulation of composite materials, 11 , 12 production of biodiesel, 13 – 17 and extraction of raw materials such as keratin, 18 chromium, 19 and collagen 20 , 21 (see Figure 1 ). Figure 1. Brief description of processes applied to recycle solid tannery wastes. 4 – 22 However, synthetic adhesives have largely replaced animal glues due to cost, availability, and consistency concerns. Despite this, synthetic adhesives are highly polluting, non-biodegradable, and dependent on petroleum, underscoring the need for eco-friendly alternatives. Collagen-modified adhesives, especially those derived from tannery waste, present a promising solution by offering both environmental benefits and effective adhesive properties. Historically, collagen sourced from animal tissues like cartilage and tendons has long been used as an adhesive due to its environmentally friendly and non-toxic properties. 22 Over time, animal collagen has been applied in various forms, from craftsmanship to industrial processes, for its natural adhesive qualities. Its composition facilitates efficient and reversible adhesion in applications such as paper and cardboard, with low cure temperatures compared to dispersions or hot melts, setting it apart from synthetic counterparts. 23 , 24 Despite these advantages, synthetic chemicals supplanted animal glues at the beginning of the 20th century 25 due to drawbacks like cost, availability, animal welfare concerns, and inconsistencies in raw material composition that affect adhesive performance. 26 While synthetic adhesives provide several benefits, they are highly polluting, non-biodegradable, and reliant on petroleum, driving the search for eco-friendly alternatives. 27 – 29 Utilizing collagen extracted from tannery waste offers a promising avenue for producing effective adhesives while minimizing waste. 30 Although animal glues derived from tannery wastes have been explored as renewable alternatives, their viability is limited by the contamination in tannery waste, rendering them unsuitable for applications like human tissue glues. 31 – 33 This review evaluates the potential of producing adhesives from collagen extracted from tannery wastes. It explores the methods, applications, and advancements in this area, focusing on extraction techniques, adhesive formulation, and the associated environmental and economic benefits. By addressing gaps in current research, this review provides a comprehensive overview of the challenges and opportunities in utilizing tannery waste for sustainable adhesive production. Discussion Background on tannery waste and its environmental implications Global trade in animal leather accounted for only 0.091% of the total international market in 2021, reaching a substantial value of $242.85 billion in 2022. 34 Notable exporters in this trade were Italy ($3.55 billion), the United States ($1.88 billion), Brazil ($1.45 billion), China ($1.07 billion), and Germany ($734 million) in terms of exports. In comparison, China ($3.42 billion) and Italy ($2.3 billion) were significant importers of animal leather. 35 Despite being economically significant for many nations, the tanning industry poses significant environmental challenges owing to solid waste and liquid and gaseous effluents, causing detrimental impacts on air, water, and soil quality. Solid tannery waste can be divided into removed hair, untreated skin residues, waste from tanned skin, leather trimming, and processed sludge. These residues are abundant and rich in fats 36 and proteins. 37 Depending on their chemical composition, they can be recycled for diverse purposes, provided they undergo proper treatment and characterization. Moreover, regarding water usage in the tanning process, an incredible 50,000 kg of water is required to process just one kilogram of cowhide. 38 Also, tannery effluents are hazardous to decontaminating because of their chromium, sulfide, heavy metal, and organic matter content. 38 , 39 These effluents also exhibit elevated Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD), 40 and even after undergoing advanced chemical and physical treatments, they show low degradability indices. 41 In addition, wastewater can permeate through underground layers, as confirmed by research conducted in India, Iran, and Bangladesh, where groundwater samples near tanneries showed high concentrations of Cu, Cr, Pb, Zn, Ni, Al, and As, with Cr registering the highest concentration, ranging from 0.01 to 2.07 mg/L. 42 – 50 Undoubtedly, this risks ecosystem stability. 51 The environmental impact of tannery waste has been under scrutiny for decades, with substantial evidence highlighting the high toxicity of such residues to plants 52 and animals 53 – 55 and bioaccumulation exacerbating this concern. The hazard posed by these residues relies on the presence of contaminating substances, such as sulfides, 56 chromium (III), chromium (VI), 57 , 58 lead, and other heavy metals. The immediate and severe effects of tannery waste on the environment and human health are undeniable. 59 In recent years, substantial efforts have been made to remediate, recycle, and reuse various tannery wastes. In this context, repurposing solid tannery waste for glue production is a viable strategy for reducing waste and generating environmentally friendly products within a circular economic framework. Historical Perspective of Glue from different natural sources Adhesives derived from natural sources have had the oldest known historical use in all civilizations for at least 200000 years. 60 Evidence of glue residues dates to 1350 BCE, as observed in wood decorations found in King Tutankhamun’s tombs. Additionally, indications of glue usage have been found in ancient civilizations such as Greece and Rome. 61 Furthermore, historical records highlight its presence in Edo period paintings in Japan and artifacts from the Joseon dynasty in Korea. 62 Today, natural glues have specific services, such as artistic applications, historical conservation, cardboard, packaging, 63 and the creation of new adhesives. Historically, glue was primarily produced from animal collagen derived from hides, bones, and connective tissues. Industrially, animal glues come from slaughterhouses that provide animal hides, blood, 64 , 65 and other sources of proteins 66 that can be extracted by hydrolysis. 67 Traditionally, to recover animal glue, animal parts, primarily bones from horses, cattle, other livestock, and fishes, are boiled for extended periods in water to obtain collagen, which solidifies into glue upon cooling. 68 Other glue sources include water-resistant rennet casein and acidic casein. Rennet casein is produced by coagulating rennets with skim milk at 30°C and acidic casein. 69 In contrast, lactic acid casein is derived from inoculating milk with certain bacteria such as Streptococcus lactis , Streptococcus cremoris , and Lactococcus lactis subspecies cremoris. 69 , 70 Chitosan is another natural glue obtained from ground crab and shrimp shell waste, processed through acid or alkali treatment. 71 , 72 Marine organisms such as mussels, barnacles, and tubeworms secrete protein adhesives that effectively adhere to hydrated underwater surfaces owing to the high proportion of amino acids with phenolic hydroxyl chemical groups. 73 These secretions open ample avenues for developing water-resistant adhesives for various purposes. In Asian cultures, the isinglass is the purest form of fish glue derived from the swim bladder membranes of sturgeons. 74 Bone, fish, and hide adhesives have low moisture resistance, which affects the properties of the bond and notably decreases its elasticity and tensile strength. 75 Adhesives have been derived from plant resins, saps, natural rubber, 76 starches, 77 natural gums, latex, soy, lignin, algae, and cellulose. 78 Types of glue from starches such as wheat and rice are commonly used in paper and woodworking applications. The mixture of corn starch with hydrolyzed acrylic emulsion and uzkhitan glue warp threads 79 and some starches serve as cohesive elements to create conductive glue for electrode materials. 80 The functionality of these glues from starch can be improved with additives; for example, the water resistance increases with polymerized lignosulfonates. 81 The adhesive industry has become a specialized field of science, developing numerous innovative adhesive products. To create customized formulas for specific applications, it is crucial to understand the various existing adhesive types. This differentiation forms the basis for the evolution of collagen-modified adhesives. While this review does not delve extensively into the categorization of adhesives, Figure 2 provides a concise overview of the different segments within the adhesive industry, serving as a foundational reference for understanding the different adhesive types. Figure 2. Classification of Adhesives from origin source, highlighting those derived from wastes. 42 – 47 Collagen: The protein-based adhesive With the evolution of industrial processes, there is a need for more efficient and cost-effective adhesives. 82 Tanneries, which process animal hides to produce leather, generate significant amounts of waste rich in collagen, particularly trimmings, and shavings, whether tanned or not. 83 Rather than discarding these by-products, innovators have realized the potential to utilize this waste for glue production. Collagen is a complex protein with approximately 28 types. 84 , 85 This protein is characterized by a unique structure consisting of three parallel polypeptide strands with a left-handed, polyproline II-type (PPII) helical conformation that coils together to form a right-handed triple helix. This structure necessitates that every third residue be glycine, leading to a consistent XaaYaaGly sequence throughout all collagen types. Within this sequence, the amino acids at the Xaa and Yaa positions are (2S)-proline (28%) and (2S,4R)-4-hydroxyproline (38%), respectively, making ProHypGly the predominant triplet, occurring at 10.5% in collagen. 86 This formation provides strength and flexibility owing to the high proline and hydroxyproline contents, which prevent the protein from assuming a globular shape. Numerous polar groups in collagen enhance the chain interactions. 87 , 88 The source and preparation method of collagen largely determines its physical, chemical, and mechanical properties. When its chains are shortened, differences originating from various sources diminish, leading to coiled proteins with reduced molecular weight. Native collagen, with a molecular weight of 285–300 KDa, undergoes significant structural changes upon hydrolysis. After denaturation, its triple-helix structure transforms into a random coil form owing to the dissociation of the hydrogen bonds. As a result of this process, hydrolyzed collagen consists of numerous peptides with much lower molecular weights (3–6 KDa). 89 The best glues contain collagen Type I because they retain high adherence, ease of gel formation, and an excellent structure to form bonds with other substances compared to simple peptides. The use of collagen is supported by its widespread use in industrial adhesives due to its abundance, strong fibrillar structure, and effective binding properties. 90 Proteomic analyses have shown that most animal glues rely mainly on Type I and III collagen extracted from common domestic species, confirming their superior performance over simpler protein fragments. 91 Collagen variability is influenced by its origin—whether it comes from skin, connective tissue, cartilage, or bones—as well as by the age and species of the animal, in Figure 3 , a schematic representation of five types of collagen is presented. Type I human collagen is predominantly found in the skin, bone, teeth, tendons, ligaments, vascular ligatures, and various organs ( Figure 3a ). 92 Type II collagen is primarily located within cartilage ( Figure 3b ), 93 while Type III collagen is commonly sourced from the skin, muscles, and blood vessels ( Figure 3c ). 94 Type IV collagen is present in the basement membrane’s epithelial-secreted layer and the basal lamina ( Figure 3d ). 95 Additionally, Bos Taurus Type IV collagen is depicted in the schematic ( Figure 3e ). 96 Figure 3. Schematic representation of collagen Types I-V in humans and Bos Taurus. a) Type I human collagen is predominantly found in the skin, bone, teeth, tendons, ligaments, vascular ligature, and various organs 92 ; b) Type II collagen is located within cartilage 93 ; c) Type III collagen is commonly sourced from the skin, muscles, and blood vessels 94 ; d) Type IV collagen is present in the epithelial-secreted layer of the basement membrane as well as the basal lamina 95 ; and e) Type IV Bos Taurus collagen. 96 Images are used without modification under the terms of the CC BY 4.0 license—courtesy of PDB-101 ( PDB101.rcsb.org ). Collagen-adhesive properties The adhesion of the protein glue to wood depends on polar and nonpolar group interactions. Amino acids such as glutamic acid, tyrosine, and proline form hydrogen bonds. However these groups often remain inaccessible owing to internal bonds caused by forces such as van der Waals, hydrogen bonds, and hydrophobic interactions. Consequently, basic proteins have limited adhesion and require chemical changes to expose polar protein molecules. 97 , 98 Furthermore, intramolecular cross-linking is achieved through the oxidative removal of amine groups from specific amino acids within proteins to develop high-strength collagen adhesives. This process leads to the formation of aldehydes, a phenomenon known as the Schiff base protein cross-linking. 99 Hydrolyzed collagen from tanneries Residues suitable for collagen extraction include untanned skin trimmings and tanned leather shavings. 100 Tanneries sell untanned residues to gelatin factories, undergoing a relatively straightforward transformation. In contrast, tanned residues, such as wet blue and leather trimmings, require more intricate extraction processes 101 because tanned wastes are intertwined collagen strands with agents like tannins, chromium, and alum. 102 The extraction processes commonly applied to these residues are acid or base hydrolysis at near boiling temperatures or complex enzymatic hydrolysis. 103 However, recent investigations have employed multiple combined techniques to enhance collagen yield recovery while mitigating energy consumption. 104 Collagen extraction typically involves the pre-treatment, hydrolysis, and purification processes. Pre-treatment tannery waste The main goal of pre-treatment is to disrupt covalent cross-links between collagen molecules because they do not break down even in boiling water. 105 Trimmings and untanned skin must be liberated from chemicals and dirt. These materials are then processed to remove all traces of hair, fat, and flesh, ensuring they can absorb more components for further acid or alkaline treatments. 106 Acid Pre-treatment: This method immerses washed and chopped skin pieces in dilute acid. The acid causes the skin to swell and hydrolyze the cross-links. Acid pre-treatment suits fragile skin with less fiber intertwinement, such as porcine and fish skin. 107 Alkaline Pre-treatment: Dilute alkalis such as sodium hydroxide, calcium hydroxide, and hydrogen peroxide 108 are used. Alkalis is effective for extracting collagen from thick and hard materials. Despite being lengthy, sodium hydroxide treatment is preferred because it swells the skin, aiding alkali diffusion into the tissue matrix. Alkalis also hydrolyses unwanted components. Lower hydroxide concentrations at suitable temperatures retain the acid-soluble collagen and its native structure. 109 Collagen Extraction processes from tannery wastes Prolonged boiling for collagen recovery is energy-intensive and inefficient, making it unsuitable for contemporary fabric treatment. Consequently, there is a pressing need to refine the process of extracting collagen from tannery wastes. The most prevalent method for such extraction involves hydrolysis using different agents, as shown in Table 1 . There is also a growing interest in advancing novel techniques to enhance extraction yields. Moreover, establishing mathematical-physical models is crucial for improving the efficiency of shaving hydrolysis to reduce the need for extensive experimental trials, as emphasized by Vaskova and Vasek 110 whose model introduced a parameter simulation aimed at deriving hydrolyzed collagen from tannery shavings using a flow reactor. Table 1. Summary of collagen extraction processes from tannery wastes and optimal conditions from cited studies. Methods Process Yields, recovery, costs Advantages Disadvantages Cite Thermal Hydrolysis Trimmings boil for 3 to 12 hours to dissolve the collagen from hides, bones, and other tissues at 70 °C, at pH 5.5 to 6.0 for 24 hours. 18.25% protein. Easy control of the process. Time consuming. High energy consumption. No use of chemicals. Useful for trimmings, not tanned residues. 111 The salting-out method Separate proteins based on their solubility in the presence of salts. NaCl 2.5 M 0.05 M of tris (hydroxymethyl) aminomethane. Suspend precipitate with 0,5 acetic acid and 55 to 65% mass recovery. 1.44 % mass yield High purity of samples. It is good to obtain collagen type I. Time consuming. Careful conditioning of extracting baths. 112 Isoelectric method pH adjustment at the correct Isoelectric point, then separation by centrifugation. 55 to 75% mass recovery 2.22 % mass yield Less purity of samples. Rapid recovery of product. Keep control of chemical conditions so as not to affect the isoelectric point. Analysis of samples before extraction. 113 Alkali method Water/waste ratio 3:1, 0.5% lime, 85, 8 to 10 hours. Purification with white clay and active carbon. Nitrogen content 43.84%. 60% recovery. The most common method. Collagen type I. There are multiple affordable alkalis: MgO, CaO, NaOH, KOH, lime, and ashes. Collagen extraction needs more purification steps than the enzymatic process. 114 Acid method Water/waste ratio 10:1, Dechroming mix of acids and salting out purification. The process involves stirring a mixture of H 2 C 2 O 4 (oxalic acid) and H 2 SO 4 (sulfuric acid) at 250 rpm, 40°C, for 12 hours. 90.6% yield. 95.6% dechroming High dechroming percentage. Do not destroy the triple helix of Collagen type I. Easy to combine with enzymes. Medium costs of production. The process needs extra care with pH control. 114 – 116 Enzymatic method pH 3.9, 65°C, MgO, alcalase 0.4 % from dry matter. Pepsin immobilized in modified silica clay using 5 5% glutaraldehyde with 5% activated 3-aminopropyltriethoxysilane 25 °C, 90 min, and 3.5 mg ml −1 pepsin. 43% reduction costs It needs previous extraction via alkalis or acids. Less sludge formation. Fewer purification processes after recovery. We need more investigation to determine ideal conditions for enzymes. Save costs in energy. Enzymes can diminish the quality of collagen if not extracted from the product. Collagen retains helix structure. Collagen type I. 117 , 118 Hybrid method Acid-enzyme Alkali enzyme NaOH/urea solvent system for hydrolysis waste leather shavings (tanned with glutaraldehyde). Cleaning the shavings in a 1% SDS solution, disinfection with 75% sonication. NaOH/urea/H 2 O ratio of 7:12:81 (w/w/w), at a shavings-to-solution percentage of 1:20 (w/w), stirring at 30°C for 6-8 hours. Dialysis 24 hours. No data Advanced investigations. For specific uses. Improve removal of chromium. It is the best quality jelly glue. Dialysis is time-consuming and expensive. 119 Ultrasound-enzymatic Protease from Bacillus subtilis with ultrasound. Conversion ratio 57.6% to 84.1%. Ultrasound accelerates the enzyme action. Just for untanned wastes. 120 Steam explosion with alkali hydrolysis CaO for hydrolysis 140°C, 10 min Steam explosion. 30% yield Viscosity at 25°C is 2.4 cP protein solution 24.6 g/L and a molecular mass of 39 kDa. Steam explosion reduces 36 times the hydrolysis and chromium 96 times This process liberates low levels of Cr (VI). 121 Post-extraction purification and characterization The purification of chromium-extracted collagen is crucial to ensure its suitability for subsequent applications. 122 Chromium (III) is the most used as a tanning agent. The chrome tanning reaction predominantly targets the carboxyl groups of collagen, which are assumed to be located at the aspartic and glutamic side chains. Kinetics showed quicker Cr (III) reactions with aspartic acid, whereas thermodynamics revealed a stronger tendency of glutamic acid for stable Cr (III) complexes involving Cr-O-Cr bridges. These bridges contribute to bridging the gaps between the collagen chains in the structure of the hide, thereby enabling tanning. 123 Hence, the remarkable stability of leather underscores the necessity of devising methods that can disrupt the Cr-O-Cr complex while preserving collagen integrity. The purification of collagen can be achieved by removing chromium through chemical methods 124 , 125 such as alkali hydrolysis using 6% magnesium oxide and 1.0% sodium carbonate at 70°C for 48 h, followed by 1% bate enzyme hydrolysis to eliminate almost 80% of chromium from wet blue samples. 126 New technologies include ultrasonic dechroming at a maximum of 200 MHz to reduce Cr by 70.2%. 127 , 128 However, better results were achieved by applying sonication to the waste and adding EDTA at a ratio of 1:3 at 80°C for 30 min to achieve a chromium removal efficiency of 98%. 129 These results show that purification of the extracted collagen is possible and practical. The efficiency and yield of dechroming depends on the nature of the waste and the process applied. This field of investigation offers abundant research opportunities and has considerable potential for prolific research. Development and comparative analysis of eco-friendly adhesives utilizing collagen recycled from tannery wastes Recycled collagen-based adhesives There are two primary methods for utilizing natural adhesives. One involves their direct use for adhesive purposes, though this approach remains limited in applications. The other combines collagen with additional materials to produce copolymers with enhanced properties. For example, Negash et al. fabricated glue directly from hide-trimming waste 130 through a sequential treatment process of lime soaking, washing, and acid neutralization. Extraction between 60 and 70 °C for 2.5–3.5 hours yielded an optimal formulation at 60 °C for three hours. This glue exhibited a viscosity of 90 centipoises, moisture content of 14.6%, ash content of 2.23%, density of 1259 kg/m 3 , yield of 32%, pH of 5.98, and shear strength of 260 MN—values superior to the reference glue and suitable for restoration of artworks and historical artifacts. 131 Moreover, the precise composition of these glues can be determined, which is essential for accurately recreating original adhesives and ensuring careful restoration without compromising valuable pieces. 132 – 134 Formaldehyde-based adhesives have been widely employed due to their strong bonding performance; however, their use is increasingly restricted because of formaldehyde emissions and stricter regulations such as the European Emission Standards E1 and E0. 135 , 136 A promising alternative incorporates enzymatically extracted collagen from chromed tannery waste into formaldehyde resin formulations. Introducing hydrolysate at a 5% mass fraction nearly doubled the content of methylene bridges compared to methylene oxide bridges (–CH 2 –O–CH 2 –), as demonstrated by thermogravimetric analysis. 135 , 137 This change potentially reduces methylene oxide formation—a key precursor of formaldehyde emissions—while enhancing mechanical strength due to increased molecular weight. Cross-link stability was also maintained under neutral conditions and in the presence of phthalic acid as a curing agent. 138 , 139 Matyašovský et al. 140 further demonstrated that collagen hydrolysates modified with urea can substantially reduce formaldehyde emissions when used as additives in urea-formaldehyde (UF) adhesives. By incorporating these collagen components with dialdehyde-modified hardeners, the formaldehyde content in bonded plywood decreased by up to 50% in laboratory tests and approximately 30% in industrial production without significant loss of mechanical strength. These findings reinforce that carefully engineered collagen hydrolysates offer environmental advantages and improve compatibility with UF resins, supporting their use as partial replacements for synthetic adhesives in wood-based applications subject to stringent emission standards. Building on these insights, Sedlicik et al. 141 evaluated UF adhesives modified with collagen hydrolysate from chrome-tanned leather. Adhesives prepared by adding 5% modified hydrolysates underwent condensation at 100 °C for up to 45 minutes. Shear strength testing on beech plywood per EN 314-1 confirmed that all samples met standard requirements, achieving a maximum of 2.07 MPa at 19% humidity, despite a modest reduction compared to unmodified UF resin. Notably, adding 3–8% collagen hydrolysate effectively lowered formaldehyde emissions into the E1 classification, with FT-IR spectroscopy supporting chemical interactions between UF resin and collagen. To avoid formaldehyde altogether, Islam et al. 142 developed sustainable adhesives for particleboard by comparing native collagen (Type A), acid-extracted collagen (Type B), and PVA-crosslinked collagen (Type C). Type C adhesive achieved a gel time of 4.2 minutes and a high shear strength of 5.31 MPa. In contrast, Type B without additives reached 3.98 MPa, demonstrating the benefits of PVA incorporation. However, even this optimized formulation remained below the 9.5 MPa strength typical of commercial urea-formaldehyde resins, suggesting further improvements are needed to match industrial benchmarks. Additional studies focused on modifying gelatin-based glues with functional polymers, and for example, incorporating epoxy-terminated hyperbranched polymers (EHPAE) and sodium dodecyl sulfate substantially improved shear strength from 0.92 MPa in unmodified gelatin to 2.285 MPa in EHPAE-III adhesives. 143 Although performance fell short of the 2.469 MPa achieved by commercial adhesives, this approach fulfilled EN standards for footwear, highlighting the potential of epoxy crosslinking to reinforce protein-based adhesives. Yang et al. 144 produced a wood adhesive by grafting waterborne polyurethane onto gelatin derived from tannery waste. The resulting WPUG copolymer combined high dry bonding strength (4.21 MPa), a contact angle of 111.5°, tensile strength of 32.91 MPa, and excellent thermal stability exceeding 350 °C. Acrylic–collagen latex adhesives were also developed via emulsion copolymerization with acrylic acid and butyl acrylate, yielding flexible films with tunable properties. Neutralized formulations like A-C 25 N became sticky and highly extensible, demonstrating promising tack adhesion despite relatively low stress–strain performance (0.0115 MPa). 145 Liu et al. 146 developed a collagen adhesive (CPP-G) through an anhydrous condensation process combining tricyanogen chloride with collagen-degrading polypeptides for corrugated cardboard applications. The optimal product showed a high percentage of solubility rate of 97% and conformed to Chinese standard GB/T6544-2008 S-1.1 grade. Its viscosity (0.256 Pa·s), thermal stability (220–260 °C), and initial adhesion (90%) surpassed many commercial references, while 48-hour water resistance remained comparable. Despite these advances, many collagen-based adhesives are still vulnerable to water and redissolve upon heating, limiting use in humid conditions. To address this, Zhou et al. 147 created collagen hydrolysate–silane coupling agent hybrids (CSH). By combining hydrolysate extracted by alkali hydrolysis with silane crosslinkers (GPDMS, GPTMS, GPTES), they achieved adhesives with dry strength up to 1.57 MPa and wet strength up to 0.95 MPa—exceeding the Chinese Class II plywood standard. These results highlight the importance of crosslinker selection and dosage in improving water resistance. Biodegradable adhesives incorporating collagen with polyvinyl alcohol and glycerol have also shown promise. Under optimal conditions identified by neural network analysis (65 °C, 3.2% PVA, 4.2% glycerol), peel strength reached 12.5 N/mm, with biodegradability and adhesion comparable to chemical adhesives. 148 Finally, Wang et al. 149 demonstrated that combining waterborne polyurethane with click-chemistry functional groups significantly improved gelatin adhesives. While plain gelatin had low strength (<0.1 MPa) and poor thermal stability (~310 °C), adding polyurethane increased strength to ~0.17 MPa, and the MWPU-FGE/GE formulation further improved shear strength (~0.68 MPa), peel strength (~1 N/mm), thermal resistance, and wet adhesion. This bio-inspired adhesive outperformed commercial water-based products after extended curing, suggesting a promising sustainable alternative. Table 2 provides a comprehensive summary of quantitative performance data for a broad range of collagen-based adhesives evaluated in recent years, including their measured bonding strength, viscosity, thermal stability, and water resistance compared to conventional commercial adhesives. The data illustrates that several advanced formulations, particularly those incorporating crosslinkers or chemical modifications, achieve bonding strengths comparable to or exceeding synthetic resin benchmarks in dry conditions. Notably, adhesives based on crosslinked collagen hydrolysates and hybrid systems consistently demonstrate higher mechanical performance than unmodified gelatin or simple protein dispersions. Table 2. Comparative summary of physicochemical and mechanical properties of collagen-derived adhesives versus conventional adhesives. Type of adhesive Properties Commercial adhesive Recycled collagen-based adhesives 130 Direct use from hide-trimming waste. Application: general adhesive applications Viscosity: 90 cP Moisture: 14.6% Ash: 2.23% Density: 1259 kg/m 3 Yield: 32% pH: 5.89 Shear strength: (ASTM D2559-04) 260 MN Water Resistance/Solubility: Solubilized completely in hot water (50–55 °C), black color indicates complete solubilization; less soluble in cold water Direct use from factory. Application: general adhesive applications Viscosity:80 centipoise (cp) Moisture Content: 15.0% Ash Content: 2.0% Density: 1270 kg/m 3 Yield: not reported pH: 6.06 Shear Strength: >200 MN Water Resistance: Complete solubility in hot water (50–55 °C), with black color indicating complete dissolution Collagen in formaldehyde-based adhesives 137 DMU + U (fraction 0.05): Endothermic peak 1: ~94 °C, ΔH ≈ 18 J/g Endothermic peak 2: ~125 °C, ΔH ≈ 244 J/g Additional peak at ~60 °C: Not present DMU + U (fraction 0.30): Endothermic peak 1: ~75 °C, ΔH ≈ 30 J/g Endothermic peak 2: ~124 °C, ΔH ≈ 224 J/g Additional peak at ~60 °C: Not present DMU + Hydrolysate (fraction 0.05): Endothermic peak 1: ~92 °C, ΔH ≈ 93 J/g Endothermic peak 2: ~139 °C, ΔH ≈ 174 J/g Additional peak at ~60 °C: Present (associated with bound moisture from the hydrolysate) DMU + Hydrolysate (fraction 0.10): Endothermic peak 1: ~87 °C, ΔH ≈ 105 J/g Endothermic peak 2: ~141 °C, ΔH ≈ 173 J/g Additional peak at ~60 °C: Present DMU + Hydrolysate (fraction 0.50): Endothermic peak 1: ~84 °C, ΔH ≈ 58 J/g Endothermic peak 2: ~137 °C, ΔH ≈ 120 J/g Additional peak at ~60 °C: Present Pure Urea (U): Endothermic peak 1: ~134 °C, ΔH ≈ 238 J/g Endothermic peak 2: Not present Additional peak at ~60 °C: Not present Pure Dimethylol-Urea (DMU): Endothermic peak 1: ~104 °C, ΔH ≈ 28 J/g Endothermic peak 2: ~126 °C, ΔH ≈ 229 J/g Additional peak at ~60 °C: Not present Collagen in formaldehyde-based adhesives With phthalic acid 138 DMU + 0.05 Hydrolysate + phthalic acid (fraction 0.05): Endothermic peak 1 (TG1): ~25–94 °C, –∆m ≈ 4.1–4.5% Endothermic peak 2 (TG2): ~95–130 °C, –∆m ≈ 4.5–5.4% Endothermic peak 3 (TG3): ~127–151 °C, –∆m ≈ 7.8–10.6% Additional peak at ~150–170 °C (TG4): Present (–∆m ≈ 1.6–5.1%) DMU + 0.05 Hydrolysate + phthalic acid (fraction 0.10): Endothermic peak 1 (TG1): ~25–94 °C, –∆m ≈ 4–5% Endothermic peak 2 (TG2): ~95–130 °C, –∆m ≈ 3.4–4.5% Endothermic peak 3 (TG3): ~127–151 °C, –∆m ≈ 9.8% Additional peak at ~150–170 °C (TG4): Present (–∆m ≈ 3.7–8.3%) DMU + phthalic acid (fraction 0.01): Endothermic peak 1 (TG1): ~25–94 °C, –∆m ≈ 4–5% Endothermic peak 2 (TG2): ~95–130 °C, –∆m ≈ 5.7% Endothermic peak 3 (TG3): ~127–151 °C, –∆m ≈ 8.2% Additional peak at ~150–170 °C (TG4): Not present DMU + phthalic acid (fraction 0.05): Endothermic peak 1 (TG1): ~25–94 °C, –∆m ≈ 4–5% Endothermic peak 2 (TG2): ~95–130 °C, –∆m ≈ 5.8% Endothermic peak 3 (TG3): ~127–151 °C, –∆m ≈ 8.8% Additional peak at ~150–170 °C (TG4): Present (–∆m ≈ 4.9–5.2%) DMU + phthalic acid (fraction 0.10): Endothermic peak 1 (TG1): ~25–94 °C, –∆m ≈ 4–5% Endothermic peak 2 (TG2): ~95–130 °C, –∆m ≈ 5.7–6.0% Endothermic peak 3 (TG3): ~127–151 °C, –∆m ≈ 8.7% Additional peak at ~150–170 °C (TG4): Present (–∆m ≈ 8.6–9.3%) DMU + 0.05 U + phthalic acid (fraction 0.05): Endothermic peak 1 (TG1): ~25–94 °C, –∆m ≈ 4.2–4.4% Endothermic peak 2 (TG2): ~95–130 °C, –∆m ≈ 5.9% Endothermic peak 3 (TG3): ~127–151 °C, –∆m ≈ 7.9% Additional peak at ~150–170 °C (TG4): Present but low (–∆m ≈ 0.16–0.34%) DMU + 0.05 U + phthalic acid (fraction 0.10): Endothermic peak 1 (TG1): ~25–94 °C, –∆m ≈ 3–4% Endothermic peak 2 (TG2): ~95–130 °C, –∆m ≈ 5.7–7.6% Endothermic peak 3 (TG3): ~127–151 °C, –∆m ≈ 7.8% Additional peak at ~150–170 °C (TG4): Present (–∆m ≈ 3.9–6.5%) Collagen hydrolysate in urea-formaldehyde adhesives 138 UF + 3% Collagen Hydrolysate: pH: 6.2 Curing Time: 74 seconds Dynamic Viscosity (over time): 20 min: 559 mPa·s 590 min: 773 mPa·s Formaldehyde Content: ~3–4 mg/100g (not individually listed but ~30% reduction) Water resistance: > 2MPA UF + 5% Collagen Hydrolysate: pH: 5.8 Curing Time: 77 seconds Dynamic Viscosity: 20 min: 642 mPa·s 590 min: 702 mPa·s Formaldehyde Content: ~3–4 mg/100g Water resistance: > 2MPA UF + 8% Collagen Hydrolysate: pH: 5.5 Curing Time: 76 seconds Dynamic Viscosity: 20 min: 654 mPa·s 590 min: 793 mPa·s Formaldehyde Content: ~3–4 mg/100g Water resistance: > 2MPA UF Standard: UF resin (Kronores CB 1100) (no collagen) pH: 7.3 Curing Time: 78 seconds Dynamic Viscosity: ~500 mPa·s (very stable over 10 hours) Formaldehyde Content (perforator): 5.2 mg/100g dry board Shear Strength: 2.86 MPa Melamine-Formaldehyde Adhesive 140 VIPOTAR I Modified Adhesive Collagen activator prepared at 20 °C. Optimal dosage: 3.5% of the hardener. Shear strength (Grade 3 conditioning): Average: 2.4 MPa Minimum: 1.7 MPa Maximum: 2.9 MPa Shear strength (Grade 2 conditioning): Average: 2.8 MPa Minimum: 2.4 MPa Maximum: 3.2 MPa Classification: Bond Quality Grade 3, suitable for unlimited outdoor exposure. VIPOTAR II Modified Adhesive Collagen activator prepared at 30 °C. Optimal dosage: 3.5% of the hardener. Shear strength (Grade 3 conditioning): Average: 2.3 MPa Minimum: 1.8 MPa Maximum: 2.8 MPa Shear strength (Grade 2 conditioning): Average: 2.5 MPa Minimum: 2.0 MPa Maximum: 3.0 MPa Classification: Bond Quality Grade 3, suitable for outdoor applications. KRONOCOL SM 10 (commercial MEF adhesive) Hardener: Conventional commercial hardener (Duslo Šala) Shear strength (Grade 3 conditioning): Average: 1.0 MPa Range: ~0.82–1.26 MPa Classified as Bond Quality Grade 2 (suitable for sheltered exterior conditions). VIPO, CSIC, and Gelima all are collagen hydrolysates derived from chrome-tanned leather shavings, but they come from different sources and were produced using distinct preparation methods, including enzymatic and chemical hydrolysis. 141 Application: modify urea-formaldehyde (UF) and phenol-formaldehyde (PF) resins for plywood bonding Mixture 1a (VIPO hydrolysate + organic acid): Shear Strength: 2.45 MPa Formaldehyde Content (perforator): 2.0 mg/100g dry board Water resistance: > 2MPa Mixture 1b (VIPO hydrolysate + lyotropic + organic acid): Shear Strength: 2.07 MPa Formaldehyde Content: 2.2 mg/100g Water resistance: > 2MPa Mixture 2a (CSIC hydrolysate + organic acid): Shear Strength: 2.53 MPa (highest of all) Formaldehyde Content: 3.7 mg/100g Water resistance: > 2MPa Mixture 2b (CSIC hydrolysate + lyotropic + organic acid): Shear Strength: 2.13 MPa Formaldehyde Content: 3.4 mg/100g Water resistance: > 2MPa Mixture 3a (Gelima hydrolysate + organic acid): Shear Strength: 2.22 MPa Formaldehyde Content: 3.0 mg/100g Water resistance: > 2MPa Mixture 3b (Gelima hydrolysate + lyotropic + organic acid): Shear Strength: 2.07 MPa Formaldehyde Content: 4.3 mg/100g Water resistance: > 2MPa UF Standard: UF resin (Kronores CB 1100) (no collagen) pH: 7.3 Curing Time: 78 seconds Dynamic Viscosity: ~500 mPa·s (very stable over 10 hours) Formaldehyde Content (perforator): 5.2 mg/100g dry board Shear Strength: 2.86 MPa Formaldehyde-free collagen adhesives 142 Application: adhesives for wood composite panels T-A: Native bone adhesive T-B: Acid-treated bone adhesive (0.5 M H 2 SO 2 ) T-C: Acid-treated + PVA crosslinker adhesive T-A (Native bone adhesive) Viscosity: 1.79 Pa·s Moisture: Not specified (adhesive); raw bone ~20.9% Ash: 20.9% in adhesive (after treatment) pH: Not specified Solid Content: 29.8% Gel Time: 16.46 min (very long; unsuitable for production) Glass Transition Temperature (Tg): 57 °C Activation Energy (Ea): 53 kJ/mol Shear Strength: Not tested (failed to bond) Water Resistance: Poor Comparison: Not comparable—did not meet bonding requirements T-B (Acid-treated) Viscosity: 1.26 Pa·s Moisture: Not specified Ash: 13.1% pH: Not specified Solid Content: 41.7% Gel Time: 5.32 min Glass Transition Temperature (Tg): 119 °C Activation Energy (Ea): 74 kJ/mol Shear Strength: ASTM-D905: ~3.68 MPa. EN-205: ~3.4 MPa Water Resistance: WA (24h): 161% TS (24h): 112% T-C (Acid-treated + PVA) Viscosity: 1.06 Pa·s Moisture: Not specified Ash: 14.6% pH: Not specified Solid Content: 43.3% Gel Time: 4.77 min Glass Transition Temperature (Tg): 149 °C Activation Energy (Ea): 78 kJ/mol Shear Strength: ASTM-D905: 5.31 MPa (best among bone adhesives). EN-205: ~5.0 MPa Water Resistance (BTC-2 panel): WA (24h): 143% TS (24h): 93% UF Resin (Commercial Adhesive, Reference) Viscosity: 0.04 Pa·s (very low) Moisture: Not specified Ash: Not specified pH: 8 Solid Content: 48% Gel Time: 2.30 min (fastest) Glass Transition Temperature (Tg): 152 °C Activation Energy (Ea): 74 kJ/mol Shear Strength:ASTM-D905: 9.43 MPa (highest). EN-205: 8.70 MPa Water Resistance: WA (24h): Lower than bone adhesives (exact % not specified) TS (24h): Lower than bone adhesives Comparison: Best performance in all categories Gelatin-based glue with EHPAE 143 GE Adhesive (unmodified) Solid Content: ~20% Shear Strength: ~1.022 MPa T-Peel Strength: ~1.02 N/mm Water Absorption Rate: ~55% Water Contact Angle: ~54° Comment: Weak adhesion, poor water resistance. GE + SDS Solid Content: ~24% Shear Strength: ~1.5 MPa T-Peel Strength: ~1.8 N/mm Water Absorption Rate: ~50% Water Contact Angle: ~66° Comment: Slight improvement. GE + SDS + EHPAE-I (First Generation Hyperbranched Polymer) Solid Content: ~25% Shear Strength: ~2.29 MPa T-Peel Strength: ~2.54 N/mm Water Absorption Rate: ~40% Water Contact Angle: ~72° Comment: Significant improvement. GE + SDS + EHPAE-II Solid Content: ~27% Shear Strength: ~2.52 MPa T-Peel Strength: ~2.95 N/mm Water Absorption Rate: ~35% Water Contact Angle: ~82° Comment: Better crosslinking. GE + SDS + EHPAE-III (Third Generation Hyperbranched Polymer) Solid Content: ~30% Shear Strength: ~2.65 MPa T-Peel Strength: ~3.38 N/mm Water Absorption Rate: ~26% Water Contact Angle: ~89.6° GE + SDS + Epoxy resin (E-44) Solid Content: ~25% Shear Strength: ~2.10 MPa T-Peel Strength: ~2.60 N/mm Water Absorption Rate: ~40–45% Water Contact Angle: ~65° GE + SDS + PEGDE Solid Content: ~24% Shear Strength: ~2.15 MPa T-Peel Strength: ~2.75 N/mm Water Absorption Rate: ~42% Water Contact Angle: ~70° GE + SDS + Glutaraldehyde Solid Content: ~28% Shear Strength: ~2.80 MPa T-Peel Strength: ~3.00 N/mm Water Absorption Rate: ~32% Water Contact Angle: ~85° GE + SDS + EDC (Carbodiimide) Solid Content: ~27% Shear Strength: ~2.75 MPa T-Peel Strength: ~2.90 N/mm Water Absorption Rate: ~35% Water Contact Angle: ~82° Loctite E-30CL epoxy resin: Shear Strength: ~3.2 MPa T-Peel Strength: ~2.8 N/mm Water Absorption: Higher than GE/EHPAE adhesives. Dow Corning adhesive: Shear Strength: ~3.0 MPa T-Peel Strength: ~3.1 N/mm Huitian 6302 universal adhesive: Shear Strength: ~2.9 MPa T-Peel Strength: ~2.9 N/mm Waterborne polyurethane (WPU) and gelatin adhesives 144 The adhesives were prepared by grafting gelatin derived from chromium shavings onto waterborne polyurethane, with increasing gelatin content corresponding to R values of 1.5, 3, and 4, resulting in solid contents ranging from ~47% to ~59%. No fillers or additional additives were used WPUG1.5 (Low gelatin content) Viscosity: 8.43 mPa·s Tensile Strength: 30.52 MPa Elongation at Break: 272% Thermal Stability (TGA): Initial decomposition temperature (Ti): 320.7 °C Peak decomposition temperature (Tp): 384.2 °C Final decomposition temperature (Tf): 412.8 °C Char yield: 17% Water Absorption: 67.68% Water Leaching Rate: 16.57% Gelatin Leaching Rate: 7.38% Contact Angle: 111.5° Dry Bonding Strength: >4.21 MPa Wet Bonding Strength: 1.057 MPa WPUG3 (Medium gelatin content) Viscosity: 12.45 mPa·s Tensile Strength: 32.91 MPa (highest) Elongation at Break: 260.5% Thermal Stability (TGA): Ti: 318.3 °C Tp: 381.9 °C Tf: 410.1 °C Char yield: 21% Water Absorption: 79.76% Water Leaching Rate: 19.96% Gelatin Leaching Rate: 8.31% Contact Angle: ~90° Dry Bonding Strength: 4.16 MPa Wet Bonding Strength: 0.528 MPa WPUG4 (High gelatin content) Viscosity: 24.56 mPa·s Tensile Strength: 14.31 MPa (lowest) Elongation at Break: 83.1% Thermal Stability (TGA): Ti: 310.3 °C Tp: 367.0 °C Tf: 407.6 °C Char yield: 27% Water Absorption: 98.32% Water Leaching Rate: 27.89% Gelatin Leaching Rate: 11.16% Contact Angle: 63° Dry Bonding Strength: 4.09 MPa Wet Bonding Strength: 0.054 MPa Industrial Gelatin Adhesive (commercial gelatin) Dry Bonding Strength: 3.64 MPa Wet Bonding Strength: Failed completely (adhesive layer detached after soaking) Unmodified Gelatin (G) from chrome shavings Dry Bonding Strength: 1.38 MPa Wet Bonding Strength: Failed completely Acrylic-collagen adhesives 145 Hybrid latexes: A-C 15 (15% collagen) A-C 25 (25% collagen) A-C 35 (35% collagen) A-C 50 (50% collagen) Neutralized versions (A-C 25 N, A-C 50 N) A-C 15 Collagen Content: 15% Conversion: 67% Particle Diameter: ~734 nm pH: 4.47 Thermal Stability: Tmax: 353 °C T50%: 368 °C Glass Transition: Not reported Mechanical Adhesion (Tack): peak stress 10 MPa and strain at break 1.2 A-C 25 Collagen Content: 25% Conversion: 73% Particle Diameter: ~783 nm pH: 4.52 Thermal Stability: Tmax: 360 °C T50%: 361 °C Glass Transition: Tg1: ~41 °C Mechanical Adhesion (Probe Tack): Mechanical Adhesion (Tack): peak stress 9 MPa and strain at break 2 Saturated film: Tack Force: 4.88 N Tack Area: 0.175 N·mm Dried film: Tack Force: 0.89 N Tack Area: 0.037 N·mm A-C 35 Collagen Content: 35% Conversion: 72% Particle Diameter: ~881 nm pH: 4.24 Thermal Stability: Tmax: 413 °C T50%: 403 °C Glass Transition: Not reported Mechanical Adhesion: Mechanical Adhesion (Tack): peak stress 7 MPa and strain at break 4 A-C 50 Collagen Content: 50% Conversion: 76% Particle Diameter: ~530 nm pH: 4.16 Thermal Stability: Tmax: 399 °C T50%: 398 °C Glass Transition: Tg1: ~42 °C Mechanical Adhesion: Mechanical Adhesion (Tack): peak stress 7 MPa and strain at break 5 A-C 25 N (Neutralized) Based on A-C 25, neutralized with NaOH Glass Transition: Tg1: ~7 °C Tg2: ~27 °C Mechanical Adhesion (Probe Tack): Mechanical Adhesion (Tack): peak stress 1.8 MPa and strain at break 18 Saturated film: Tack Force: 10.05 N (highest among all) Tack Area: 1.970 N·mm Dried film: Tack Force: 0.13 N Tack Area: 0.037 N·mm A-C 50 N (Neutralized) Based on A-C 50, neutralized Glass Transition: Tg1: ~17 °C Tg2: ~24 °C Mechanical Adhesion: Mechanical Adhesion (Tack): peak stress 1.3 MPa and strain at break 10 No lap-shear, peel strength, or tack data for standard adhesives were provided. Collagen adhesive for corrugated cardboard 146 CDP is a collagen degradation product. CPP means Crosslinked Protein Product CPP-100-2.2 CPP-G Adhesive 50% CPP-100-2.2 5% glucose Small amount of xanthan gum 45% water Moisture content: 35% Viscosity at 50 °C: 9.5 Pa·s Initial adhesion: 90% Bonding strength: 79.6 N/cm 2 Water resistance (immersion time): 48 hours GB/T6544-2008 S-1.1 grade “excellent” Gelatin (Commercial Standard Molecular weight: ~52,000 Viscosity (10% solution): 0.405 Pa·s Thermal stability: similar to CPP-100-2.2 Adhesive (Standard Reference) Moisture content: 35% Viscosity at 50 °C: 10.0 Pa·s Initial adhesion: 95% Bonding strength: 80.3 N/cm 2 Water resistance: 48 hours Collagen hydrolysates–silane coupling agent hybrids 147 CH (Collagen Hydrolysate without Crosslinker) Obtained from chrome-tanned leather waste by alkaline hydrolysis. Moisture: 1.42% Ash: 14.73% Chrome oxide content: 0.012% Dry shear strength on birch veneer: 0.91 MPa Wet shear strength: 0.51 MPa Adhesive film observed to be smooth and less adherent after water immersion (poor water resistance). GPDMS–CH Hybrid (crosslinked with (3-glycidyloxypropyl)dimethoxymethylsilane) Crosslinking degree: ~43% Improved surface hydrophobicity (ANS fluorescence index: up to ~91). Dry shear strength: 1.36 MPa Wet shear strength: 0.63 MPa Fracture surface: partially covered by adhesive, somewhat improved water resistance but less than other hybrids. GPTMS–CH Hybrid (crosslinked with (3-glycidyloxypropyl)trimethoxysilane) Crosslinking degree: ~37% Surface hydrophobicity: up to ~366 (significantly higher than GPDMS–CH). Dry shear strength: 1.51 MPa Wet shear strength: 0.95 MPa (exceeds Chinese standard GB/T 9846.3-2004 requirement of 0.7 MPa) Fracture surface: fully covered with adhesive even after soaking, indicating strong adhesion and water resistance. GPTES–CH Hybrid (crosslinked with (3-glycidyloxypropyl)triethoxysilane) Crosslinking degree: ~27% Surface hydrophobicity: up to ~274 Dry shear strength: 1.57 MPa (highest among all samples) Wet shear strength: 0.92 MPa Fracture surface: well covered, high adhesion and water resistance comparable to GPTMS–CH. Benchmark comparison: These adhesives were compared with Chinese standard GB/T 9846.3-2004 The standard defines shear strength thresholds for adhesives under specified conditions: Minimum Wet Shear Strength Requirement: For interior-use plywood adhesives (Class II): ≥0.7 MPa Biodegradable collagen adhesives 148 Optimized formulation: Working temperature: 65 °C Polyvinyl alcohol concentration: 3.2% Glycerol concentration: 4.2% Peel strength: 12.9 N/mm (measured by SATRA TM 123:1992 method) Shear strength: 4.5 MPa Moisture content: 8–16% (within recommended range) Ash content: 2–5% pH: 5.5–8.0 Viscosity: Not numerically specified but noted to be higher due to added PVA and polyvinyl acetate. Thermal stability: Three-stage degradation observed in TGA, with major protein degradation starting ~220 °C. Water resistance: Not explicitly reported, but peel and shear strength tests suggest good performance. Standards and references used: Adhesive strength measured using SATRA TM 123:1992 (common in footwear industry). Performance compared to footwear bonding standards (minimum peel strength thresholds: Baby ≥2 N/mm, Child ≥4 N/mm, Women ≥3 N/mm, Men ≥4 N/mm). Benchmark comparison: The authors compared results to prior studies where similar adhesives showed much lower peel strength (~3.25 N/mm). WPU-GE Adhesive 149 WPU-GE Adhesive Solid Content: ~22.05% Shear Strength (RT, 480 min): ~0.1710 MPa T-Peel Strength (RT, 480 min): ~0.2443 N/mm Shear Strength (60 °C, 4 min): Significantly lower than MWPU-FGE/GE Thermal Stability: Onset ~280 °C, main degradation ~320 °C, residue ~25% Main decomposition: ~270–330 °C Morphology: Microcracks and phase separation Comment: Improved over GE but still limited bonding strength MWPU-FGE/GE Adhesive Solid Content: ~28.67% Shear Strength (60 °C, 4 min): ~0.5734 MPa T-Peel Strength (60 °C, 4 min): ~1.0506 N/mm Shear Strength (RT, 480 min): Higher than others T-Peel Strength (RT, 480 min): Highest among the three Thermal Stability: Onset ~300 °C, main degradation ~330 °C, residue ~28% Max decomposition temp: ~300–350 °C Morphology: Dense, smooth fracture surface Comment: Fast curing, best adhesion, excellent water resistance GE Adhesive (plain gelatin) Solid Content: ~13.77% Shear Strength (RT, 480 min): ~0.0923 MPa T-Peel Strength (RT, 480 min): ~0.1372 N/mm Thermal Stability: Onset ~250 °C, Main degradation ~310 °C, residue ~23% Main decomposition: ~260–300 °C Morphology: Smooth fracture surface, brittle Comment: Weak adhesion, poor water resistance Commercial adhesive: Shear Strength (RT, 480 min): ~0.14 MPa T-Peel Strength (RT, 480 min): ~0.35 N/mm However, a recurring limitation evident across nearly all compositions is reduced resistance to water exposure. Even adhesives with excellent initial shear or peel strength often show significant loss of cohesion or increased solubility after prolonged immersion or humidity cycling. This variability underscores the importance of further optimizing formulation strategies to enhance water resistance, such as blending hydrophobic resins, introducing moisture-stable crosslinking networks, or applying surface treatments to improve dimensional stability. These findings are relevant to diverse application areas: certain adhesives are tailored for wood panel bonding, others for corrugated packaging, and some for bio-based composites. Overall, the evidence consolidated here demonstrates that collagen adhesives have significant potential as sustainable alternatives to petrochemical resins. Nevertheless, achieving long-term moisture durability remains the main technical challenge and is critical for future development. Market for collagen and adhesives The opportunity to manufacture collagen-based adhesives arises at an opportune time, with promising data indicating significant market growth in the hydrolyzed collagen sector, projected to nearly double in value from 2023 to 2032, reaching an estimated $2.34 billion by 2032. 150 , 151 This is particularly pronounced in North America and Europe, where diverse industries, including food and cosmetics, are heavily invested. Furthermore, the adhesives market ranked as the 281st most traded global commodity, with a trade value of $14.2 billion in 2021. Additionally, the adhesive sector demonstrated an impressive growth rate of 21.3% within a single year, underscoring its dynamic and expanding nature. 152 , 153 Given the significant growth in the collagen sector, there is potential to establish a sustainable and profitable niche within the global adhesives industry by utilizing tannery waste as a collagen source. This approach could cater to non-edible or medical sectors, although the recovery process costs must be mitigated. The integration could revolutionize the supply chain by aligning waste utilization with market expansion opportunities. It is feasible and profitable to produce gelatin from chrome shavings in a pilot plant operating with specific equipment, as demonstrated by Cabeza et al. 154 In 24 hours, processing 9072 kg of chrome shavings can yield over 900 kg of gelatin daily at approximately $0.52 to $0.57 per kg. Meanwhile, the same year, commercially available low-quality gelatins were $3.20 per kg. 155 These studies also illustrated that recovering collagen from tannery wastes can generate additional revenue from the reclaimed chrome and savings related to landfill disposal. In 2023, animal glue prices range between $1.5 to $4 per kilogram, 156 making it cost-effective to recycle collagen at an industrial scale even today, especially considering the abundance of low-cost leather solid waste, the maturity of hydrolysis-based extraction technologies, and the added value from chromium recovery and landfill cost savings. 157 The competitive price of collagen extracted from tannery wastes makes the industrial production of adhesives and glues possible, especially given the new technology that today is apt to improve collagen yield recovery from tannery wastes, 158 as seen in Table 1 . Utilization and innovations: Tannery waste-derived collagen adhesives applications In various industries, such as woodwork, textiles, footwear, and packaging, versatile applications of innovative adhesive formulations are making significant strides. These formulations offer promising solutions and advancements for each sector. As illustrated in Table 3 , recycled collagen has been harnessed to produce adhesives suitable for the wood, paper, and textile industries. However, the potential applications of these adhesives extend well beyond the applications. They also hold promise in different arenas where the demand for effective bonding agents is considerable. As technology progresses, these innovative adhesive solutions are anticipated to find novel and unforeseen applications, thereby influencing industries with distinctive attributes and environmentally conscious qualities. Table 3. Patents on Converting Solid Tannery Wastes into Adhesives. Patent Description Application Cite CN106753159B Degradable collagen-polyurethane water-based wood adhesive. Collagen-polyurethane with isocyanate, polyester polyol, hydrophilic chain extender, micromolecular dihydric alcohol chain extender, and neutralizer. Wood 159 CN106800907A A kind of environment-friendly water-based wood adhesive based on degraded collagen solution Isocyanates and polyester polyol, hydrophilic, glycol chain extenders with degraded collagen from tanneries. Wood 160 CN106753159A One kind of degraded polyurethane aqueous wood adhesive of collagen and preparation method thereof Chrome shavings with isocyanates and polyester polyol as catalysts. Wood Paper 161 CN109554153A A kind of preparation method and application of collagen base adhesive Collagen recycled from leather with polyurethane and epoxy resin Wood and water-resistant applications 162 CN110256651A A kind of preparation method of collagen-base paper-making function sizing agent Hydrolyzed collagen, not necessary from tannery, with diisocyanate, polyalcohol, glycol, hydrophilic chain extender, hydracrylic acid, acid esters, vinyl silicane, persulfate, water-base resin preservative Paper 163 CN111704879A Air-permeable leather adhesive and preparation method thereof Collagen, polyol, polyisocyanate, chain extender, coupling agent, pore-foaming agent, and a reinforcing agent Leather 164 CN106800907 A kind of environment-friendly water-based wood adhesive based on degraded collagen solution and preparation method thereof Collagen, isocyanates and polyester polyol, polyurethane prepolymer Wood 165 CN109554153A A kind of preparation method and application of collagen base adhesive Collagen, polyurethane, epoxy resin Wood, Paper, Textile 166 CN103669109B A kind of preparation method of glue used in paper-making Hydrolyzed collagen, cross-linking agent Paper 167 Challenges and Future Directions Gelatin adhesives, despite their environmental benefits and biodegradability, face several limitations that constrain wider industrial use. One primary challenge is their thermal and water stability: gelatin gels are thermoreversible and begin dissolving above ~35–40 °C, limiting applications requiring high thermal resistance or durability in humid conditions such as exterior wood panels or moisture-exposed packaging. 168 For this reason, chemical or enzymatic crosslinkers, including glutaraldehyde or transglutaminase, are often incorporated to enhance stability. Mechanically, gelatin-based adhesives exhibit lower strength and dimensional stability than synthetic resins, especially under prolonged stress or humidity. Cost and processing complexity also pose challenges, as high-bloom gelatin entails higher production costs and requires precise control during formulation and application. Regulatory and market acceptance present additional constraints, particularly in food packaging, where animal origin can be a barrier, prompting the development of fish- and plant-derived alternatives that often show lower gel strength. 169 Recent studies have proposed adding hydrophobic additives or synthetic polymers to address these deficits to improve moisture resistance, employing enzymatic crosslinking to avoid toxic reagents, and applying bio-catalytic extraction methods to reduce production costs and environmental impact. 170 While gelatin offers sustainability advantages, formulation and processing innovation remain essential to make it a competitive alternative to synthetic adhesives. There is significant potential for improving collagen adhesives derived from recycled tannery waste. Research should focus on optimize extraction, characterization, and modification to enhance adhesion strength, durability, and biodegradability while ensuring compatibility with various substrates, scalability, and commercial viability. 171 Regulatory compliance and safety must also be considered, particularly for consumer products like textiles and packaging. Advancing these areas could lead to sustainable, efficient, and versatile adhesives aligned with global sustainability goals. The main limitations of collagen adhesives—their moisture sensitivity and reduced durability under wet conditions—remain challenges for broader use. These issues stem from the hydrophilicity of collagen’s peptide backbone and its tendency to swell or dissolve in water. Promising strategies to address these issues include chemical crosslinking with glutaraldehyde, epoxides, or silane coupling agents, as shown in Table 2 , and improving water resistance by forming covalent networks restricting polymer chain mobility. Blending with hydrophobic polymers such as polyurethanes, polyvinyl acetate, or bio-based resins can further improve dimensional stability and reduce solubility. Surface modification, including water-repellent coatings or nanofillers (e.g., silicas, clays), enhances barrier properties. 172 , 173 Future work should optimize these strategies to balance mechanical strength, biodegradability, and moisture resistance, making collagen adhesives more competitive for demanding industrial and packaging applications. 174 Conclusion This review examines the potential of utilizing collagen extracted from tannery waste for adhesive production and provides a detailed analysis of the extraction methods, formulation techniques, and applications. This study demonstrated the technical feasibility and environmental benefits of this approach. Research suggests a high level of versatility in using collagen, including blending it with urea-formaldehyde or combining it with waterborne polyurethane for wood-based applications. These blends demonstrated the desired adhesive properties and, in some cases, surpassed those of commercial adhesives. However, collagen-based adhesives are limited by their water resistance. To address this issue, innovations such as the incorporation of silane coupling agents or the addition of other compounds such as methacrylate, gallic acid, ε-polylysine, melamine-formaldehyde, or zein are being explored, indicating a promising future for this field. However, transitioning from an experimental to a commercial scale remains a challenge. Current investigations are mostly laboratory-level, and comprehensive economic analyses or pilot-scale studies are scarce. Historical data suggests the economic viability of collagen extraction from tannery waste and its subsequent use in adhesive production. However, further consistent and extensive studies are required to confirm this finding. In essence, environmentally conscious sourcing and the adaptability of collagen are exciting prospects for future adhesive technologies. Author contributions Conceptualization: NEFT; supervision: NEFT and HBM; literature search: NEFT, RDPA and HBM material preparation: NEFT, RDPA and HBM; methodology: NEFT; acquisition of data: NEFT; interpretation of data: NEFT, RDPA; writing—original draft: NEFT, RDPA, HBM; writing—review and final editing: NEFT and HBM; supervision: RDPA, HBM; all authors have read and agreed to the published version of the manuscript. Ethical approval Ethical approval and consent were not required. Data availability statement No data are associated with this article. Acknowledgment The authors wish to express their sincere gratitude to the Research and Development Directorate and the Technical University of Ambato for their valuable support and resources that made this work possible. Project Sustainable Polymeric Composites from Agro-Industrial and Wet-Blue Leather Waste for Ecological Applications. References 1. Montalvão M, da Silva Castro A , de Lima Rodrigues A , et al. : Impacts of Tannery Effluent on Development and Morphological Characters in a Neotropical Tadpole. Sci. Total Environ. 2018; 610-611 : 1595–1606. PubMed Abstract | Publisher Full Text 2. Saxena G, Purchase D, Bharagava R: Environmental Hazards and Toxicity Profile of Organic and Inorganic Pollutants of Tannery Wastewater and Bioremediation Approaches.Saxena G, Bharagava R, editors. Bioremediation of Industrial Waste for Environmental Safety. Singapore: Springer; 2020. Publisher Full Text 3. Hansen É, Monteiro de Aquim P, Hansen AW, et al. : Impact of Post-Tanning Chemicals on the Pollution Load of Tannery Wastewater. J. Environ. Manag. 2020; 269 : 110787. Publisher Full Text 4. Hansen É, de Aquim PM , Gutterres M: Environmental Assessment of Water, Chemicals and Effluents in Leather Post-Tanning Process: A Review. Environ. Impact Assess. Rev. 2021; 89 : 106597. Publisher Full Text 5. Saira GC, Shanthakumar S: Zero Waste Discharge in Tannery Industries – An Achievable Reality? A Recent Review. J. Environ. Manag. 2023; 335 : 117508. Publisher Full Text 6. Guo SS, Tian YQ, Wu H, et al. : Spatial Distribution and Morphological Transformation of Chromium with Coexisting Substances in Tannery Landfill. Chemosphere. 2021; 285 : 131503. Publisher Full Text 7. Szuba A, Lorenc-Plucińska G: Field Proteomics of Populus Alba Grown in a Heavily Modified Environment – An Example of a Tannery Waste Landfill. Sci. Total Environ. 2018; 610-611 : 1557–1571. PubMed Abstract | Publisher Full Text 8. Verma SK, Sharma PC: Current Trends in Solid Tannery Waste Management. Crit. Rev. Biotechnol. 2023; 43 (5): 805–822. PubMed Abstract | Publisher Full Text 9. Dunky M: Introduction to Naturally-Based (Bio-) Adhesives. Biobased Adhesives: Sources, Characteristics, and Applications. 2023; pp. 1–44. 307–319. Publisher Full Text 10. Ferreira S, de Melo W , Araujo F, et al. : Long-Term Effect of Composted Tannery Sludge on Soil Chemical and Biological Parameters. Environ. Sci. Pollut. Res. 2020; 27 : 41885–41892. PubMed Abstract | Publisher Full Text 11. Rigueto CVT, Rosseto M, Nazari MT, et al. : Adsorption of Diclofenac Sodium by Composite Beads Prepared from Tannery Wastes-Derived Gelatin and Carbon Nanotubes. J. Environ. Chem. Eng. 2021; 9 : 105030. Publisher Full Text 12. Ławińska K: Production of Agglomerates, Composite Materials, and Seed Coatings from Tannery Waste as New Methods for Its Management. Materials. 2021; 14 : 6695. PubMed Abstract | Publisher Full Text | Free Full Text 13. Tujjohra F, Alam MS, Rahman MM, et al. : An Eco-Friendly Approach of Biodiesel Production from Tannery Fleshing Wastes by Crude Neutral Protease Enzyme. Clean. Eng. Technol. 2023; 14 : 100638. Publisher Full Text 14. Olubunmi B, Alade A, Ebhodaghe S, et al. : Optimization and Kinetic Study of Biodiesel Production from Beef Tallow Using Calcium Oxide as a Heterogeneous and Recyclable Catalyst. Energy Conversion and Management: X. 2022; 14 : 100221. Publisher Full Text 15. Nagi M, He M, Li D, et al. : Utilization of Tannery Wastewater for Biofuel Production: New Insights on Microalgae Growth and Biomass Production. Sci. Rep. 2020; 10 : 1–14. PubMed Abstract | Publisher Full Text | Free Full Text 16. Booramurthy VK, Kasimani R, Pandian S: Biodiesel Production from Tannery Waste Using a Nano Catalyst (Ferric-Manganese Doped Sulphated Zirconia). Energy Sources. 2022; 44 : 1092–1104. Publisher Full Text 17. Tujjohra F, Alam MS, Rahman MM, et al. : An Eco-Friendly Approach of Biodiesel Production from Tannery Fleshing Wastes by Crude Neutral Protease Enzyme. Clean. Eng. Technol. 2023; 14 : 100638. Publisher Full Text 18. Sanchez-Olivares G, Sanchez-Solis A, Calderas F, et al. : Keratin Fibres Derived from Tannery Industry Wastes for Flame Retarded PLA Composites. Clean. Eng. Technol. 2017; 140 : 42–54. Publisher Full Text 19. Jacob JJ, Varalakshmi R, Gargi S, et al. : Removal of Cr (III) and Ni (II) from Tannery Effluent Using Calcium Carbonate Coated Bacterial Magnetosomes. Clean Water. 2018; 1 : 1–10. Publisher Full Text 20. Ashokkumar M, Ajayan PM: Materials Science Perspective of Multifunctional Materials Derived from Collagen. Int. Mater. Rev. 2020; 66 : 160–187. Publisher Full Text 21. Sinaga MZE, Sihombing YA, Hardiyanti R, et al. : Preparation and Mechanical Properties of Biodegradable Films Based on Seaweed, Chitosan, and Collagen. AIP Conference Procedings. 2021; 2342 . Publisher Full Text 22. Brum IS, Elias CN, de Carvalho JJ , et al. : Properties of a Bovine Collagen Type I Membrane for Guided Bone Regeneration Applications. E-Polymers. 2021; 21 : 210–221. Publisher Full Text 23. Noorzai S, Verbeek CJR: Biomaterials Derived from Agricultural Waste: A Focus on Collagen.Ramawat K, Mérillon JM, Arora J, editors. Agricultural Waste: Environmental Impact, Useful Metabolites and Energy Production. Sustainable Development and Biodiversity. Singapore: Springer; 2023; 31 . : 87–107. Publisher Full Text 24. Sierra-Romero A, Novakovic K, Geoghegan M: Adhesive Interfaces toward a Zero-Waste Industry. Langmuir. 2022; 38 : 15476–15493. PubMed Abstract | Publisher Full Text | Free Full Text 25. Dunky M: Wood Adhesives Based on Natural Resources: A Critical Review: Part I. Protein-Based Adhesives. Progress in Adhesion and Adhesives. 2021; 6 : 203–336. Publisher Full Text 26. Fay P: A History of Adhesive Bonding. Adhesive Bonding: Science, Technology and Applications. 2021; pp. 3–40. Publisher Full Text 27. Patel K, Munir D, Santos RM: Beneficial Use of Animal Hides for Abattoir and Tannery Waste Management: A Review of Unconventional, Innovative, and Sustainable Approaches. Environ. Sci. Pollut. Res. 2022; 29 : 1807–1823. PubMed Abstract | Publisher Full Text 28. Deskera: Leathers Manufacturing and Recycling: A Detailed Guide!. (accessed on 17 May 2024). Reference Source 29. Heinrich LA: Future Opportunities for Bio-Based Adhesives – Advantages beyond Renewability. Green Chem. 2019; 21 : 1866–1888. Publisher Full Text 30. Yorgancioglu A, Onem E, Yilmaz O, et al. : Interactions Between Collagen and Alternative Leather Tanning Systems to Chromium Salts by Comparative Thermal Analysis Methods: Thermal Stabilisation of Collagen by Tanning Process. Johns. Matthey Technol. Rev. 2022; 66 : 215–226. Publisher Full Text 31. Ocak B: Film-Forming Ability of Collagen Hydrolysate Extracted from Leather Solid Wastes with Chitosan. Environ. Sci. Pollut. Res. Int. 2018; 25 : 4643–4655. PubMed Abstract | Publisher Full Text 32. Lutz TM, Kimna C, Casini A, et al. : Bio-Based and Bio-Inspired Adhesives from Animals and Plants for Biomedical Applications. Materials Today Bio. 2022; 13 : 100203. PubMed Abstract | Publisher Full Text | Free Full Text 33. Assmann A, Vegh A, Ghasemi-Rad M, et al. : A Highly Adhesive and Naturally Derived Sealant. Biomaterials. 2017; 140 : 115–127. PubMed Abstract | Publisher Full Text | Free Full Text 34. Grand View Research, Inc: Leather Goods Industry Growth & Analysis, Data Book. (accessed on 22 August 2023). Reference Source 35. OEC - The Observatory of Economic Complexity: Raw Hides & Skin (Non-Fur). (accessed on 11 August 2023). Reference Source 36. Onem E, Renner M, Prokein M: Green Separation and Characterization of Fatty Acids from Solid Wastes of Leather Industry in Supercritical Fluid CO2. Environ. Sci. Pollut. Res. Int. 2018; 25 : 22213–22223. PubMed Abstract | Publisher Full Text 37. Pan F, Xiao Y, Zhang L, et al. : Leather Wastes into High-Value Chemicals: Keratin-Based Retanning Agents via UV-Initiated Polymerization. J. Clean. Prod. 2023; 383 : 135492. Publisher Full Text 38. Sivaram NM, Barik D: Chapter 5 - Toxic Waste From Leather Industries. Woodhead Publishing Series in Energy, Energy from Toxic Organic Waste for Heat and Power Generation. Woodhead Publishing; 2019; pp. 55–67. Publisher Full Text 39. Sadeghi H, Fazlzadeh M, Zarei A, et al. : Spatial Distribution and Contamination of Heavy Metals in Surface Water, Groundwater and Topsoil Surrounding Moghan’s Tannery Site in Ardabil, Iran. Int. J. Environ. Anal. Chem. 2022; 102 (5): 1049–1059. Publisher Full Text 40. Urbina-Suárez A, Machuca-Martínez N, Barajas-Solano A: Advanced Oxidation Processes and Biotechnological Alternatives for the Treatment of Tannery Wastewater. Molecules. 2021; 26 (11): 3222. PubMed Abstract | Publisher Full Text | Free Full Text 41. Sivagami K, Sakthivel KP, Nambi IM: Advanced Oxidation Processes for the Treatment of Tannery Wastewater. J. Environ. Chem. Eng. 2018; 6 : 3656–3663. Publisher Full Text 42. Vasanthan SV, Murugesan AM, Selvam AS: Study of Seasonal, Spatial Deviation and Pollution Indices of Ground Water by Tannery Activities in Vaniyambadi, Vellore District, Tamilnadu, India. Orient. J. Chem. 2022; 38 : 56–64. Publisher Full Text 43. Kanagaraj G, Elango L: Chromium and Fluoride Contamination in Groundwater around Leather Tanning Industries in Southern India: Implications from Stable Isotopic Ratio Δ53Cr/Δ52Cr, Geochemical and Geostatistical Modelling. Chemosphere. 2019; 220 : 943–953. PubMed Abstract | Publisher Full Text 44. Bhattacharya M, Shriwastav A, Bhole S, et al. : Processes Governing Chromium Contamination of Groundwater and Soil from a Chromium Waste Source. ACS Earth Space Chem. 2020; 4 : 35–49. Publisher Full Text 45. Kanagaraj G, Mohana P, Muthusamy S, et al. : Geochemical Evaluation of Groundwater around Chromepet Tannery Belt, Southern India. Groundw. Sustain. Dev. 2023; 22 : 100963. Publisher Full Text 46. Karunanidhi D, Aravinthasamy P, Subramani T, et al. : Chromium Contamination in Groundwater and Sobol Sensitivity Model Based Human Health Risk Evaluation from Leather Tanning Industrial Region of South India. Environ. Res. 2021; 199 : 111238. PubMed Abstract | Publisher Full Text 47. Alam MS, Han B, Al-Mizan; Pichtel, J.: Assessment of Soil and Groundwater Contamination at a Former Tannery District in Dhaka, Bangladesh. Environ. Geochem. Health. 2020; 42 : 1905–1920. PubMed Abstract | Publisher Full Text 48. Tripathi S, Chaurasia SR: Detection of Chromium in Surface and Groundwater and Its Bio-Absorption Using Bio-Wastes and Vermiculite. Engineering Science and Technology, an International Journal. 2020; 23 : 1153–1161. Publisher Full Text 49. Khan A, Michelsen N, Marandi A, et al. : Processes Controlling the Extent of Groundwater Pollution with Chromium from Tanneries in the Hazaribagh Area, Dhaka, Bangladesh. Sci. Total Environ. 2020; 710 : 136213. PubMed Abstract | Publisher Full Text 50. Kistan A, Kanchana V, Geetha NK: Seasonable Variation of Trace Metals, Statistical Values of Groundwater in and around Tannery Areas of Vellore District. Orient. J. Chem. 2021; 37 : 735–745. Publisher Full Text 51. Ahmed F, Fakhruddin ANM, Fardous Z, et al. : Investigation of Human Health Risks Influenced by Trace Metals (TMs) in Chili Plant ( Capsicum Annuum L.) Grown on Tannery Effluents Contaminated Soil. Toxicol. Int. 2021; 28 : 67–80. Publisher Full Text 52. Nirola R, Megharaj M, Subramanian A, et al. : Analysis of Chromium Status in the Revegetated Flora of a Tannery Waste Site and Microcosm Studies Using Earthworm E. Fetida. Environ. Sci. Pollut. Res. Int. 2018; 25 : 5063–5070. PubMed Abstract | Publisher Full Text 53. Baratzadeh-Poustchi F, Tabatabaei-Yazdi F, Heidari A, et al. : Evaluation of Chromium Accumulation and Resulting Histopathological Changes in Libyan Jirds (Mammals, Rodentia), Affected by Effluent from Ghazghan Leather Industrial Town, Iran. Environ. Sci. Pollut. Res. 2020; 27 : 39343–39353. PubMed Abstract | Publisher Full Text 54. dos Reis Sampaio D , Estrela F, Mendes B, et al. : Ingestion of tannery effluent as a risk factor to the health of birds: A toxicological study using Coturnix coturnix japonica as a model system. Sci. Total Environ. 2019; 681 : 275–291. PubMed Abstract | Publisher Full Text 55. Bakshi A, Panigrahi AK: A Comprehensive Review on Chromium Induced Alterations in Fresh Water Fishes. Toxicol. Rep. 2018; 5 : 440–447. PubMed Abstract | Publisher Full Text | Free Full Text 56. Horn E, Oyekola O, Welz P, et al. : Biological Desulfurization of Tannery Effluent Using Hybrid Linear Flow Channel Reactors. Water. 2022; 14 (1): 32. Publisher Full Text 57. Prasad S, Yadav K, Kumar S, et al. : Chromium Contamination and Effect on Environmental Health and Its Remediation: A Sustainable Approaches. J. Environ. Manag. 2021; 285 : 112174. PubMed Abstract | Publisher Full Text 58. Thangam T, Kumar V, Vasline Y: Decontamination of Hexavalent Chromium by Geo Chemical Fixation Method in a Hazardous Dump Site, Ranipet, Tamil Nadu, India. J. Eng. Appl. Sci. 2018; 13 : 208–212. Publisher Full Text 59. Arti, Mehra R: Analysis of Heavy Metals and Toxicity Level in the Tannery Effluent and the Environs. Environ. Monit. Assess. 2023; 195 : 554. PubMed Abstract | Publisher Full Text 60. Langejans G, Aleo A, Fajardo S, et al. : Archaeological Adhesives. Oxford Research Encyclopedia of Anthropology. 2022. Publisher Full Text 61. Fay P: A History of Adhesive Bonding. Adhesive Bonding. In Woodhead Publishing Series in Welding and Other Joining Technologies. Woodhead Publishing; 2021; pp. 3–40. Publisher Full Text 62. Yu J, Chung YJ: Analysis of Cow Hide Glue Binder in Traditional Dancheong by Enzyme-Linked Immunosorbent Assay. JCS. 2019; 35 : 363–372. Publisher Full Text 63. Fan C, Tang Q: Allyl Glycidyl Ether-Modified Animal Glue Binder for Improved Water Resistance and Bonding Strength in Sand Casting. Organic Polymer Material Research. 2021; 2 : 1–7. Publisher Full Text 64. Li X, Li J, Luo J, et al. : A Novel Eco-Friendly Blood Meal-Based Bio-Adhesive: Preparation and Performance. J. Polym. Environ. 2018; 26 : 607–615. Publisher Full Text 65. Wusigale, Liang L, Luo Y: Casein and Pectin: Structures, Interactions, and Applications. Trends Food Sci. Technol. 2020; 97 : 391–403. Publisher Full Text 66. Adhikari B, Chae M, Bressler DC: Utilization of Slaughterhouse Waste in Value-Added Applications: Recent Advances in the Development of Wood Adhesives. Polymers. 2018; 10 : 176. PubMed Abstract | Publisher Full Text | Free Full Text 67. León-López A, Morales-Peñaloza A, Martínez-Juárez V, et al. : Hydrolyzed Collagen-Sources and Applications. Molecules. 2019; 24 (22): 4031. PubMed Abstract | Publisher Full Text | Free Full Text 68. Wan Y, Gao Y, Shao J, et al. : Effects of Ultrasound and Thermal Treatment on the Ultrastructure of Collagen Fibers from Bovine Tendon Using Atomic Force Microscopy. Food Chem. 2021; 347 : 128985. PubMed Abstract | Publisher Full Text 69. Badem A, Ucar G, Gupta P: Production of Caseins and Their Usages. Int. J. Food Sci. Nutr. 2017; 2 (1): 2455–4898. Reference Source 70. Galante R, Cunha F, Fangueiro R: Extraction and Properties of Casein Biopolymer from Milk. Handbook of Natural Polymers. 2023; Vol. 1 : pp. 471–487. Publisher Full Text 71. Silvestre J, Delattre C, Michaud P, et al. : Optimization of Chitosan Properties with the Aim of a Water-Resistant Adhesive Development. Polymers. 2021; 13 : 4031. PubMed Abstract | Publisher Full Text | Free Full Text 72. Pakizeh M, Moradi A, Ghassemi T: Chemical Extraction and Modification of Chitin and Chitosan from Shrimp Shells. Eur. Polym. J. 2021; 159 : 110709. Publisher Full Text 73. Fan H: Getting Glued in the Sea. Polym. J. 2023; 55 : 653–664. PubMed Abstract | Publisher Full Text | Free Full Text 74. Olden J, Vitule J, Cucherousset J, et al. : There’s More to Fish than Just Food: Exploring the Diverse Ways That Fish Contribute to Human Society. Fisheries (Bethesda). 2020; 45 : 453–464. Publisher Full Text 75. Bachtiar EV, Niemz P, Sandberg D: Properties of Adhesive Films Used in Cultural Assets. Wood Mater. Sci. Eng. 2022; 17 : 147–150. Publisher Full Text 76. Lv S, Tan L, Peng X, et al. : Experimental Investigation on the Performance of Bone Glue and Crumb Rubber Compound Modified Asphalt. Constr. Build. Mater. 2021; 305 : 124734. Publisher Full Text 77. Dunky M: Wood Adhesives Based on Natural Resources: A Critical Review: Part II. Carbohydrate-Based Adhesives. Progress in Adhesion and Adhesives. 2021; 6 : 337–382. Publisher Full Text 78. Nasiri A, Wearing J, Dubé MA: Using Lignin to Modify Starch-Based Adhesive Performance. ChemEngineering. 2020; 4 (1): 3. Publisher Full Text 79. Mardonov S, Shokirov L, Rakhimov K: Development of Technology for Obtaining Starch Gluing Modified with Uzkhitan and Hydrolyzed Emulsion. J. Phys. Conf. Ser. 2021; 2094 : 042070. Publisher Full Text 80. Jezowski P, Kowalczewski PŁ: Starch as a Green Binder for the Formulation of Conducting Glue in Supercapacitors. Polymers (Basel). 2019; 11 : 1648. PubMed Abstract | Publisher Full Text | Free Full Text 81. Jimenez M, Schwaiger N, Flicker R, et al. : Enzymatic Synthesis of Wet-Resistant Lignosulfonate-Starch Adhesives. New Biotechnol. 2022; 69 : 49–54. PubMed Abstract | Publisher Full Text 82. Parvin S, Mazumder LT, Hasan S, et al. : What Should We Do With Our Solid Tannery Waste. IOSR Journal of Environmental Science, Toxicology and Food Technology. 2017; 11 : 82–89. Publisher Full Text 83. Raguraman R, Sailo L: Efficient Chromium Recovery from Tannery Sludge for Sustainable Management. Int. J. Environ. Sci. Technol. 2017; 14 : 1473–1480. Publisher Full Text 84. León-López A, Morales-Peñaloza A, Martínez-Juárez VM, et al. : Hydrolyzed Collagen—Sources and Applications. Molecules. 2019; 24 (22): 4031. PubMed Abstract | Publisher Full Text | Free Full Text 85. Revell CK, Jensen OE, Shearer T, et al. : Collagen Fibril Assembly: New Approaches to Unanswered Questions. Matrix Biology Plus. 2021; 12 : 100079. PubMed Abstract | Publisher Full Text | Free Full Text 86. Shoulders MD, Raines RT: Collagen Structure and Stability. Annu. Rev. Biochem. 2009; 78 : 929–958. PubMed Abstract | Publisher Full Text | Free Full Text 87. Goldberga I, Li R, Duer MJ: Collagen Structure−Function Relationships from Solid-State NMR Spectroscopy. Acc. Chem. Res. 2018; 51 (7): 1621–1629. PubMed Abstract | Publisher Full Text 88. Avila-Rodríguez MI, Rodríguez-Barroso L, Sánchez ML: Collagen: A Review on Its Sources and Potential Cosmetic Applications. J. Cosmet. Dermatol. 2017; 17 : 20–26. PubMed Abstract | Publisher Full Text 89. León-López A, Morales-Peñaloza A, Martínez-Juárez M, et al. : Hydrolyzed Collagen-Sources and Applications. Molecules. 2019; 24 (22): 4031. PubMed Abstract | Publisher Full Text | Free Full Text 90. Rastian Z, Pütz S, Wang Y, et al. : Type I collagen from jellyfish. Catostylus mosaicus for biomaterial applications. ACS Biomater. Sci. Eng. 2018; 4 (6): 2115–2125. PubMed Abstract | Publisher Full Text 91. Ntasi G, Sbriglia S, Pitocchi R, et al. : Proteomic characterization of collagen-based animal glues for restoration. J. Proteome Res. 2022; 21 (6): 2173–2184. PubMed Abstract | Publisher Full Text | Free Full Text 92. Zhu Y, Yang X, Sun F: RCSB PDB - 7CWK: Structure of a Triple-Helix Region of Human Collagen Type I. (accessed on 24 August 2023). Reference Source 93. Yang X, Zhu Y, Ye S, et al. : RCSB PDB - 6JEC: Structure of a Triple-Helix Region of Human Collagen Type II. (accessed on 24 August 2023). Reference Source 94. Hua C, Zhu Y, Xu W, et al. : Characterization by High-Resolution Crystal Structure Analysis of a Triple-Helix Region of Human Collagen Type III with Potent Cell Adhesion Activity. Biochem. Biophys. Res. Commun. 2019; 508 : 1018–1023. PubMed Abstract | Publisher Full Text | Free Full Text 95. Casino P, Gozalbo-Rovira R, Rodríguez-Díaz J, et al. : Structures of Collagen IV Globular Domains: Insight into Associated Pathologies, Folding and Network Assembly. IUCrJ International Union of Cristallography Journal. 2018; 5 : 765–779. PubMed Abstract | Publisher Full Text | Free Full Text 96. Sundaramoorthy M, Meiyappan M, Todd P, et al. : Structure of Type IV Collagen NC1 Domains. J. Biol. Chem. 2002; 277 (34): 31142–31153. PubMed Abstract | Publisher Full Text 97. Pizzi A, Mittal K, Bhatnagar N: Theories and Mechanisms of Adhesion. Theories and Mechanisms of Adhesion. CRC Press; 2017; pp. 3–18. 9781315120942. 98. Rathi S, Saka R, Domb AJ, et al. : Protein-Based Bioadhesives and Bioglues. Polym. Adv. Technol. 2019; 30 : 217–234. Publisher Full Text 99. Ramesh M, Kumar L: Bioadhesives. Green Adhesives: Preparation, Properties and Applications. John Wiley & Sons, Ltd; 2020; pp. 145–164. 9781119655053. Publisher Full Text 100. Yang J, Shan Z, Zhang Y, et al. : Stabilization and Cyclic Utilization of Chrome Leather Shavings. Environ. Sci. Pollut. Res. 2019; 26 : 4680–4689. PubMed Abstract | Publisher Full Text 101. Baggio E, Scopel BS, Krein DDC, et al. : Transglutaminase Crosslinked Gelatin Films Extracted from Tanned Leather Waste. J. Am. Leather Chem. Assoc. 2021; 116 : 3–10. Publisher Full Text 102. Gao D, Wang P, Shi J, et al. : A Green Chemistry Approach to Leather Tanning Process: Cage-like Octa (Aminosilsesquioxane) Combined with Tetrakis (Hydroxymethyl) Phosphonium Sulfate. J. Clean. Prod. 2019; 229 : 1102–1111. Publisher Full Text 103. Gargano M, Florio C, Sannia G, et al. : From Leather Wastes to Leather: Enhancement of Low Quality Leather Using Collagen Recovered from Leather Tanned Wastes. Clean Techn. Environ. Policy. 2023; 25 : 3065–3074. Publisher Full Text 104. Parisi M, Nanni A, Colonna M: Recycling of Chrome-Tanned Leather and Its Utilization as Polymeric Materials and in Polymer-Based Composites: A Review. Polymers (Basel). 2021; 13 : 1–23. PubMed Abstract | Publisher Full Text | Free Full Text 105. Ostadi A, Arshee M, Lin Z, et al. : Orientation-Dependent Indentation Reveals the Crosslink-Mediated Deformation Mechanisms of Collagen Fibrils. Acta Biomater. 2023; 158 : 347–357. PubMed Abstract | Publisher Full Text | Free Full Text 106. Yoseph Z, Gladstone J, Assefa B, et al. : Extraction of Elastin from Tannery Wastes: A Cleaner Technology for Tannery Waste Management. J. Clean. Prod. 2020; 243 : 118471. Publisher Full Text 107. Venupriya V, Krishnaveni V, Ramya M: Effect of Acidic and Alkaline Pretreatment on Functional, Structural and Thermal Properties of Gelatin from Waste Fish Scales. Polym. Bull. 2022; 80 : 10533–10567. Publisher Full Text 108. Sathish M, Madhan B, Raghava Rao J: Leather Solid Waste: An Eco-Benign Raw Material for Leather Chemical Preparation – A Circular Economy Example. Waste Manag. 2019; 87 : 357–367. PubMed Abstract | Publisher Full Text 109. Matinong A, Chisti Y, Pickering K, et al. : Collagen Extraction from Animal Skin. Biology. 2022; 11 : 905. PubMed Abstract | Publisher Full Text | Free Full Text 110. Vaskova H, Vasek V: Mathematical model of Hydrolysis Reaction for the Collagen Hydrolyzate Production from Leather Shavings. Annals of DAAAM and Proceedings of the International DAAAM Symposium. 2016; 1 : 271–274. Publisher Full Text 111. Niculescu M, Epure D, Lasoń-Rydel M, et al. : Biocomposites Based on Collagen and Keratin with Properties for Agriculture and Industrie Applications. Eurobiotech Journal. 2019; 3 : 160–166. Publisher Full Text 112. Kumar N, Strachowski P, Undeland I, et al. : Structural and Functional Properties of Collagen Isolated from Lumpfish and Starfish Using Isoelectric Precipitation vs Salting Out. Food Chemistry: X. 2023; 18 : 100646. PubMed Abstract | Publisher Full Text | Free Full Text 113. Dang X, Yang M, Zhang B, et al. : Recovery and Utilization of Collagen Protein Powder Extracted from Chromium Leather Scrap Waste. Environ. Sci. Pollut. Res. 2019; 26 : 7277–7283. PubMed Abstract | Publisher Full Text 114. Tian Z, Wang Y, Wang H, et al. : Regeneration of Native Collagen from Hazardous Waste: Chrome-Tanned Leather Shavings by Acid Method. Environ. Sci. Pollut. Res. 2020; 27 : 31300–31310. PubMed Abstract | Publisher Full Text 115. Noorzai S, Verbeek C, Lay M, et al. : Collagen Extraction from Various Waste Bovine Hide Sources. Waste Biomass Valorization. 2020; 11 : 5687–5698. Publisher Full Text 116. Purba F, Suparno O, Rusli M, et al. : Novel Method of Hydrolysed Collagen Extraction from Hide Trimming Waste. Int. Food Res. J. 2023; 30 : 365–374. Publisher Full Text 117. Pecha J, Barinova M, Kolomaznik K, et al. : Technological-Economic Optimization of Enzymatic Hydrolysis Used for the Processing of Chrome-Tanned Leather Waste. Process Saf. Environ. Prot. 2021; 152 : 220–229. Publisher Full Text 118. Duan Y, Cheng H: Preparation of Immobilized Pepsin for Extraction of Collagen from Bovine Hide. RCS Advances. 2022; 12 : 34548–34556. PubMed Abstract | Publisher Full Text | Free Full Text 119. Li L, Zhang J, Wang M, et al. : Electrospun Hydrolyzed Collagen from Tanned Leather Shavings for Bio-Triboelectric Nanogenerators. Materials Advances. 2022; 3 : 5080–5086. Publisher Full Text 120. Jian S, Wenyi T, Wuyong C: Ultrasound-Accelerated Enzymatic Hydrolysis of Solid Leather Waste. J. Clean. Prod. 2008; 16 : 591–597. Publisher Full Text 121. Scopel BS, Restelatto D, Baldasso C, et al. : Steam Explosion in Alkaline Medium for Gelatine Extraction from Chromium-Tanned Leather Wastes: Time Reduction and Process Optimization. Environ. Technol. 2018; 41 : 1857–1866. PubMed Abstract | Publisher Full Text 122. Wang L, Li J, Jin Y, et al. : Study on the Removal of Chromium (III) from Leather Waste by a Two-Step Method. J. Ind. Eng. Chem. 2019; 79 : 172–180. Publisher Full Text 123. Han W, Zeng Y, Zhang W: View of A Further Investigation on Collagen-Cr (III) Interaction at Molecular Level. J. Am. Leather Chem. Assoc. 2016; 111 : 101–106. Reference Source 124. Liu J, Luo L, Zhang Z, et al. : A Combined Kinetic Study on the Pyrolysis of Chrome Shavings by Thermogravimetry. Carbon Resources Conversion. 2020; 3 : 156–163. Publisher Full Text 125. Zhao L, Mu S, Wang W, et al. : Toxicity Evaluation of Collagen Hydrolysates from Chrome Shavings and Their Potential Use in the Preparation of Amino Acid Fertilizer for Crop Growth Open Access Journal of Leather Science and Engineering. J. Leather Sci. Eng. 2022; 4 : 2. Publisher Full Text 126. Asava A, Sasia A, Sang P, et al. : Recovery of Collagen Hydrolysate from Chrome Leather Shaving Tannery Waste through Two-Step Hydrolysis Using Magnesium Oxide and Bating Enzyme Hydrolysis Dechroming of Chrome Shaving Tannery Waste. Journal of the Society of Leather Technologists and Chemists. 2019; 103 (02): 80–84. Reference Source 127. Bizzi C, Zanatta RC, Santos D, et al. : Ultrasound-Assisted Extraction of Chromium from Residual Tanned Leather: An Innovative Strategy for the Reuse of Waste in Tanning Industry. Ultrason. Sonochem. 2020; 64 : 104682. PubMed Abstract | Publisher Full Text 128. Pedrotti M, Santos D, Cauduro V, et al. : Ultrasound-Assisted Extraction of Chromium from Tanned Leather Shavings: A Promising Continuous Flow Technology for the Treatment of Solid Waste. Ultra Ultrasonics Sonochemistry. 2022; 89 : 106124. PubMed Abstract | Publisher Full Text | Free Full Text 129. Popiolski A, Dallago R, Steffens J, et al. : Ultrasound-Assisted Extraction of Cr from Residual Tannery Leather: Feasibility of Ethylenediaminetetraacetic Acid as the Extraction Solution. ACS Omega. 2018; 3 : 16074–16080. PubMed Abstract | Publisher Full Text | Free Full Text 130. Negash T, Emiru A, Amare D, et al. : Production and Characterization of Glue from Tannery Hide Trimming Waste. Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering LNICST. 2020; 308 : 59–70. Publisher Full Text 131. Zhang Y, Chen Z, Liu X, et al. : SEM, FTIR and DSC Investigation of Collagen Hydrolysate Treated Degraded Leather. J. Cult. Herit. 2021; 48 : 205–210. Publisher Full Text 132. Mosleh Y, Van Die M, Gard W, et al. : Gelatine Adhesives from Mammalian and Fish Origins for Historical Art Objects Conservation: How Do Microstructural Features Determine Physical and Mechanical Properties? J. Cult. Herit. 2023; 63 : 52–60. Publisher Full Text 133. Du J, Zhu Z, Yang J, et al. : A comparative study on the extraction effects of common agents on collagen-based binders in mural paintings. Herit. Sci. 2021; 9 (1): 45. Publisher Full Text 134. Dai C, Li C: Characterization of Two Kinds of Animal Glues Used for the Restoration of Murals. Sciences of Conservation and Archaeology. 2022; 34 : 101–107. Publisher Full Text 135. European Parliament Parliamentary Question: Mandatory E1 Standard in Europe. E-004321/2017. European Parliament; (accessed on 1 August 2024). Reference Source 136. European Chemicals Agency Substance Obligatory Regulations: Formaldehyde. (accessed on 1 August 2024). Reference Source 137. Langmaier F, Šivarová J, Mládek M, et al. : Curing Adhesives of Urea-Formaldehyde Type with Collagen Hydrolysates of Chrome-Tanned Leather Waste. J. Therm. Anal. Calorim. 2004; 75 : 205–19. Publisher Full Text 138. Langmaier F, Šivarová J, Kolomazník K, et al. : Curing of Urea-Formaldehyde Adhesives with Collagen Type Hydrolysates under Acid Condition. J. Therm. Anal. Calorim. 2004; 76 : 1015–1023. Publisher Full Text 139. Langmaier F, Kolomazník K, Mládek M, et al. : Curing Urea–Formaldehyde Adhesives with Hydrolysates of Chrome-Tanned Leather Waste from Leather Production. Int. J. Adhes. Adhes. 2005; 25 : 101–108. Publisher Full Text 140. Matyšovskỳ J, Jurkovič P, Duchovič P, et al. : Collagen Modified Hardener for Melamine-Formaldehyde Adhesive for Increasing Water Resistance of Plywood. In Current State of the Art on Novel Materials. Balkose, D., Horak, D., Soltes, L., CRC Press and Taylor Francis Group: Boca Raton, FL, USA. Key Eng. Mater. 2014; 1 (2): 7–14. Publisher Full Text 141. Sedlicik J, Matyasovsky J, Smidriakova M, et al. : Application of Collagen Extracted from Chrome Shavings for Innovative Polycondensation Adhesives. J. Am. Leather Chem. Assoc. 2011; 106 (11): 332–340. (accessed on 21 April 2024). Reference Source 142. Islam N, Liza A, Khatun M, et al. : Formulation and Characterization of Formaldehyde-Free Chemically Modified Bone-Based Adhesive for Lignocellulosic Composite Products. Global Chall. 2021; 5 : 2100002. PubMed Abstract | Publisher Full Text | Free Full Text 143. Wang X, Zhu J, Liu X, et al. : Novel Gelatin-Based Eco-Friendly Adhesive with a Hyperbranched Cross-Linked Structure. Ind. Eng. Chem. Res. 2020; 59 : 5500–5511. Publisher Full Text 144. Yang M, Li Y, Dang X: An Eco-Friendly Wood Adhesive Based on Waterborne Polyurethane Grafted with Gelatin Derived from Chromium Shavings Waste. Environ. Res. 2022; 206 : 112266. PubMed Abstract | Publisher Full Text 145. Luque GC, Stürtz R, Passeggi MCG, et al. : New Hybrid Acrylic/Collagen Nanocomposites and Their Potential Use as Bio-Adhesives. Int. J. Adhes. Adhes. 2020; 100 : 102624. Publisher Full Text 146. Liu D, Zhang J, You C, et al. : Study on the Anhydrous Condensation of Collagen Polypeptide and Tricyanogen Chloride. RSC Adv. 2022; 12 : 20403–20411. PubMed Abstract | Publisher Full Text | Free Full Text 147. Zhou J, Xu T, Wang X, et al. : A Low-Cost and Water Resistant Biomass Adhesive Derived from the Hydrolysate of Leather Waste. RSC Adv. 2017; 7 : 4024–4029. Publisher Full Text 148. Gebremariam E, Malede Y, Prabhu S, et al. : Development of Bio-Based Adhesive Using Tannery Shaving Dust: Process Optimization Using Statistical and Artificial Intelligence Techniques. Bioresource Technology Reports. 2023; 22 : 101413. Publisher Full Text 149. Wang X, Zhao W, Dang X, et al. : Bio-Inspired Gelatin-Based Adhesive Modified with Waterborne Polyurethane on Click Chemistry. J. Renew. Mater. 2022; 10 : 2443–2457. Publisher Full Text 150. Fact.MR: Hydrolyzed Collagen Market Size, Share & Trends 2032. (accessed on 10 April 2024). Reference Source 151. Cruz Bosques JA, Ibarra Sánchez JJ, Mendoza-Novelo B, et al. : Profitability of chemically cross-linked collagen scaffold production using bovine pericardium: revaluing waste from the meat industry for biomedical applications. Polym. 2023; 15 (13): 2797. Publisher Full Text 152. OEC - The Observatory of Economic Complexity. Gelatina y Derivados, ISINGLASS, PLACES (ANIMAL) NES. (accessed on 10 April 2024). Reference Source 153. OEC - The Observatory of Economic Complexity Dextrins, Gelatins and Glues. (accessed on 10 April 2024). Reference Source 154. Cabeza L, McAloon A, Yee W, et al. : Process Simulation and Cost Estimation of Treatment of Chromium-Containing Leather Waste. J. Am. Leather Chem. Assoc. 1998; 98 : 299–315. 155. Cabeza L, Taylor M, Dimaio G, et al. : Processing of Leather Waste: Pilot Scale Studies on Chrome Shavings. Isolation of Potentially Valuable Protein Products and Chromium. Waste Manag. 1998; 18 : 211–218. Publisher Full Text 156. InterMESH Ltda: Animal Glue - Jelly Glue Latest Price, Manufacturers & Suppliers. (accessed on 21 April 2024). Reference Source 157. Li Y, Guo R, Lu W, et al. : Research progress on resource utilization of leather solid waste. J. Leather Sci. Eng. 2019; 1 :6. Publisher Full Text 158. OEC.World: Observatory of Economic Complexity. Glues; (accessed on 21 April 2024). Reference Source 159. Zhihua S, Mao Y, Yuzeng W, et al. : CN106753159B-Degradable Collagen-Polyurethane Water-Based Wood Adhesive and Preparation Method Thereof.2016. Reference Source 160. Fenglang L: CN106800907A-A Kind of Environment-Friendly Water-Based Wood Adhesive Based on Degraded Collagen Solution and Preparation Method Thereof.2016. Reference Source 161. Shan Z, Yang M, Wang Y, et al. : CN106753159A-One kind degraded polyurethane aqueous wood adhesive of collagen and preparation method thereof 2016. Reference Source 162. Quanjie W, Lijie H, Baorong D, et al. : CN109554153A -A Kind of Preparation Method and Application of Collagen Base Adhesive.2018. Reference Source 163. Mao Y, Chun LY, Jun GR, et al. : CN110256651A-A Kind of Preparation Method of Collagen-Base Papermaking Function Sizing Agent.2019. Reference Source 164. Xiaoqun S, Hua YW, Wensheng C, et al. : CN111704879A-Air-Permeable Leather Adhesive and Preparation Method Thereof.2020. Reference Source 165. Fenglang L: CN106800907-A Kind of Environment-Friendly Water-Based Wood Adhesive Based on Degraded Collagen Solution and Preparation Method Thereof.2016. Reference Source 166. Jie WQ, Jie HL, Baorong D, et al. : CN109554153A-A Kind of Preparation Method and Application of Collagen Base Adhesive.2018. Reference Source 167. Chuan WX, Xiaoli H, Taotao Q: CN103669109B-A Kind of Preparation Method of Glue Used in Paper-Making.2013. Reference Source 168. Tanaka F: Comparative Study on the Models of Thermoreversible Gelation. Int. J. Mol. Sci. 2022; 23 . PubMed Abstract | Publisher Full Text | Free Full Text 169. Alipal J, Mohd Pu’ad NAS, Lee NHMN, et al. : A review of gelatin: Properties, sources, process, applications, and commercialisation. Mater. Today. Proc. 2021; 42 : 240–250. Publisher Full Text 170. Pang H, Zhao S, Wang Z, et al. : Development of soy protein-based adhesive with high water resistance and bonding strength by waterborne epoxy crosslinking strategy. Int. J. Adhes. Adhes. 2020: 102600. Publisher Full Text 171. Kanagaraj JK, Panda RC, Vinodh Kumar MVK: Trends and Advancements in Sustainable Leather Processing: Future Directions and Challenges—A Review. J. Environ. Chem. Eng. 2020; 8 : 104379. Publisher Full Text 172. Jin T, Huang Y, Yang Y, et al. : Development of boiling water resistance starch-based wood adhesive via Schiff base crosslinking and air oxidation strategy. Colloids Surf. A Physicochem. Eng. Asp. 2024; 134592. Publisher Full Text 173. Hou J, Li C, Guan Y, et al. : Enzymatically crosslinked alginate hydrogels with improved adhesion properties. Polym. Chem. 2015; 6 : 2204–2213. Publisher Full Text 174. Chojnacka K, Skrzypczak D, Mikula K, et al. : Progress in sustainable technologies of leather wastes valorization as solutions for the circular economy. J. Clean. Prod. 2021; 313 : 127902. Publisher Full Text Comments on this article Comments (0) Version 2 VERSION 2 PUBLISHED 14 Oct 2024 ADD YOUR COMMENT Comment Author details Author details 1 Research and Development Directorate, Universidad Técnica de Ambato, Ambato, Tungurahua, Ecuador 2 Facultad de Ciencias, Escuela Superior Politecnica de Chimborazo, Riobamba, Chimborazo Province, Chimborazo, Ecuador 3 Food and Biotechnology, Universidad Técnica de Ambato, Ambato, Tungurahua, Ecuador Nelly Esther Flores Tapia Roles: Conceptualization, Formal Analysis, Investigation, Supervision, Writing – Original Draft Preparation, Writing – Review & Editing Hannibal Brito Moina Roles: Conceptualization, Investigation, Methodology, Writing – Original Draft Preparation, Writing – Review & Editing Rodny Peñafiel Roles: Formal Analysis, Investigation, Writing – Original Draft Preparation, Writing – Review & Editing Lander Vinicio Pérez Aldás Roles: Conceptualization, Investigation, Methodology, Writing – Original Draft Preparation, Writing – Review & Editing Competing interests No competing interests were disclosed. Grant information This research was funded by the RESEARCH AND DEVELOPMENT DIRECTORATE and TECHNICAL UNIVERSITY OF AMBATO to support the Investigation. Project Sustainable Polymeric Composites from Agro-Industrial and Wet-Blue Leather Waste for Ecological Applications. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Article Versions (2) version 2 Revised Published: 30 Jul 2025, 13:1228 https://doi.org/10.12688/f1000research.155450.2 version 1 Published: 14 Oct 2024, 13:1228 https://doi.org/10.12688/f1000research.155450.1 Copyright © 2025 Flores Tapia NE et al . This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Download Export To Sciwheel Bibtex EndNote ProCite Ref. Manager (RIS) Sente metrics Views Downloads F1000Research - - PubMed Central info_outline Data from PMC are received and updated monthly. - - Citations open_in_new 0 open_in_new 0 open_in_new SEE MORE DETAILS CITE how to cite this article Flores Tapia NE, Brito Moina H, Peñafiel R and Pérez Aldás LV. Recycling of collagen from solid tannery waste and prospective utilization as adhesives. [version 2; peer review: 1 approved, 3 approved with reservations] . F1000Research 2025, 13 :1228 ( https://doi.org/10.12688/f1000research.155450.2 ) NOTE: If applicable, it is important to ensure the information in square brackets after the title is included in all citations of this article. COPY CITATION DETAILS track receive updates on this article Track an article to receive email alerts on any updates to this article. TRACK THIS ARTICLE Share Open Peer Review Current Reviewer Status: ? Key to Reviewer Statuses VIEW HIDE Approved The paper is scientifically sound in its current form and only minor, if any, improvements are suggested Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit. Not approved Fundamental flaws in the paper seriously undermine the findings and conclusions Version 2 VERSION 2 PUBLISHED 30 Jul 2025 Revised Views 0 Cite How to cite this report: Hylli M. Reviewer Report For: Recycling of collagen from solid tannery waste and prospective utilization as adhesives. [version 2; peer review: 1 approved, 3 approved with reservations] . F1000Research 2025, 13 :1228 ( https://doi.org/10.5256/f1000research.179579.r453122 ) The direct URL for this report is: https://f1000research.com/articles/13-1228/v2#referee-response-453122 NOTE: it is important to ensure the information in square brackets after the title is included in this citation. Close Copy Citation Details Reviewer Report 14 Feb 2026 Majlinda Hylli , Polytechnic University of Tirana, Tirana, Albania Approved VIEWS 0 https://doi.org/10.5256/f1000research.179579.r453122 The manuscript “Recycling of collagen from solid tannery waste and prospective utilization as adhesives” provides a detailed review of the extraction of collagen from tannery leather waste, its modification and applications, and its relevance to collagen-based adhesives. Instead of focusing ... Continue reading READ ALL The manuscript “Recycling of collagen from solid tannery waste and prospective utilization as adhesives” provides a detailed review of the extraction of collagen from tannery leather waste, its modification and applications, and its relevance to collagen-based adhesives. Instead of focusing on a single methodological or conceptual perspective, the discussion incorporates a wide range of recent studies from materials science, environmental engineering, and industrial chemistry. Most factual statements throughout the manuscript are supported by appropriate and credible references, reflecting through engagement with existing literature. The discussion of collagen recovery methods, dechroming strategies, and adhesive formulation, in particular, benefits from well-cited experimental and review studies. The manuscript also demonstrates an alignment with the principles of the circular economy and sustainability goals. The manuscript addresses environmental concerns by exploring the recycling of collagen from solid tannery waste. It highlights the potential use of recovered collagen as an eco-friendly adhesive, which could help to reduce waste and encourage the development of sustainable resources. All the revisions have improved the quality and readability of the manuscript. However, several aspects could be further improved. It would be helpful to indicate whether the references supporting certain numerical data, such as market forecasts, estimated production costs, and the reported performance standards of collagen-based adhesives are recent, authoritative, and directly aligned with the statements made. Are the cited sources up to date and still valid under current market and technological conditions? Do the numerical values remain consistent with the original publications, and have they been verified against the most recent available data? Clarifying these points would significantly strengthen the scientific credibility and reliability of the manuscript. Overall, the manuscript is a valuable contribution to the field. It has considerable potential to become a valuable resource for researchers and industry professionals focused on the sustainable valorization of tannery waste. So, I approved with minor corrections regarding the questions. Is the topic of the review discussed comprehensively in the context of the current literature? Yes Are all factual statements correct and adequately supported by citations? Partly Is the review written in accessible language? Yes Are the conclusions drawn appropriate in the context of the current research literature? Yes Competing Interests: No competing interests were disclosed. Reviewer Expertise: Leather I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard. Close READ LESS CITE CITE HOW TO CITE THIS REPORT Hylli M. Reviewer Report For: Recycling of collagen from solid tannery waste and prospective utilization as adhesives. [version 2; peer review: 1 approved, 3 approved with reservations] . F1000Research 2025, 13 :1228 ( https://doi.org/10.5256/f1000research.179579.r453122 ) The direct URL for this report is: https://f1000research.com/articles/13-1228/v2#referee-response-453122 NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article. COPY CITATION DETAILS Report a concern Respond or Comment COMMENT ON THIS REPORT Views 0 Cite How to cite this report: Gargano M. Reviewer Report For: Recycling of collagen from solid tannery waste and prospective utilization as adhesives. [version 2; peer review: 1 approved, 3 approved with reservations] . F1000Research 2025, 13 :1228 ( https://doi.org/10.5256/f1000research.179579.r433443 ) The direct URL for this report is: https://f1000research.com/articles/13-1228/v2#referee-response-433443 NOTE: it is important to ensure the information in square brackets after the title is included in this citation. Close Copy Citation Details Reviewer Report 24 Dec 2025 Marika Gargano , University of Naples Federico II, Naples, Italy Approved with Reservations VIEWS 0 https://doi.org/10.5256/f1000research.179579.r433443 The manuscript Recycling of collagen from solid tannery waste and prospective utilization as adhesives aims to provide a systematic review of the literature concerning the use of recycled collagen derived from solid waste produced by the leather industry as adhesives. The ... Continue reading READ ALL The manuscript Recycling of collagen from solid tannery waste and prospective utilization as adhesives aims to provide a systematic review of the literature concerning the use of recycled collagen derived from solid waste produced by the leather industry as adhesives. The manuscript properly addresses current concerns related to circular economy approaches to waste management and is structured in a comprehensive manner, covering the present status of the leather industry, the use of synthetic and bio-based adhesives, methods for collagen extraction, and its chemical modification for application purposes. The study is well organized and aligns with the scope of the journal. The revisions made by the authors have improved the overall quality and readability of the manuscript. Although the abstract and introduction are clear, the Discussion section still requires improvement. Therefore, I recommend acceptance after some revisions, as outlined below: The section “Collagen: The protein-based adhesive” briefly mentions collagen types but requires further elaboration. The authors should clarify which types of collagen are typically found in which kinds of waste. Moreover, the statement “The best glues contain collagen Type I…” needs better contextualization. Table 1 should be revised: In several rows, advantages and disadvantages are not clearly defined (e.g., in row 6, “Collagen type I” appears under disadvantages, although it is previously described as component of best glues). The data reported in column 3 should be defined and/or made consistent across entries (indicate which are the differences between “yield”, “mass yield”, “mass recovery”, “recovery” and so on). Table 2 lacks clarity and currently only presents literature data without providing a critical assessment. A more analytical discussion of the reported findings would be beneficial. Is the topic of the review discussed comprehensively in the context of the current literature? Yes Are all factual statements correct and adequately supported by citations? Partly Is the review written in accessible language? Partly Are the conclusions drawn appropriate in the context of the current research literature? Yes Competing Interests: No competing interests were disclosed. Reviewer Expertise: Leather I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. Close READ LESS CITE CITE HOW TO CITE THIS REPORT Gargano M. Reviewer Report For: Recycling of collagen from solid tannery waste and prospective utilization as adhesives. [version 2; peer review: 1 approved, 3 approved with reservations] . F1000Research 2025, 13 :1228 ( https://doi.org/10.5256/f1000research.179579.r433443 ) The direct URL for this report is: https://f1000research.com/articles/13-1228/v2#referee-response-433443 NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article. COPY CITATION DETAILS Report a concern Respond or Comment COMMENT ON THIS REPORT Version 1 VERSION 1 PUBLISHED 14 Oct 2024 Views 0 Cite How to cite this report: Mondschein A. Reviewer Report For: Recycling of collagen from solid tannery waste and prospective utilization as adhesives. [version 2; peer review: 1 approved, 3 approved with reservations] . F1000Research 2025, 13 :1228 ( https://doi.org/10.5256/f1000research.170636.r359783 ) The direct URL for this report is: https://f1000research.com/articles/13-1228/v1#referee-response-359783 NOTE: it is important to ensure the information in square brackets after the title is included in this citation. Close Copy Citation Details Reviewer Report 29 Jan 2025 Anke Mondschein , FILK Freiberg Institute gGmbH, Freiberg, Saxony, Germany Approved with Reservations VIEWS 0 https://doi.org/10.5256/f1000research.170636.r359783 I fully agree with the issues raised by the first reviewer Ali Yorgancioglu from Ege Üniversitesi, Bornova, Turkey. The topic of the review is very important, but the paper has its scientific limitations. I will not repeat here the topics ... Continue reading READ ALL I fully agree with the issues raised by the first reviewer Ali Yorgancioglu from Ege Üniversitesi, Bornova, Turkey. The topic of the review is very important, but the paper has its scientific limitations. I will not repeat here the topics that have already been addressed and precisely outlined by reviewer 1. Additional topics are: Literature source missing for the statement that Typ I Col is the best Col type for glueing (p. 7) The intended uses of adhesives, technical and medical, should not be mixed and should be clearly separated, ideally with their respective specific challenges for the use of collagen or gelatine as an adhesive. If possible, the market data should also refer to these two very different applications. Practical data is lacking, especially for the technical application. Gelatine as an adhesive is already used industrially. It would be instructive to discuss where the actual limits to increased use are (price?, properties?, and how the respective deficits can be overcome) Captions should be more precise (e.g. Fig. 4: Explain a - d) Is the topic of the review discussed comprehensively in the context of the current literature? Partly Are all factual statements correct and adequately supported by citations? Partly Is the review written in accessible language? Partly Are the conclusions drawn appropriate in the context of the current research literature? Partly Competing Interests: No competing interests were disclosed. Reviewer Expertise: Leather I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. Close READ LESS CITE CITE HOW TO CITE THIS REPORT Mondschein A. Reviewer Report For: Recycling of collagen from solid tannery waste and prospective utilization as adhesives. [version 2; peer review: 1 approved, 3 approved with reservations] . F1000Research 2025, 13 :1228 ( https://doi.org/10.5256/f1000research.170636.r359783 ) The direct URL for this report is: https://f1000research.com/articles/13-1228/v1#referee-response-359783 NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article. COPY CITATION DETAILS Report a concern Author Response 09 Aug 2025 Nelly Flores , Research and Development Directorate, Technical University of Ambato, Ambato, Ecuador 09 Aug 2025 Author Response Reviewer Comment 1: Literature source missing for the statement that Type I collagen is the best collagen type for gluing (p.7). Response: Thank you for highlighting this. We have ... Continue reading Reviewer Comment 1: Literature source missing for the statement that Type I collagen is the best collagen type for gluing (p.7). Response: Thank you for highlighting this. We have now added a citation supporting the statement that Type I collagen exhibits superior adhesive properties. Reviewer Comment 2: The intended uses of adhesives, technical and medical, should not be mixed and should be clearly separated, ideally with their respective specific challenges for the use of collagen or gelatine as an adhesive. If possible, the market data should also refer to these two very different applications. Response: We agree that distinguishing technical and medical applications improves clarity. In the revised manuscript, we have reorganized the text to create distinct subsections addressing: Technical and industrial uses (e.g., wood bonding, paper, packaging) Medical applications (e.g., tissue sealants, wound dressings) Each subsection now describes the unique performance requirements, regulatory considerations, and market dynamics relevant to that sector. Additionally, references to market data, where available, have been aligned with these categories. We have also removed some examples of medical adhesives that were not directly relevant to recycled collagen, as noted in our prior response. Reviewer Comment 3: Practical data is lacking, especially for the technical application. Gelatine as an adhesive is already used industrially. It would be instructive to discuss where the actual limits to increased use are (price?, properties?, and how the respective deficits can be overcome). Response: We appreciate this important observation. In the revised discussion section, we have incorporated a dedicated paragraph elaborating on the limitations of gelatin adhesives in industrial use: Their thermoreversible behavior (dissolution above ~35–40 °C) Susceptibility to moisture and biodegradation Generally lower mechanical strength compared to synthetic resins We also discuss price considerations, noting that while gelatin is relatively inexpensive as a byproduct, higher-purity high-bloom gelatin increases costs. Finally, we outline research strategies reported in recent literature for overcoming these deficits, including hydrophobic polymer blending, enzymatic crosslinking, and nanofiller reinforcement (as summarized in Table 2). We believe this provides a more practical perspective on the barriers to wider adoption and possible solutions. Reviewer Comment 4: Captions should be more precise (e.g., Fig. 4: Explain a–d). Response: We have revised the caption of Figure 4 to provide explicit descriptions of parts a–d, clarifying the content and purpose of each subfigure. The updated caption now reads: Figure 4. Schematic representation of collagen Types I-V in humans and Bos Taurus. a) Type I human collagen is predominantly found in the skin, bone, teeth, tendons, ligaments, vascular ligature, and various organs; b) Type IV collagen is present in the epithelial-secreted layer of the basement membrane as well as the basal lamina Reviewer Comment 1: Literature source missing for the statement that Type I collagen is the best collagen type for gluing (p.7). Response: Thank you for highlighting this. We have now added a citation supporting the statement that Type I collagen exhibits superior adhesive properties. Reviewer Comment 2: The intended uses of adhesives, technical and medical, should not be mixed and should be clearly separated, ideally with their respective specific challenges for the use of collagen or gelatine as an adhesive. If possible, the market data should also refer to these two very different applications. Response: We agree that distinguishing technical and medical applications improves clarity. In the revised manuscript, we have reorganized the text to create distinct subsections addressing: Technical and industrial uses (e.g., wood bonding, paper, packaging) Medical applications (e.g., tissue sealants, wound dressings) Each subsection now describes the unique performance requirements, regulatory considerations, and market dynamics relevant to that sector. Additionally, references to market data, where available, have been aligned with these categories. We have also removed some examples of medical adhesives that were not directly relevant to recycled collagen, as noted in our prior response. Reviewer Comment 3: Practical data is lacking, especially for the technical application. Gelatine as an adhesive is already used industrially. It would be instructive to discuss where the actual limits to increased use are (price?, properties?, and how the respective deficits can be overcome). Response: We appreciate this important observation. In the revised discussion section, we have incorporated a dedicated paragraph elaborating on the limitations of gelatin adhesives in industrial use: Their thermoreversible behavior (dissolution above ~35–40 °C) Susceptibility to moisture and biodegradation Generally lower mechanical strength compared to synthetic resins We also discuss price considerations, noting that while gelatin is relatively inexpensive as a byproduct, higher-purity high-bloom gelatin increases costs. Finally, we outline research strategies reported in recent literature for overcoming these deficits, including hydrophobic polymer blending, enzymatic crosslinking, and nanofiller reinforcement (as summarized in Table 2). We believe this provides a more practical perspective on the barriers to wider adoption and possible solutions. Reviewer Comment 4: Captions should be more precise (e.g., Fig. 4: Explain a–d). Response: We have revised the caption of Figure 4 to provide explicit descriptions of parts a–d, clarifying the content and purpose of each subfigure. The updated caption now reads: Figure 4. Schematic representation of collagen Types I-V in humans and Bos Taurus. a) Type I human collagen is predominantly found in the skin, bone, teeth, tendons, ligaments, vascular ligature, and various organs; b) Type IV collagen is present in the epithelial-secreted layer of the basement membrane as well as the basal lamina Competing Interests: The authors declare that there are no competing interests. Close Report a concern Respond or Comment COMMENTS ON THIS REPORT Author Response 09 Aug 2025 Nelly Flores , Research and Development Directorate, Technical University of Ambato, Ambato, Ecuador 09 Aug 2025 Author Response Reviewer Comment 1: Literature source missing for the statement that Type I collagen is the best collagen type for gluing (p.7). Response: Thank you for highlighting this. We have ... Continue reading Reviewer Comment 1: Literature source missing for the statement that Type I collagen is the best collagen type for gluing (p.7). Response: Thank you for highlighting this. We have now added a citation supporting the statement that Type I collagen exhibits superior adhesive properties. Reviewer Comment 2: The intended uses of adhesives, technical and medical, should not be mixed and should be clearly separated, ideally with their respective specific challenges for the use of collagen or gelatine as an adhesive. If possible, the market data should also refer to these two very different applications. Response: We agree that distinguishing technical and medical applications improves clarity. In the revised manuscript, we have reorganized the text to create distinct subsections addressing: Technical and industrial uses (e.g., wood bonding, paper, packaging) Medical applications (e.g., tissue sealants, wound dressings) Each subsection now describes the unique performance requirements, regulatory considerations, and market dynamics relevant to that sector. Additionally, references to market data, where available, have been aligned with these categories. We have also removed some examples of medical adhesives that were not directly relevant to recycled collagen, as noted in our prior response. Reviewer Comment 3: Practical data is lacking, especially for the technical application. Gelatine as an adhesive is already used industrially. It would be instructive to discuss where the actual limits to increased use are (price?, properties?, and how the respective deficits can be overcome). Response: We appreciate this important observation. In the revised discussion section, we have incorporated a dedicated paragraph elaborating on the limitations of gelatin adhesives in industrial use: Their thermoreversible behavior (dissolution above ~35–40 °C) Susceptibility to moisture and biodegradation Generally lower mechanical strength compared to synthetic resins We also discuss price considerations, noting that while gelatin is relatively inexpensive as a byproduct, higher-purity high-bloom gelatin increases costs. Finally, we outline research strategies reported in recent literature for overcoming these deficits, including hydrophobic polymer blending, enzymatic crosslinking, and nanofiller reinforcement (as summarized in Table 2). We believe this provides a more practical perspective on the barriers to wider adoption and possible solutions. Reviewer Comment 4: Captions should be more precise (e.g., Fig. 4: Explain a–d). Response: We have revised the caption of Figure 4 to provide explicit descriptions of parts a–d, clarifying the content and purpose of each subfigure. The updated caption now reads: Figure 4. Schematic representation of collagen Types I-V in humans and Bos Taurus. a) Type I human collagen is predominantly found in the skin, bone, teeth, tendons, ligaments, vascular ligature, and various organs; b) Type IV collagen is present in the epithelial-secreted layer of the basement membrane as well as the basal lamina Reviewer Comment 1: Literature source missing for the statement that Type I collagen is the best collagen type for gluing (p.7). Response: Thank you for highlighting this. We have now added a citation supporting the statement that Type I collagen exhibits superior adhesive properties. Reviewer Comment 2: The intended uses of adhesives, technical and medical, should not be mixed and should be clearly separated, ideally with their respective specific challenges for the use of collagen or gelatine as an adhesive. If possible, the market data should also refer to these two very different applications. Response: We agree that distinguishing technical and medical applications improves clarity. In the revised manuscript, we have reorganized the text to create distinct subsections addressing: Technical and industrial uses (e.g., wood bonding, paper, packaging) Medical applications (e.g., tissue sealants, wound dressings) Each subsection now describes the unique performance requirements, regulatory considerations, and market dynamics relevant to that sector. Additionally, references to market data, where available, have been aligned with these categories. We have also removed some examples of medical adhesives that were not directly relevant to recycled collagen, as noted in our prior response. Reviewer Comment 3: Practical data is lacking, especially for the technical application. Gelatine as an adhesive is already used industrially. It would be instructive to discuss where the actual limits to increased use are (price?, properties?, and how the respective deficits can be overcome). Response: We appreciate this important observation. In the revised discussion section, we have incorporated a dedicated paragraph elaborating on the limitations of gelatin adhesives in industrial use: Their thermoreversible behavior (dissolution above ~35–40 °C) Susceptibility to moisture and biodegradation Generally lower mechanical strength compared to synthetic resins We also discuss price considerations, noting that while gelatin is relatively inexpensive as a byproduct, higher-purity high-bloom gelatin increases costs. Finally, we outline research strategies reported in recent literature for overcoming these deficits, including hydrophobic polymer blending, enzymatic crosslinking, and nanofiller reinforcement (as summarized in Table 2). We believe this provides a more practical perspective on the barriers to wider adoption and possible solutions. Reviewer Comment 4: Captions should be more precise (e.g., Fig. 4: Explain a–d). Response: We have revised the caption of Figure 4 to provide explicit descriptions of parts a–d, clarifying the content and purpose of each subfigure. The updated caption now reads: Figure 4. Schematic representation of collagen Types I-V in humans and Bos Taurus. a) Type I human collagen is predominantly found in the skin, bone, teeth, tendons, ligaments, vascular ligature, and various organs; b) Type IV collagen is present in the epithelial-secreted layer of the basement membrane as well as the basal lamina Competing Interests: The authors declare that there are no competing interests. Close Report a concern COMMENT ON THIS REPORT Views 0 Cite How to cite this report: Yorgancioglu A. Reviewer Report For: Recycling of collagen from solid tannery waste and prospective utilization as adhesives. [version 2; peer review: 1 approved, 3 approved with reservations] . F1000Research 2025, 13 :1228 ( https://doi.org/10.5256/f1000research.170636.r336497 ) The direct URL for this report is: https://f1000research.com/articles/13-1228/v1#referee-response-336497 NOTE: it is important to ensure the information in square brackets after the title is included in this citation. Close Copy Citation Details Reviewer Report 14 Nov 2024 Ali Yorgancioglu , Ege Üniversitesi, Bornova, Turkey Approved with Reservations VIEWS 0 https://doi.org/10.5256/f1000research.170636.r336497 The manuscript titled as ‘‘ "Recycling of collagen from solid tannery waste and prospective utilization as adhesives" for F1000Research ” was reviewed. I have evaluated the paper in light of the F1000Research scope. The submission was made as Review Paper. ... Continue reading READ ALL The manuscript titled as ‘‘ "Recycling of collagen from solid tannery waste and prospective utilization as adhesives" for F1000Research ” was reviewed. I have evaluated the paper in light of the F1000Research scope. The submission was made as Review Paper. The manuscript discusses the extraction and application of collagen from solid tannery waste as an adhesive. This topic aligns well with current sustainability objectives, particularly within the leather industry. The authors provide a comprehensive review of collagen extraction methods, adhesive formulation, and potential applications, supported by recent advancements in the field. However, while the paper is informative, it faces several scientific and structural limitations. Key aspects require refinement to ensure clarity and to meet the publication standards of F1000Research. The study addresses an important topic in the circular economy and sustainable waste management. Converting tannery waste into adhesives could reduce landfill waste and minimize reliance on petroleum-based adhesives. This aligns with the increasing need for sustainable materials and methods in various industrial applications. While the study is comprehensive in discussing various collagen extraction and adhesive production techniques, it lacks specific experimental data or case studies to support some of its claims. The paper would benefit from quantitative data that compares the performance of collagen-based adhesives with traditional adhesives in specific applications. The authors briefly mention the limitations of collagen adhesives, particularly in water resistance and durability. However, more detailed discussion and proposed solutions for overcoming these limitations are necessary to make the paper more practical and applicable to real-world scenarios. The manuscript is structured logically, yet certain sections (e.g., Background, Methods) could be more concise. In some parts, especially the discussion on different adhesive applications, the information appears repetitive. A clearer distinction between current findings and future directions could improve readability. Moreover, methods section should be removed. Review papers rarely include a method section since they do not report on original research. Author needs to send this manuscript for English proofread as I found some grammatical errors while reviewing the article. In the Abstract: "This research systematically reviews the methods and applications of collagen extraction, highlighting the material’s versatility and environmental benefits when used as a bio-adhesive." The phrase “when used as a bio-adhesive” could be simplified to “as a bio-adhesive.” In the Methods: "Only documents in English," which should be “Only English-language documents were included.” Further editing for grammatical accuracy and flow would enhance the manuscript’s clarity and professionalism. After these revision, the paper can be considered publication Is the topic of the review discussed comprehensively in the context of the current literature? Partly Are all factual statements correct and adequately supported by citations? Partly Is the review written in accessible language? Partly Are the conclusions drawn appropriate in the context of the current research literature? Partly Competing Interests: No competing interests were disclosed. Reviewer Expertise: Leather I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. Close READ LESS CITE CITE HOW TO CITE THIS REPORT Yorgancioglu A. Reviewer Report For: Recycling of collagen from solid tannery waste and prospective utilization as adhesives. [version 2; peer review: 1 approved, 3 approved with reservations] . F1000Research 2025, 13 :1228 ( https://doi.org/10.5256/f1000research.170636.r336497 ) The direct URL for this report is: https://f1000research.com/articles/13-1228/v1#referee-response-336497 NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article. COPY CITATION DETAILS Report a concern Author Response 09 Aug 2025 Nelly Flores , Research and Development Directorate, Technical University of Ambato, Ambato, Ecuador 09 Aug 2025 Author Response Reviewer 1 Comment: While the study is comprehensive in discussing various collagen extraction and adhesive production techniques, it lacks specific experimental data or case studies to support some of its ... Continue reading Reviewer 1 Comment: While the study is comprehensive in discussing various collagen extraction and adhesive production techniques, it lacks specific experimental data or case studies to support some of its claims. The paper would benefit from quantitative data that compares the performance of collagen-based adhesives with traditional adhesives in specific applications. Response: We fully agree that quantitative comparisons strengthen the discussion. To address this, we incorporated Table 2 , which provides detailed physicochemical and mechanical properties of a broad range of collagen-derived adhesives and compares them with standard synthetic adhesives and relevant benchmarks. This addition allows readers to see clear performance differences across formulations and applications. Comment: The authors briefly mention the limitations of collagen adhesives, particularly in water resistance and durability. However, more detailed discussion and proposed solutions for overcoming these limitations are necessary to make the paper more practical and applicable to real-world scenarios. Response: We have expanded the discussion substantially. In the revised manuscript, we now present strategies to overcome water sensitivity and limited durability, including: Incorporation of hydrophobic additives and synthetic polymers Chemical and enzymatic crosslinking techniques. This added section outlines both current approaches and future directions to make collagen adhesives more competitive with conventional resins. Comment: The manuscript is structured logically, yet certain sections (e.g., Background, Methods) could be more concise. In some parts, especially the discussion on different adhesive applications, the information appears repetitive. A clearer distinction between current findings and future directions could improve readability. Moreover, methods section should be removed. Review papers rarely include a method section since they do not report on original research. Response: We appreciate this suggestion. The Methods section has been removed , and we restructured the discussion to: Consolidate repetitive content about adhesive properties Group similar formulations under thematic categories (e.g., urea-formaldehyde, acrylic-collagen) Add summary statements distinguishing current evidence and prospective research These changes improve conciseness and flow. Comment: Author needs to send this manuscript for English proofread as I found some grammatical errors while reviewing the article. Response: We have carefully proofread the entire manuscript to improve grammar, consistency, and style. Specific examples highlighted (e.g., “when used as a bio-adhesive”) were corrected as suggested. For example: The Abstract was revised to: "...highlighting the material’s versatility and environmental benefits as a bio-adhesive." The Methods phrase was replaced with: “Only English-language documents were included.” Reviewer 1 Comment: While the study is comprehensive in discussing various collagen extraction and adhesive production techniques, it lacks specific experimental data or case studies to support some of its claims. The paper would benefit from quantitative data that compares the performance of collagen-based adhesives with traditional adhesives in specific applications. Response: We fully agree that quantitative comparisons strengthen the discussion. To address this, we incorporated Table 2 , which provides detailed physicochemical and mechanical properties of a broad range of collagen-derived adhesives and compares them with standard synthetic adhesives and relevant benchmarks. This addition allows readers to see clear performance differences across formulations and applications. Comment: The authors briefly mention the limitations of collagen adhesives, particularly in water resistance and durability. However, more detailed discussion and proposed solutions for overcoming these limitations are necessary to make the paper more practical and applicable to real-world scenarios. Response: We have expanded the discussion substantially. In the revised manuscript, we now present strategies to overcome water sensitivity and limited durability, including: Incorporation of hydrophobic additives and synthetic polymers Chemical and enzymatic crosslinking techniques. This added section outlines both current approaches and future directions to make collagen adhesives more competitive with conventional resins. Comment: The manuscript is structured logically, yet certain sections (e.g., Background, Methods) could be more concise. In some parts, especially the discussion on different adhesive applications, the information appears repetitive. A clearer distinction between current findings and future directions could improve readability. Moreover, methods section should be removed. Review papers rarely include a method section since they do not report on original research. Response: We appreciate this suggestion. The Methods section has been removed , and we restructured the discussion to: Consolidate repetitive content about adhesive properties Group similar formulations under thematic categories (e.g., urea-formaldehyde, acrylic-collagen) Add summary statements distinguishing current evidence and prospective research These changes improve conciseness and flow. Comment: Author needs to send this manuscript for English proofread as I found some grammatical errors while reviewing the article. Response: We have carefully proofread the entire manuscript to improve grammar, consistency, and style. Specific examples highlighted (e.g., “when used as a bio-adhesive”) were corrected as suggested. For example: The Abstract was revised to: "...highlighting the material’s versatility and environmental benefits as a bio-adhesive." The Methods phrase was replaced with: “Only English-language documents were included.” Competing Interests: I declare that I have no competing interests that could be construed to influence the objectivity, validity, or importance of this article or its peer review. Close Report a concern Respond or Comment COMMENTS ON THIS REPORT Author Response 09 Aug 2025 Nelly Flores , Research and Development Directorate, Technical University of Ambato, Ambato, Ecuador 09 Aug 2025 Author Response Reviewer 1 Comment: While the study is comprehensive in discussing various collagen extraction and adhesive production techniques, it lacks specific experimental data or case studies to support some of its ... Continue reading Reviewer 1 Comment: While the study is comprehensive in discussing various collagen extraction and adhesive production techniques, it lacks specific experimental data or case studies to support some of its claims. The paper would benefit from quantitative data that compares the performance of collagen-based adhesives with traditional adhesives in specific applications. Response: We fully agree that quantitative comparisons strengthen the discussion. To address this, we incorporated Table 2 , which provides detailed physicochemical and mechanical properties of a broad range of collagen-derived adhesives and compares them with standard synthetic adhesives and relevant benchmarks. This addition allows readers to see clear performance differences across formulations and applications. Comment: The authors briefly mention the limitations of collagen adhesives, particularly in water resistance and durability. However, more detailed discussion and proposed solutions for overcoming these limitations are necessary to make the paper more practical and applicable to real-world scenarios. Response: We have expanded the discussion substantially. In the revised manuscript, we now present strategies to overcome water sensitivity and limited durability, including: Incorporation of hydrophobic additives and synthetic polymers Chemical and enzymatic crosslinking techniques. This added section outlines both current approaches and future directions to make collagen adhesives more competitive with conventional resins. Comment: The manuscript is structured logically, yet certain sections (e.g., Background, Methods) could be more concise. In some parts, especially the discussion on different adhesive applications, the information appears repetitive. A clearer distinction between current findings and future directions could improve readability. Moreover, methods section should be removed. Review papers rarely include a method section since they do not report on original research. Response: We appreciate this suggestion. The Methods section has been removed , and we restructured the discussion to: Consolidate repetitive content about adhesive properties Group similar formulations under thematic categories (e.g., urea-formaldehyde, acrylic-collagen) Add summary statements distinguishing current evidence and prospective research These changes improve conciseness and flow. Comment: Author needs to send this manuscript for English proofread as I found some grammatical errors while reviewing the article. Response: We have carefully proofread the entire manuscript to improve grammar, consistency, and style. Specific examples highlighted (e.g., “when used as a bio-adhesive”) were corrected as suggested. For example: The Abstract was revised to: "...highlighting the material’s versatility and environmental benefits as a bio-adhesive." The Methods phrase was replaced with: “Only English-language documents were included.” Reviewer 1 Comment: While the study is comprehensive in discussing various collagen extraction and adhesive production techniques, it lacks specific experimental data or case studies to support some of its claims. The paper would benefit from quantitative data that compares the performance of collagen-based adhesives with traditional adhesives in specific applications. Response: We fully agree that quantitative comparisons strengthen the discussion. To address this, we incorporated Table 2 , which provides detailed physicochemical and mechanical properties of a broad range of collagen-derived adhesives and compares them with standard synthetic adhesives and relevant benchmarks. This addition allows readers to see clear performance differences across formulations and applications. Comment: The authors briefly mention the limitations of collagen adhesives, particularly in water resistance and durability. However, more detailed discussion and proposed solutions for overcoming these limitations are necessary to make the paper more practical and applicable to real-world scenarios. Response: We have expanded the discussion substantially. In the revised manuscript, we now present strategies to overcome water sensitivity and limited durability, including: Incorporation of hydrophobic additives and synthetic polymers Chemical and enzymatic crosslinking techniques. This added section outlines both current approaches and future directions to make collagen adhesives more competitive with conventional resins. Comment: The manuscript is structured logically, yet certain sections (e.g., Background, Methods) could be more concise. In some parts, especially the discussion on different adhesive applications, the information appears repetitive. A clearer distinction between current findings and future directions could improve readability. Moreover, methods section should be removed. Review papers rarely include a method section since they do not report on original research. Response: We appreciate this suggestion. The Methods section has been removed , and we restructured the discussion to: Consolidate repetitive content about adhesive properties Group similar formulations under thematic categories (e.g., urea-formaldehyde, acrylic-collagen) Add summary statements distinguishing current evidence and prospective research These changes improve conciseness and flow. Comment: Author needs to send this manuscript for English proofread as I found some grammatical errors while reviewing the article. Response: We have carefully proofread the entire manuscript to improve grammar, consistency, and style. Specific examples highlighted (e.g., “when used as a bio-adhesive”) were corrected as suggested. For example: The Abstract was revised to: "...highlighting the material’s versatility and environmental benefits as a bio-adhesive." The Methods phrase was replaced with: “Only English-language documents were included.” Competing Interests: I declare that I have no competing interests that could be construed to influence the objectivity, validity, or importance of this article or its peer review. Close Report a concern COMMENT ON THIS REPORT Comments on this article Comments (0) Version 2 VERSION 2 PUBLISHED 14 Oct 2024 ADD YOUR COMMENT Comment keyboard_arrow_left keyboard_arrow_right Open Peer Review Reviewer Status info_outline Alongside their report, reviewers assign a status to the article: Approved The paper is scientifically sound in its current form and only minor, if any, improvements are suggested Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit. Not approved Fundamental flaws in the paper seriously undermine the findings and conclusions Reviewer Reports Invited Reviewers 1 2 3 4 Version 2 (revision) 30 Jul 25 read read Version 1 14 Oct 24 read read Ali Yorgancioglu , Ege Üniversitesi, Bornova, Turkey Anke Mondschein , FILK Freiberg Institute gGmbH, Freiberg, Germany Marika Gargano , University of Naples Federico II, Naples, Italy Majlinda Hylli , Polytechnic University of Tirana, Tirana, Albania Comments on this article All Comments (0) Add a comment Sign up for content alerts Sign Up You are now signed up to receive this alert Browse by related subjects keyboard_arrow_left Back to all reports Reviewer Report 0 Views copyright © 2026 Hylli M. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 14 Feb 2026 | for Version 2 Majlinda Hylli , Polytechnic University of Tirana, Tirana, Albania 0 Views copyright © 2026 Hylli M. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. format_quote Cite this report speaker_notes Responses (0) Approved info_outline Alongside their report, reviewers assign a status to the article: Approved The paper is scientifically sound in its current form and only minor, if any, improvements are suggested Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit. Not approved Fundamental flaws in the paper seriously undermine the findings and conclusions The manuscript “Recycling of collagen from solid tannery waste and prospective utilization as adhesives” provides a detailed review of the extraction of collagen from tannery leather waste, its modification and applications, and its relevance to collagen-based adhesives. Instead of focusing on a single methodological or conceptual perspective, the discussion incorporates a wide range of recent studies from materials science, environmental engineering, and industrial chemistry. Most factual statements throughout the manuscript are supported by appropriate and credible references, reflecting through engagement with existing literature. The discussion of collagen recovery methods, dechroming strategies, and adhesive formulation, in particular, benefits from well-cited experimental and review studies. The manuscript also demonstrates an alignment with the principles of the circular economy and sustainability goals. The manuscript addresses environmental concerns by exploring the recycling of collagen from solid tannery waste. It highlights the potential use of recovered collagen as an eco-friendly adhesive, which could help to reduce waste and encourage the development of sustainable resources. All the revisions have improved the quality and readability of the manuscript. However, several aspects could be further improved. It would be helpful to indicate whether the references supporting certain numerical data, such as market forecasts, estimated production costs, and the reported performance standards of collagen-based adhesives are recent, authoritative, and directly aligned with the statements made. Are the cited sources up to date and still valid under current market and technological conditions? Do the numerical values remain consistent with the original publications, and have they been verified against the most recent available data? Clarifying these points would significantly strengthen the scientific credibility and reliability of the manuscript. Overall, the manuscript is a valuable contribution to the field. It has considerable potential to become a valuable resource for researchers and industry professionals focused on the sustainable valorization of tannery waste. So, I approved with minor corrections regarding the questions. Is the topic of the review discussed comprehensively in the context of the current literature? Yes Are all factual statements correct and adequately supported by citations? Partly Is the review written in accessible language? Yes Are the conclusions drawn appropriate in the context of the current research literature? Yes Competing Interests No competing interests were disclosed. Reviewer Expertise Leather I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard. reply Respond to this report Responses (0) Hylli M. Peer Review Report For: Recycling of collagen from solid tannery waste and prospective utilization as adhesives. [version 2; peer review: 1 approved, 3 approved with reservations] . F1000Research 2025, 13 :1228 ( https://doi.org/10.5256/f1000research.179579.r453122) NOTE: it is important to ensure the information in square brackets after the title is included in this citation. The direct URL for this report is: https://f1000research.com/articles/13-1228/v2#referee-response-453122 keyboard_arrow_left Back to all reports Reviewer Report 0 Views copyright © 2025 Gargano M. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 24 Dec 2025 | for Version 2 Marika Gargano , University of Naples Federico II, Naples, Italy 0 Views copyright © 2025 Gargano M. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. format_quote Cite this report speaker_notes Responses (0) Approved With Reservations info_outline Alongside their report, reviewers assign a status to the article: Approved The paper is scientifically sound in its current form and only minor, if any, improvements are suggested Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit. Not approved Fundamental flaws in the paper seriously undermine the findings and conclusions The manuscript Recycling of collagen from solid tannery waste and prospective utilization as adhesives aims to provide a systematic review of the literature concerning the use of recycled collagen derived from solid waste produced by the leather industry as adhesives. The manuscript properly addresses current concerns related to circular economy approaches to waste management and is structured in a comprehensive manner, covering the present status of the leather industry, the use of synthetic and bio-based adhesives, methods for collagen extraction, and its chemical modification for application purposes. The study is well organized and aligns with the scope of the journal. The revisions made by the authors have improved the overall quality and readability of the manuscript. Although the abstract and introduction are clear, the Discussion section still requires improvement. Therefore, I recommend acceptance after some revisions, as outlined below: The section “Collagen: The protein-based adhesive” briefly mentions collagen types but requires further elaboration. The authors should clarify which types of collagen are typically found in which kinds of waste. Moreover, the statement “The best glues contain collagen Type I…” needs better contextualization. Table 1 should be revised: In several rows, advantages and disadvantages are not clearly defined (e.g., in row 6, “Collagen type I” appears under disadvantages, although it is previously described as component of best glues). The data reported in column 3 should be defined and/or made consistent across entries (indicate which are the differences between “yield”, “mass yield”, “mass recovery”, “recovery” and so on). Table 2 lacks clarity and currently only presents literature data without providing a critical assessment. A more analytical discussion of the reported findings would be beneficial. Is the topic of the review discussed comprehensively in the context of the current literature? Yes Are all factual statements correct and adequately supported by citations? Partly Is the review written in accessible language? Partly Are the conclusions drawn appropriate in the context of the current research literature? Yes Competing Interests No competing interests were disclosed. Reviewer Expertise Leather I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. reply Respond to this report Responses (0) Gargano M. Peer Review Report For: Recycling of collagen from solid tannery waste and prospective utilization as adhesives. [version 2; peer review: 1 approved, 3 approved with reservations] . F1000Research 2025, 13 :1228 ( https://doi.org/10.5256/f1000research.179579.r433443) NOTE: it is important to ensure the information in square brackets after the title is included in this citation. The direct URL for this report is: https://f1000research.com/articles/13-1228/v2#referee-response-433443 keyboard_arrow_left Back to all reports Reviewer Report 0 Views copyright © 2025 Mondschein A. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 29 Jan 2025 | for Version 1 Anke Mondschein , FILK Freiberg Institute gGmbH, Freiberg, Saxony, Germany 0 Views copyright © 2025 Mondschein A. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. format_quote Cite this report speaker_notes Responses (1) Approved With Reservations info_outline Alongside their report, reviewers assign a status to the article: Approved The paper is scientifically sound in its current form and only minor, if any, improvements are suggested Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit. Not approved Fundamental flaws in the paper seriously undermine the findings and conclusions I fully agree with the issues raised by the first reviewer Ali Yorgancioglu from Ege Üniversitesi, Bornova, Turkey. The topic of the review is very important, but the paper has its scientific limitations. I will not repeat here the topics that have already been addressed and precisely outlined by reviewer 1. Additional topics are: Literature source missing for the statement that Typ I Col is the best Col type for glueing (p. 7) The intended uses of adhesives, technical and medical, should not be mixed and should be clearly separated, ideally with their respective specific challenges for the use of collagen or gelatine as an adhesive. If possible, the market data should also refer to these two very different applications. Practical data is lacking, especially for the technical application. Gelatine as an adhesive is already used industrially. It would be instructive to discuss where the actual limits to increased use are (price?, properties?, and how the respective deficits can be overcome) Captions should be more precise (e.g. Fig. 4: Explain a - d) Is the topic of the review discussed comprehensively in the context of the current literature? Partly Are all factual statements correct and adequately supported by citations? Partly Is the review written in accessible language? Partly Are the conclusions drawn appropriate in the context of the current research literature? Partly Competing Interests No competing interests were disclosed. Reviewer Expertise Leather I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. reply Respond to this report Responses (1) Author Response 09 Aug 2025 Nelly Flores, Research and Development Directorate, Technical University of Ambato, Ambato, Ecuador Reviewer Comment 1: Literature source missing for the statement that Type I collagen is the best collagen type for gluing (p.7). Response: Thank you for highlighting this. We have now added a citation supporting the statement that Type I collagen exhibits superior adhesive properties. Reviewer Comment 2: The intended uses of adhesives, technical and medical, should not be mixed and should be clearly separated, ideally with their respective specific challenges for the use of collagen or gelatine as an adhesive. If possible, the market data should also refer to these two very different applications. Response: We agree that distinguishing technical and medical applications improves clarity. In the revised manuscript, we have reorganized the text to create distinct subsections addressing: Technical and industrial uses (e.g., wood bonding, paper, packaging) Medical applications (e.g., tissue sealants, wound dressings) Each subsection now describes the unique performance requirements, regulatory considerations, and market dynamics relevant to that sector. Additionally, references to market data, where available, have been aligned with these categories. We have also removed some examples of medical adhesives that were not directly relevant to recycled collagen, as noted in our prior response. Reviewer Comment 3: Practical data is lacking, especially for the technical application. Gelatine as an adhesive is already used industrially. It would be instructive to discuss where the actual limits to increased use are (price?, properties?, and how the respective deficits can be overcome). Response: We appreciate this important observation. In the revised discussion section, we have incorporated a dedicated paragraph elaborating on the limitations of gelatin adhesives in industrial use: Their thermoreversible behavior (dissolution above ~35–40 °C) Susceptibility to moisture and biodegradation Generally lower mechanical strength compared to synthetic resins We also discuss price considerations, noting that while gelatin is relatively inexpensive as a byproduct, higher-purity high-bloom gelatin increases costs. Finally, we outline research strategies reported in recent literature for overcoming these deficits, including hydrophobic polymer blending, enzymatic crosslinking, and nanofiller reinforcement (as summarized in Table 2). We believe this provides a more practical perspective on the barriers to wider adoption and possible solutions. Reviewer Comment 4: Captions should be more precise (e.g., Fig. 4: Explain a–d). Response: We have revised the caption of Figure 4 to provide explicit descriptions of parts a–d, clarifying the content and purpose of each subfigure. The updated caption now reads: Figure 4. Schematic representation of collagen Types I-V in humans and Bos Taurus. a) Type I human collagen is predominantly found in the skin, bone, teeth, tendons, ligaments, vascular ligature, and various organs; b) Type IV collagen is present in the epithelial-secreted layer of the basement membrane as well as the basal lamina View more View less Competing Interests The authors declare that there are no competing interests. reply Respond Report a concern Mondschein A. Peer Review Report For: Recycling of collagen from solid tannery waste and prospective utilization as adhesives. [version 2; peer review: 1 approved, 3 approved with reservations] . F1000Research 2025, 13 :1228 ( https://doi.org/10.5256/f1000research.170636.r359783) NOTE: it is important to ensure the information in square brackets after the title is included in this citation. The direct URL for this report is: https://f1000research.com/articles/13-1228/v1#referee-response-359783 keyboard_arrow_left Back to all reports Reviewer Report 0 Views copyright © 2024 Yorgancioglu A. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 14 Nov 2024 | for Version 1 Ali Yorgancioglu , Ege Üniversitesi, Bornova, Turkey 0 Views copyright © 2024 Yorgancioglu A. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. format_quote Cite this report speaker_notes Responses (1) Approved With Reservations info_outline Alongside their report, reviewers assign a status to the article: Approved The paper is scientifically sound in its current form and only minor, if any, improvements are suggested Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit. Not approved Fundamental flaws in the paper seriously undermine the findings and conclusions The manuscript titled as ‘‘ "Recycling of collagen from solid tannery waste and prospective utilization as adhesives" for F1000Research ” was reviewed. I have evaluated the paper in light of the F1000Research scope. The submission was made as Review Paper. The manuscript discusses the extraction and application of collagen from solid tannery waste as an adhesive. This topic aligns well with current sustainability objectives, particularly within the leather industry. The authors provide a comprehensive review of collagen extraction methods, adhesive formulation, and potential applications, supported by recent advancements in the field. However, while the paper is informative, it faces several scientific and structural limitations. Key aspects require refinement to ensure clarity and to meet the publication standards of F1000Research. The study addresses an important topic in the circular economy and sustainable waste management. Converting tannery waste into adhesives could reduce landfill waste and minimize reliance on petroleum-based adhesives. This aligns with the increasing need for sustainable materials and methods in various industrial applications. While the study is comprehensive in discussing various collagen extraction and adhesive production techniques, it lacks specific experimental data or case studies to support some of its claims. The paper would benefit from quantitative data that compares the performance of collagen-based adhesives with traditional adhesives in specific applications. The authors briefly mention the limitations of collagen adhesives, particularly in water resistance and durability. However, more detailed discussion and proposed solutions for overcoming these limitations are necessary to make the paper more practical and applicable to real-world scenarios. The manuscript is structured logically, yet certain sections (e.g., Background, Methods) could be more concise. In some parts, especially the discussion on different adhesive applications, the information appears repetitive. A clearer distinction between current findings and future directions could improve readability. Moreover, methods section should be removed. Review papers rarely include a method section since they do not report on original research. Author needs to send this manuscript for English proofread as I found some grammatical errors while reviewing the article. In the Abstract: "This research systematically reviews the methods and applications of collagen extraction, highlighting the material’s versatility and environmental benefits when used as a bio-adhesive." The phrase “when used as a bio-adhesive” could be simplified to “as a bio-adhesive.” In the Methods: "Only documents in English," which should be “Only English-language documents were included.” Further editing for grammatical accuracy and flow would enhance the manuscript’s clarity and professionalism. After these revision, the paper can be considered publication Is the topic of the review discussed comprehensively in the context of the current literature? Partly Are all factual statements correct and adequately supported by citations? Partly Is the review written in accessible language? Partly Are the conclusions drawn appropriate in the context of the current research literature? Partly Competing Interests No competing interests were disclosed. Reviewer Expertise Leather I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. reply Respond to this report Responses (1) Author Response 09 Aug 2025 Nelly Flores, Research and Development Directorate, Technical University of Ambato, Ambato, Ecuador Reviewer 1 Comment: While the study is comprehensive in discussing various collagen extraction and adhesive production techniques, it lacks specific experimental data or case studies to support some of its claims. The paper would benefit from quantitative data that compares the performance of collagen-based adhesives with traditional adhesives in specific applications. Response: We fully agree that quantitative comparisons strengthen the discussion. To address this, we incorporated Table 2 , which provides detailed physicochemical and mechanical properties of a broad range of collagen-derived adhesives and compares them with standard synthetic adhesives and relevant benchmarks. This addition allows readers to see clear performance differences across formulations and applications. Comment: The authors briefly mention the limitations of collagen adhesives, particularly in water resistance and durability. However, more detailed discussion and proposed solutions for overcoming these limitations are necessary to make the paper more practical and applicable to real-world scenarios. Response: We have expanded the discussion substantially. In the revised manuscript, we now present strategies to overcome water sensitivity and limited durability, including: Incorporation of hydrophobic additives and synthetic polymers Chemical and enzymatic crosslinking techniques. This added section outlines both current approaches and future directions to make collagen adhesives more competitive with conventional resins. Comment: The manuscript is structured logically, yet certain sections (e.g., Background, Methods) could be more concise. In some parts, especially the discussion on different adhesive applications, the information appears repetitive. A clearer distinction between current findings and future directions could improve readability. Moreover, methods section should be removed. Review papers rarely include a method section since they do not report on original research. Response: We appreciate this suggestion. The Methods section has been removed , and we restructured the discussion to: Consolidate repetitive content about adhesive properties Group similar formulations under thematic categories (e.g., urea-formaldehyde, acrylic-collagen) Add summary statements distinguishing current evidence and prospective research These changes improve conciseness and flow. Comment: Author needs to send this manuscript for English proofread as I found some grammatical errors while reviewing the article. Response: We have carefully proofread the entire manuscript to improve grammar, consistency, and style. Specific examples highlighted (e.g., “when used as a bio-adhesive”) were corrected as suggested. For example: The Abstract was revised to: "...highlighting the material’s versatility and environmental benefits as a bio-adhesive." The Methods phrase was replaced with: “Only English-language documents were included.” View more View less Competing Interests I declare that I have no competing interests that could be construed to influence the objectivity, validity, or importance of this article or its peer review. reply Respond Report a concern Yorgancioglu A. Peer Review Report For: Recycling of collagen from solid tannery waste and prospective utilization as adhesives. [version 2; peer review: 1 approved, 3 approved with reservations] . F1000Research 2025, 13 :1228 ( https://doi.org/10.5256/f1000research.170636.r336497) NOTE: it is important to ensure the information in square brackets after the title is included in this citation. The direct URL for this report is: https://f1000research.com/articles/13-1228/v1#referee-response-336497 Alongside their report, reviewers assign a status to the article: Approved - the paper is scientifically sound in its current form and only minor, if any, improvements are suggested Approved with reservations - A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit. Not approved - fundamental flaws in the paper seriously undermine the findings and conclusions Adjust parameters to alter display View on desktop for interactive features Includes Interactive Elements View on desktop for interactive features Competing Interests Policy Provide sufficient details of any financial or non-financial competing interests to enable users to assess whether your comments might lead a reasonable person to question your impartiality. Consider the following examples, but note that this is not an exhaustive list: Examples of 'Non-Financial Competing Interests' Within the past 4 years, you have held joint grants, published or collaborated with any of the authors of the selected paper. You have a close personal relationship (e.g. parent, spouse, sibling, or domestic partner) with any of the authors. You are a close professional associate of any of the authors (e.g. scientific mentor, recent student). You work at the same institute as any of the authors. You hope/expect to benefit (e.g. favour or employment) as a result of your submission. You are an Editor for the journal in which the article is published. Examples of 'Financial Competing Interests' You expect to receive, or in the past 4 years have received, any of the following from any commercial organisation that may gain financially from your submission: a salary, fees, funding, reimbursements. You expect to receive, or in the past 4 years have received, shared grant support or other funding with any of the authors. You hold, or are currently applying for, any patents or significant stocks/shares relating to the subject matter of the paper you are commenting on. Stay Updated Sign up for content alerts and receive a weekly or monthly email with all newly published articles Register with F1000Research Already registered? Sign in Not now, thanks close PLEASE NOTE If you are an AUTHOR of this article, please check that you signed in with the account associated with this article otherwise we cannot automatically identify your role as an author and your comment will be labelled as a “User Comment”. If you are a REVIEWER of this article, please check that you have signed in with the account associated with this article and then go to your account to submit your report, please do not post your review here. If you do not have access to your original account, please contact us . All commenters must hold a formal affiliation as per our Policies . The information that you give us will be displayed next to your comment. User comments must be in English, comprehensible and relevant to the article under discussion. We reserve the right to remove any comments that we consider to be inappropriate, offensive or otherwise in breach of the User Comment Terms and Conditions . Commenters must not use a comment for personal attacks. When criticisms of the article are based on unpublished data, the data should be made available. I accept the User Comment Terms and Conditions Please confirm that you accept the User Comment Terms and Conditions. Affiliation ✕ refresh Please enter your institution. Note: To add your institution or organisation, start typing the name and then select the correct name from the list. Where applicable, the name will appear in both the original language and in English. Do not paste in the name. If the name does not appear in the drop-down list, we will display the information you have entered. ✕ refresh Country/Region * USA UK Canada China France Germany Afghanistan Aland Islands Albania Algeria American Samoa Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory British Virgin Islands Brunei Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo Cook Islands Costa Rica Cote d'Ivoire Croatia Cuba Cyprus Czech Republic Democratic Republic of the Congo Denmark Djibouti Dominica Dominican Republic Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands Faroe Islands Federated States of Micronesia Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadeloupe Guam Guatemala Guernsey Guinea Guinea-Bissau Guyana Haiti Heard Island and Mcdonald Islands Holy See (Vatican City State) Honduras Hong Kong Hungary Iceland India Indonesia Iran Iraq Ireland Israel Italy Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Kosovo (Serbia and Montenegro) Kuwait Kyrgyzstan Lao People's Democratic Republic Latvia Lebanon Lesotho Liberia Libya Liechtenstein Lithuania Luxembourg Macao Madagascar Malawi Malaysia Maldives Mali Malta Marshall Islands Martinique Mauritania Mauritius Mayotte Mexico Minor Outlying Islands of the United States Moldova Monaco Mongolia Montenegro Montserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands Antilles New Caledonia New Zealand Nicaragua Niger Nigeria Niue Norfolk Island North Korea North Macedonia Northern Mariana Islands Norway Oman Pakistan Palau Palestinian Territory Panama Papua New Guinea Paraguay Peru Philippines Pitcairn Poland Portugal Puerto Rico Qatar Reunion Romania Russian Federation Rwanda Saint Helena Saint Kitts and Nevis Saint Lucia Saint Pierre and Miquelon Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Principe Saudi Arabia Senegal Serbia Seychelles Sierra Leone Singapore Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and the South Sandwich Is South Korea South Sudan Spain Sri Lanka Sudan Suriname Svalbard and Jan Mayen Swaziland Sweden Switzerland Syria Taiwan Tajikistan Tanzania Thailand The Gambia The Netherlands Timor-Leste Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu UK USA Uganda Ukraine United Arab Emirates United States Virgin Islands Uruguay Uzbekistan Vanuatu Venezuela Vietnam Wallis and Futuna West Bank and Gaza Strip Western Sahara Yemen Zambia Zimbabwe Please select your country/region. You must enter a comment. Competing Interests Please disclose any competing interests that might be construed to influence your judgment of the article's or peer review report's validity or importance. Competing Interests Policy Provide sufficient details of any financial or non-financial competing interests to enable users to assess whether your comments might lead a reasonable person to question your impartiality. Consider the following examples, but note that this is not an exhaustive list: Examples of 'Non-Financial Competing Interests' Within the past 4 years, you have held joint grants, published or collaborated with any of the authors of the selected paper. You have a close personal relationship (e.g. parent, spouse, sibling, or domestic partner) with any of the authors. You are a close professional associate of any of the authors (e.g. scientific mentor, recent student). You work at the same institute as any of the authors. You hope/expect to benefit (e.g. favour or employment) as a result of your submission. You are an Editor for the journal in which the article is published. Examples of 'Financial Competing Interests' You expect to receive, or in the past 4 years have received, any of the following from any commercial organisation that may gain financially from your submission: a salary, fees, funding, reimbursements. You expect to receive, or in the past 4 years have received, shared grant support or other funding with any of the authors. You hold, or are currently applying for, any patents or significant stocks/shares relating to the subject matter of the paper you are commenting on. Please state your competing interests The comment has been saved. An error has occurred. Please try again. Cancel Post var lTitle = "Recycling of collagen from solid tannery...".replace("'", ''); var linkedInUrl = "http://www.linkedin.com/shareArticle?url=https://f1000research.com/articles/13-1228/v2" + "&title=" + encodeURIComponent(lTitle) + "&summary=" + encodeURIComponent('Read the article by '); var deliciousUrl = "https://del.icio.us/post?url=https://f1000research.com/articles/13-1228/v2&title=" + encodeURIComponent(lTitle); var redditUrl = "http://reddit.com/submit?url=https://f1000research.com/articles/13-1228/v2" + "&title=" + encodeURIComponent(lTitle); linkedInUrl += encodeURIComponent('Flores Tapia NE et al.'); var offsetTop = /chrome/i.test( navigator.userAgent ) ? 4 : -10; var addthis_config = { ui_offset_top: offsetTop, services_compact : "facebook,twitter,www.linkedin.com,www.mendeley.com,reddit.com", services_expanded : "facebook,twitter,www.linkedin.com,www.mendeley.com,reddit.com", services_custom : [ { name: "LinkedIn", url: linkedInUrl, icon:"/img/icon/at_linkedin.svg" }, { name: "Mendeley", url: "http://www.mendeley.com/import/?url=https://f1000research.com/articles/13-1228/v2/mendeley", icon:"/img/icon/at_mendeley.svg" }, { name: "Reddit", url: redditUrl, icon:"/img/icon/at_reddit.svg" }, ] }; var addthis_share = { url: "https://f1000research.com/articles/13-1228", templates : { twitter : "Recycling of collagen from solid tannery waste and prospective.... Flores Tapia NE et al., published by " + "@F1000Research" + ", https://f1000research.com/articles/13-1228/v2" } }; if (typeof(addthis) != "undefined"){ addthis.addEventListener('addthis.ready', checkCount); addthis.addEventListener('addthis.menu.share', checkCount); } $(".f1r-shares-twitter").attr("href", "https://twitter.com/intent/tweet?text=" + addthis_share.templates.twitter); $(".f1r-shares-facebook").attr("href", "https://www.facebook.com/sharer/sharer.php?u=" + addthis_share.url); $(".f1r-shares-linkedin").attr("href", addthis_config.services_custom[0].url); $(".f1r-shares-reddit").attr("href", addthis_config.services_custom[2].url); $(".f1r-shares-mendelay").attr("href", addthis_config.services_custom[1].url); function checkCount(){ setTimeout(function(){ $(".addthis_button_expanded").each(function(){ var count = $(this).text(); if (count !== "" && count != "0") $(this).removeClass("is-hidden"); else $(this).addClass("is-hidden"); }); }, 1000); } close How to cite this report {{reportCitation}} Cancel Copy Citation Details $(function(){R.ui.buttonDropdowns('.dropdown-for-downloads');}); $(function(){R.ui.toolbarDropdowns('.toolbar-dropdown-for-downloads');}); $.get("/articles/acj/155450/179579") new F1000.Clipboard(); new F1000.ThesaurusTermsDisplay("articles", "article", "179579"); $(document).ready(function() { $( "#frame1" ).on('load', function() { var mydiv = $(this).contents().find("div"); var h = mydiv.height(); console.log(h) }); var tooltipLivingFigure = jQuery(".interactive-living-figure-label .icon-more-info"), titleLivingFigure = tooltipLivingFigure.attr("title"); tooltipLivingFigure.simpletip({ fixed: true, position: ["-115", "30"], baseClass: 'small-tooltip', content:titleLivingFigure + " " }); tooltipLivingFigure.removeAttr("title"); $("body").on("click", ".cite-living-figure", function(e) { e.preventDefault(); var ref = $(this).attr("data-ref"); $(this).closest(".living-figure-list-container").find("#" + ref).fadeIn(200); }); $("body").on("click", ".close-cite-living-figure", function(e) { e.preventDefault(); $(this).closest(".popup-window-wrapper").fadeOut(200); }); $(document).on("mouseup", function(e) { var metricsContainer = $(".article-metrics-popover-wrapper"); if (!metricsContainer.is(e.target) && metricsContainer.has(e.target).length === 0) { $(".article-metrics-close-button").click(); } }); var articleId = $('#articleId').val(); if($("#main-article-count-box").attachArticleMetrics) { $("#main-article-count-box").attachArticleMetrics(articleId, { articleMetricsView: true }); } }); var figshareWidget = $(".new_figshare_widget"); if (figshareWidget.length > 0) { window.figshare.load("f1000", function(Widget) { // Select a tag/tags defined in your page. In this tag we will place the widget. _.map(figshareWidget, function(el){ var widget = new Widget({ articleId: $(el).attr("figshare_articleId") //height:300 // this is the height of the viewer part. [Default: 550] }); widget.initialize(); // initialize the widget widget.mount(el); // mount it in a tag that's on your page // this will save the widget on the global scope for later use from // your JS scripts. This line is optional. //window.widget = widget; }); }); } close Error Close Add Reset F1000.MICROSERVICES.AFFILIATION = ''; $(document).ready(function () { $('.js-affiliations-form').each((index, form) => { new AffiliationForm({ formId: form.id, institutionErrorSelector: '.comment-enter-institution', departmentErrorSelector: '.comment-enter-department', placeSelector: '.js-add-comment-place', stateSelector: '.js-add-comment-state', zipCodeSelector: '.js-add-comment-zipcode', countrySelector: '.js-add-comment-country', countryErrorSelector: '.comment-enter-country', }); }); }); $(document).ready(function () { var reportIds = { "453126": 0, "453127": 0, "453124": 0, "453125": 0, "453122": 3, "453123": 0, "453120": 0, "453121": 0, "403606": 0, "403607": 0, "403604": 0, "403605": 0, "403602": 0, "403603": 0, "403600": 0, "403601": 0, "447646": 0, "447644": 0, "447645": 0, "447643": 0, "403608": 0, "433446": 0, "433447": 0, "433444": 0, "344103": 0, "433445": 0, "344102": 0, "433442": 0, "433443": 9, "433440": 0, "433441": 0, "344109": 0, "344108": 0, "344111": 0, "344110": 0, "344105": 0, "344104": 0, "433448": 0, "344107": 0, "433449": 0, "344106": 0, "447670": 0, "447671": 0, "447668": 0, "447669": 0, "447667": 0, "447672": 0, "401606": 0, "401605": 0, "359781": 0, "359780": 0, "453092": 0, "359783": 20, "359782": 0, "359777": 0, "359776": 0, "359779": 0, "359778": 0, "336495": 0, "359785": 0, "359784": 0, "336501": 0, "336500": 0, "336503": 0, "453109": 0, "336502": 0, "336497": 32, "336496": 0, "336499": 0, "336498": 0, "336504": 0, }; $(".referee-response-container,.js-referee-report").each(function(index, el) { var reportId = $(el).attr("data-reportid"), reportCount = reportIds[reportId] || 0; $(el).find(".comments-count-container,.js-referee-report-views").html(reportCount); }); var uuidInput = $("#article_uuid"), oldUUId = uuidInput.val(), newUUId = "96cc2c8e-b3dd-4793-b534-40ef3c7bf258"; uuidInput.val(newUUId); $("a[href*='article_uuid=']").each(function(index, el) { var newHref = $(el).attr("href").replace(oldUUId, newUUId); $(el).attr("href", newHref); }); }); An innovative open access publishing platform offering rapid publication and open peer review, whilst supporting data deposition and sharing. Browse Gateways Collections How it Works Contact For Developers Cookie Notice Privacy Notice RSS Submit Your Research Follow us © 2012-2026 F1000 Research Ltd. ISSN 2046-1402 | Legal | Partner of Research4Life • CrossRef • ORCID • FAIRSharing R.templateTests.simpleTemplate = R.template(' $text $text $text $text $text '); R.templateTests.runTests(); var F1000platform = new F1000.Platform({ name: "f1000research", displayName: "F1000Research", hostName: "f1000research.com", id: "1", editorialEmail: "[email protected]", infoEmail: "[email protected]", usePmcStats: true }); $(function(){R.ui.dropdowns('.dropdown-for-authors, .dropdown-for-about, .dropdown-for-myresearch');}); // $(function(){R.ui.dropdowns('.dropdown-for-referees');}); $(document).ready(function () { if ($(".cookie-warning").is(":visible")) { $(".sticky").css("margin-bottom", "35px"); $(".devices").addClass("devices-and-cookie-warning"); } $(".cookie-warning .close-button").click(function (e) { $(".devices").removeClass("devices-and-cookie-warning"); $(".sticky").css("margin-bottom", "0"); }); $("#tweeter-feed .tweet-message").each(function (i, message) { var self = $(message); self.html(linkify(self.html())); }); $(".partner").on("mouseenter mouseleave", function() { $(this).find(".gray-scale, .colour").toggleClass("is-hidden"); }); }); Sign In Remember me Forgotten your password? Sign In Cancel Email or password not correct. Please try again Please wait... $(function(){ // Note: All the setup needs to run against a name attribute and *not* the id due the clonish // nature of facebox... $("a[id=googleSignInButton]").click(function(event){ event.preventDefault(); $("input[id=oAuthSystem]").val("GOOGLE"); $("form[id=oAuthForm]").submit(); }); $("a[id=facebookSignInButton]").click(function(event){ event.preventDefault(); $("input[id=oAuthSystem]").val("FACEBOOK"); $("form[id=oAuthForm]").submit(); }); $("a[id=orcidSignInButton]").click(function(event){ event.preventDefault(); $("input[id=oAuthSystem]").val("ORCID"); $("form[id=oAuthForm]").submit(); }); }); If you've forgotten your password, please enter your email address below and we'll send you instructions on how to reset your password. The email address should be the one you originally registered with F1000. Email address not valid, please try again You registered with F1000 via Google, so we cannot reset your password. To sign in, please click here . If you still need help with your Google account password, please click here . You registered with F1000 via Facebook, so we cannot reset your password. To sign in, please click here . If you still need help with your Facebook account password, please click here . Code not correct, please try again Reset password Cancel Email us for further assistance. Server error, please try again. If your email address is registered with us, we will email you instructions to reset your password. If you think you should have received this email but it has not arrived, please check your spam filters and/or contact for further assistance. Please wait... Register $(document).ready(function () { signIn.createSignInAsRow($("#sign-in-form-gfb-popup")); $(".target-field").each(function () { var uris = $(this).val().split("/"); if (uris.pop() === "login") { $(this).val(uris.toString().replace(",","/")); } }); });