Design and Theoretical Performance Evaluation of a Small-Scale Downdraft Biomass Gasifier Using Groundnut Shells for Rural Energy Access in the Gambia

Design and Theoretical Performance Evaluation of a Small-Scale Downdraft Biomass Gasifier Using Groundnut Shells for Rural Energy Access in the Gambia | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (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;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Design and Theoretical Performance Evaluation of a Small-Scale Downdraft Biomass Gasifier Using Groundnut Shells for Rural Energy Access in the Gambia Ousman Bojang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8845807/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Energy poverty and rising fossil fuel costs present significant barriers to socio-economic development in rural Gambia. This research presents the design and theoretical performance evaluation of a small-scale, fixed-bed downdraft biomass gasifier specifically engineered to utilize locally abundant groundnut shells ( Arachis hypogaea ) for decentralized power generation. Addressing the technical challenge of high tar content associated with lignin-rich agricultural residues, the study proposes a reactor with an optimized internal diameter of 175 mm, derived from a specific hearth load of 125 kg/h/m². The methodology integrates a high-temperature oxidation zone reaching 1000∘C to facilitate the thermal cracking of tars, coupled with a multi-stage cleaning circuit comprising an 80 mm cyclone separator and a lime-charcoal scrubber. Utilizing thermodynamic modeling and established engineering benchmarks, the system is designed to process 3 kg/h of feedstock at an optimal moisture content of 10.62%. Theoretical validation indicates a Cold Gas Efficiency (CGE) of 70% and a predicted syngas energy density of 2965.6 kJ/Nm³, consisting of approximately 13.0% CO and 8.0% H₂. These parameters satisfy the operational requirements for a 2.5 kVA internal combustion engine while maintaining tar concentrations below the 100 mg/Nm³ safety threshold. Beyond technical feasibility, the study establishes a "zero-waste" framework by repurposing solid bio-char and gypsum byproducts as agricultural soil amendments. This research provides a scalable technical blueprint for converting agricultural liabilities into sustainable energy assets, offering a viable strategy for mitigating deforestation and enhancing energy sovereignty in the North Bank and Lower River regions of The Gambia. Mechanical Engineering Energy Engineering Renewable Resources Biomass Gasification Downdraft Reactor Groundnut Shells The Gambia Syngas Quality Rural Electrification Full Text Additional Declarations The authors declare no competing interests. Supplementary Files SupplementaryStatement.docx Supplementary Statement: Author Motivation, Context, and Research Significance Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8845807","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":589264320,"identity":"8c888299-c8eb-4076-88d5-5835cdbdd92c","order_by":0,"name":"Ousman Bojang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAz0lEQVRIiWNgGAWjYBADAwP2BhBlQYoWngMgSoIULRIJIJoILfwS6U83/NxhZ2wu+fzqhh8FEgz87d0JeLVIzsgxu9l7JtnMcnZO2c0eoMMkzpzdgN9BN3LYbvC2MdsY3M5Ju8ED1GIgkUtIS/qzm3/b6m0Mbp5Ju/mHOC0JZrd52w6bGdxgP3abKFske96Y3ZZtO25s2ZPDdlvGQIKHoF/42YEOe9tWbbid/fizm2/+2Mjxt/fi14IEeAzAJLHKQYD9ASmqR8EoGAWjYAQBANZVSMaJ+IyqAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0009-0009-0487-9845","institution":"The Gambia University of Applied Science, Engineering and Technology","correspondingAuthor":true,"prefix":"","firstName":"Ousman","middleName":"","lastName":"Bojang","suffix":""}],"badges":[],"createdAt":"2026-02-11 00:19:43","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":true,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":true},"doi":"10.21203/rs.3.rs-8845807/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8845807/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":102746565,"identity":"b2907985-a31e-4ae6-b76f-f9ff25c3d07b","added_by":"auto","created_at":"2026-02-16 08:58:14","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":582268,"visible":true,"origin":"","legend":"","description":"","filename":"DOWNDRAFTBIOMASSGASIFIERFINAL.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8845807/v1_covered_83fdde56-4160-49b8-a1f9-f1b9e646b681.pdf"},{"id":102484777,"identity":"1d8d19c2-bda2-4181-a995-be548874070e","added_by":"auto","created_at":"2026-02-12 07:29:40","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":14552,"visible":true,"origin":"","legend":"\u003cp\u003eSupplementary Statement: Author Motivation, Context, and Research Significance\u003c/p\u003e","description":"","filename":"SupplementaryStatement.docx","url":"https://assets-eu.researchsquare.com/files/rs-8845807/v1/84aab70b6ec0a4aaf4d3e19e.docx"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eDesign and Theoretical Performance Evaluation of a Small-Scale Downdraft Biomass Gasifier Using Groundnut Shells for Rural Energy Access in the Gambia\u003c/p\u003e","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Indepent Research ( Self-Initiated and Self-Conducted).","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Biomass Gasification, Downdraft Reactor, Groundnut Shells, The Gambia, Syngas Quality, Rural Electrification","lastPublishedDoi":"10.21203/rs.3.rs-8845807/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8845807/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eEnergy poverty and rising fossil fuel costs present significant barriers to socio-economic development in rural Gambia. This research presents the design and theoretical performance evaluation of a small-scale, fixed-bed downdraft biomass gasifier specifically engineered to utilize locally abundant groundnut shells (\u003cem\u003eArachis hypogaea\u003c/em\u003e) for decentralized power generation. Addressing the technical challenge of high tar content associated with lignin-rich agricultural residues, the study proposes a reactor with an optimized internal diameter of 175 mm, derived from a specific hearth load of 125 kg/h/m².\u003c/p\u003e\n\u003cp\u003eThe methodology integrates a high-temperature oxidation zone reaching 1000∘C to facilitate the thermal cracking of tars, coupled with a multi-stage cleaning circuit comprising an 80 mm cyclone separator and a lime-charcoal scrubber. Utilizing thermodynamic modeling and established engineering benchmarks, the system is designed to process 3 kg/h of feedstock at an optimal moisture content of 10.62%. Theoretical validation indicates a Cold Gas Efficiency (CGE) of 70% and a predicted syngas energy density of 2965.6 kJ/Nm³, consisting of approximately 13.0% CO and 8.0% H₂.\u003c/p\u003e\n\u003cp\u003eThese parameters satisfy the operational requirements for a 2.5 kVA internal combustion engine while maintaining tar concentrations below the 100 mg/Nm³ safety threshold.\u003c/p\u003e\n\u003cp\u003eBeyond technical feasibility, the study establishes a \"zero-waste\" framework by repurposing solid bio-char and gypsum byproducts as agricultural soil amendments. 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