Characterization and Enhancement of Household Solid Waste Composting Using Effective Microorganisms (EM)

Characterization and Enhancement of Household Solid Waste Composting Using Effective Microorganisms (EM) | 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 Characterization and Enhancement of Household Solid Waste Composting Using Effective Microorganisms (EM) Khamis M Said, Jecha Jecha This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9454230/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 Household organic solid waste represents a growing environmental burden in Zanzibar and similar low-income settings, where collection infrastructure is limited and open dumping remains common. This study evaluated Effective Microorganism (EM) inoculation as a means of accelerating household organic waste composting and improving final compost quality. Composting was conducted in controlled bins with EM applied as a liquid inoculum (20–100 mL) mixed with feedstock, while controls received no inoculation. Temperature, moisture, pH, and electrical conductivity (EC) were monitored throughout; chemical indices (organic matter, C/N ratio, N–P–K, humic substances, heavy metals) and biological indicators (germination index, microbial counts, Shannon diversity, qPCR/sequencing of dominant taxa) were measured in mature compost. EM-inoculated bins reached 65°C within 3 days versus 55°C in controls and sustained thermophilic conditions (≥ 55°C) for 10 versus 6 days (F = 8.23, p = 0.01). Moisture remained within 50–60% in EM treatments (p = 0.03). EM compost showed faster organic matter loss (28% vs. 35% at day 60; p = 0.02), higher nitrogen retention (2.1% vs. 1.7%; p = 0.01), improved phosphorus and potassium content (+ 15% and + 18%; p < 0.05), a lower final C/N ratio (18 vs. 22; p = 0.02), earlier EC stabilization (3.5 vs. 4.0 dS/m; p = 0.04), greater humification (+ 35% vs. +20%; p = 0.03), higher microbial diversity (Shannon 3.8 vs. 3.1; p = 0.02), and superior maturity (germination index 85% vs. 70%; p = 0.01). Heavy metals stayed below permissible limits in all treatments (p > 0.1). These findings indicate that EM inoculation accelerates composting, yields a nutrient-dense and phytotoxicity-safe product, and can support decentralized waste management in resource-constrained communities. Household solid waste Effective Microorganisms Composting Nutrient retention Microbial dynamics Germination index Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. INTRODUCTION Municipal solid waste generation is increasing worldwide as populations grow and urbanize, placing strain on collection, treatment, and disposal systems (Barma et al., 2022 ). In many low- and middle-income countries the problem is compounded by inadequate infrastructure, open dumping, uncontrolled burning, and weak policy enforcement (Almokmesh et al., 2024 ; Bundhoo, 2018 ). Organic materials food scraps, yard trimmings, and other biodegradable household residues typically constitute more than half of domestic waste streams, yet recycling and composting rates remain low (Manea et al., 2024 ). Zanzibar illustrates these challenges. Limited waste collection coverage, poor disposal practices, and low community participation leave organic waste largely unmanaged, contributing to environmental contamination and public-health risks (Mukama et al., 2016 ). Composting offers a practical route for diverting organics from landfills while generating nutrient-rich soil amendments that support agriculture and reduce greenhouse gas emissions (Larney et al., 2006 ; Manea et al., 2024 ). The approach is particularly attractive for decentralized settings because it requires modest capital investment and can be scaled to household or community level (Katranci et al., 2026 ). Effective Microorganisms (EM) are mixed-culture inoculants containing lactic acid bacteria, photosynthetic bacteria, yeasts, and actinomycetes that have been reported to accelerate organic matter decomposition, suppress pathogens, and reduce odors during composting (Weissert et al., 2025 ; Greff et al., 2021 ). Laboratory and field trials on substrates ranging from rice straw to mushroom waste have shown that EM application can shorten composting duration, raise peak temperatures, and improve compost nutrient content and maturity (Ansari et al., 2022 ; Jusoh et al., 2013 ; Raimi et al., 2024 ). However, much of this work was conducted on agricultural or industrial feedstocks rather than mixed household organic waste, and few studies have combined physical, chemical, and molecular-biological indicators within a single experimental design. The present study therefore aimed to (1) characterize the composting process of household organic solid waste inoculated with EM relative to uninoculated controls, and (2) quantify the effects of EM inoculation on process performance (temperature, moisture, pH, EC), chemical composition (organic matter, C/N, N–P–K, humic substances, heavy metals), microbial community dynamics, and compost maturity (germination index). The results are intended to inform low-cost, decentralized waste management strategies applicable in Zanzibar and comparable resource-constrained settings. 2. MATERIALS AND METHODS 2.1 Experimental design Composting experiments were conducted in controlled bins of varying volumes (6, 9, and 21 L). Each bin was loaded with household organic waste (food waste, yard trimmings) to approximately 60% of its capacity, leaving sufficient void space for aeration. Treatments comprised two groups: (1) EM-inoculated bins, in which EM solution was applied at doses of 20–100 mL and mixed homogeneously with the feedstock; and (2) uninoculated control bins receiving no microbial additive. Each treatment was replicated three times. Composting duration was 60 days, with conditions maintained to promote thermophilic development: target moisture of approximately 60%, periodic manual aeration, and temperature monitoring (Raimi et al., 2024 ; Lew et al., 2021 ). 2.2 Sample collection and preparation Household solid waste was sampled using a stratified random design across households of different socioeconomic strata to capture variability in waste generation and composition (Bolaane & Ali, 2004 ; Monavari et al., 2011 ). Collected waste was sorted into organic and inorganic fractions; the organic fraction was shredded to a particle size below 20 mm, homogenized, and loaded into composting bins. Segregation bins were installed at participating households to facilitate source separation and improve sample quality (Requena-Sanchez et al., 2022 ). EM inoculum was prepared by activating a commercial EM stock culture in a molasses-water medium (1:1:20 v/v) under anaerobic conditions for 7 days at ambient temperature, following standard preparation protocols. The activated EM, containing lactic acid bacteria, photosynthetic bacteria, yeasts, and actinomycetes, was diluted to working concentration and applied at the time of bin loading (Jusoh et al., 2013 ; Raimi et al., 2024 ). 2.3 Analytical methods Physical parameters were measured as follows. Temperature was recorded daily at three depths within each bin using calibrated thermocouples. Moisture content was determined gravimetrically by drying sub-samples at 105°C to constant weight. pH and electrical conductivity (EC) were measured in 1:10 (w/v) aqueous extracts using calibrated meters. Chemical analyses included organic matter content by loss on ignition at 550°C, total nitrogen by Kjeldahl digestion, total phosphorus by spectrophotometry after acid digestion, and total potassium by flame photometry. The C/N ratio was calculated from organic carbon (OM/1.724) and total nitrogen values. Humic substance fractionation (humic and fulvic acids) followed the IHSS alkali-extraction protocol. Heavy metals (Pb, Cd, Zn) were determined by atomic absorption spectrometry after acid digestion (Gao & Xu, 2014 ). Microbiological assessments combined culture-based and molecular methods. Total viable counts of thermophilic and mesophilic bacteria were obtained on nutrient agar incubated at 55°C and 30°C respectively. Microbial community composition was characterized by 16S rRNA gene amplicon sequencing (V3–V4 region) and quantitative PCR (qPCR) targeting dominant EM-associated taxa (lactic acid bacteria, photosynthetic bacteria, yeasts, actinomycetes). Shannon diversity indices were calculated from sequence data. Compost maturity was assessed by the germination index (GI) using cress seed bioassays (Cangelosi & Meschke, 2014 ; Nemati et al., 2016 ). 2.4 Data analysis All data were tested for normality (Shapiro–Wilk) and homogeneity of variances (Levene's test) prior to analysis. Differences between EM-inoculated and control treatments were evaluated using independent-samples t-tests for single time-point comparisons and repeated-measures ANOVA for time-series data (temperature, moisture). One-way ANOVA was applied to compare treatment means for chemical and biological parameters at maturity. Significance was set at α = 0.05. Analyses were performed with R (v. 4.4) (Abbasnasab Sardareh et al., 2021 ). 3. RESULTS 3.1 Physical characteristics during composting Temperature profiles for the two treatments are presented in Fig. 2 . EM-inoculated compost reached a peak thermophilic temperature of 65°C within 3 days, compared with 55°C in controls. Temperatures above 55°C were sustained for 10 days in EM bins versus 6 days in controls; this difference was statistically significant (ANOVA, F = 8.23, p = 0.01). Both treatments returned to ambient levels by day 40, though the EM treatment remained consistently warmer during the first three weeks. Moisture content in EM-treated compost stayed within the optimal range of 50–60% throughout the process, with fluctuations limited to ± 5%, whereas control compost ranged from 45% to 65% and occasionally dropped below 40% (t-test, p = 0.03). pH rose from an initial 6.5 to 8.2 during the thermophilic phase in EM compost and stabilized at 7.5 at maturity; controls stabilized at 7.0 (p < 0.05). EC increased from 1.2 to 3.5 dS/m in EM compost but leveled off earlier than in controls, where EC reached 4.0 dS/m before stabilizing (repeated-measures ANOVA, p = 0.04). Table 1 Physical characteristics of compost during the 60-day composting period. Parameter EM-Inoculated Control Statistical test Peak temperature 65°C (day 3) 55°C (day 5) p 55°C 10 days 6 days F = 8.23, p = 0.01 Moisture range 50–60% (± 5%) 45–65% t-test, p = 0.03 pH (mature) 7.5 7.0 p < 0.05 EC (dS/m) 3.5 (early plateau) 4.0 RM-ANOVA, p = 0.04 3.2 Chemical composition of mature compost Organic matter content declined from an initial 65% (dry weight) to 28% in EM-inoculated compost by day 60, compared with 35% in controls (p = 0.02), confirming accelerated decomposition under EM treatment (Fig. 3 ). The C/N ratio dropped from 30 to 18 in EM compost and to 22 in controls over the same period (p = 0.02), reflecting faster carbon mineralization and better nitrogen conservation. Total nitrogen averaged 2.1% dry weight in mature EM compost versus 1.7% in controls (p = 0.01). Phosphorus and potassium concentrations were approximately 15% and 18% higher in EM treatments (P: 0.45% vs. 0.39%; K: 1.2% vs. 1.0%; both p 0.1), indicating that EM inoculation did not introduce additional contamination. Table 2 Chemical composition of mature compost after 60 days. Parameter EM-Inoculated (%) Control (%) p-value Organic matter (day 60) 28 (from 65) 35 (from 65) 0.02 Total nitrogen 2.1 1.7 0.01 Total phosphorus 0.45 0.39 < 0.05 Total potassium 1.2 1.0 0.1 3.3 Microbial community dynamics Thermophilic bacterial populations peaked at 1.2 × 10⁸ CFU/g in EM compost on day 7, significantly higher than 7.5 × 10⁷ CFU/g in controls (p = 0.03). Mesophilic populations increased during maturation in both treatments, but EM compost maintained roughly 20% higher microbial diversity throughout the process (Shannon index: 3.8 vs. 3.1 at maturity; p = 0.02). Amplicon sequencing revealed that Firmicutes (notably Bacillus spp.) dominated the thermophilic phase, while Actinobacteria and Proteobacteria became more abundant during cooling and maturation. Fungal communities were dominated by Ascomycota, with Cladosporium and Penicillium contributing to lignocellulose degradation. Quantitative PCR confirmed that EM-associated taxa lactic acid bacteria, photosynthetic bacteria, yeasts, and actinomycetes were 10–25% more abundant in EM bins than in controls (p < 0.05), consistent with successful establishment and proliferation of the inoculated consortium. Table 3 Microbial community dynamics during composting. Parameter EM-Inoculated Control p-value Thermophilic bacteria (CFU/g, day 7) 1.2 × 10⁸ 7.5 × 10⁷ 0.03 Shannon diversity index 3.8 3.1 0.02 EM-taxa relative abundance increase 10–25% above control Baseline < 0.05 3.4 Compost maturity and stability The germination index (GI) of EM-inoculated compost reached 85% after 45 days, compared with 70% in controls (p = 0.01). A GI above 80% is generally considered indicative of mature, non-phytotoxic compost (De Moraes Cunha Goncalves et al., 2020 ). Humic substance content increased by 35% relative to initial levels in EM compost, significantly exceeding the 20% increase in controls (p = 0.03). Together with the lower C/N ratio and higher GI, these results indicate that EM treatment produced a more mature and stable end product. Table 4 Compost maturity and stability indicators. Parameter EM-Inoculated Control p-value Germination index (%) 85 (day 45) 70 0.01 C/N ratio (day 60) 18 22 0.02 Humic substance increase (%) 35 20 0.03 4. DISCUSSION 4.1 Temperature, moisture, and pH dynamics The rapid attainment of thermophilic temperatures in EM-inoculated bins (65°C within 3 days) and the extended duration above 55°C are consistent with reports that EM inoculation stimulates early microbial metabolic activity, generating greater heat output from labile substrate decomposition (Mckinley & Vestal, 1985 ; Lai et al., 2025 ). Thermophilic temperatures above 55°C for several consecutive days are important for pathogen destruction under international composting standards, so the 10-day exceedance in EM bins represents a practical advantage for sanitation. Moisture stability in the 50–60% range observed in EM compost aligns with the optimal window for microbial activity. At moisture levels below 40%, microbial metabolism slows due to water-stress limitation, while levels above 65–70% restrict oxygen diffusion and promote anaerobic conditions (Richard et al., 2002 ; Zhang et al., 2022 ). The narrower moisture range in EM treatments may reflect more uniform microbial heat production, which moderates water evaporation rates. The pH trajectory initial rise during ammonification followed by stabilization near neutrality is typical of well-managed composting (Anayet et al., 2024 ). The slightly higher mature-compost pH in EM bins (7.5 vs. 7.0) may reflect greater ammonia release during more intense nitrogen mineralization, though both values fall within the acceptable range for agricultural application. 4.2 Chemical transformations and nutrient dynamics The faster decline in organic matter and C/N ratio in EM compost indicates that inoculation accelerated the breakdown of labile carbon substrates and promoted earlier entry into the humification phase. Nutrient enrichment during composting is driven by concentration effects as carbon is lost as CO₂ and by microbial assimilation that retains nitrogen in biomass (Kominoski et al., 2017 ; Brown et al., 2022 ). The 24% increase in total nitrogen in EM compost relative to controls (2.1% vs. 1.7%) is consistent with enhanced microbial biomass and reduced ammonia volatilization, as EM-associated lactic acid bacteria can lower local pH and suppress NH₃ loss (Jusoh et al., 2013 ). Phosphorus and potassium gains of 15–18% over controls likely reflect greater mineralization of organically bound nutrients by the more active microbial community in EM treatments. The absence of heavy-metal differences between treatments confirms that EM inoculation does not mobilize or introduce contaminants a prerequisite for safe agricultural use (Hemidat et al., 2018 ). 4.3 Microbial dynamics and EM effectiveness The higher thermophilic bacterial counts and sustained microbial diversity in EM compost are consistent with EM reported ability to augment indigenous communities rather than simply replacing them (Mironov et al., 2024 ). The dominance of Firmicutes (Bacillus spp.) during the thermophilic phase and the shift toward Actinobacteria during cooling follow the classical microbial succession pattern in composting (Chandna et al., 2013 ; Ren et al., 2016 ), but EM inoculation shifted the relative abundances toward higher representation of functional decomposers. qPCR data confirmed that EM-associated taxa persisted and proliferated throughout the 60-day process, with 10–25% higher relative abundances than in controls. These organisms produce extracellular enzymes cellulases, proteases, and lipases that facilitate the breakdown of recalcitrant substrates such as cellulose and lignin (Huang et al., 2018 ; Kaiser et al., 2010 ). The positive feedback between enzyme production, substrate availability, and microbial growth helps explain the faster decomposition kinetics observed in EM treatments (Cleveland et al., 2006 ; Campbell et al., 2022 ). 4.4 Compost quality and potential applications A germination index of 85% in EM compost exceeds the 80% threshold widely used to classify compost as mature and non-phytotoxic (Bazrafshan et al., 2016 ; Helfrich et al., 1998 ). The 35% increase in humic substances further confirms advanced humification, which improves the soil-amendment value of the compost by enhancing cation-exchange capacity and water-holding properties (Filcheva & Tsadilas, 2002 ). By contrast, control compost at 70% GI would still require additional curing before safe field application. The nutrient profile of mature EM compost (N 2.1%, P 0.45%, K 1.2%) compares favorably with established quality standards for soil improvers (Silva et al., 2007 ; Al-Sari et al., 2018 ). Taken together, these results suggest that EM-inoculated household composting produces a product suitable for direct agricultural use, supporting smallholder farming and urban greening programs in Zanzibar. 5. CONCLUSION EM inoculation of household organic waste significantly improved composting performance across physical, chemical, and biological indicators. Compared with uninoculated controls, EM treatments reached higher thermophilic temperatures sooner, maintained more stable moisture, achieved faster organic matter decomposition and nutrient concentration, produced higher microbial diversity, and yielded a more mature and less phytotoxic final product. Heavy metals remained within safe limits regardless of treatment. These results support the use of EM-inoculated composting as a low-cost, decentralized strategy for managing household organic waste in Zanzibar and similar settings. Scaling this approach could reduce landfill pressure, lower greenhouse gas emissions from open dumping, and provide nutrient-rich soil amendments for local agriculture. Future work should evaluate the long-term effects of EM-compost application on soil health, crop yield, and emissions under field conditions, and should assess the economic feasibility and community acceptance of household-scale EM composting programs. Declarations CONFLICT OF INTEREST The authors declare no conflicts of interest. Author Contribution Khamis M Said: Conceptualization; investigation; writing—original draft; methodology; Jecha S Jecha: investigation; writing – original draft; methodology; review and editing. Acknowledgement The authors thank residents of local villages in Zanzibar who facilitated data collection. This study did not receive specific funding from any agency in the public, commercial, or not-for-profit sectors. 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Assessment of municipal solid waste compost quality using standardized methods before preparation of plant growth media. Waste Management & Research , 25 (2), 99–108. https://doi.org/10.1177/0734242x07075514 Weissert, J., Henzler, K., & Kassahun, S. K. (2025). Towards sustainable municipal solid waste management: an SDG-based sustainability assessment methodology for innovations in Sub-Saharan Africa. Waste , 3 (1), 6. https://doi.org/10.3390/waste3010006 Zhang, S., Zhong, B., An, X., et al. (2022). Effect of moisture content on the evolution of bacterial communities and organic matter degradation during bioaugmented biogas residues composting. World Journal of Microbiology and Biotechnology , 39 (1). https://doi.org/10.1007/s11274-022-03454-7 Additional Declarations No competing interests reported. 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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-9454230","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":625286874,"identity":"97290a50-8c84-4088-b4c1-3277db1c3793","order_by":0,"name":"Khamis M Said","email":"","orcid":"","institution":"Zanzibar University","correspondingAuthor":false,"prefix":"","firstName":"Khamis","middleName":"M","lastName":"Said","suffix":""},{"id":625286875,"identity":"8620c362-94c5-407b-82d2-6bb93cc7adce","order_by":1,"name":"Jecha Jecha","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+0lEQVRIiWNgGAWjYBACxgYGNgaGChjXgGgtZ+BaoHoO4NfFxsDYBucQoYW5vfnZg5/z6uTNJZKfffxR8Cexgf3wA+YPf/A4rOeYuWHvNjbDnTPSjGfzGBgkNvCkGTAc4MGjZUYOmwTvNh7GDWcOGDMzgLQw5AAdJoFHy/w3bJJ/50jYbzhz/DPjD5AW/jdALXiCjnEGD5s0b4NB4objPcYMYIdJgGxJwOeXNDNpmWMJyUAtxcw8BsbGbRLPDA6cOYBbi2H74WeSb2rqbDccZt/M+OOPnGw/f/LDBxV4QsywAU3AERRHeOxgYJBHF7DHp3oUjIJRMApGJgAA6SVOuGMckw4AAAAASUVORK5CYII=","orcid":"","institution":"Zanzibar University","correspondingAuthor":true,"prefix":"","firstName":"Jecha","middleName":"","lastName":"Jecha","suffix":""}],"badges":[],"createdAt":"2026-04-18 05:08:51","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9454230/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9454230/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":107436039,"identity":"a47d37f5-397f-444f-b39b-b90c3ff3f9d2","added_by":"auto","created_at":"2026-04-21 13:18:23","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":406508,"visible":true,"origin":"","legend":"\u003cp\u003eAccumulation of solid waste in open space near households in the study area.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9454230/v1/3e8f1405d23bc92907e3fd4b.jpeg"},{"id":107488627,"identity":"d98e1035-4b32-4fd5-bc43-513f5200f034","added_by":"auto","created_at":"2026-04-22 02:45:21","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":124088,"visible":true,"origin":"","legend":"\u003cp\u003eTemperature profiles during composting of household organic waste. Dashed line indicates the 55°C thermophilic threshold. Error bars omitted for clarity; n = 3 per treatment.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-9454230/v1/702e701915cfd929570f3561.png"},{"id":107436040,"identity":"6b3073a4-aa29-4333-b1f8-f17a0b305740","added_by":"auto","created_at":"2026-04-21 13:18:24","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":171919,"visible":true,"origin":"","legend":"\u003cp\u003eOrganic matter content (left axis, blue) and C/N ratio (right axis, red) during composting. Solid lines and filled markers: EM-inoculated; dashed lines and open markers: control. n = 3 per treatment.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-9454230/v1/3d327b037ddd48be6efd8c0d.png"},{"id":107436042,"identity":"dbeec3b0-9503-44bc-b794-ee8cb15f22e0","added_by":"auto","created_at":"2026-04-21 13:18:24","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":57251,"visible":true,"origin":"","legend":"\u003cp\u003eNutrient content (N, P, K) in mature compost. Blue: EM-inoculated; orange: control. Asterisks denote significant differences (p \u0026lt; 0.05). Error bars represent standard deviation; n = 3.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-9454230/v1/14c55c1f2c31ee122f0d6457.png"},{"id":107436043,"identity":"da4da943-8796-45a9-be56-4b90caeb0ce7","added_by":"auto","created_at":"2026-04-21 13:18:24","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":80884,"visible":true,"origin":"","legend":"\u003cp\u003eCompost maturity and stability indicators. Left: Shannon diversity index; center: germination index (%); right: humic substance increase (%). Blue: EM-inoculated; orange: control. Asterisks denote p \u0026lt; 0.05.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-9454230/v1/8662c29c7e31f00403f5d5c2.png"},{"id":109067358,"identity":"47445a75-69ae-4296-9fda-069bed34ed0d","added_by":"auto","created_at":"2026-05-12 09:37:31","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1061964,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9454230/v1/1c56db75-092b-4da9-be2a-986ffdc1a1f4.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Characterization and Enhancement of Household Solid Waste Composting Using Effective Microorganisms (EM)","fulltext":[{"header":"1. INTRODUCTION","content":"\u003cp\u003eMunicipal solid waste generation is increasing worldwide as populations grow and urbanize, placing strain on collection, treatment, and disposal systems (Barma et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). In many low- and middle-income countries the problem is compounded by inadequate infrastructure, open dumping, uncontrolled burning, and weak policy enforcement (Almokmesh et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Bundhoo, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Organic materials food scraps, yard trimmings, and other biodegradable household residues typically constitute more than half of domestic waste streams, yet recycling and composting rates remain low (Manea et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eZanzibar illustrates these challenges. Limited waste collection coverage, poor disposal practices, and low community participation leave organic waste largely unmanaged, contributing to environmental contamination and public-health risks (Mukama et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Composting offers a practical route for diverting organics from landfills while generating nutrient-rich soil amendments that support agriculture and reduce greenhouse gas emissions (Larney et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Manea et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The approach is particularly attractive for decentralized settings because it requires modest capital investment and can be scaled to household or community level (Katranci et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2026\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eEffective Microorganisms (EM) are mixed-culture inoculants containing lactic acid bacteria, photosynthetic bacteria, yeasts, and actinomycetes that have been reported to accelerate organic matter decomposition, suppress pathogens, and reduce odors during composting (Weissert et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2025\u003c/span\u003e; Greff et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Laboratory and field trials on substrates ranging from rice straw to mushroom waste have shown that EM application can shorten composting duration, raise peak temperatures, and improve compost nutrient content and maturity (Ansari et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Jusoh et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Raimi et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). However, much of this work was conducted on agricultural or industrial feedstocks rather than mixed household organic waste, and few studies have combined physical, chemical, and molecular-biological indicators within a single experimental design.\u003c/p\u003e \u003cp\u003eThe present study therefore aimed to (1) characterize the composting process of household organic solid waste inoculated with EM relative to uninoculated controls, and (2) quantify the effects of EM inoculation on process performance (temperature, moisture, pH, EC), chemical composition (organic matter, C/N, N\u0026ndash;P\u0026ndash;K, humic substances, heavy metals), microbial community dynamics, and compost maturity (germination index). The results are intended to inform low-cost, decentralized waste management strategies applicable in Zanzibar and comparable resource-constrained settings.\u003c/p\u003e"},{"header":"2. MATERIALS AND METHODS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Experimental design\u003c/h2\u003e \u003cp\u003eComposting experiments were conducted in controlled bins of varying volumes (6, 9, and 21 L). Each bin was loaded with household organic waste (food waste, yard trimmings) to approximately 60% of its capacity, leaving sufficient void space for aeration. Treatments comprised two groups: (1) EM-inoculated bins, in which EM solution was applied at doses of 20\u0026ndash;100 mL and mixed homogeneously with the feedstock; and (2) uninoculated control bins receiving no microbial additive. Each treatment was replicated three times. Composting duration was 60 days, with conditions maintained to promote thermophilic development: target moisture of approximately 60%, periodic manual aeration, and temperature monitoring (Raimi et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Lew et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Sample collection and preparation\u003c/h2\u003e \u003cp\u003eHousehold solid waste was sampled using a stratified random design across households of different socioeconomic strata to capture variability in waste generation and composition (Bolaane \u0026amp; Ali, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Monavari et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Collected waste was sorted into organic and inorganic fractions; the organic fraction was shredded to a particle size below 20 mm, homogenized, and loaded into composting bins. Segregation bins were installed at participating households to facilitate source separation and improve sample quality (Requena-Sanchez et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eEM inoculum was prepared by activating a commercial EM stock culture in a molasses-water medium (1:1:20 v/v) under anaerobic conditions for 7 days at ambient temperature, following standard preparation protocols. The activated EM, containing lactic acid bacteria, photosynthetic bacteria, yeasts, and actinomycetes, was diluted to working concentration and applied at the time of bin loading (Jusoh et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Raimi et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Analytical methods\u003c/h2\u003e \u003cp\u003ePhysical parameters were measured as follows. Temperature was recorded daily at three depths within each bin using calibrated thermocouples. Moisture content was determined gravimetrically by drying sub-samples at 105\u0026deg;C to constant weight. pH and electrical conductivity (EC) were measured in 1:10 (w/v) aqueous extracts using calibrated meters.\u003c/p\u003e \u003cp\u003eChemical analyses included organic matter content by loss on ignition at 550\u0026deg;C, total nitrogen by Kjeldahl digestion, total phosphorus by spectrophotometry after acid digestion, and total potassium by flame photometry. The C/N ratio was calculated from organic carbon (OM/1.724) and total nitrogen values. Humic substance fractionation (humic and fulvic acids) followed the IHSS alkali-extraction protocol. Heavy metals (Pb, Cd, Zn) were determined by atomic absorption spectrometry after acid digestion (Gao \u0026amp; Xu, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2014\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eMicrobiological assessments combined culture-based and molecular methods. Total viable counts of thermophilic and mesophilic bacteria were obtained on nutrient agar incubated at 55\u0026deg;C and 30\u0026deg;C respectively. Microbial community composition was characterized by 16S rRNA gene amplicon sequencing (V3\u0026ndash;V4 region) and quantitative PCR (qPCR) targeting dominant EM-associated taxa (lactic acid bacteria, photosynthetic bacteria, yeasts, actinomycetes). Shannon diversity indices were calculated from sequence data. Compost maturity was assessed by the germination index (GI) using cress seed bioassays (Cangelosi \u0026amp; Meschke, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Nemati et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Data analysis\u003c/h2\u003e \u003cp\u003eAll data were tested for normality (Shapiro\u0026ndash;Wilk) and homogeneity of variances (Levene's test) prior to analysis. Differences between EM-inoculated and control treatments were evaluated using independent-samples t-tests for single time-point comparisons and repeated-measures ANOVA for time-series data (temperature, moisture). One-way ANOVA was applied to compare treatment means for chemical and biological parameters at maturity. Significance was set at α\u0026thinsp;=\u0026thinsp;0.05. Analyses were performed with R (v. 4.4) (Abbasnasab Sardareh et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e"},{"header":"3. RESULTS","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Physical characteristics during composting\u003c/h2\u003e \u003cp\u003eTemperature profiles for the two treatments are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. EM-inoculated compost reached a peak thermophilic temperature of 65\u0026deg;C within 3 days, compared with 55\u0026deg;C in controls. Temperatures above 55\u0026deg;C were sustained for 10 days in EM bins versus 6 days in controls; this difference was statistically significant (ANOVA, F\u0026thinsp;=\u0026thinsp;8.23, p\u0026thinsp;=\u0026thinsp;0.01). Both treatments returned to ambient levels by day 40, though the EM treatment remained consistently warmer during the first three weeks.\u003c/p\u003e \u003cp\u003eMoisture content in EM-treated compost stayed within the optimal range of 50\u0026ndash;60% throughout the process, with fluctuations limited to \u0026plusmn;\u0026thinsp;5%, whereas control compost ranged from 45% to 65% and occasionally dropped below 40% (t-test, p\u0026thinsp;=\u0026thinsp;0.03). pH rose from an initial 6.5 to 8.2 during the thermophilic phase in EM compost and stabilized at 7.5 at maturity; controls stabilized at 7.0 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). EC increased from 1.2 to 3.5 dS/m in EM compost but leveled off earlier than in controls, where EC reached 4.0 dS/m before stabilizing (repeated-measures ANOVA, p\u0026thinsp;=\u0026thinsp;0.04).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePhysical characteristics of compost during the 60-day composting period.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEM-Inoculated\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eControl\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eStatistical test\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePeak temperature\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e65\u0026deg;C (day 3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e55\u0026deg;C (day 5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDuration\u0026thinsp;\u0026gt;\u0026thinsp;55\u0026deg;C\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10 days\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6 days\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eF\u0026thinsp;=\u0026thinsp;8.23, p\u0026thinsp;=\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMoisture range\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e50\u0026ndash;60% (\u0026plusmn;\u0026thinsp;5%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e45\u0026ndash;65%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et-test, p\u0026thinsp;=\u0026thinsp;0.03\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH (mature)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEC (dS/m)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.5 (early plateau)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRM-ANOVA, p\u0026thinsp;=\u0026thinsp;0.04\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Chemical composition of mature compost\u003c/h2\u003e \u003cp\u003eOrganic matter content declined from an initial 65% (dry weight) to 28% in EM-inoculated compost by day 60, compared with 35% in controls (p\u0026thinsp;=\u0026thinsp;0.02), confirming accelerated decomposition under EM treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The C/N ratio dropped from 30 to 18 in EM compost and to 22 in controls over the same period (p\u0026thinsp;=\u0026thinsp;0.02), reflecting faster carbon mineralization and better nitrogen conservation.\u003c/p\u003e \u003cp\u003eTotal nitrogen averaged 2.1% dry weight in mature EM compost versus 1.7% in controls (p\u0026thinsp;=\u0026thinsp;0.01). Phosphorus and potassium concentrations were approximately 15% and 18% higher in EM treatments (P: 0.45% vs. 0.39%; K: 1.2% vs. 1.0%; both p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Heavy metal concentrations (Pb, Cd, Zn) remained below regulatory limits in both treatments with no significant difference between them (p\u0026thinsp;\u0026gt;\u0026thinsp;0.1), indicating that EM inoculation did not introduce additional contamination.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eChemical composition of mature compost after 60 days.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEM-Inoculated (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eControl (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOrganic matter (day 60)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e28 (from 65)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e35 (from 65)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal nitrogen\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal phosphorus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal potassium\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC/N ratio (day 60)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHeavy metals (Pb, Cd, Zn)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBelow limits\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBelow limits\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;0.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Microbial community dynamics\u003c/h2\u003e \u003cp\u003eThermophilic bacterial populations peaked at 1.2 \u0026times; 10⁸ CFU/g in EM compost on day 7, significantly higher than 7.5 \u0026times; 10⁷ CFU/g in controls (p\u0026thinsp;=\u0026thinsp;0.03). Mesophilic populations increased during maturation in both treatments, but EM compost maintained roughly 20% higher microbial diversity throughout the process (Shannon index: 3.8 vs. 3.1 at maturity; p\u0026thinsp;=\u0026thinsp;0.02).\u003c/p\u003e \u003cp\u003eAmplicon sequencing revealed that Firmicutes (notably Bacillus spp.) dominated the thermophilic phase, while Actinobacteria and Proteobacteria became more abundant during cooling and maturation. Fungal communities were dominated by Ascomycota, with Cladosporium and Penicillium contributing to lignocellulose degradation. Quantitative PCR confirmed that EM-associated taxa lactic acid bacteria, photosynthetic bacteria, yeasts, and actinomycetes were 10\u0026ndash;25% more abundant in EM bins than in controls (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), consistent with successful establishment and proliferation of the inoculated consortium.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMicrobial community dynamics during composting.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEM-Inoculated\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eControl\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThermophilic bacteria (CFU/g, day 7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.2 \u0026times; 10⁸\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.5 \u0026times; 10⁷\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.03\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eShannon diversity index\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEM-taxa relative abundance increase\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u0026ndash;25% above control\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBaseline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Compost maturity and stability\u003c/h2\u003e \u003cp\u003eThe germination index (GI) of EM-inoculated compost reached 85% after 45 days, compared with 70% in controls (p\u0026thinsp;=\u0026thinsp;0.01). A GI above 80% is generally considered indicative of mature, non-phytotoxic compost (De Moraes Cunha Goncalves et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Humic substance content increased by 35% relative to initial levels in EM compost, significantly exceeding the 20% increase in controls (p\u0026thinsp;=\u0026thinsp;0.03). Together with the lower C/N ratio and higher GI, these results indicate that EM treatment produced a more mature and stable end product.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCompost maturity and stability indicators.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEM-Inoculated\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eControl\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGermination index (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e85 (day 45)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC/N ratio (day 60)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHumic substance increase (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.03\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. DISCUSSION","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Temperature, moisture, and pH dynamics\u003c/h2\u003e \u003cp\u003eThe rapid attainment of thermophilic temperatures in EM-inoculated bins (65\u0026deg;C within 3 days) and the extended duration above 55\u0026deg;C are consistent with reports that EM inoculation stimulates early microbial metabolic activity, generating greater heat output from labile substrate decomposition (Mckinley \u0026amp; Vestal, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e1985\u003c/span\u003e; Lai et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Thermophilic temperatures above 55\u0026deg;C for several consecutive days are important for pathogen destruction under international composting standards, so the 10-day exceedance in EM bins represents a practical advantage for sanitation.\u003c/p\u003e \u003cp\u003eMoisture stability in the 50\u0026ndash;60% range observed in EM compost aligns with the optimal window for microbial activity. At moisture levels below 40%, microbial metabolism slows due to water-stress limitation, while levels above 65\u0026ndash;70% restrict oxygen diffusion and promote anaerobic conditions (Richard et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Zhang et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The narrower moisture range in EM treatments may reflect more uniform microbial heat production, which moderates water evaporation rates.\u003c/p\u003e \u003cp\u003eThe pH trajectory initial rise during ammonification followed by stabilization near neutrality is typical of well-managed composting (Anayet et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The slightly higher mature-compost pH in EM bins (7.5 vs. 7.0) may reflect greater ammonia release during more intense nitrogen mineralization, though both values fall within the acceptable range for agricultural application.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Chemical transformations and nutrient dynamics\u003c/h2\u003e \u003cp\u003eThe faster decline in organic matter and C/N ratio in EM compost indicates that inoculation accelerated the breakdown of labile carbon substrates and promoted earlier entry into the humification phase. Nutrient enrichment during composting is driven by concentration effects as carbon is lost as CO₂ and by microbial assimilation that retains nitrogen in biomass (Kominoski et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Brown et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The 24% increase in total nitrogen in EM compost relative to controls (2.1% vs. 1.7%) is consistent with enhanced microbial biomass and reduced ammonia volatilization, as EM-associated lactic acid bacteria can lower local pH and suppress NH₃ loss (Jusoh et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2013\u003c/span\u003e).\u003c/p\u003e \u003cp\u003ePhosphorus and potassium gains of 15\u0026ndash;18% over controls likely reflect greater mineralization of organically bound nutrients by the more active microbial community in EM treatments. The absence of heavy-metal differences between treatments confirms that EM inoculation does not mobilize or introduce contaminants a prerequisite for safe agricultural use (Hemidat et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e4.3 Microbial dynamics and EM effectiveness\u003c/h2\u003e \u003cp\u003eThe higher thermophilic bacterial counts and sustained microbial diversity in EM compost are consistent with EM reported ability to augment indigenous communities rather than simply replacing them (Mironov et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The dominance of Firmicutes (Bacillus spp.) during the thermophilic phase and the shift toward Actinobacteria during cooling follow the classical microbial succession pattern in composting (Chandna et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Ren et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), but EM inoculation shifted the relative abundances toward higher representation of functional decomposers.\u003c/p\u003e \u003cp\u003eqPCR data confirmed that EM-associated taxa persisted and proliferated throughout the 60-day process, with 10\u0026ndash;25% higher relative abundances than in controls. These organisms produce extracellular enzymes cellulases, proteases, and lipases that facilitate the breakdown of recalcitrant substrates such as cellulose and lignin (Huang et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Kaiser et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). The positive feedback between enzyme production, substrate availability, and microbial growth helps explain the faster decomposition kinetics observed in EM treatments (Cleveland et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Campbell et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e4.4 Compost quality and potential applications\u003c/h2\u003e \u003cp\u003eA germination index of 85% in EM compost exceeds the 80% threshold widely used to classify compost as mature and non-phytotoxic (Bazrafshan et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Helfrich et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e1998\u003c/span\u003e). The 35% increase in humic substances further confirms advanced humification, which improves the soil-amendment value of the compost by enhancing cation-exchange capacity and water-holding properties (Filcheva \u0026amp; Tsadilas, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). By contrast, control compost at 70% GI would still require additional curing before safe field application.\u003c/p\u003e \u003cp\u003eThe nutrient profile of mature EM compost (N 2.1%, P 0.45%, K 1.2%) compares favorably with established quality standards for soil improvers (Silva et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Al-Sari et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Taken together, these results suggest that EM-inoculated household composting produces a product suitable for direct agricultural use, supporting smallholder farming and urban greening programs in Zanzibar.\u003c/p\u003e \u003c/div\u003e"},{"header":"5. CONCLUSION","content":"\u003cp\u003eEM inoculation of household organic waste significantly improved composting performance across physical, chemical, and biological indicators. Compared with uninoculated controls, EM treatments reached higher thermophilic temperatures sooner, maintained more stable moisture, achieved faster organic matter decomposition and nutrient concentration, produced higher microbial diversity, and yielded a more mature and less phytotoxic final product. Heavy metals remained within safe limits regardless of treatment.\u003c/p\u003e \u003cp\u003eThese results support the use of EM-inoculated composting as a low-cost, decentralized strategy for managing household organic waste in Zanzibar and similar settings. Scaling this approach could reduce landfill pressure, lower greenhouse gas emissions from open dumping, and provide nutrient-rich soil amendments for local agriculture. Future work should evaluate the long-term effects of EM-compost application on soil health, crop yield, and emissions under field conditions, and should assess the economic feasibility and community acceptance of household-scale EM composting programs.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eCONFLICT OF INTEREST\u003c/h2\u003e \u003cp\u003eThe authors declare no conflicts of interest.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eKhamis M Said: Conceptualization; investigation; writing\u0026mdash;original draft; methodology; Jecha S Jecha: investigation; writing \u0026ndash; original draft; methodology; review and editing.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors thank residents of local villages in Zanzibar who facilitated data collection. This study did not receive specific funding from any agency in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eData supporting the findings of this study are available from the corresponding author upon request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAbbasnasab Sardareh, S., Brown, G. T. L., \u0026amp; Denny, P. (2021). Comparing four contemporary statistical software tools for introductory data science and statistics in the social sciences. \u003cem\u003eTeaching Statistics\u003c/em\u003e, \u003cem\u003e43\u003c/em\u003e(S1). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/test.12274\u003c/span\u003e\u003cspan address=\"10.1111/test.12274\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlmokmesh, S. 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Effect of moisture content on the evolution of bacterial communities and organic matter degradation during bioaugmented biogas residues composting. \u003cem\u003eWorld Journal of Microbiology and Biotechnology\u003c/em\u003e, \u003cem\u003e39\u003c/em\u003e(1). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11274-022-03454-7\u003c/span\u003e\u003cspan address=\"10.1007/s11274-022-03454-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"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":"Household solid waste, Effective Microorganisms, Composting, Nutrient retention, Microbial dynamics, Germination index","lastPublishedDoi":"10.21203/rs.3.rs-9454230/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9454230/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eHousehold organic solid waste represents a growing environmental burden in Zanzibar and similar low-income settings, where collection infrastructure is limited and open dumping remains common. This study evaluated Effective Microorganism (EM) inoculation as a means of accelerating household organic waste composting and improving final compost quality. Composting was conducted in controlled bins with EM applied as a liquid inoculum (20\u0026ndash;100 mL) mixed with feedstock, while controls received no inoculation. Temperature, moisture, pH, and electrical conductivity (EC) were monitored throughout; chemical indices (organic matter, C/N ratio, N\u0026ndash;P\u0026ndash;K, humic substances, heavy metals) and biological indicators (germination index, microbial counts, Shannon diversity, qPCR/sequencing of dominant taxa) were measured in mature compost. EM-inoculated bins reached 65\u0026deg;C within 3 days versus 55\u0026deg;C in controls and sustained thermophilic conditions (\u0026ge;\u0026thinsp;55\u0026deg;C) for 10 versus 6 days (F\u0026thinsp;=\u0026thinsp;8.23, p\u0026thinsp;=\u0026thinsp;0.01). Moisture remained within 50\u0026ndash;60% in EM treatments (p\u0026thinsp;=\u0026thinsp;0.03). EM compost showed faster organic matter loss (28% vs. 35% at day 60; p\u0026thinsp;=\u0026thinsp;0.02), higher nitrogen retention (2.1% vs. 1.7%; p\u0026thinsp;=\u0026thinsp;0.01), improved phosphorus and potassium content (+\u0026thinsp;15% and +\u0026thinsp;18%; p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), a lower final C/N ratio (18 vs. 22; p\u0026thinsp;=\u0026thinsp;0.02), earlier EC stabilization (3.5 vs. 4.0 dS/m; p\u0026thinsp;=\u0026thinsp;0.04), greater humification (+\u0026thinsp;35% vs. +20%; p\u0026thinsp;=\u0026thinsp;0.03), higher microbial diversity (Shannon 3.8 vs. 3.1; p\u0026thinsp;=\u0026thinsp;0.02), and superior maturity (germination index 85% vs. 70%; p\u0026thinsp;=\u0026thinsp;0.01). Heavy metals stayed below permissible limits in all treatments (p\u0026thinsp;\u0026gt;\u0026thinsp;0.1). These findings indicate that EM inoculation accelerates composting, yields a nutrient-dense and phytotoxicity-safe product, and can support decentralized waste management in resource-constrained communities.\u003c/p\u003e","manuscriptTitle":"Characterization and Enhancement of Household Solid Waste Composting Using Effective Microorganisms (EM)","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-21 13:18:18","doi":"10.21203/rs.3.rs-9454230/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","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}}],"origin":"","ownerIdentity":"27e7a922-bbdb-44c9-8b3f-04a30e48cb2b","owner":[],"postedDate":"April 21st, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Rejected","date":"2026-04-30T09:05:48+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-30T09:10:17+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-21 13:18:18","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9454230","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9454230","identity":"rs-9454230","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}