DESIGN AND ASSESSMENT OF AN AFFORDABLE TARPAULIN-BASED BIOGAS SYSTEM FOR ECO-FRIENDLY COOKING IN COMMUNITIES WITH LIMITED ENERGY RESOURCES

International Journal of Advanced Scientific and Technical Research ISSN 2249-9954 Available online on http://www.rspublication.com/ijst/index.html volume 15, No. 5, 2025 DOI: 10.5281/zenodo.17284467 Original Article ©2025 RS Publication, [email protected] 229 DESIGN AND ASSESSMENT OF AN AFFORDABLE TARPAULIN-BASED BIOGAS SYSTEM FOR ECO-FRIENDLY COOKING IN COMMUNITIES WITH LIMITED ENERGY RESOURCES Itoro A. Sampson Department of Science Technology, Akwa Ibom State Polytechnic Ikot Osurua, Akwa Ibom State, Nigeria | +234 806 399 0815 |✉ [email protected] Inyang J. Udo Department of Science Technology, Akwa Ibom State Polytechnic Ikot Osurua, Akwa Ibom State, Nigeria|  +234 706 347 1343 |✉ [email protected] Umoren F. Alphonsus Department of Physics Education, Federal College of Education Bichi, Kano State, Nigeria | +234 803 834 2071 | ✉ [email protected] ARTICLE INFO ABSTRACT Paper ID: IJASTR68DE510BC8688 Received: 2025-09-06 Published: 2025-10-07 DOI: https://dx.doi.org /10.5281/zenodo.17 284467 Page No: 229-242 For low-income areas, biogas technology offers a long-term answer to the problems of energy poverty and environmental damage. Sustainable energy for cooking was the focus of this research. A pliable HDPE chamber served as the system's primary housing, and it was fitted with an organic biomass intake, an effluent discharge outlet, and a gas output that linked to a simple three-stage purification unit made up of water, silica gel, and iron sponge. Under batch digestion settings, three kinds of organic feedstock were subjected to anaerobic digestion: cow dung, cassava residues (fufu and garri), and fruit waste. Due to its consistent methanogenic activity and balanced carbon-to-nitrogen ratio (25:1), cow dung produced the most biogas (430± 2.0 L/kg VS) out of all the substrates evaluated during a 34-day hydraulic retention time (HRT). The acidification, as shown by a decrease in pH from 6.88 to 6.78, was the main cause of the fruit waste producing the lowest yield (200 ± 5.0 L/kg VS). Using sandbag ballast, the system was able to keep the pressure stable (0.15-0.25 Bar) while operating under passive solar heating (29-32°C). Gas leakage was limited, at less than 2%. Greenhouse gas emissions might be reduced by 2.1 metric tons of CO₂ equivalent each year, and the method could help slow down deforestation by 1.5 metric tons per family per year. Although there is a lack of longterm testing and methane quantification, the technology nevertheless provides a good way to produce clean energy decentralized in areas with limited resources. Keywords: Anaerobic digestion, Biogas production, Cassava residues, Cow dung, Fruit waste, Renewable energy International Journal of Advanced Scientific and Technical Research Available online on http://www.rspublication.com/ijst/index.html ISSN 2249-9954 Cite This Paper : Itoro Akpan Sampson Inyang John Udo and Umoren Friday Alphonsus(2025). "DESIGN AND ASSESSMENT OF AN AFFORDABLE TARPAULINBASED BIOGAS SYSTEM FOR ECO-FRIENDLY COOKING IN COMMUNITIES WITH LIMITED ENERGY RESOURCES". INTERNATIONAL JOURNAL OF ADVANCED SCIENTIFIC AND TECHNICAL RESEARCH (IJASTR), vol. 15, no. 5, 2025, pp. 229-242. DOI: https://dx.doi.org/10.5281/zenodo.17284467 International Journal of Advanced Scientific and Technical Research ISSN 2249-9954 Available online on http://www.rspublication.com/ijst/index.html volume 15, No. 5, 2025 DOI: 10.5281/zenodo.17284467 Original Article ©2025 RS Publication, [email protected] 230 INTRODUCTION Accessible and sustainable energy solutions are desperately needed, as seen by the ongoing problem of energy poverty in emerging nations, especially in sub-Saharan Africa. Due to their accessibility and affordability, households in many rural and peri-urban areas still primarily use traditional biomass fuels for cooking and heating, such as firewood, charcoal, and agricultural waste (IEA, 2020). However, human health, environmental sustainability, and socioeconomic development are all severely harmed by this reliance. Ineffective energy conversion and the release of hazardous pollutants occur when biomass is burned over open flames or in crude stoves. One of the main causes of respiratory ailments is exposure to indoor air pollution, especially for women and children who spend a lot of time near kitchen areas (Bruce et al. 2000). Furthermore, the extensive fuelwood collection exacerbates climate change and jeopardizes the ecological resilience of sensitive areas by causing deforestation, soil erosion, and biodiversity loss (FAO, 2010) The magnitude of this energy issue is considerable, as almost 2.4 billion individuals globally do not have access to clean cooking facilities, with more than 900 million in sub-Saharan Africa depending on traditional biomass fuels. In addition to the health consequences, as home air pollution is responsible for around 3.8 million premature deaths each year, this energy poverty significantly constrains social and economic growth prospects. Women and children, who generally assume the duty of fuel collection, frequently invest 15-30 hours per week harvesting biomass, time that could be allocated to education, money generating, or community engagement. Biogas technology provides a feasible and sustainable substitute for traditional biomass utilization. Biogas systems produce a combustible gas mixture, primarily consisting of methane (CH₄) and carbon dioxide (CO₂), through the anaerobic digestion of organic materials, including animal manure, food waste, and agricultural residues. This gas can be utilized for cooking, heating, and electricity generation. Moreover, biogas generation facilitates efficient waste management, decreases greenhouse gas emissions, and generates nutrient-dense digestate appropriate for agricultural use (Appels et al. 2008). The biogas production process involves four biochemical stages: hydrolysis, acidogenesis, acetogenesis, and methanogenesis, in which complex organic compounds are systematically decomposed by various microbial communities (Chandra et al. 2012). This biological process is affected by various operating parameters, including temperature, pH, carbon-to-nitrogen ratio, organic loading rate, and hydraulic retention duration. Optimizing these parameters is essential for maximizing methane yield and guaranteeing process stability, especially in small-scale systems designed for residential use. Notwithstanding its potential, the implementation of biogas technology in low-income and energy-deficient regions is still constrained. Substantial initial investment, insufficient technical skills, and socio-cultural obstacles impede extensive implementation, particularly in distant regions (Bond & Templeton, 2011). Furthermore, numerous current biogas systems are either overly intricate or prohibitively expensive for the intended users, forcing the creation of streamlined, economical designs adapted to local conditions. Although traditional fixed-dome and floating-drum digesters are extensively utilized in poor nations, they frequently necessitate considerable financial commitment, specific building expertise, and ongoing maintenance. Cost-effective alternatives, including as bag digesters and plastic tubular digesters, have surfaced as more attainable solutions for resource-limited environments (Mulinder et al. 2013). Nonetheless, these systems often encounter difficulties with durability, gas storage capacity, International Journal of Advanced Scientific and Technical Research ISSN 2249-9954 Available online on http://www.rspublication.com/ijst/index.html volume 15, No. 5, 2025 DOI: 10.5281/zenodo.17284467 Original Article ©2025 RS Publication, [email protected] 231 and compatibility with established cooking techniques, hence constraining their long-term viability and consumer adoption. This research tackles these deficiencies by creating and assessing an economical, tarpaulinbased methane digester appropriate for dispersed energy production. The system was constructed with locally sourced materials and functioned under batch digestion settings utilizing three prevalent biomass feedstocks: cow dung, cassava wastes (fufu and garri), and fruit refuse. The research evaluated biogas production, system pressure consistency, temperature regulation, and fundamental gas purification, emphasizing replicability, costeffectiveness, and community significance. This study illustrates the viability of a streamlined biogas system that corresponds with the resource limitations of rural families, thereby enhancing the existing knowledge on localized renewable energy technology. The results offer pragmatic insights into sustainable energy generation, emphasizing the necessity for policy assistance, community involvement, and additional research to enhance biogas implementation in energy-scarce areas. This research is significant as it aims to bridge technological and socio-economic gaps by creating an affordable, user-friendly biogas system that employs locally sourced materials and organic waste streams. This project intends to democratize access to clean cooking energy by concentrating on a tarpaulin-based design that features straightforward building and maintenance needs, specifically targeting homes below the poverty line that cannot afford traditional biogas systems. The comparative examination of various feedstocks offers essential insights into substrate selection and management, filling a significant knowledge gap in the optimization of small-scale biogas systems in tropical environments. This research corresponds with multiple Sustainable Development Goals (SDGs), specifically SDG 7 (Affordable and Clean Energy), SDG 13 (Climate Action), and SDG 3 (Good Health and Well-being) (UN, 2015). The effective deployment of contextually suitable biogas technology can greatly enhance energy availability in underserved populations, while concurrently facilitating climate mitigation by decreasing biomass usage and capturing methane from organic waste. Moreover, the shift from conventional biomass combustion to clean cooking fuels directly tackles a significant public health issue in developing nations, potentially enhancing respiratory health outcomes and alleviating the disease load linked to household air pollution. REVIEW OF RELATED WORKS Manonmani et al. (2017) conducted an experimental investigation of the biogas production rate in a laboratory-scale biogas digester model for the effective conversion of food waste (starchrich materials) generated from a university campus. The studies were conducted over a duration of 40 days, and the gas generation rate was quantified using the water displacement method. The pH of cow dung and food waste was originally measured and corrected to near neutral, then gradually elevated to acidic levels before stabilizing again at neutral pH, which facilitated biogas production. The total solids percentages were 69.86, 93.56, and 25.67 for cow dung, food waste, and digested slurry, respectively. The percentages of volatile substances were 52.5, 86.3, and 18.9 for cow dung, food waste, and digested slurry, respectively. The percentages of volatile fatty acids were 285, 356, and 365 for cow dung, food waste, and digested slurry, respectively. The biogas production rate consistently rose over time, reaching its maximum yield after 20 days. Budiyono et al. (2018) investigated biogas generation from organic waste, aiming to assess the influence of substrate type and content on the volume of biogas generated. They utilized fruit waste (including oranges, apples, papayas, and tomatoes), bovine rumen, urea, bovine manure, International Journal of Advanced Scientific and Technical Research ISSN 2249-9954 Available online on http://www.rspublication.com/ijst/index.html volume 15, No. 5, 2025 DOI: 10.5281/zenodo.17284467 Original Article ©2025 RS Publication, [email protected] 232 Na2CO3 buffer, NH4HCO3 buffer, and distilled water, incorporating modifications in substrate materials, F/W ratios, and buffer types. Enhanced biogas production was seen with the incorporation of cow manure and Na2CO3 buffer at a 1:2 F/W ratio compared to the variable utilizing NH4HCO3 buffer and the absence of cow dung. The variables using cow dung at a 1:1 ratio of F/W, utilizing a Na2CO3 buffer, yielded superior results compared to those employing the same buffer without cow dung, as well as those with a 1:1 ratio of F/W that included both cow dung and the Na2CO3 buffer. Variables with identical feed and absent cow dung supplementation generated higher biogases than those utilizing the NH4HCO3 buffer, at a 1:1 ratio of feed to water, and also without cow dung addition. Deressa et al. (2015) investigated biogas production from a combination of fruit and vegetable waste with cow dung in an anaerobic digester. The total solids, volatile solids, moisture content, and ash content of the garbage were analyzed. The feed ingredients were avocado, papaya, mango, tomato, banana peel, and cow manure. Different volumes of digesters were utilized for biogas production, and the combustibility of the generated gas was assessed. The anaerobic digestion of fruit and vegetable waste combined with various other waste materials required 55 days to provide biogas, indicating complete digestion. Da Silva et al. (2022) investigated the quality of biogas produced in a small-scale biodigester utilizing food waste decomposition from a university setting. A mobile laboratory examined the composition of the produced biogas. The findings indicated that this substrate and its heterogeneity possess significant potential for biogas production, with methane (CH4) content ranging from a minimum of 58.46% to a maximum of 68.41%, and an average of 65.44%. The biogas analysis revealed a low CO2 concentration of 38.02%, a maximum of 44.39%, and an average of 38.55%. The smallest value of hydrogen in the composition was 7.41 ppm, the maximum was 13.42 ppm, and the average was 9.63 ppm. Kabeyi and Olanrewaju (2022) conducted a study on biogas production and applications, outlining the avenues for utilizing biogas in the energy transition through power generation and fuel manufacturing. It was observed that diesel engines, gasoline engines, turbines, microturbines, and Stirling engines present viable alternatives for converting biogas into energy as prime movers. Their results indicated that biogas fuel may be utilized in both spark ignition (petrol) and compression ignition (diesel) engines, albeit with differing levels of modifications to traditional internal combustion engines. Furthermore, they asserted that biogas can be utilized in fuel cells for direct power conversion and as a precursor for hydrogen and transportation fuel production, representing a crucial avenue for development of sustainable energy. Enriched biogas or biomethane can be stored in containers or injected into gas supply networks for utilization as renewable natural gas. Polatci et al. (2016) conducted studies under controlled conditions from July to December. The daily quantity of incoming solid waste to the biogas production facility (kg), energy generation (MW), and methane gas output were quantified. Furthermore, temperature and relative humidity were analyzed. The daily solid trash processed ranged from 4,494 to 7,239 kg. The solid waste yielded a minimum methane output of 43.33 m³ and a high of 54.91 m³, correlating to a minimum electricity generation of 1.58 MW and a maximum of 5.85 MW during a single day. METHODOLOGY This study employed a pragmatic, design-focused methodology to create and assess a tarpaulinbased biogas system tailored for small-scale cooking energy uses in energy-deficient areas. The methodology included system design and fabrication, feedstock characterisation, batch International Journal of Advanced Scientific and Technical Research ISSN 2249-9954 Available online on http://www.rspublication.com/ijst/index.html volume 15, No. 5, 2025 DOI: 10.5281/zenodo.17284467 Original Article ©2025 RS Publication, [email protected] 233 anaerobic digestion experiments, gas purification, and performance assessment under mesophilic conditions. DESIGN AND CONSTRUCTION The biogas digester was fabricated from high-density polyethylene (HDPE) tarpaulin as shown in figure 1. The tarpaulin, measuring 0.5 mm in thickness, was chosen for its affordability, flexibility, and gas impermeability. The room was constructed in a cuboidal form (2 m × 1.5 m × 1 m), resulting in a total volume of 3 m³. PVC pipes with a diameter of 50 mm were utilized for the intake and outflow ports, whereas reinforced rubber tubing with a thickness of 10 mm transported gas from the chamber to the purification unit. To ensure structural integrity and safe operation, a basic pressure stabilization device incorporating four 5 kg sandbags and a pressure relief valve (threshold: 0.25 Bar) was implemented. The chamber's seams were thermally fused at 300°C and evaluated for leaks by hydrostatic testing and soap solution leak detection. A pressure gauge (0–0.5 Bar range) and a mercury-in-glass thermometer (0–100°C range) were placed to observe internal conditions. Pressure Guage Thermometer Fig. 1: Image of the Biogas Digester Inlet, showing the integration of a pressure gauge and thermometer for monitoring system pressure and temperature conditions. FEEDSTOCK SELECTION AND PREPARATION Three categories of organic substrates were chosen based on their availability, biodegradability, and significance to local waste streams. The organic substrates included fresh cow dung from cattle farms, cassava processing wastes (Fufu and Garri trash), and fruit waste (pineapple, watermelon, and banana peels). The substrates were mechanically pulverized to particle sizes of 1–2 cm and combined with water in a 1:1 ratio to attain total solids (TS) of 10–15%. The slurries were homogenized using an industrial mixer and adjusted to a neutral pH (6.5–7.5) using NaOH or HCl. Physicochemical tests were performed to ascertain moisture content, International Journal of Advanced Scientific and Technical Research ISSN 2249-9954 Available online on http://www.rspublication.com/ijst/index.html volume 15, No. 5, 2025 DOI: 10.5281/zenodo.17284467 Original Article ©2025 RS Publication, [email protected] 234 volatile solids (VS), and ash concentration by established drying and igniting methods (APHA, 2017). Each test was conducted in triplicate to ensure accuracy and reproducibility. EXPERIMENTAL SETUP AND BIOGAS PRODUCTION The anaerobic digestion experiments were performed utilizing a batch mode system. In each trial, 10 kg of slurry (5 kg substrate and 5 kg water) was introduced into the digester and sealed for a predetermined hydraulic retention time (HRT) of 30–34 days for cow dung, and 24 days for cassava residues and fruit waste. Biogas output was assessed utilizing a calibrated wet gas meter (Ritter TG05, ±1% accuracy), and cumulative yield was standardized per kilogram of volatile solids (L/kg VS). Measurements were documented bi-daily between 8:00 AM and 6:00 PM. Temperature was recorded hourly (6:00 AM–6:00 PM) with an internal thermometer, whilst gas pressure was documented daily utilizing a Bourdon tube gauge. The pH of the slurry was assessed bi-daily utilizing a digital pH meter (Hanna HI98107, ± 0.01 resolution). BIOGAS PURIFICATION The gas that was produced went through a three-stage purification process that included an iron sponge (Fe₂O₃·H₂O) to remove hydrogen sulfide, silica gel beads (Type B) to absorb moisture, and a distilled water chamber to scrub any residual gas. The flow was regulated through each stage of the process with brass needle valves, and the materials that were used for purification were either replaced or regenerated at regular intervals (for example, silica gel heated at 150°C once a week). DATA ANALYSIS AND QUALITY CONTROL A centralized Excel sheet was used to record all experimental data, including biogas volume, pressure, temperature, and pH. Biogas yield was compared between substrates using IBMSPSS v28 and a one-way analysis of variance (ANOVA). Post-hoc comparisons were conducted using Tukey's HSD test, and outliers were identified using Grubbs' test (p < 0.01). Triplicates of each substrate trial were performed. To ensure that no exogenous gas was produced, a control digester that solely contained water was used. The instruments were adjusted once a week, and where values were absent, they were filled in using the mean imputation method. RESULT AND DISCUSSION This section delineates the efficacy of the tarpaulin-based biogas system under batch digestion circumstances utilizing three distinct substrates: cow dung, cassava residues (Fufu and Garri), and fruit trash. The results encompass biogas yield, system stability (pressure, temperature, pH), and the efficacy of the purification system. All findings are examined about their significance for energy accessibility in resource-limited environments. PHYSICOCHEMICAL PROPERTIES OF FEEDSTOCKS All three substrates' physicochemical characteristics are listed in Table 1. The best-performing component was cow dung, which had a balanced carbon-to-nitrogen ratio (25:1), a high moisture content (75.2%), and an 85.4% volatile solids (VS) concentration. It is possible that the moderate gas output was caused by the cassava residues' greater C/N ratio (35:1). The low International Journal of Advanced Scientific and Technical Research ISSN 2249-9954 Available online on http://www.rspublication.com/ijst/index.html volume 15, No. 5, 2025 DOI: 10.5281/zenodo.17284467 Original Article ©2025 RS Publication, [email protected] 235 VS content (70.3%) and somewhat acidic PH of fruit waste, despite its substantial simple sugar content, made digestion difficult. Table 1. Feedstock physicochemical properties Substrate Moisture (%) Volatile solids, VS (%) C/N ratio Total solids (g/kg) Cow dung 75.2 ± 2.1 85.4 ± 3.2 25:1 248 ± 12 Fufu and Garri 68.3 ± 3.5 78.9 ± 2.8 35:1 210 ± 15 Fruit waste 80.5 ± 4.2 70.3 ± 3.7 20:1 195 ± 18 BIOGAS YIELD COMPARISON ACROSS SUBSTRATES There is a large range of biogas yields observed for various feedstocks and retention periods. According to Table 2, the biogas yield at a 34-day HRT is 430 ± 2.0 L/kg VS for cow dung, 250 ± 5.0 L/kg VS for cassava residues at 24 days, and 200 ± 5.0 L/kg VS for fruit waste. Figure 2 shows the biogas generation for each substrate over time. Based on the data presented in the image, it is clear that the materials used in this research had the following order of performance: Fufu and Garri (24 days), Fruit waste, and finally, cow dung. Biogas output varies non-linearly with time (in days) across all instances. The ideal methanogenic activity supported by the cow dung's balanced nutritional profile and well-buffered pH conditions is the reason for its outstanding performance. While fruit waste is highly biodegradable, it has acidity symptoms that prevent methane generation. Figure 2: Cumulative biogas yield curves for different substrates International Journal of Advanced Scientific and Technical Research ISSN 2249-9954 Available online on http://www.rspublication.com/ijst/index.html volume 15, No. 5, 2025 DOI: 10.5281/zenodo.17284467 Original Article ©2025 RS Publication, [email protected] 236 Table 2.Cumulative biogas yield Substrate HRT (Days) Mean ± SD Cow dung 30 411.0 ± 3.5 34 430.0 ± 2.0 Fufu and Garri 20 190.0 ± 5.0 24 250.0 ± 5.0 Fruit waste 20 150.0 ± 5.0 24 200.0 ± 5.0 pH STABILITY AND DIGESTION PERFORMANCE According to Table 3, the pH trend shows that after digestion, cow dung kept a consistent slightly alkaline pH (7.40 ± 0.02), which is perfect for methanogenesis. The slight increase in pH observed in fufu and garri residues during digestion is most likely caused by the buffer effects that result from the conversion of volatile fatty acids (VFAs). Pitfalls associated with acidogenesis and inadequate volatile fatty acid (VFA) conversion to methane are indicated by a decrease in P in fruit waste (from 6.88 to 6.78). Table 3. Preand Post-digestion P H Values for each substrate Substrate PH Mean ± SD Cow dung Before 7.12 ± 0.03 (30-day HRT) After 7.40 ± 0.02 Fufu&Garri Before 6.99 ± 0.05 (24-Day HRT) After 7.32 ± 0.03 Fruit waste Before 6.88 ± 0.04 (24-Day HRT) After 6.78 ± 0.04 CHAMBER AND SYSTEM PERFORMANCE The digester chamber's operational stability was assessed by controlling the temperature, gas pressure, and leakage. Considering the importance of sustainability, efficiency, and costeffectiveness, these metrics are crucial for evaluating the performance of the constructed chamber. In this study, the tarpaulin-based system was chosen because of these concerns. The passive solar heating made possible by the matte black coating keeps the interior temperature within the mesophilic range (29-32°C), as shown in Table 4. Thanks to the sandbag ballast mechanism, the system was able to keep the pressure at between 0.15 and 0.25 Bar very reliably. Throughout the experiments, leakage tests confirmed that gas loss stayed below 2%. User observations (no smell and consistent flame characteristics) proved that the simple International Journal of Advanced Scientific and Technical Research ISSN 2249-9954 Available online on http://www.rspublication.com/ijst/index.html volume 15, No. 5, 2025 DOI: 10.5281/zenodo.17284467 Original Article ©2025 RS Publication, [email protected] 237 purification system successfully decreased the levels of hydrogen sulfide (H₂S) and moisture. Table 4: Chamber Operational Performance Metrics Parameter Cow dung (30 Days) Fufu and Garri (24 Days) Fruit waste (24 Days) Avg temp. (°C) 32.5 ± 1.8 30.2 ± 2.1 29.8 ± 2.5 Pressure (Bar) 0.19 ± 0.03 0.15 ± 0.04 0.14 ± 0.05 P H Before digestion 7.12 ± 0.03 6.99 ± 0.05 6.88 ± 0.04 P H After digestion 7.40 ± 0.02 7.32 ± 0.03 6.78 ± 0.04 Leakage rate (%) < 2 < 2 < 2 STATISTICAL ANALYSIS OF BIOGAS YIELD To evaluate the statistical significance of changes in biogas yield between substrates, a oneway ANOVA test was used. There is a statistically significant difference (p < 0.001), according to the results in Table 5. Cow dung has a substantially larger yield than cassava residues and fruit waste, according to Tukey's HSD post-hoc test, proving that the substrate is superior. Table 5: ANOVA Summary for biogas yield across substrates Source df Sum of squares Mean square F-value p-value Substrate 3 28,450 9,483 18.7 < 0.001 Residual 16 8,120 507.5 - - Total 19 36,570 - - - DISCUSSION OF KEY FINDINGS The results confirm that low-resource communities can benefit from localized clean energy production using a biogas digester made of inexpensive tarps. Because of its good physicochemical qualities and steady microbiological composition, cow dung is the most reliable feedstock. Strategies to minimize acidification, such as PH buffering or co-digestion, are necessary due to the lower performance of fruit waste. From an engineering perspective, the system shows great promise for deployment on a household or small community scale because to its low leakage rate, pressure stability, and ease of manufacture. Consistent with previous research in rural energy applications, cow dung performs better than other substrates (Garfi et al. 2016). According to previous research on mesophilic digestion of cattle dung, the biogas yield in this study, which was 430 ± 2.0 L/kg VS, is within the predicted range of 350-450 L/kg VS (Gu et al. 2022). One reason for the relatively high yield is that cow manure