Modeling of biogas production efficiency from different sources of waste by anaerobic digestion
Date
2025-07
Authors
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Journal ISSN
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Publisher
Federal University of Technology, Owerri
Abstract
This research focused on the modeling of biogas production efficiency from different sources of waste using anaerobic digestion. The objectives of the work are to determine the biogas production capacities of the selected feedstocks (organic wastes), determine the compositions of the biogas produced, and derive/validate a model that optimizes the biogas production. The process of producing the biogas from the mini-biodigester involves sourcing the feedstocks, mixing them with water to a suitable proportion, pouring the slurry mixture into the mini biodigester while ensuring that the mini-biodigester is airtight, and allowing anaerobic bacteria to break down the waste. The study was conducted in a controlled laboratory environment employing mini-biodigesters with capacities of 120 and 40liters respectively. Four different feedstocks—sewage, pig waste, poultry waste, and homemade waste (a mixture of watermelon and pineapple)—were used as substrates to feed the biodigesters singly and in various combinations. The experimental results over a 14-day peak production periods indicated average daily biogas production rates of 0.0329, 0.0372, 0.0354, 0.0296, 0.0344, 0.0336, 0.0362,0.0356, 0.0328, 0.0319, 0.0384, 0.0332, 0.0326, 0.0340 and 0.0381 liters per day for the following substrate samples: Sample 1, Sample 2, Sample 3, Sample 7, Sample 8, Sample 9, Sample 10, Sample 11, Sample 12, Sample 13, Sample 14, and Sample 15 respectively. The percentage methane content in the biogas produced from these substrates (Samples) was found to be 54.80%, 58.70%, 56.60%, 51.70%, 68.10%, 66.84%, 68.20%, 69.18%, 66.24%, 64.98%, 65.50%, 68.04%, 65.24%, 66.50% and 66.73%, respectively. To optimize biogas production, a mathematical model was formulated with the variables X1, X2, X3, and X4 subjected to retention time, moisture content, carbon/nitrogen, temperature, and pH constraints. The Simplex Method was employed to solve the model, resulting in an objective function value of 2.6669. The optimal values of the variables were X1 = 0.0075, X2 = 1.1981, X3 = 0.0027, and X4 = 0.0227, indicating the most efficient combination of feedstocks for biogas production. The developed optimization model serves as a valuable tool for maximizing biogas yields using small scale biodigester in an anaerobic environment, thereby contributing significantly to the field of renewable energy and environmental sustainability.
Description
This research focused on the modeling of biogas production efficiency from different sources of waste using anaerobic digestion
Keywords
Anaerobic digestion, biogas production, methane content, sewage waste, pig waste, poultry wastes, watermelon wastes, pineapple wastes, mini-biodigester, optimization model
Citation
Abaraogu, U. J. (2025). Modeling of biogas production efficiency from different sources of waste by anaerobic digestion (Unpublished Doctoral Thesis). Federal University of Technology, Owerri, Nigeria