Optimization of Biogas Production from Agricultural Waste under Variable Temperature Conditions

Thesis Abstract

The increasing global demand for sustainable energy sources necessitates the optimization of biogas production from organic waste materials, particularly agricultural waste, which remains underutilized despite its significant energy potential. This study addresses the challenge of maximizing biogas yield when agricultural waste undergoes anaerobic digestion under fluctuating temperature conditions typical of small-scale biogas systems in developing regions. The primary aim is to identify optimal operational parameters that enhance biogas output efficiency while accounting for temperature variability inherent in real-world settings. Specific objectives include assessing the effects of temperature fluctuations on biogas yield, developing a predictive model for biogas production under variable temperature regimes, and proposing operational strategies for improved biogas efficiency. To achieve these objectives, a mixed-method research design was adopted, integrating experimental laboratory investigations with field data collection. The population comprised agricultural waste samples locally sourced from 150 farms within the region, with a stratified random sampling technique used to select 50 representative farms for field data collection. Laboratory experiments involved micro-scale digesters subjected to controlled temperature variations reflecting diurnal and seasonal fluctuations, with biogas volume measured using gas meters and methane content analyzed via gas chromatography. Field data on ambient temperatures and waste characteristics were collected using portable sensors and standardized sampling protocols over a 12-month period. The validity and reliability of data collection instruments were ensured through calibration of sensors and pilot testing of procedures. Quantitative data were analyzed using analysis of variance (ANOVA) to examine the effects of different temperature regimes on biogas volume and methane content, while regression analysis facilitated the development of a predictive model for biogas output based on temperature fluctuations and waste composition. Complementary qualitative data from structured interviews with farm operators were analyzed thematically to contextualize laboratory findings within real-world operational challenges. The study hypothesizes that temperature variability significantly impacts biogas yield and that strategic operational adjustments can mitigate adverse effects. Expected findings include the quantification of biogas production differences under various temperature profiles and the development of a robust model capable of predicting yields under fluctuating conditions. It is anticipated that results will reveal critical temperature thresholds that optimize biogas output, providing empirical evidence to inform guidelines for decentralized biogas systems operating under natural temperature fluctuations. This research makes a significant contribution to knowledge by empirically demonstrating the relationship between temperature variability and biogas productivity, and by developing a predictive framework adaptable to diverse climatic regions. The main conclusion suggests that incorporating localized temperature management strategies can substantially improve biogas yields from agricultural waste, thereby promoting renewable energy adoption in rural communities. Consequently, recommendations include the integration of passive temperature regulation techniques and the development of simple, context-specific operational protocols for farmers. The study also advocates for further research into the scalability of these strategies across different climatic zones and socio-economic contexts, emphasizing the importance of multidisciplinary approaches to optimize biogas systems under variable environmental conditions.