Design and performance evaluation of small-scale biogas digesters using locally available materials in rural Uganda

Abstract

This research explores the design, fabrication, and performance evaluation of small-scale biogas digesters constructed from locally available materials in rural Uganda. The study evaluates the impact of different operational conditions, specifically temperature and hydraulic retention time (HRT), on the efficiency of biogas production. A series of digesters were constructed and tested under varying temperatures (35 °C, 45 °C, and 55 °C) and HRTs (5, 10, 15, 20, and 25 days). Performance metrics, including daily and cumulative biogas yields, were recorded and analyzed. Results indicated that digesters operating at 45 °C with a 25-day HRT yielded the highest cumulative biogas production, highlighting this combination as optimal for the local context. In contrast, higher temperatures (55 °C) resulted in decreased efficiency due to thermal stress, while lower temperatures (35 °C) produced lower yields. The study also examined the durability and maintenance requirements of digesters made from locally sourced materials, highlighting cost reductions as key advantages. A cost-benefit analysis revealed that the initial investment cost of the digester is recoverable in less than one year, depending on fuel savings and maintenance expenses. However, scaling up biogas technology in rural settings faces challenges, including initial costs, durability concerns, and limited community awareness.