A Low-Cost Tubular Biogas Digester for Rural Households in Malawi

Abstract

Effective development and promotion of biogas technology can offer numerous benefits to any country. However, development and adoption this technology in Malawi has for a long time been constrained by locally unaffordable biogas digester designs. Hence the aim of the study was to develop biogas digester from locally available materials and assess its performance under Malawian environmental conditions. The study consisted of three pairs of locally constructed tubular polyethylene digesters (same design) that were fed with pig dung, goat stomach waste and kitchen food wastes. One digester in each pair was enclosed in a greenhouse structure made from transparent polyethylene. Gas production onset was quickest in digesters containing pig dung (1 day) followed by those containing goat stomach wastes (3-4 days) and lastly kitchen food wastes (14 days). Average daily gas production from digesters was 35.7 L/day and the average percentage of methane content in the biogas was 62.1 %. We therefore conclude that the overall performance of the tubular polyethylene digesters that were feed with goat stomach waste and pig dung was superior compared to other studies done at similar ambient temperatures. The flame was sustainable and usable for home and industrial purposes as the methane content was above 52%. We therefore further conclude that tubular digesters can be fabricated and used under Malawi conditions.

Key words: Energy sources, Biogas, digester, methane, design, wastes, Malawi.