Journals Proceedings

Abstract

A biogas production unit was designed, fabricated and tested. It consists of a 168-litres anaerobic digester and a 38-litres gas storage tank connected together with 19 mm PVC pipes and locks. The digester and the separator tanks were fabricated from a high torsional strength 20 mm x 20 mm x 4 mm mild steel sheet supported by 60 mm x 60 mm x 4 mm angle iron welded together. Filler paste was applied to the two tanks for air tightness. The digester has a 900 mm shaft with blades attached that stirs the substrate. The machine is powered by a 0.75 kW electric motor connected to the side of the digester tank. A rubber seal was attached to the top of the stirrer to prevent the escape of gas from the tank. A pressure gauge and a gas connecting hose were attached for the measurement of the amount of gas produced, stored and released to the cooker respectively. Air and water tightness tests were carried out to avoid unnecessary leakage at any point. Plant and animal wastes were utilized as feedstock for the biogas plant. A 50 kg of blended water hyacinth and 100 litres of water were fed as feedstock in the digester. The result after 4 days retention was 0.178 bar. Further, a mixture of 70 kg pig dung, poultry droppings and cow dung and 50 litres of water were also fed as the feedstock to the digester for another 4 days retention period. The result obtained from the pressure gauge was 0.307 bar. The mixture of both waste (45 kg of animal dung, 45 kg of blended water hyacinth and 55 litres of water) was also tested and the result obtained was 0.619 bar. From the result of the test, it was concluded that the mixture of plant and animal waste is the best feedstock for the digester to attain optimum production of methane gas.