Design and construction of fixed dome digester for biogas production using cow dung and water hyacinth

Abstract

Engineered biological systems used for resource recovery often utilize anaerobic digestion to treat organic wastes by reclaiming the carbon as energy (methane gas) and a soil amendment (biosolids). This study explored the production of biogas from co-digestion of cow dung waste and water hyacinth (Eichhornia crassipes) using anaerobic biological conversion. Cow dung and water hyacinth biomass feedstock were collected from Abattoir and Ologbo River in Benin City, Nigeria. Samples were blended and substrate mixed in ratio 10:1 v/v due to balanced carbon/nitrogen (C: N) ratio of plant biomass and cattle rumen manure and charged into the fixed dome. Performance test was carried out after the biogas had been produced after twenty-one (21) days. The percentage composition of biogas produced shows that methane gas (CH 4) has 56.4%, carbon-dioxide (CO 2) is 35% and nitrogen (N 2) is 6.9%. Optimal production was found to be a function of temperature, hydraulic retention time, pH, concentration of bacterial population and overall design consideration of the digester. Scrubbers were fitted to rid the gas of hydrogen sulphide (H 2 S), CO 2 , ammonia (NH 3) and moisture. The gas was directed through a gas pipe to a burner for cooking in the staff canteen. This study is relevant for the implementation of Sustainable Development Goals (SDGs) and strengthening of the bio-based economy with respect to waste management. This can facilitate environmental and socioeconomic sustainability leading to reduced carbon foot print and reduction in solid waste accumulation.