DESIGN AND FABRICATION OF AN ANAEROBIC DIGESTER FOR THE PRODUCTION OF BIOGAS USING COW DUNG AND POULTRY WASTES AS RAW MATERIALS

ABSTRACT

The production of organic wastes from household food wastes, agricultural wastes, human and animal wastes has increased drastically over time based on increased in population and human activities. Waste not properly disposed can result to health diseases like malaria, cholera, typhoid etc. Different waste management techniques which includes source-separation, compositing and anaerobic digestion with regards to biogas production are been considered as substitute for the control of waste. Therefore, this study aims at the production of biogas by anaerobic digestion using biologically degradable wastes. In this study, a fifty (50) litres cylindrical anaerobic digester of diameter 420mm and height 950mm was designed and fabricated. The digester with inlet and outlet openings was fitted with different check valves to control production process. A day old Poultry waste and Cow dung collected from Poultry and Cow farms in Benin, were fed into the digester after mixing the substrate in different proportions. In the first experiment, the Cow dung was mixed with water in a ratio 1:5 (50kg Cow dung and 250kg water) and 25 litres of the mixture fed into the anaerobic digester and allowed to ferment for biogas production. In the second experiment, the Poultry waste was mixed with water in a ratio 1:5 (50kg Poultry waste and 250kg water) and 25 litres of the mixture fed into the anaerobic digester and allowed to ferment for biogas production. The third experiment was the mixture of Cow dung, Poultry waste with water in a ratio 1:1:5 (25kg Cow dung, 25kg Poultry waste, 125kg water) and 25 litres of the mixture was fed into the anaerobic digester for fermentation. Each of the Experiment was run and observed for 30 days. The results from the experiments shown that Biogas from Cow dung has a maximum yield of 0.35N/mm2 . Biogas from Poultry waste has a maximum yield of 0.37N/mm2 . While Biogas from both Cow dung and Poultry waste has a maximum yield of 0.30N/mm2 . In addition, it was observed that Biogas production was low at the beginning and end of the retention period of the anaerobic digestion process. This reveals that biogas production rate is directly proportional to the specific growth rate of methanogens. The study shows that Cow dung and Poultry waste are a potential substrate in Biogas production using anaerobic digester