Design and Fabrication of Biogas Plants, Comparing the Biogas Output of Three Agricultural Wastes

Energy is a crucial element in the industrialization and socio-economic development process of any nation. While in developing economies, proactive measures are taken towards making for energy adequacy, the need to develop an alternative source of energy cannot be over-emphasized. This project suggests a way forward in exploiting and developing biogas from different substrates for rural communities. Biogas technology from animal dung is feasible for smallholders with livestock producing 5kg manure per day, an equivalent of 4 pigs or 2 cows. The size of the digester was focused on achieving the desired output which is the biogas itself using anaerobic digestion and the substrates used were cow dung, pig dung, and poultry droppings. This fabrication was made to show a simple demonstration of biogas production by decomposition of cow dung, pig dung, and poultry dropping. Three digesters were made from plastic tanks of 9-liter capacity. The digester was connected to the water displacement setup for the gas collection. Each substrate had two (2) replicas, so as to get average and more accurate results, making a total of nine (9) fabricated digesters. The water displacement method of gas collection was adopted. The mode of feeding used was batch feeding (discontinued feeding). From the comparisons, it was evaluated that 5kg of Poultry droppings produced approximately 0.0133 liters of biogas per day. An adult pig, which produces about 5kg of manure daily (out of which is 90% water, a 7% volatile solid), produces an average of 0.2301 liters of biogas daily, and 5 kg of Cow dung produces about 0.0052 liters of biogas – all under 30 days retention time, and same environmental conditions.