COMPARATIVE STUDY OF THE KINETICS OF BIOGAS YIELD FROM THE CODIGESTION OF POULTRY DROPPINGS WITH WATERLEAF AND POULTRY DROPPINGS WITH ELEPHANT GRASS

Abstract

This study was carried out to produce biogas from two sets of feedstock poultry droppings with waterleaf (Talinum triangulare) and poultry droppings with elephant grass (Pennisetum Purpureum S.). Two 25 litre-plastic drums were modified and used as bio-digesters. One digester was used to digest poultry droppings with waterleaf while the other was used to digest poultry droppings with elephant grass. A fixed mass (8kg) of the feedstock and distilled water (4kg) were anaerobically digested in the ratio of 2:1 in each digester and their derivable energy were measured for biogas. The feed materials where sourced locally. It was observed that the pH for each set of feedstock was stable and within the optimal range of 6.5-7.5 indicating that the by-product obtained from the digester can be used as organic fertilizer after biogas recovery. Biogas production started on the 18th day for the poultry droppings with waterleaf, whereas, it started on the 26th day for poultry droppings with elephant grass. The cumulative mass of gas produced was 2600g for poultry droppings with waterleaf; and 1300g for poultry droppings with elephant grass. The average temperature range in the bio-digester during this study was between 37-40℃ for poultry droppings with waterleaf and 35-40℃ for poultry droppings with elephant grass. Hence, this study has shown that biogas can be produced from poultry droppings with lignocellulosic materials like elephant grass and waterleaf, but using waterleaf as co-digestate gives higher biogas energy potential than elephant grass, thus, waterleaf is a better seeding agent.