PRODUCTION OF BIOGAS FROM Desmodium triflorum (L.) THROUGH ANAEROBIC CO-DIGESTION WITH COW DUNG

Abstract

Biogas is a methane rich gas produced by anaerobic breakdown of organic wastes with the help of methanogenic Archaebacteria under oxygen free environment. The objective of this study was to evaluate the potential of Desmodium triflorum (DT) to produce biogas through anaerobic digestion alone or in combination with cow dung (CD). In this study, biogas production from co-digestion of the Desmodium triflorum with cow dung in five mix ratios was evaluated under mesophilic conditions (38ºC) using batch digesters for 30 days of fermentation. In all treatments, physico-chemical parameters such as total solids, volatile solids, organic carbon, nitrogen, C: N ratio and pH values were determined before and after anaerobic digestion. All measured physico-chemical parameters of each substrate significantly varied between before and after AD (p <5%). Comparison of pH values between before and after anaerobic digestion showed that pH values were significantly increased after anaerobic digestion for all treatments. Maximum reduction of total solid and volatile solid was observed in mix ratio of 25% CD+75 DT. Similarly, high % of carbon reduction was observed in 25% CD+75% DT. Assessment of cumulative biogas production revealed that the substrate in a mix ratio of 25% CD and 75% DT (2329ml) showed the highest biogas production, suggesting this mix ratio of the two substrates is an optimal mix ratio to yield maximum amount of biogas. Overall the results of this study indicated that the increase in biogas yield and reduction in volatile solids and total solids can be significantly enhanced when Desmodium triflorum is co-digested with Cow dung in a 25%:75% mix ratio. However, in order to get more biogas from this substrate mix ratio several factors affecting the production other than the studied ones should be evaluated at certain time intervals during anaerobic digestion (AD)