EVALUATION OF BIOGAS YIELD FROM Vernonia amygdalina (Grawa) LEAVES CO-DIGESTED WITH COW DUNG UNDER ANAEROBIC CONDITION

Abstract

Biogas is an alternative renewable energy sources and a mixture of different gases, mainly methane and carbon dioxide, resulting from anaerobic digestion of organic matter. In this study, production of biogas from Vernonia amygdalina leaves co-digested with cow dung in anaerobic condition were evaluated under mesophilic condition at 38ºC using a batch mode digester. Biogas production was evaluated from treatments with different mix ratios A (100%VA) B (75%VA+25%CD), C (75%CD+25%VA), D (50%VA+50%CD) and E (100%CD) in three replicates. In all the treatments, physico-chemical parameters such as pH, total solid, volatile solid, organic carbon, total nitrogen and carbon to nitrogen ratio weremeasured before and after anaerobic digestion. The results showed that all measured physico chemical parameters of each substrate significantly (P<0.05) different before and after anaerobic digestion.Biogas production started in all of the digesters from first day of anaerobic digestion and decreased to zero at about 30 days in all digesters. The maximum cumulative biogas production was obtained from a substrate mix ratio of 75% VA+25%CD yielded (1784.12mL) biogas was produced, while the minimum (910.84mL) was measured in 100% cow dung mix ratio. Finally overall results indicated for the biogas yield, total solids (TS), volatile solid (VS), and percent of organic carbon was reduced. The highest reductions in TS (12.81%) and VS (12.38%) were recorded in 75%VA+25%CD (B). Therefore, the treatment (B) was significantly enhanced mix ratio among all other treatments which produced high cumulative biogas production.