Co-digestion of microbial biomass with animal manure in three-stage anaerobic digestion

Abstract

Microbial biomass (MB) was co-digested with different animal manures namely, chicken manure (CM), pig manure (PM) and cow dung (CD) at the ratios of 1:1:1:1, 2:1:1:1 and 3:1:1:1, and analyzed for biogas production. Maximum biogas yield and methane concentration were found at the ratio of 1:1:1:1. The optimization of biogas production was carried out using different pH values, temperatures, and substrate concentrations. The yield of methane was measured at different temperatures (35, 40, 50 and 55 ˚C). The optimum was 40 ˚C giving 62% CH4/d yield on the 6th day. The result of this study showed that co-digestion with microbes is beneficial for maximizing biogas production when compared to the anaerobic digestion of animal manure alone. A digester with a three-stage anaerobic digesting facility was designed, fabricated and analyzed for biogas production using the co-digestion of yeast biomass with pig manure. The reactor had separate chambers for hydrolysis, acidogenesis and methanogenesis. Each of them was optimized independently for simultaneous production and improvement of biogas and to analyze the performance of the reactor. The average methane yield with a three-stage anaerobic digester was 0.442 L/gVS. Higher volatile solids (VS) reduction of about 68% was seen at the third stage pf anaerobic digesting. Based on the findings from this study, the three stage anaerobic digestion was identified to be advantageous for high solids anaerobic digestion of microbial biomass with animal manure. Solid organic matters in the substrate was solubilized which leads to the formation of improved biogas production and volatile fatty acids.