Influence of solids concentration on microbial diversity and methane yield in the anaerobic digestion of rice husk

Anaerobic digestion of rice husk at high solids concentration is emerging as a sustainable technology for the production of methane rich biogas and nutrient rich biomanure. In this context, the main objective of the study is to determine the biomethanation potential of the rice husk at different solid concentrations and understand the efficiency of the methane generation with respect to the microbial diversity. Experiments are organised with rice husk at different total solids (TS) concentrations of 10 %, 20 %, 30 %, 40 %, and 50 %, and the highest methane yield of 0.33 L CH4/(g VS reduced) was observed at a TS of 40 %. It is observed that Bacteroidetes is found as the dominant phylum, 90 % of the methanogens are Methanosaeta, and their abundance is proportional to the concentration of solids in the reactor. It is also observed that acetoclastic methanogenesis is the dominant methane metabolic pathway in the process.