Enrichment of the hydrogenotrophic methanogens for, in-situ biogas up-gradation by recirculation of gases and supply of hydrogen in methanogenic reactor.

During in situ biogas up-gradation by supplying hydrogen from an external source and enrichment of hydrogenotrophic methanogens, high pressure of H negatively affects hydrolytic and fermentative activities. To overcome this problem, the present study aimed to enrich the hydrogenotrophic methanogens by optimization of various parameters associated with gas recirculation along-with hydrogen supply from the external source. Due to recirculation of gases and supplied hydrogen, methane generation was two-fold higher in the optimal condition than in conventional anaerobic digestion, with the highest methane content of 99%. Additionally, the hydrogenotrophic methanogens were enriched, with a decrease in acetoclastic methanogens and an increase in Bathyarchaeia population, which utilizes H and CO to produce acetate and lactate as end products. The study concludes that recirculation increases methane production by converting H and CO into methane and enhances the degradation of organic matter left over undigested in the hydrolytic reactor.