Anaerobic Co-Digestion Changes Microbial Community and Synergistically Increases Biogas Production in Municipal Digesters

Co-digestion of certain wastes (i.e., synergistic wastes) has been observed to produce more biogas than predicted based on the additional COD of the co-digestate alone. The objectives of this study were to determine the influence of co-digestion on microbial community structure and activity and quantify performance of full-scale anaerobic co-digestion using primary sludge and acid whey from cheese production. Biochemical methane potential tests were performed to identify the co-digestion outcomes. Methanogenic activity was determined using standard specific methanogenic activity (SMA) assays against acetate, propionate and H2. Denaturing gradient gel electrophoresis (DGGE) and quantitative PCR (qPCR) analyses were performed on the methyl coenzyme M reductase (mcrA) gene to compare methanogen communities. SMA increased when co-digestion was practiced. The increased SMA in co-digesters was putatively due to changes in the relative number of different methanogens present in co-digesters (i.e., the microbial community structure), and not due to an increase in the total number of all methanogens. The increased abundance of Methanospirillum, an H2-utilizing methanogen genus, played a significant role in higher methanogenic activity of co-digesters. Full scale co-digestion of acid whey with primary sludge synergistically increased CH4 production. Co-digestion of synergistic wastes is one method to increase biogas yield by changing methanogen community and enhancing microbial activity.