Methane Production, Microbial Community, and Volatile Fatty Acids Profiling During Anaerobic Digestion Under Different Organic Loading

Long-term anaerobic co-digestion of lignocellulosic biomass Sida hermaphrodita and cattle manure was investigated under different organic loading rates (OLRs) (S1 – 2 kgVS/(m3·d), S2 – 3 kgVS/(m3·d), S3 – 4 kgVS/(m3·d)). The study examined the methane production, microbial community, and volatile fatty acids (VFAs). During the S1 and S2, the methane production was stable, and it reached 446.3±153.7 NL/kgVS and 773.4±107.8 NL/kgVS, respectively. In the S3, the methane production was reduced, the pH dropped from 7.68 to 6.11, the FOS/TAC ratio increased from 0.272 to 0.35, and the accumulation of acetic and propionic acid at the end of digester cycle was observed. The abundance of Firmicutes increased with increasing the OLR in the digester (reached 93.6% in the S3), while Bacteroidota abundance decreased with increasing the OLR in the digester (reached 3.0% in the S3). In the S1, the methane was produced through the acetoclastic and hydrogenotrophic pathways.