System Performance and Microbial Communities of Anaerobic Digestion Systems Fed Dairy Manure

摘要

Anaerobic digestion (AD) is the most feasible technology to harness the energy of dairy manure as biogas. However, long retention time (21 days or longer) is needed because of recalcitrance of dairy manure fiber. In this study, we evaluated a thermophilic one-stage AD (T-1stg-AD), a thermophilic-mesophilic two-stage AD (referred to as temperature-phased AD, TPAD), and a mesophilic two-stage AD (M-2stg-AD) system, all at a 15-day retention time, for performance in digesting dairy manure and for variations of microbial populations. The T-1stg-AD system achieved the best performance, followed by the TPAD and the M-2stg-AD systems. For the TPAD system, its first-stage thermophilic digester outperformed its second-stage mesophilic digester, whereas the two digesters of the M-2stg-AD system had similar performance. Each digester harbored distinctive microbial populations, several of which were significantly correlated with system performance. Microbiomes of the two digesters of the TPAD system differed greater than the microbiomes of the two digesters of the M-2stg-AD system. Methanosarcina and Methanobacterium were the most predominant methanogen genera in the first-stage digesters of TPAD and M-2stg-AD and in the T-1stg-AD system, whereas Methanosaeta was the most predominant genus in the second-stage digesters of TPAD and M-2stg-AD. Population size of these genera appeared to be adversely correlated to VFA concentrations. The T-1stg-AD and the TPAD system can be better suited to digest dairy manure, with an additional benefit to kill off pathogens. Results may help further understand the microbiological underpinning of these digester systems and future implementation of AD systems on dairy farms.