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

Abstract

Abstract 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...