The relationships among sCOD, VFAs, microbial community, and biogas production during anaerobic digestion of rice straw pretreated with ammonia

This study investigated the effects of soluble chemical oxygen demand (sCOD), volatile fatty acids (VFAs), and microbial community on biogas production in the process of rice straw (RS) anaerobic digestion (AD). The results showed that the sCOD concentrations and VFA production appeared the same trend, which was inversely related with that of daily biogas production. The cumulative methane yield of RS was 194.9 ml·(g VS)-1·−1. The modified Gompertz model is the best fit for measured methane yields of RS in the three kinetic models of first-order kinetic, Cone and modified Gompertz. Firmicutes, Bacteroidetes, and Euryarchaeota were the dominant microbial phyla throughout AD process. At the genus level, the microorganisms mainly composed of Clostridium, Vadin, Terrisporobacter, Methanosaeta, Methanobacterium, and Methanosarcina. Proteiniphilum showed strong relationship with sCOD and VFA production. Clostridium and Terrisporobacter displayed relationship with biogas production. Therefore, in order to improve the stability of the AD system, the parameter changes of VFAs, sCOD, and biogas yield were monitored in the RS AD process. The study can provide theoretical basis for improving the efficiency of RS AD.