Effect of staged anaerobic digestion and staged regulation on biogas production performance of rice straw and micromechanism analysis at the level of functional genes

Single stage anaerobic digestion (AD) is a process comprised of distinct stages, each with specific optimal conditions for the microbial communities involved. In this study, the AD process of rice straw (RS) was divided into two-phase (TP), two-stage (TS) and three-stage (ThS) systems by adjusting hydraulic retention time (HRT) to enhance the biomethane yield. Following system stabilization, the parameters of different stage were adjusted. The result showed that the biogas production of TP, TS and ThS systems was 26.4 %, 9.0 % and 10.4 % higher than single-stage system. Furthermore, after thermal adjustment, the biomethane production in TP, TS and ThS systems increased by 12.6 %, 17.6 % and 28.2 %, respectively. Metagenomic analysis revealed inhibition of CO2 and methyl methanogenesis in TP1 and ThS1, and multi-stage AD divided the AD process into different functional stages. The function of polysaccharide degradation and microbial activity were enhanced by staged regulation. Thus, the multi-stage AD is a promising strategy for enhancing biomethane production from RS, and judicious regulation of parameters can further improve AD performance.