A Novel Batched Four-Stage–Two-Phase Anaerobic Digestion System to Facilitate Methane Production from Rice Straw and Cow Manure with Low Inoculum/Substrate Ratios

In order to improve the performance of methane production from agro-waste, a batched four-stage–two-phase anaerobic digestion (4S2P-AD) system was designed combine advantages both co-digestion (co-AD) and two-phase AD. The initial separation two phases performed using rice straw (RS) as feedstock in acidogenic phase cow manure (CM) methanogenic at low inoculum/substrate (I/S) ratios 0.5 0.2 high organic loading 60 g volatile solid (VS)/L. periodic round-trip reflux leachate during 4S2P-AD process facilitated re-inoculation throughout four stages. results showed that this also dispersed toxic ammonia, balanced carbon/nitrogen ratio, unified microbial community structure, led selection Methanosarcina (relative abundance > 80%) dominant methanogens. With abilities overcome fatty acid accumulation, shorten lag times, biodegradability, foster synergistic effects, it verified can maintain efficient stable methanogenesis high-solid lignocellulosic feedstock. averaged stages 234 mL/g VS. This result is 96% higher than obtained one-step AD groups mono-feedstock, 91% co-feedstock. study provides scientific reference for development new processes bio-methane agro-waste with fermentation capacity stability future.