Enhancing methane production from corn stover through thermophilic anaerobic digestion and digestate recirculation: performance and the microbial community.

Agricultural residues, such as corn stover, generate more than 2 billion tons of biomass annually, presenting challenges for efficient bioenergy conversion due to their lignocellulosic structure and microbial instability under suboptimal conditions. These limitations reduce methane yields and hinder system scalability in anaerobic digestion processes. This study examined the effects of temperature variations and digestate recirculation on methane production from corn stover. Batch biochemical methane potential assays were conducted at 25 °C, 37 °C, and 55 °C, followed by continuous stirred-tank reactor experiments with organic loading rates of 2.1-3.1 g VS/(L·d); microbial community analysis involved 16 S rRNA sequencing and correlation assessments. The thermophilic conditions (55 °C) resulted in methane yields of 218 mL/g VS, representing increases of 169% and 12% over the psychrophilic (25 °C) and mesophilic (37 °C) conditions; digestate recirculation in the continuous reactors reduced volatile fatty acid accumulation by 23-55% and increased yields to 162 mL/g VS at 2.6 g VS/(L·d), with shifts in the bacterial and archaeal communities favoring lignocellulose degradation and methanogenesis. These results demonstrate improved anaerobic digestion efficiency through integrated strategies, advanced bioenergy production and waste conversion by optimizing microbial stability and process kinetics.