Enhancing biomethane production from corn stover via anaerobic digestion incorporated with microbial electrolysis cell

Abstract

Bioelectrochemical regulation has been proved to enhance the traditional anaerobic digestion (AD) of organic wastes. However, few investigations have explored whether it is possible to enhance the production of biomethane from raw corn stover (CS). A single-chamber microbial electrolysis cell (MEC) was incorporated with an AD to form a new system (MEC-AD) with aiming at more efficient bioconversion of CS to biomethane. The performance and microbiological characteristics of MEC-AD was investigated, and compared with conventional AD, which were inoculated with original inoculum (UAD) and electrically domesticated inoculum (EAD), respectively. The results showed that MEC-AD achieved the highest CH₄ yield of 239.13 ml·g⁻¹ VS, which was 29.28% and 12.44% higher than those of UAD and EAD, respectively. MEC-AD also achieved higher substance conversion rates of 73.24% VS, 91.16% cellulose, and 77.24% hemicellulose, respectively. The community characteristics of microorganisms revealed that the relative abundance and interactions of functional microorganisms in MEC-AD were obviously different from UAD and EAD. In MEC-AD, Electroactive bacteria (Sedimentibacter) with electrotrophic methanogens (Methanosarcina and Methanosaeta) in anodic biofilms established electrotrophic methanogenesis through direct interspecies electron transfer (DIET). The process of methanotrophic methanogenesis was facilitated by the interactions between fermentative acid-producing bacteria (FABs), syntrophic organic acid oxidation bacteria (SOBs), and methylotrophic methanogens (Methyl-HMs) in MEC-AD suspensions. Efficient synergistic interactions between these functional microorganisms improved the performance of MEC-AD in converting CS to produce biomethane. The study could provide an effective means for achieving higher AD biomethane production from raw CS.