Synergistic bioelectrodes and dynamic microbial community enable high-efficiency methanization of corn stalk in a novel hybrid bioelectrochemical-anaerobic digestion system.

Abstract

This study developed a hybrid bioelectrochemical-anaerobic digestion (BEAD) system by integrating synergistic bioelectrodes with dynamic microbial communities. Carbon-based electrode materials, including activated carbon@Ni/stainless steel mesh (AC@Ni/SSM), carbon black@Ni/stainless steel mesh (CB@Ni/SSM), and varying doses of corn stalk (CS, 1.0-8.0 g/L), were systematically optimized. Among them, the AC@Ni/SSM electrode exhibited superior performance, achieving a cumulative methane production of 493.08 ± 1.0 mL/g VS 2.8 times higher than that of conventional anaerobic digestion (155.1 ± 1.2 mL/g VS). Electrochemical analyses indicated that the hierarchical structure of AC@Ni/SSM reduced charge transfer resistance by 42 % and minimized ionic diffusion barriers, thereby facilitating direct interspecies electron transfer (DIET) through conductive biofilms. An optimal CS dose of 2.0 g/L enhanced substrate-microbe interactions, resulting in 68.25 % methane content and 90.23 % COD removal. Microbial community analysis revealed an enrichment of Firmicutes (56 %) and Bacteroidota (22 %), key taxa involved in lignocellulose degradation and DIET-mediated methanogenesis. These results demonstrate the potential of the BEAD system to overcome electron transfer limitations, providing a sustainable strategy for the high-efficiency valorization of lignocellulosic biomass.