Effects of electrolyte composition and applied voltage on methane generation and microbial community shifts in the electromethanogenesis system

An electromethanogenesis (EM) system was successfully established using non-acclimated anaerobic digestion sludge as the inoculum. This study aimed to evaluate the EM performance by varying the electrolyte composition and the applied voltage. Alterations in the microbial community associated with CH 4 generation and bioelectrochemchemical performance were also investigated. The findings indicated that the use of organic-rich electrolyte with a low applied voltage of 0.15 V showed a positive correlation with enhanced CH 4 generation up to 59% and a CH 4 yield of 223.13 mmol day -1 m -2 which was ten times higher than the operation using the same electrolyte with an applied voltage of 0.35 V. Microbial community analysis revealed a shift of dominant methanogens from Methanosaeta to Methanosarcina and Methanoculleus at the cathodic biofilms when operated with organic-rich electrolyte at low voltage of 0.15 V. The presence of electroactive bacteria, such as DMER64 and JGI-0000079-D21 , and syntrophic bacteria, including Desulfovibrio and Petrimonas , suggested the development of syntrophic interactions that strengthen biofilm resilience and the overall performance of the EM system. The microbial interaction network also emphasized the significance of electrolyte composition and adequate applied voltage in shaping microbial biofilms for efficient CH 4 generation. The findings of this study accentuate the roles of sufficient electrolyte composition and low-voltage in enhancing the EM performance and corroborate the synergistic advantages of the EM system. • CH₄ production increased by 59% under PYE electrolyte and 0.15 V. • Methanogens at the cathode biofilms shifted to Methanosarcina and Methanoculleus . • PYE and 0.15 V promoted enrichment of electroactive and syntrophic microbes. • Functional co-occurrence network revealed key microbial correlations. • Organic-rich electrolyte and low voltage enabled energy-efficient CH₄ generation.