Optimized Electrical Stimulation Period Facilitated Microbial Electromethane Generation with CO2 Conversion

In order to improve microbial electromethane generation (mEMG) with CO 2 conversion using excess renewable power, an electrical stimulation period was optimized to enrich active microorganisms on a biocathode and directionally strengthened electron transfer with a start-up mode of stepwise-promoted intermittent voltage. A highly adaptive microbial community was enriched on the biocathode for an electrical stimulation period of 1 h with the highest population abundance and diversity of archaea and bacteria. The living cell density and average coverage area ratio on the biocathode were 81.37 and 22.07%, respectively. The tryptophan, fulvic acid, and humic acid substances with peak fluorescence intensities in extracelluar polymers effectively improved electron transport in the mEMG system. The highest area capacitance of the biocathode was 13.96 mF/cm 2 . The biofilm and solution resistances first decreased to valleys (102.3 and 1.541 Ω) and then increased. The highest faradaic efficiency (95.37%) of CH 4 was obtained with 2.35 μmol/L coenzyme F420, leading to an increased CH 4 production rate by 39.68%.