Bioelectrochemical methane (CH₄) production in anaerobic digestion at different supplemental voltages

Microbial electrolysis cells (MECs) at various cell voltages (0.5, 0.7 1.0 and 1.5V) were operated in anaerobic fermentation. During the start-up period, the cathode potential decreased from -0.63 to -1.01V, and CH₄ generation increased from 168 to 199ml. At an applied voltage of 1.0V, the highest methane yields of 408.3ml CH₄/g COD glucose was obtained, which was 30.3% higher than in the control tests (313.4ml CH₄/g COD glucose). The average current of 5.1mA was generated at 1.0V at which the maximum methane yield was obtained. The other average currents were 1.42, 3.02, 0.53mA at 0.5, 0.7, and 1.5V, respectively. Cyclic voltammetry and EIS analysis revealed that enhanced reduction currents were present at all cell voltages with biocatalyzed cathode electrodes (no reduction without biofilm), and the highest value was obtained with 1V external voltage.