Enhanced methane production from acetate intermediate by bioelectrochemical anaerobic digestion at optimal applied voltages

Bioelectrochemical anaerobic digestion of acetate, the main intermediate product in anaerobic digestion of methane, was evaluated at different applied voltages (0.5, 1.0 and 1.5 V) in comparison to the control (without electrodes). At 1.0 V, the maximum methane yield (0.351 L CH4.g(-1) COD) and soluble chemical oxygen demand removal (83.6% SCOD) were observed with an acetate concentration of 2 g L-1. These values were 2.1 and 1.5 times higher than in the control reactor (0.167 L CH4.g(-1) COD and 54% SCOD), respectively. At the applied voltages of 0.5 and 1.5 V, lower efficiency of methane production was observed due to insufficient potential drive and high-voltage inhibition, respectively, although the methane yields were still higher than that of the control. The maximum current generation of 19.5 mA was obtained at 1.0 V condition, suggesting that a high electron transport rate was closely related to higher methane production. The lower Tafel slopes and polarization resistances indicated better bioelectrochemical anaerobic digestion performance with enhanced redox reactions and low electron transfer resistances.