This study investigated the effects of applied voltage on methane fermentation using separate reactors for the anode and cathode, with activated carbon felt as electrodes and a constant voltage of 0.7 V. Compared to the control, the cathode reactor exhibited approximately 1.2 times higher methane production and 1.3 times higher methane concentration, whereas the anode reactor showed a reduction to about 0.5 times and 0.8 times, respectively. Microbial analysis revealed that the anode reactor created an electron-accepting environment, promoting the growth of Clostridium sensu stricto 1 and Fastidiosipila, both contributing to organic acid (electron) production. Conversely, the cathode reactor established an electron-donating environment, enhancing methane production by hydrogenotrophic methanogens such as Methanoculleus and Methanobacterium. Although similar methanogen levels were found in the anode reactor, methane production was higher in the cathode reactor. These findings indicate that the anode facilitates organic acid production via electron acceptance, while the cathode acts as an electron donor that promotes hydrogenotrophic methanogenesis. This study provides a clear evaluation of the effects of microbial electrochemical technologies on methane fermentation, demonstrating their potential to stimulate microbial activities and enhance methane production.
Kaneko et al. (Thu,) studied this question.