Effects of electrode distance and mixing velocity on current density and methane production in an anaerobic digester equipped with a microbial methanogenesis cell

Abstract

The microbial methanogenesis cell (MMC) has been studied to enhance organic removal efficiency and methane production in an anaerobic digester (AD). However, its applicability remains limited without practical approaches to scale-up the design for commercialization. Internal resistance within MMC is closely related to the transfer of hydrogen ions between electrodes. We analyzed the effects of various electrode distances and mixing velocities on the current density and methane production in a single AD equipped with an MMC. As the distance between electrodes increased from 1 cm to 5 cm, methane production and current density decreased to 51% and 92%, respectively. Although an increase in mixing velocity decreased the internal resistance, this effect was not significant below a certain distance. For larger distances, an increase in mixing velocity not only increased current density by a factor of approximately 2.5, but also enhanced methane production by a factor of approximately 1.4.