Efficient Methane Production from Beer Wastewater in a Membraneless Microbial Electrolysis Cell with a Stacked Cathode: The Effect of the Cathode/Anode Ratio on Bioenergy Recovery

Abstract

A methane-producing microbial electrolysis cell (MEC) is a promising energy-recovery technology, yet its performance is generally inhibited by the insufficient cathode/anode ratio. In this study, a novel stacked stainless-steel-mesh cathode was designed to investigate the effect of the cathode/anode ratio on methane production in semi-continuous MECs. Overall, energy recovery was significantly enhanced by increasing the cathode/anode ratio. The methane production rate in R3 (cathode/anode ratio of 4 cm2/cm3) reached 0.14 m3 m–3 day–1 with an applied voltage of 0.9 V, which increased by 56–180% compared to the methane production rates in R2 (2.5 cm2/cm3) and R1 (1 cm2/cm3). The overall energy efficiency in R3 was 66–94% higher than the overall energy efficiencies in R2 and R1. The cathode area was sufficient for obtaining and maintaining a maximum current when the cathode/anode ratio was higher than 2.5 cm2/cm3. According to electron balance analysis, when the cathode/anode ratio was less than 2.5 cm2/cm3,...