Addition of carbon dioxide enhances electrical power production in a microbial reverse electrodialysis cell

Carbon dioxide utilization technology is essential for achieving carbon neutrality. In this study, we propose a promising method to produce renewable electricity and improve wastewater treatability and system stability by simply dissolving carbon dioxide in a microbial reverse electrodialysis cell (MRC). MRC is an environmental energy system that combines a microbial fuel cell and a reverse electrodialysis stack. Increasing the bicarbonate buffer concentrations in the anolyte and the catholyte improved power generation, reduced internal resistances, and improved energy recovery and treatability. The MRC with the 200 mM-bicarbonate anolyte and 200 mM-bicarbonate catholyte produced 5124 mW m⁻² at 7636 mA m⁻² with 127-Ω internal resistance, 32 % energy efficiency, 25 % coulombic efficiency and 36 COD-mg (L·h)⁻¹. Both the anolyte buffer and catholyte buffer are important in MRC performance, but the anolyte buffer had the greater impact than the catholyte buffer. After the MRC operation, all the anolyte conductivities increased, but it was not the case in the catholyte. The anolyte improved energy and coulombic efficiencies more and the catholyte improved substrate treatability more. The 100-mM anolyte buffer was the best for anode performance; however, the 200-mM catholyte buffer was the best for cathode and RED. This is the first study to comprehensively analyze the effect of electrolyte bicarbonate concentration on MRC system.