A 20 L electrochemical continuous stirred-tank reactor for high rate microbial electrosynthesis of methane from CO₂

Microbial electrosynthesis (MES) is a promising technology for CO₂ utilization and renewable electricity storage. The practical application of MES requires high current density and scalable reactor design. Here, we reported a novel 20 L electrochemical continuous stirred-tank reactor (E-CSTR) for methane production from CO₂. The E-CSTR was constructed by inserting a tubular electrochemical cell into a CSTR. At 4 A (119.94 A·m⁻²), the average and maximum methane production rates achieved in the reactor were 317.84 L·m⁻²·d⁻¹ (0.53 L·L⁻¹·d⁻¹) and 407.8 L·m⁻²·d⁻¹ (0.68 L·L⁻¹·d⁻¹), respectively, and the average coulombic efficiency was about 98%. The reactor outperformed most reported MES reactors. Increasing the current to 6 A resulted in a deterioration of the performance because O₂ across the membrane changed the microbial community composition. However, the reactor quickly recovered when the current was switched back to 4 A, which indicated the excellent robustness of the reactor. These results demonstrated that the E-CSTR holds great potential for scaling up and practical application.