A single microbial electrochemical system for CO₂ reduction and simultaneous biogas purification, upgrading and sulfur recovery

In this work, a single microbial electrochemical system was developed for multiple goals simultaneously – CO₂ reduction, biogas purification, upgrading and sulfur recovery. This system consists of a methanogen-inoculated biocathode for CO₂ reduction and a ferrous ion (Fe²⁺)-mediated abiotic anode for hydrogen sulfide (H₂S) oxidation. In the cathodic chamber, methane production rate of 20.6 ± 1.0 μmol·h⁻¹ and high upgrading level (up to 98.3% methane content) were achieved. In the anodic chamber, H₂S was completely removed and selectively converted into elemental sulfur particles. The system showed stable performance during continuous operation for treating both pure CO₂ and mixed gases, with a cathodic coulombic efficiency of up to 85.2%. This simple system holds a great potential for practical application for biogas upgrading and sulfur recovery from waste water/gases.