Ambient CO₂ capture and storage in bioelectrochemically mediated wastewater treatment

This study reports that wastewater can be used to capture and store CO₂ directly from ambient air and produce energy. The proof-of-concept system consisted of an ion exchange resin column that captures and concentrates ambient CO₂ using a moisture-driven cycle. The concentrated CO₂ was then transferred into a microbial electrochemical carbon capture (MECC) reactor for carbon sequestration and hydrogen production. Data from an average batch cycle showed that approximately 8 mmol/L CO₂ was captured in the MECC cathode when 0.14 g/L COD was removed in the anode. With 90% hydrogen conversion efficiency, the energy intensity and CO₂ absorption from the process could be 11.3 kJ/gCOD and 0.49 gCO₂/gCOD respectively. If the proposed process is applied, over 68 million tons of atmospheric CO₂ can be captured yearly during wastewater treatment in the US, which equates to significant economic values if CO₂ taxes were to be implemented more widely.