Microbial electro synthesis from CO₂ and methanol — methanol-assisted microbial electrosynthesis

In microbial electrosynthesis (MES), CO₂ is converted to carboxylates by utilizing renewable electricity. To accelerate the production of longer-chain carboxylates, butyrate, and caproate, additional electron donors, such as methanol, could be utilized. Methanol is present in some industrial wastewaters and could be produced in the future via renewable routes. Methanol-assisted MES with a mixed culture has been reported to enhance butyrate production rates and yields. Similar to MES studies fed with only CO₂, the performance of methanol-assisted MES is affected by pH, temperature, and pressure. Furthermore, the methanol to CO₂ ratio is crucial. The highest butyrate production rate of 107 m−2 d−1 has been reported in methanol-assisted MES, comparable to the best-performing MES studies. In methanol-assisted MES studies, Eubacterium limosum and Eubacterium callanderi have dominated the mixed microbial cultures. Initial experiments indicate that methanol and CO₂ assimilation and butyrate production proceed through the Wood-Ljundahl pathway and the reverse β-oxidation pathway.