Enhancing bio-alcohol production from volatile fatty acids by suppressing methanogenic activity in single chamber microbial electrosynthesis cells (SCMECs)

Abstract

This study explored alcohol production from volatile fatty acids (VFAs) in single-chambered microbial electrosynthesis systems (MES) under continuous pH control (≤pH 5.5) for methanogen inhibition. MES with 2 g-COD/l VFA could produce highest current of 5.3 mA followed by 3.6 mA in 6 g-COD/l and 0.44 mA in 8 g-COD/l, implying active bioelectrochemical reactions of microorganisms on the electrodes. Ethanol, methanol and propanol were detected as fermented bio-alcohols without methane production, and ethanol was the main product with a cumulative recovery of 7.14 mM in 2 g-COD/l, 13.6 mM in 6 g-COD/l and 17.9 mM in 8 g-COD/l. Maximum bio-alcohol yield of 0.71 g-CODAlcohols/g-CODVFAs with a recovery efficiency of 35% was obtained from MES under 2.0 g-COD/l, followed by 6 and 8 g-COD/l. The results demonstrate that pH adjustment method is an effective strategy to suppress methanogens for improved bioelectrochemical performance of alcohol production from VFAs in MES.