Enhanced production and utilization of biosynthesized acetate using a packed-fluidized bed cathode based MES system

Abstract

Microbial electrosynthesis (MES) appears as a promising approach for mitigating carbon foot prints via converting carbon dioxide to value added products and biofuels. Technology still can’t be taken to an industrial level due to low production rates, high cost and energy consumptions. Enhancement in the bioavailability of CO2 is crucial for improving production rates. Current study has addressed this issue with the introduction of a cost effective packed-fluidized cathode consisting of stainless steel (SS) & granular activated carbon (GAC). Pre acclimatized GACs (with active anaerobic microbes on its surface) were packed in SS and CO2 was directly flushed on the GAC surface via pipe to ensure its availability to the biocatalyst. This novel cathode has achieved acetate volumetric production rate of 0.16 g L−1 d−1 during 43 days of study. Comparative analysis has been performed with systems in which GACs were not pre-acclimatized (bare GACs) and a system with no packed GACs. Both systems gave lesser production rates, where bare GAC system gave 0.12 g L−1 d−1 and non packed SS (no GACs) gave 0.1 g L−1 d−1acetate volumetric production rate. Issue of high energy and cost involve in acetate extraction and separation was also addressed in the current study via converting dilute acetate in catholyte to bioalcohols in a separate reactor without extracting it from the medium. This way separation of acetogensis and solvatogenesis phases was also done to ensure enhanced biofuel production. Cost evaluation of cathode, electrochemical study, and overall carbon balance has been performed as well.