Bioelectrosynthesis of renewable energy carriers from carbon dioxide

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Microbial electrosynthesis (bioelectrosynthesis) of renewable fuels is an emerging research area, which attracts significant attention of researchers, as can be evidenced from the exponential growth in the number of publications dedicated to this area. In microbial electrosynthesis, electroactive microorganisms catalyze cathodic reactions (e.g. CO2 reduction) acting as biocatalysts. Importantly, electroactive microorganisms were also shown to interact with metal catalysts resulting in enhanced bioreactions rates. Several bioelectrochemical cathodic transformations were demonstrated, including CO2 conversion to CH4 (electromethanogenesis) and electrosynthesis of C2-C4 compounds such as acetate, ethanol, and butanol. Although our knowledge of direct and indirect electron transfer mechanisms at the anode of such bioelectrochemical systems as microbial fuel cells (MFCs) significantly advanced in recent years, much less is known about the electron transfer mechanisms at a biocathode. Also, very few existing studies are dedicated to biocathode modeling. All existing studies on electromethanogenesis and production of C2-C4 compounds from CO2 are limited to laboratory-scale proof-of-concept demonstrations. In particular, multiple electromethanogenesis studies showed either an incomplete conversion of CO2 or presence of H2 catalytically (or biocatalytically) produced at the cathode. The proposed research program seeks to advance the understanding of bioelectrochemical processes and commercialization of CO2 conversion to renewable energy carriers by applying a thorough system engineering approach, where experimental work is combined with modelling and operational optimization aimed at maximizing yields, reducing operational costs, and developing practical control algorithms for stable system operation. The following objectives will be pursued (i) Enhanced understanding of pathways and electron transfer mechanisms, and identification of electroactive microorganisms capable of CO2 reduction to CH4 and C2-C4 compounds; (ii) Development of a dynamic mathematical model capable of adequate description of the biocathode kinetics and electroactive biofilm formation; (iii) application of the mathematical model to operational optimization and real-time control of the bioelectrosynthesis process, including experimental validation of the proposed on-line process control algorithms.