Electrochemical Conversion of CO2 to CO for Use as a Fermentation Feedstock

Relative to CO2 fixation by photosynthesis as the basis for biofeedstocks, industrial-scale electrochemical CO2 conversion could improve the overall efficiency by more than 10X and use a fraction of the land area. Moreover, electrochemical conversion of CO2 can utilize excess renewable electricity during periods of overgeneration. At scale, using renewable electricity to recycle waste CO2 emissions to make a feedstock for biological processes could significantly reduce greenhouse gas emissions and provide an alternate carbon and energy source for the bioeconomy. By coupling electrochemical CO2 reduction, which is efficient but limited to low carbon molecules, with biological systems, which can more easily manipulate simple organic molecules to produce complex products, a new type of industrial chemical production can be realized. Such hybrid systems would be modular, efficient, highly selective, and offer significant environmental benefits. The proposed effort will demonstrate such a hybrid electrochemical-biological system. An efficient, cost-effective, and modular reactor for the electrochemical reduction of CO2 to syngas will be developed and coupled with a novel bioreactor that converts syngas into acetone. The proposed effort aims to show the commercial viability of electrochemical CO2 conversion to fermentation feedstocks, followed by biological conversion from feedstock to bioproducts. During Phase I, both the electrochemical and the biochemical pathways were optimized to suitable levels for industrial scaling. In Phase II, membrane electrode assemblies that were tuned in Phase I will be used to scale and develop a CO2-to-syngas electrolyzer. Performance of the biological syngas to acetone pathway will be further enhanced. An end-to-end demonstration of CO2 to acetone using waste CO2 will be conducted in year 2 of the project. Phase II will determine the operating conditions at a system level for the most economically and environmentally viable process. This demonstration unit will form the basis for commercialization. Commercial deployment of this technology would enable distributed production of renewable acetone and other valuable products from carbon dioxide, which is currently being discarded as a waste product. This system would provide a valuable sink for low-cost renewable electricity.