Utilization of waste CO2 to make renewable chemicals and fuels

Utilization of waste carbon dioxide from industrial sources could (1) provide an additional income stream for CO2 emitting industries and (2) provide a distributed and domestic source of carbon-based compounds for use as chemicals and fuels. An efficient, cost-effective, and modular reactor for electrochemical reduction of CO2 (ECO2R) to carbon-neutral or –negative compounds is needed to make this a reality. Compounds produced though ECO2R can be used as feedstocks into biological processes to produce higher value materials. Using only water and electricity as inputs, ECO2R has been demonstrated to produce over 16 different fuels and chemicals. This Phase II grant will develop and scale up an electrochemical process to convert CO2 and water into syngas for use as a feedstock for gas fermentation to make bioproducts. This breakthrough process uses a polymer-electrolyte membrane (PEM) electrolyzer design. PEM water electrolyzers are used commercially for hydrogen generation and with modifications, the same commercially viable design can be used for CO2 electrolysis. This repurposing of water electrolyzers will be achieved with the support of a world-leader in PEM water electrolysis for hydrogen generation with the capacity to manufacture electrolyzers on the MW-scale. This use of an existing electrolyzer architecture that has undergone years of optimization to increase efficiency and bring down cost provides a clear path to reach market scale. Phase I demonstrated that high CO2 utilization is feasible in a novel PEM CO2 electrolyzer by modifying the CO2 flow rate, cell compression, gas diffusion layer type, and flow field pattern. Increased CO2 utilization resulted in high syngas (H2+CO) product concentrations that can be fed directly into a fermentation reactor without the need for further product concentration or purification. Avoiding this extra purification step is a significant cost savings when coupling the ECO2R process to a bioreactor. In addition, this proposal will also demonstrate that waste CO2 emissions are a suitable reactant for ECO2R electrolyzer and the resulting product syngas can be used as a feedstock for gas fermentation. An ethanol producer will provide waste CO2 emissions for conversion to syngas within an ECO2R reactor. This syngas will then be used by a leading bioproducts company in their gas fermentation process to make ethanol, which can be further reacted to make renewable jet fuel if desired. Through a Phase II award, it will be demonstrated that waste CO2 emissions can be used to make bioproducts by coupling the ECO2R syngas generation process to gas fermentation and that ECO2R electrolyzers can scale up to the tons/day scale needed to manufacture bioproducts.