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 IIB grant will take the next step in scaling 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 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 work demonstrated that high single pass CO2 utilization is possible in a CO2 electrolyzer. Phase II demonstrated the scalability of CO2 electrolyzers to the megawatt-scale (MW-) and the ability to achieve high single pass CO2 utilization at this larger scale. The suitability of CO2 electrolysis product gas as a feedstock for gas fermentation was verified by the leader in gas fermentation technology. A PhIIB award will increase the production rate and decrease production cost of large-area membrane electrode assemblies (MEAs), a key component of MW-scale CO2 electrolyzers. A concept design of a full-scale plant utilizing CO2 electrolysis and gas fermentation technology will be developed. This will lay the groundwork for the future deployment of large-scale commercial systems to make cost-competitive biofuels directly from CO2.