Conceptual design and evaluation of membrane gas separation-based CO2 recovery unit for CO2 electrolyzers employing anion exchange membranes

•Membrane process for CO2/O2 separation at AEM-based CO2 electrolyzers is designed.•CO2 separation cost is minimized by optimizing the membrane areas.•Economic and environmental indicators are compared with amine scrubbing.•Membrane process is competitive when CO2/O2 ratio of anode outlet stream is high.•Membrane process will become more promising when greener electricity is available. Anion exchange membrane (AEM)-based electrolysis for CO2 reduction reaction (CO2RR) has garnered attention as a promising carbon dioxide utilization technology due to its superior energy efficiency at high current densities. The major drawback of AEM-based electrolysis for CO2RR is CO2 crossover, which leads to the loss of introduced CO2 feedstock and thus detrimentally affects the process's overall economic and environmental viability. We design a 3-stage membrane-based CO2 recovery unit to capture CO2 from the mixture of CO2 and O2 discharged from the anode side of AEM-based CO2 electrolyzers. The membrane area is optimized via a hybrid of genetic algorithm and ‘fmincon’ in MATLAB. The estimated CO2 capture cost ranges from 43.3 to 109.3 USD/tCO2, which is economically comparable to piperazine-based amine scrubbing units when recovering CO2 at a purity of up to 99.5 mol.% under a CO2/O2 molar ratio of 1.5∼2. The carbon footprint of the designed process ranges from −0.936 to −0.838 tCO2eq/tCO2-captured, indicating superior environmental performance compared to those of the piperazine-based amine scrubbing units.