Energy comparison of sequential and integrated CO₂ capture and electrochemical conversion

Integrating carbon dioxide (CO₂) electrolysis with CO₂ capture provides exciting new opportunities for energy reductions by simultaneously removing the energy-demanding regeneration step in CO₂ capture and avoiding critical issues faced by CO₂ gas-fed electrolysers. However, understanding the potential energy advantages of an integrated process is not straightforward due to the interconnected processes which require knowledge of both capture and electrochemical conversion processes. Here, we identify the upper limits of the integrated process from an energy perspective by comparing the working principles and performance of integrated and sequential approaches. Our high-level energy analyses unveil that an integrated electrolyser must show similar performance to the gas-fed electrolyser to ensure an energy benefit of up to 44% versus the sequential route. However, such energy benefits diminish if future gas-fed electrolysers resolve the CO₂ utilisation issue and if an integrated electrolyser shows lower conversion efficiencies than the gas-fed system.