Economic Viability of Integrated CO₂ Capture and Conversion

The capture of CO 2 using alkaline solutions requires significant thermal energy to release CO 2 from a (bi)carbonate-enriched solution. This release of CO 2 can instead be performed electrochemically with a “bicarbonate electrolyzer”. The bicarbonate electrolyzer forms acid equivalents to convert a (bi)carbonate-enriched eluent from a CO 2 capture unit into CO 2 and, in turn, an upgraded carbon product such as CO and ethylene. There exists a tension for this closed-loop cycle to be put into practice: a smaller CO 2 capture unit is required when using a more caustic CO 2 capture solution, yet the electrolyzer works more effectively at a lower pH. Here, we elaborate on three different methods to align different pH regimes to couple air capture to CO 2 electrolysis. We also use a mass-balance model to assess the commercial viability of a reactive carbon capture system that integrates the CO 2 capture unit with a bicarbonate electrolyzer to show a levelized CO breakeven price below $1 kg CO –1 . These economics, coupled with the other practical advantages of providing an electrolyzer with a liquid feedstock, present a compelling case for reactive carbon capture.