Economic Viability of Integrated CO2 Capture and Conversion

Abstract

The capture of CO₂ using alkaline solutions requires significant thermal energy to release CO₂ from a (bi)carbonate-enriched solution. This release of CO₂ can instead be performed electrochemically with a “bicarbonate electrolyzer”. The bicarbonate electrolyzer forms acid equivalents to convert a (bi)carbonate-enriched eluent from a CO₂ capture unit into CO₂ 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 CO₂ capture unit is required when using a more caustic CO₂ 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 CO₂ electrolysis. We also use a mass-balance model to assess the commercial viability of a reactive carbon capture system that integrates the CO₂ 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.