Toward the feasible direct air capture of carbon dioxide with molecular sieves by water management

Engineered systems for the direct air capture (DAC) of carbon dioxide (CO2) are being investigated worldwide. Here, we demonstrate a technology for DAC that uses molecular sieves and, in some cases, H2O harvesting. A combination of a commercially available desiccant, AQSOA-Z02A, and a mordenite-type zeolite (MOR) enables continuous operation of a designed DAC system comprised of two parallel units with a regeneration temperature of 100°C. The system using pure zeolite alone requires regeneration at temperatures between 200°C and 300°C. Techno-economic analyses of 12 process scenarios reveal that the energy requirement of the best scenario investigated is 71 GJ/tCO2, while the conventional pure zeolite-based system requires 200 GJ/tCO2. The optimized system gives a cost between $246 and $568 per ton CO2 captured, depending on the energy costs. The price can be dramatically lowered or profitable when the system operates at sub-0°C temperatures or with integration of water harvesting, respectively.