Energy-Efficient and Low-Temperature Gaseous Concentration Swing Adsorption (GCSA)-Based Regeneration Method Utilizing Hydrogen Sweep for Direct Air Capture

Abstract

Solid sorbent-based direct air capture (DAC) is a promising pathway for durable carbon dioxide removal (CDR), but large-scale deployment remains constrained by sorbent degradation and the high cost and energy associated with temperature-vacuum swing adsorption (TVSA). Here, we introduce a hydrogen (H2)-enabled gaseous concentration swing adsorption (GCSA) process that eliminates vacuum and enables regeneration at 35–70 °C using a closed-loop H2 sweep with a commercial amine sorbent. By lowering the CO2 partial pressure under reducing conditions near ambient pressure, H2-GCSA achieves effective regeneration with reduced thermal severity and suppressed oxidative degradation. Accelerated testing between 65 and 95 °C under oxidative and anaerobic environments demonstrates superior sorbent stability over 100 h under oxygen-free conditions. A process-integrated techno-economic analysis for a 100,000 tCO2/yr modular DAC plant, utilizing a total of less than 8.5 tons of H2 and incorporating downstream H2/CO2 separation via pressure swing adsorption (PSA), projects an energy demand of 2.78 GJ/tCO2 (775 KWh/tCO2) and a capture cost of 81 USD/tCO2, representing a 2–3× lower capital cost and 1.5–4× lower energy demand relative to TVSA. Further process integration using low-grade waste heat and PSA elimination reduces the energy demand to 0.85 GJ/tCO2 (235 KWh/tCO2), with projected costs approaching 31 USD/tCO2. Sensitivity analysis indicates that the sorbent cost below 95 USD/kg enables DAC below 100 USD/tCO2. Collectively, these results demonstrate that H2 sweep-mediated GCSA offers a scalable, lower-energy alternative to vacuum-driven (TVSA) regeneration on a wide range of sorbents, eliminating the sorbent material development risks and addressing a central bottleneck in solid-sorbent DAC.