Comparative Techno-Economic-Environmental Assessment of Direct Air Capture Technologies and Energy Systems

Abstract

To meet climate goals, efforts to reduce greenhouse gas emissions, such as carbon dioxide removal, should be made a priority, along with promoting low-carbon energy systems. Direct air capture is a technological solution that removes carbon dioxide directly from the air using chemical reactions. However, direct air capture technologies are energy-intensive, requiring electricity and heat to trap and release carbon dioxide. Costs and environmental implications are still under debate. This paper presents a comparative study of life-cycle carbon removal efficiencies of two direct air capture technologies, coupled with natural gas, nuclear, and renewable resources, using the Hybrid Energy System Optimization model. The results showed that all systems achieved a negative net carbon capture, meaning that they captured more carbon dioxide than they produced. The most significant improvement in carbon capture efficiency was from nuclear and renewable technologies. The levelized costs of direct air capture ranged between 320 and 380 $/tCO₂ for liquid solvent systems and between 793 and 2,098 $/tCO₂ for solid absorbent systems. The lower cost of liquid solvent was because nuclear provided a large amount of low-carbon and constant-output electricity with free low-temperature waste heat that improved carbon capture efficiency. Finally, although the NGCC system with CCS technically resulted in negative emissions, the benefit may not be the true solution for climate change mitigation.