Life cycle assessment of ionic liquid-based absorption direct air capture technology: Environmental trade-offs and comparison with conventional technologies

Direct air capture (DAC) technologies enable the removal of atmospheric CO 2 and are increasingly considered essential for achieving the goals of the Paris Agreement. Currently, two DAC approaches, KOH-based absorption and amine-based adsorption, are deployed at an industrial scale. Ionic liquids (ILs) have emerged as promising sorbent alternatives due to their favorable properties for CO 2 capture; however, their environmental performance remains largely unassessed. This study conducts a life cycle assessment (LCA) of a DAC system using the ionic liquid [P 66614 ][Im], comparing it with existing KOH absorption and amine-based adsorption systems. The analysis includes the environmental impacts of plant operation and sensitivity to energy sources. A full inventory was developed for the IL-based system, while data for conventional systems were drawn from literature. Results show that in the baseline scenario (plant located in Spain and supplied by grid electricity and natural gas), the IL-based DAC system emits more CO 2 than it captures. However, when powered by renewable electricity and alternative heat sources, its performance improves significantly, matching or outperforming conventional DAC systems. Under optimal conditions, it achieves higher CO 2 removal efficiencies with lower infrastructure demands. Finally, geographic analysis identifies the selected regions in China and the United States as favorable locations due to their cleaner electricity mixes and shorter transport distances to storage. • First LCA of ionic liquid (IL)-based DAC compared to KOH and amine-based systems. • IL-based DAC outperforms others when powered by renewables and waste heat. • Carbon removal efficiency of IL-based DAC reaches 82 % in the best-case scenario. • Energy source and siting critically affect the DAC system's environmental impact. • IL-based DAC is a promising alternative for scalable CO₂ removal solutions.