A comparative energy and costs assessment and optimization for direct air capture technologies

This work provides a comparative technical assessment of three technologies for CO₂ removal from air: two aqueous-scrubbing processes and one solid sorbent process. We compute productivity and exergy and energy consumption using process simulations and mathematical optimization. Moreover, we evaluate the cost range and discuss the challenges for large-scale deployment. We show that all technologies can provide high-purity CO₂ and that the solid-based process has the potential to offer the best performance, owing to an exergy demand of 1.4–3.7 MJ.kg_CO2⁻¹ and a productivity of 3.8–10.6 kg_CO2.m⁻³.h⁻¹. Translating productivity and energy into cost of CO₂ capture via a simple model, we show that the capital cost is the main cost driver. All technologies have the potential to operate below 200 $.ton_CO2⁻¹ under favorable, yet realistic, energy and reactor costs. The solid-sorbent process achieves this under a broader range of conditions and is less dependent on the installation cost when a high mass transfer is achieved.