Water management and heat integration in direct air capture systems

Water plays a pivotal role in direct air capture technologies, impacting materials, regeneration processes and product streams. CO2 removal methods, including absorption, adsorption and electrochemical techniques, encounter challenges associated with water, thus reducing their efficacy. Water fluxes into and out of aqueous solvents affect the concentration and overall capture performance. Solid adsorbents co-adsorb water in greater quantities than CO2 and will require effective strategies to address the substantial energy penalty associated with water desorption each cycle. Water-management strategies are imperative for economic viability and minimizing the environmental impact, but the high energy intensity necessitates heat recovery techniques. Feed dehydration can be combined with strategic heat integration of process streams and standard recovery techniques for front-end water management. For back-end approaches, mechanical vapor compression is a viable solution for coupling heat integration with water management, and we highlight potential heat recovery benefits of three implementation methods. Further research into variable climate conditions and water quality impacts is essential for the success of direct air capture technologies. Water management is crucial for enhancing economic viability and minimizing the environmental impact of direct air capture (DAC) technologies, but the high energy intensity necessitates heat recovery techniques. This Perspective discusses several front-end and back-end strategies for coupling water management with heat integration in DAC processes.