Technological Options for Direct Air Capture: A Comparative Process Engineering Review
Xiaowei Wu, Ramanan Krishnamoorti, Praveen Bollini
Abstract
The direct capture of CO 2 from ambient air presents a means of decelerating the growth of global atmospheric CO 2 concentrations. Considerations relating to process engineering are the focus of this review and have received significantly less attention than those relating to the design of materials for direct air capture (DAC). We summarize minimum thermodynamic energy requirements, second law efficiencies, major unit operations and associated energy requirements, capital and operating expenses, and potential alternative process designs. We also highlight process designs applied toward more concentrated sources of CO 2 that, if extended to lower concentrations, could help move DAC units closer to more economical continuous operation. Addressing shortcomings highlighted here could aid in the design of improved DAC processes that overcome trade-offs between capture performance and DAC cost.