Alkalinity Concentration Swing for Direct Air Capture of Carbon Dioxide

Area of Science:

• Environmental Science
• Chemical Engineering
• Climate Technology

Background:

• Direct air capture (DAC) is crucial for mitigating climate change.
• Current DAC technologies face challenges in energy efficiency and cost.
• Alkaline solutions can absorb atmospheric carbon dioxide.

Purpose of the Study:

• To introduce and evaluate the alkalinity concentration swing (ACS) process for direct air capture of CO2.
• To assess the feasibility of integrating desalination technologies into the ACS process.
• To compare the ACS process with existing DAC methods regarding resource requirements.

Main Methods:

• Concentrating an alkaline solution loaded with dissolved inorganic carbon to increase CO2 partial pressure.
• Investigating reverse osmosis and capacitive deionization as potential ACS implementation technologies.
• Developing energy models for the selected desalination technologies and comparing them with incumbent DAC approaches.

Main Results:

• Higher concentration factors and initial alkalinity concentrations lead to increased CO2 outgassing pressure.
• Energy models indicate favorable energy requirements for ACS, especially at the lower end of the range.
• ACS demonstrates competitive water, land, and energy footprints compared to solid sorbent and calcining methods for large-scale CO2 capture.

Conclusions:

• The alkalinity concentration swing (ACS) process presents a viable and potentially more energy-efficient approach for direct air capture of CO2.
• Integration with desalination technologies like reverse osmosis and capacitive deionization is feasible for ACS implementation.
• ACS offers a promising alternative to current DAC technologies, with competitive resource demands for significant CO2 removal.