Harvard University is conducting experimental verification of a novel approach for direct air capture (DAC) of carbon dioxide (CO2) that employs an alkalinity concentration swing (ACS) process. ACS involves concentrating an aqueous alkaline solution (that has equilibrated with air) using commercially available technologies such as reverse osmosis (RO) or capacitive deionization (CDI). The concentrated solution has a higher partial pressure of CO2 relative to the initial solution, allowing the CO2 to be separated and stored.