A Novel Approach to Electrochemical Direct Air Capture Using Aqueous l -Arginine Amino Acid Solutions as an Absorption Solvent: Proof-of-Concept and Technoeconomics

CO2 capture using an l-arginine solution as the sorbent, combined with its regeneration via bipolar membrane electrodialysis (BPMED), is adapted to direct air capture (DAC). Results show that DAC using this approach is possible with a specific energy demand of around 2000 kWh tCO2–1 for regeneration. Using a measuring method based on electrical conductivity developed within this work, we found the maximum loading of the l-arginine solution from ambient air to be 0.35 molCO2 molArg–1 (0.95 molCO2 molArg–1 with pure CO2). For absorption, different 3D-printed gyroid structures were manufactured and tested. These structures enhanced the gas–liquid contact, resulting in an increase of CO2 capture as compared to a reference pall ring packing, achieving competitive mass transfer coefficients (kla) of up to 0.69 s–1. Technoeconomic analysis revealed an achievable capture cost of less than 350€ tCO2–1 with water loss, energy cost, and BPMED capex being the most relevant cost drivers.