Methods of Direct Air Capture
Current
Technological Approaches
*This categorization and the associated definitions are reproduced from The Applied Innovation Roadmap for CDR by RMI (2023).
Many methods of direct air capture have been commercialized and can be broadly categorized by capture mechanism and regeneration type. These categories are useful to sort related companies and compare the technical progress of DAC by approach. Select a method below to view the companies involved, current deployments, key innovations, and more.
Definition:
Carbon dioxide absorption with an alkaline solvent (where it is dissolved or diffused in a liquid to form a solution), followed by a desorption process in which carbon dioxide is mineralized out of the solution and then regenerated by high-grade heat (700-900 °C).*
1
Liquid
Absorption and High-Grade Heat Regeneration
Definition:
Adsorption onto a solid sorbent (where CO2 is captured on the surface of a solid material) followed by a desorption step in which a swing in humidity (high humidity for regeneration) is used to separate CO₂ from the sorbent (i.e., a resin); further purification of CO2 may be necessary, depending on the water concentration in the product stream.*
7
Solid
Adsorption and Humidity/Water Regeneration
Definition:
CO2 absorption with a liquid solvent (e.g., amines or amino acids, where CO2 is dissolved or diffused in a liquid to form a solution), followed by a desorption process in which low-grade heat (120 °C or lower) is used to release the captured CO2 and regenerate the solvent.*
2
Liquid
Absorption and Low-Grade Heat Regeneration
Definition:
CO₂ adsorption onto the surface of a solid sorbent material (where CO₂ is captured on the surface of a porous solid material), followed by a desorption process where mainly low-grade heat (<120 °C) is used to release the CO₂ from the sorbent.*
5
Solid
Adsorption and Low-Grade Heat Regeneration
Definition:
Polymeric membrane separation in which the CO2 is separated from other gases via differences in the molecular ability to pass through a polymer membrane (i.e., permeability); multiple capture stages, in which several membrane units are stacked together, may be required to achieve a concentrated CO2 product.*
8
Membrane
Membrane-Based Pressure Gradient Separation
Definition:
CO2 absorption with an alkaline solvent (where CO2 is dissolved or diffused in a liquid to form a solution) followed by CO2 release and solvent regeneration in an electrochemical cell where a change in voltage is used to separate CO2 from the solvent.*
3
Liquid
Absorption and Electrochemical Regeneration
Definition:
CO2 adsorption onto a solid sorbent (where CO2 is captured on the surface of a solid material), followed by CO2 release and sorbent regeneration in an electrochemical cell in which a voltage change is used to separate the CO2 from the sorbent.*
6
Solid
