Defining Direct Air Capture

Direct Air Capture and Storage is a carbon dioxide (CO₂) removal method that uses large fans to extract CO₂ from air before storing it sustainably and permanently. It consists of two steps, the technology ‘Direct Air Capture’ (DAC) and the Storage.

DAC refers to the process of capturing CO₂ directly from ambient air. Technology now exists that uses large fans to pull air over special filters that extract the carbon dioxide. When these filters are “full” the fans are closed off and the filters heated up to 100ºC. As the temperature rises, concentrated CO₂ is released from the filters and can be pumped for industrial use or storage.

Storage of Captured Carbon Dioxide

The carbon dioxide can then be used for sequestration or industrial applications. In the case of sequestration the gas must be stored permanently. Certain rocks and geological formations naturally react with CO₂ and it has now been demonstrated in Iceland that pumping CO₂ deep underground in Basaltic rock - formed from lava flows - can accelerate natural mineralisation and turn the CO₂ into a solid that is locked away forever.

Another approach is to fill large underground caves that used to contain oil. These empty spaces can be filled with highly concentrated carbon dioxide and sealed off to permanently store it away.