What carbon capture is
Carbon capture and storage (CCS) refers to technologies that trap CO2 either at the point of emission — at a power plant or industrial facility — or directly from the ambient atmosphere (Direct Air Capture, or DAC), and store it so it does not enter the atmosphere.
Point-source CCS
Capturing CO2 from concentrated sources — cement plants, steel mills, natural gas power stations — is the most mature form of CCS. The CO2 is separated from exhaust gases, compressed and transported to geological storage sites, where it is injected and stored. The Sleipner project in Norway has been injecting CO2 into a sandstone formation under the North Sea since 1996.
Direct Air Capture
DAC removes CO2 directly from the atmosphere, where it is far more dilute (about 420 parts per million) than in industrial flue gases. This makes it far more energy-intensive: current DAC technology requires between 1,500 and 2,000 kilowatt-hours of energy per tonne of CO2 removed, costing between $300 and $1,000 per tonne at current energy prices.
The controversy
Critics argue that the existence of CCS gives fossil fuel industries a licence to continue operating when the priority should be eliminating emissions at source. Proponents counter that there are industrial processes — cement, steel, aviation fuels — where emissions are very hard to eliminate and where CCS or carbon removal is necessary even in a decarbonised world.