How Does Carbon Capture Work?

Carbon capture technologies fall into three main categories. Post-combustion capture removes CO2 from flue gases after fossil fuel combustion, typically using chemical solvents (like amines) that absorb CO2 and release it when heated. Pre-combustion capture converts fossil fuels to hydrogen and CO2 before combustion, capturing the CO2 stream. Direct air capture (DAC) pulls CO2 directly from ambient air using specialised chemical filters or solvents — much harder because atmospheric CO2 concentration (about 420 ppm) is far lower than in flue gas (about 10-15%). Once captured, CO2 is compressed to a supercritical fluid and injected into deep geological formations — depleted oil/gas reservoirs, deep saline aquifers, or basalt formations where it mineralises into carbonate rock. The Climeworks Orca plant in Iceland (2021) was the first large-scale DAC facility, capturing about 4,000 tonnes of CO2 per year; its successor, Mammoth, is ten times larger.