Capture
How CO2 is separated from a gas stream in the first place — before or after combustion, or straight from the air.
Post-combustion
Strip CO2 from flue gas after the fuel has burned
flue gas → solvent absorption → CO2 + regenerated solvent
TRL 8–9 — commercial
Pre-combustion
Remove the carbon before the fuel is burned
fuel → syngas → water-gas shift → H2 + concentrated CO2
TRL 6–8 — pilot to commercial
Direct air capture
Pull CO2 straight out of ambient air
air → sorbent → concentrated CO2 + regenerated sorbent
TRL 6–7 — pilot