Choosing the specific capture mechanism is heavily dictated by these metrics:

  • Post-Combustion Capture (Amine): Highly preferred for retrofits because it treats flue gas after combustion using liquid solvents (e.g., MEA or MDEA) and requires minimal modifications to core process equipment, though it carries a high thermal energy penalty (2.5 to 3.5 GJ/tCO₂).

  • Pre-Combustion Capture: Applied in gasification setups where fuel is shifted to syngas via the Water-Gas Shift reaction (), separating using physical solvents before combustion occurs.

  • Oxy-Fuel Combustion: Replaces ambient air with pure oxygen, producing a flue gas composed almost entirely of easily condensable water vapor and high-purity , though it demands high upfront capital for Air Separation Units (ASUs).