**2.1. Postconversion capture**

The separation of CO2 from waste gas streams after the conversion (mainly combustion) of the carbon source is known as postconversion process. Different technologies are developed for this capture process such as adsorption by solid sorbents, vacuum swing adsorption, absorption by solvents, and cryogenic separation. These methods are still considered energy demanding. Solvent absorption is elaborated here as an example of the capture. In particular, physical absorption of CO2 relies on its solubility based on Henry's Law without inducing a chemical reaction. Thus, low temperatures and elevated CO2 partial pressures are needed for this application. In contrast, chemical absorption depends on the chemical reaction between CO2 (at low partial pressure) and the used solvent forming weak bonds. The latter is more adjusted to capture CO2 emissions in industrial processes given the flue gas conditions of ambient pressure and large volumes with varied concentrations of CO2 , which might be low in some processes.
