CO₂ accounts for about 15 percent, by volume, of the flue gas of a coal-fired power plant. To capture it, conventional flue-gas purification equipment, which has been in use for decades, is enhanced by an additional process in which the flue gas column is exposed to a solvent that absorbs CO₂.

The CO₂-saturated solvent is piped into a second fractionating column and heated with steam until the CO₂ is separated and washed out. The regenerated solvent is recycled into the carbon-capture process, resulting a closed scrubbing cycle.

The chemical industry already uses CO₂ scrubbing processes but in applications that differ significantly (in terms of gas composition and volumes) from the operating conditions of a large coal-fired power plant. In addition, heating the solvent to absorb CO₂ consumes energy. A key R&D task is to minimize this energy drain and thus reduce operating costs.

The decisive advantage of post-combustion over other capture methods is that it can be easily retrofitted onto existing power plants. One prerequisite, of course, is that plants have enough room on site to install capture equipment.