Post-Combustion Capture

Post-combustion CO₂ capture applies mainly to conventional coal-fired power generation but can also apply to combustion turbines fired by natural gas. In this case, the CO₂ is captured from flue gases after the fossil fuel has been burned.

More than 95% of the coal-fired plants in the world use coal combustion technology . About one-third of this capacity worldwide is less than 10 years old. Installing PCC on these plants is essential to avoiding the worst impacts of climate change.

Shidongkou PCC Power Plant, outside of Shanghai, China

The Process

Post-combustion capture uses a chemical solvent to remove CO₂ from the exhaust gas of a traditional coal power plant. The solvent-- typically an amine solution-- binds with the CO₂. The solvent-CO₂ combination is separated from the rest of the exhaust gas and heated. The heat drives off relatively pure CO₂ which is ready for compression and sequestration. The solvent is cooled and reused.

Diagram of the post-combustion process

Many variations on this basic approach exist, and new technologies using selective membranes and solid materials instead of liquid solvents are under development. Chapter three of the report "Coal Without Carbon" (.pdf) >> details current and emerging technologies. These alternatives hold promise of significant performance improvements over current technology, but also require significant development work prior to commercialization.

Natural Gas

Natural gas with carbon capture uses post-combustion capture technology on natural gas power plants. For the US to meet mid-century near zero carbon emissions, CCS will need to be installed not just on coal, but natural gas too. Natural gas is expected to be abundant in the US due to recently developed shale gas fields. Gas will increasingly displace some coal. But even if all coal plants were replaced with natural gas, the reduction in CO₂ would be about 50%. Therefore CCS on gas is important.

Natural gas can be an advantageous fuel for power generation with CCS for several reasons:

Natural gas combined cycle combustion turbines capital costs roughly one third those of conventional coal power plants.

NGCC produce roughly 60% less CO₂ than conventional coal for an equivalent amount of electricity generated, CCS results in considerably less CO2 to capture, compress, and sequester with gas.

Natural gas appears to be quite a promising fuel for advanced technologies like solid oxide fuel cells (“SOFC”), which may be able to both operate at extremely high efficiency and inherently separate CO₂ from other exhaust gases. Utilizing coal in a fuel cell is a much more daunting technological prospect (though there are companies making the attempt).

CATF is working to

Establish carbon capture and storage as a major global industry.
Create a new generation of technologies and institutions capable of removing carbon dioxide that has already been released to the atmosphere.
Work directly with industry on getting more federal and state money to support these projects.
Communicate with national and international news outlets, seeking to be seen as an honest arbitrator in coal and climate factual disagreements