Skip to content
Know.itKnow.it
Create an animated lesson
On request

This article is free to read. Creating a lesson uses your daily or stored credits; review the language and settings before starting.

How does carbon capture work?

TechnologyLesson on requestFree to read

Quick answer

Carbon capture pulls carbon dioxide out of exhaust gas before it reaches the air. The gas flows through a solvent, often an amine, that bonds with CO2. Heating the solvent later releases pure CO2, which is compressed and pumped deep underground into sealed rock layers, or used to make chemicals and other products.

Carbon capture separates carbon dioxide from a gas stream, usually power-plant or factory exhaust, and then compresses it for permanent underground storage or industrial use. Most systems pass the gas through a chemical solvent that grabs CO2, then heat that solvent to release a nearly pure stream of the gas.

Step by step

  1. Exhaust gas from a power plant or factory is cooled and cleaned of dust and sulphur before treatment.
  2. The gas rises through an absorber tower where a falling amine solvent chemically captures most of the carbon dioxide.
  3. The loaded solvent is heated in a stripper column, releasing a concentrated stream of CO2 and regenerating the solvent.
  4. Compressors pressurise the carbon dioxide into a dense phase so pipelines or ships can carry it efficiently.
  5. Wells inject the CO2 more than about 800 metres underground into porous rock sealed beneath an impermeable caprock layer.

Key things to understand

  1. Flue gas from burning coal, gas or making cement contains carbon dioxide mixed mostly with nitrogen and water vapour.
  2. In an absorber tower the gas meets an amine solvent that chemically binds carbon dioxide while letting nitrogen pass.
  3. The CO2-rich solvent is pumped to a stripper and heated, which breaks the bond and releases concentrated carbon dioxide.
  4. Compressors squeeze the released CO2 into a dense, liquid-like state that can travel through pipelines or on ships.
  5. It is injected deep underground into porous rock beneath an impermeable caprock, or used to make chemicals and fuels.

Labelled diagram

  1. Flue gas

    Exhaust containing carbon dioxide, nitrogen and water vapour leaves the boiler or kiln.

  2. Absorber

    An amine solvent binds carbon dioxide while cleaned gas exits the top.

  3. Stripper

    Heat releases concentrated CO2 and the regenerated solvent returns to the absorber.

  4. Compressor

    Squeezes CO2 into a dense state ready for pipeline or ship transport.

  5. Storage rock

    Porous rock deep underground holds the CO2 beneath an impermeable caprock seal.

Capturing CO2 from smokestack to deep storage

Real-world examples

  • Norway's Sleipner gas field has injected separated CO2 into a sandstone layer under the North Sea since 1996.
  • The Boundary Dam coal power station in Saskatchewan, Canada, captures CO2 from part of its exhaust.
  • In Iceland, captured CO2 is dissolved in water and injected into basalt, where it turns into carbonate minerals.
  • A chemical plant in Thoothukudi, Tamil Nadu, captures CO2 from its coal boiler to manufacture soda ash.

Common mistake

✗ Myth: Carbon capture on power plants removes carbon dioxide that is already in the atmosphere.

✓ Fact: Capturing CO2 at a smokestack only prevents new emissions from that source. Lowering atmospheric CO2 requires methods such as direct air capture or capturing emissions from burning biomass.

People also ask

How does carbon capture and storage work?
Carbon capture and storage separates CO2 from industrial exhaust, usually with an amine solvent that absorbs it and releases it when heated. The concentrated gas is compressed, transported by pipeline or ship, and injected deep underground into porous rock capped by an impermeable layer that keeps it trapped for very long periods.
Is carbon capture effective?
Modern capture units can remove most of the CO2 in the exhaust they treat, often designed for around 90 percent. In practice many projects have captured less than planned, costs remain high, and the process uses extra energy. It is most useful for industries like cement where emissions are hard to avoid.
Where is captured carbon stored?
Captured carbon dioxide is usually stored in deep saline aquifers, which are porous rock layers filled with salty water, or in depleted oil and gas fields. These sit well below drinking-water supplies, typically more than 800 metres down, under dense caprock that stops the gas rising back to the surface.
What is direct air capture?
Direct air capture uses large fans to pull ordinary air across solid or liquid sorbents that grab carbon dioxide. Because air holds only about 0.04 percent CO2, it needs far more energy per tonne than capturing CO2 from concentrated smokestack exhaust.
Can stored carbon dioxide leak back out?
Well-chosen sites trap CO2 beneath a tight caprock, and over time some dissolves in brine or turns into minerals. Operators monitor storage sites with seismic surveys and wells, and the main leak risks are old boreholes and poorly sealed injection wells.
Why is carbon capture expensive?
Heating the solvent to release CO2 consumes a large share of a plant's energy, and absorbers, compressors and pipelines are costly to build. A power station fitted with capture must burn extra fuel to deliver the same electricity.
What happens to captured CO2 that is used?
Some is used to make soda ash, urea fertiliser or carbonated drinks, and much is injected into oil fields to push out extra crude. Uses that release the gas again soon afterwards do not lock carbon away permanently.

Part of the guide: Energy & Electricity at Home →