Basics of carbon capture technology
Carbon capture involves removing carbon dioxide (CO2) from point sources such as power plants and industrial facilities, or directly from the ambient air, and then concentrating it for use or storage. The primary goal is to prevent CO2 from entering the atmosphere and contributing to climate change.
Main capture methods
- Post-combustion capture: CO2 is separated from flue gases after fuel combustion using chemical solvents, adsorbents, or membranes. This is common in retrofit applications.
- Pre-combustion capture: fuel is converted into a mixture of hydrogen and CO2 before combustion; CO2 is separated out, and hydrogen is used as the fuel.
- Oxy-fuel combustion: fuel burns in nearly pure oxygen, producing flue gas that is mostly CO2 and water, simplifying separation.
- Direct air capture (DAC): machines pull CO2 directly from ambient air using chemical sorbents or filters, though this requires more energy due to low atmospheric CO2 concentration.
Capture process steps
- Separation: chemical solvents (like amines) or solid sorbents bind CO2 from gas streams.
- Regeneration: the CO2-rich solvent is heated or processed to release concentrated CO2 and recycle the solvent.
- Compression and conditioning: captured CO2 is compressed and purified for transport or storage.
Key considerations
- Energy demand: capture and regeneration require heat and electricity, which affect overall system efficiency and emissions footprint.
- Cost: capture adds capital and operational costs; costs depend on concentration of CO2 in the source gas and process design.
- Integration: best results come from integrating capture systems with plant heat and power flows to minimize energy penalties.
Outlook
Carbon capture technologies are ready for deployment in many industrial settings and provide a pathway to decarbonize sectors where emissions are hard to eliminate. Direct air capture offers long-term negative emissions potential but currently at higher cost and energy intensity. Scale-up, policy support, and lowering energy requirements are critical to wider adoption.