Carbon capture is the process of capturing carbon dioxide (CO2) from flue gas streams, industrial processes or atmospheric air and storing it in a solid, liquid or gaseous form. It is an important technology for mitigating climate change by reducing greenhouse gas emissions.
CO2 can be captured from flue gas using a variety of technologies including absorption, adsorption, membrane separation and cryogenic separation. Once captured, the CO2 can be stored in a number of ways including underground geological formations, abandoned mines, deep saline aquifers and depleted oil and gas fields.
The most common type of capture technology used today is absorption. In this process, CO2 is absorbed into a solution or “scrubbing liquor”. The scrubbing liquor usually contains an amine-based solvent which reacts with the CO2 to form a weakly bound complex. This complex is then separated from the flue gas and the CO2 is stripped from the solution using water or steam before being compressed and stored.
Adsorption technologies are also used for carbon capture. In this process, CO2 is adsorbed onto the surface of a solid material such as activated carbon or zeolites. The advantage of adsorption over absorption is that it can be easily reversed by desorption – heating the solid material to release the CO2 back into the atmosphere or compressing it for storage.
Membrane separation involves passing flue gas through a selective membrane that only allows CO2 molecules to pass through while holding back other gases such as nitrogen (N₂) and oxygen (O₂). This technique can be used to concentrated CO₂ prior to its storage.
Carbon capture and storage (CCS) projects are typically very costly due to the need for specialized equipment and infrastructure as well as extensive monitoring requirements. For this reason, CCS has been slow to develop despite its potential benefits. However, with increasing concerns about climate change, there has been renewed interest in CCS technology in recent years