Carbon capture and storage (CCS), or carbon capture and sequestration and carbon control and sequestration, is the process of capturing waste carbon dioxide (CO2), transporting it to a storage site, and depositing it where it will not enter the atmosphere.
Usually, the CO2 is captured from large point sources, such as a cement factory or biomass power plant, and normally it is stored in an underground geological formation.
The aim is to prevent the release of large quantities of CO2 into the atmosphere from heavy industry, and so help to limit climate change.
Although CO2 has been injected into geological formations for several decades for various purposes, including enhanced oil recovery, the long-term storage of CO2 is a relatively new concept.
Carbon dioxide can be captured directly from an industrial source, such as a cement kiln, by using a variety of technologies, including absorption, adsorption, chemical looping, membrane gas separation or gas hydrate technologies.
Geologic carbon sequestration
It is the process of storing carbon dioxide (CO2) in underground geologic formations. The CO2 is usually pressurized until it becomes a liquid, and then it is injected into porous rock formations in geologic basins.
This method of carbon storage is also sometimes a part of enhanced oil recovery, otherwise known as tertiary recovery, because it is typically used later in the life of a producing oil well.
In enhanced oil recovery, the liquid CO2 is injected into the oil-bearing formation in order to reduce the viscosity of the oil and allow it to flow more easily to the oil well.
Biologic carbon sequestration
It refers to storage of atmospheric carbon in vegetation, soils, woody products, and aquatic environments. For example, by encouraging the growth of plants—particularly larger plants like trees—advocates of biologic sequestration hope to help remove CO2 from the atmosphere.
Storage of the CO2 is envisaged either in deep geological formations, or in the form of mineral carbonates. Pyrogenic carbon capture and storage (PyCCS) is also being researched.
Deep ocean storage is not used, because it could acidify the ocean. A general problem is that long term predictions about submarine or underground storage security are very difficult and uncertain, and there is still the risk that some CO2 might leak into the atmosphere.
