Carbon capture and storage technology aims to prevent fossil fuel CO2 emissions from polluting the atmosphere, by collecting gas at power plants or industrial facilities before depositing it underground in geological formations for permanent storage.
Captured CO2 is transported either via pipeline or ship for storage, typically by using structural trapping, in which impermeable rock layers seal supercritical CO2.
CCUS
Carbon capture and storage (CCUS) technology could play an integral role in reaching net zero emissions targets. CCUS helps decarbonise energy-intensive industries which may struggle to switch away from fossil fuels while simultaneously capturing CO2 from entering the atmosphere at its source.
CCUS begins at power plants and industrial facilities that produce CO2, using solvent or membrane extraction to capture it before transporting it by pipeline or ship to permanent storage sites.
Once at its storage site, CO2 captured from emissions sources is injected underground in geological formations where it will remain protected from atmospheric conditions for millennia. Captured CO2 may also be utilized for other industrial applications like enhanced oil recovery (EOR). EOR projects inject CO2 into old oil fields to increase crude oil extraction rates from those locations.
Capture
CCUS captures carbon dioxide emissions from power plants and other industrial sources and uses or stores it so that it does not enter the atmosphere. Carbon capture and utilization (CCU) practices use this method of carbon sequestration and use it productively – building materials are one use or enhanced oil recovery is another example.
Once captured, CO2 is compressed and deep chilled into liquid form so it can be transported via pipelines, ships or tanker trucks to its storage site – usually depleted oil and gas reservoirs or deep saline formations.
CCUS projects can be built concurrently with fossil fuel plants or retrofitted onto existing facilities, with some already capturing and storing millions of tonnes of CO2, but many more projects will be needed to reach climate goals. Hubs combining multiple capture technologies at one facility may help expedite this process through economies of scale in transport and storage as well as standardization on capture technology.
Transport
CCUS technology seeks to capture carbon emissions at their source before they reach the atmosphere, providing an effective tool for climate change mitigation. This approach stands in stark contrast with processes such as carbon dioxide removal (or EOR), which removes CO2 already present in the air, or reversible climate mitigation techniques such as bioenergy with CCS or direct air capture and storage (DACS).
Once carbon has been captured, it must be transported to its storage site using pipelines similar to those used to transport oil and natural gas, over long distances. Ships or trucks may also be employed if distance is short or terrain difficult.
Once at its location, carbon dioxide (CO2) is injected deep underground in rock formations which are suitable for geologic storage, typically saline aquifers or depleted oil and gas reservoirs that lie several miles beneath the surface. CO2 is then covered by impermeable rock layers to prevent upward migration.
Storage
Carbon dioxide that has been captured is then stored permanently underground using porous geological formations such as depleted oil and gas reservoirs, unmineable coal areas or deep saline formations that occur naturally around the world.
Mineral carbonation can also be used to store CO2, by reacting it with cement-like materials in porous rock formations. Although this process takes many thousands of years naturally, industrial processes may accelerate it significantly.
Hager says the industry has begun implementing “fairly standard techniques for testing whether a site is suitable for long-term storage.” These tests largely draw upon tools used by oil and gas industries when searching for deposits of crude oil; companies conduct seismic tests and characterize rock properties to locate locations where carbon dioxide injection could occur.