Carbon capture and storage (CCS) is an approach used to mitigate greenhouse gas (GHG) emissions from large industrial sources, such as power stations or steel and cement production facilities. CCS involves collecting CO2, transporting it underground, storing it safely for long-term storage, then disposing of any excess emissions through emission trading schemes or carbon trading agreements.
CCUS can also involve using CO2 from power plant emissions to make low-carbon products such as fuels or concrete additives, creating new low-carbon solutions. There are currently many large-scale CCS projects underway worldwide.
Capturing CO2
Carbon capture and storage (CCS) technologies offer proven ways to combat climate change emissions, by extracting CO2 from industrial exhaust gas or the atmosphere for storage deep underground in geologic formations.
Large-scale CCS projects such as Norway’s Sleipner CO2 Storage Site and Canada’s Weyburn-Midale CO2 Project are already successfully storing millions of tons of carbon dioxide (CO2) annually, showing that CO2 can be safely and permanently stored at depths greater than 800 meters.
CO2 captured at capture plants is first compressed into dense liquid form known as supercritical CO2, before being transported by pipeline or special-designed ships known as carbon dioxide carriers to its storage site.
3D animation of a coastal carbon capture facility shows tall red and white chimneys surrounded by two silver storage vessels with yellow bands and two yellow-banded silos. As the camera zooms closer, we see that these systems work: tall white cylindrical tanks filled with dark grey vapor are connected via blue pipes which feed them vapor.
Transporting CO2
Over many years, humans have burned fossil fuels such as coal, oil and natural gas and conducted industrial processes that release CO2. This has contributed to climate change. Carbon capture and storage (CCS) technology offers one way out: capture and storage before carbon dioxide emissions escape into the air.
Carbon can be stored safely and permanently underground using various proven technologies. Structural trapping involves reacting CO2 with minerals in basalt formations to form carbonates that trap it. Solubility trapping involves dissolving it into brine water that exists within rock pores to store CO2.
CO2 emissions are transported to storage sites where it will remain isolated in geological formations for long-term storage. In 2009, LP Parties amended Article 6 of the Protocol to permit CO2 streams exported for subseabed geological storage as long as certain criteria are met.
Injecting CO2
CCS allows CO2 to be transported from its point of capture (such as exhaust gas from power plants or industrial processes, or directly from the atmosphere) and stored underground at storage sites – this technology offers a permanent solution to climate change!
Once injected, CO2 remains in a supercritical state due to elevated temperatures and pressures below Earth’s surface. Structural trapping – consisting of rock layers and faults acting as seals – ensures it does not migrate up towards its surface.
CO2 can be stored safely underground in geological formations like saline aquifers and depleted oil fields, as well as being injected into mature oilfields for enhanced oil recovery (EOR), driving out more oil from fields while simultaneously remaining permanently stored underground – known as carbon dioxide utilisation and potentially offering tax credits as part of this strategy.
Storing CO2
Burning fossil fuels like coal, oil and natural gas or operating certain industrial processes such as cement and steel making releases CO2. Over time this emission of greenhouse gases has built up in our atmosphere, leading to global warming. Humanity has made the commitment to limit global temperature rise by reducing CO2 levels; CCS can be an invaluable asset in accomplishing this goal.
Capture technology employs both chemical and mechanical means to isolate carbon dioxide from exhaust gases. In certain instances, direct capture occurs, as at power plants with biofuels which produce pure CO2 streams that can be siphoned off; or production plants for fertilisers and ethanol production.
Potential storage sites for CO2 include saline formations, depleted oil and gas reservoirs, unmineable coal areas and basalt formations. Each potential site must be carefully assessed using well and geological data in order to make sure it can accommodate long-term CO2 storage. When CO2 is injected it becomes supercritical and buoyant – meaning that when it reaches impermeable layers above, it floats upward through rock pores until reaching an impermeable barrier layer above.