Carbon Capture and Storage (CCS) involves collecting CO2 emissions from fossil fuel power plants, industrial facilities such as cement and steel manufacturing and fertiliser production facilities and storing them underground. CCS technology can also be utilized to enhance oil recovery or produce clean hydrogen from natural gas.
CO2 can be collected and stored in geological formations like used oil and gas reservoirs and deep saline formations.
What is CCS?
Carbon capture and storage (CCS) technology involves extracting greenhouse gas emissions from fossil fuel power stations, energy intensive industries or gas fields and transporting them underground for permanent storage. CCS operations currently exist around the world with five large-scale CCS operations serving coal and oil projects; although CCS can never become a zero emissions solution due to energy requirements required to capture CO2 from flue gases generated from fossil fuel sources.
CO2 can be stored safely in geological formations such as saline aquifers or depleted oil and gas fields for long-term storage, or converted to synthetic fuels for reuse by products like concrete and chemicals; these technologies must also be combined with an increased reduction of fossil fuel use to effectively address climate change.
Capture
Carbon capture technology can remove CO2 from a source such as a fossil fuel power plant or industrial facility, as well as from existing emissions such as those released through bioenergy with carbon capture and storage (BECCS) plants or direct air capture (DAC).
Capturing carbon dioxide involves isolating it from other gases released into the atmosphere at these facilities and compressing and transporting it for permanent storage.
Some sites for CO2 storage are underground while others use depleted oil and gas reservoirs or deep saline aquifers as the medium for its release into the atmosphere, mitigating climate change and ocean acidification, while there has also been an upsurge in efforts to reinforce natural processes that remove carbon from the air, such as planting trees.
Compression
Carbon Capture and Storage (CCS) technologies prevent carbon dioxide (CO2) emissions from industrial processes or power stations from escaping into the atmosphere. CO2 can be captured either from large point sources like fossil fuel power plants, or through industrial processes such as ethanol fermentation.
CO2 is then stored underground by pumping it into rock formations that can store it, such as depleted oil and gas reservoirs or saline aquifers.
Carbon dioxide (CO2) is typically injected at the bottom of formations and then stored under dense and impermeable rock layers such as shale or limestone to ensure it doesn’t escape into surrounding formations or into the atmosphere. Monitoring is used to ensure this does not happen and other storage methods, including seawater storage or underground aquifer storage, are being considered.
Transport
Carbon capture and storage allows large industrial processes, like power generation, steel production, cement manufacturing and petrochemical processing to continue without significantly impacting the climate. Carbon capture can also help reduce historical emissions through direct air capture or bioenergy with carbon capture and storage (BECCS).
CO2 captured through capture methods is transported for long-term storage via pipeline or ship or train, depending on its volume. Energy is required to compress and chill it into liquid state as well as maintain high pressures and low temperatures along its journey.
CO2 is then injected into deep geological formations where it will remain permanently stored – such as old oil and gas reservoirs, depleted coal beds or deep saline aquifers – where its risk of leakage is considered minimal.
Storage
Carbon Capture and Storage technologies aim to reverse climate change by capturing CO2 emissions before they enter the atmosphere, such as power plant emissions. These techniques range from collecting it directly in the air or underground storage facilities.
Once CO2 has been captured it can be compressed into liquid form for transport via pipeline, ship or rail tanker to its storage site. CO2 injection sites include depleted oil and gas reservoirs, coalbeds or deep saline aquifers where rocks provide suitable storage conditions.
CO2 can then be sealed away within the formation using techniques such as structural trapping, where carbon dioxide rises up through porous rock layers until reaching an impermeable seal rock and being trapped by it. Alternatively, it can be pumped into an existing oil field for enhanced oil recovery but this would not be carbon neutral.