Carbon capture and storage (CCS) is an emerging technology with great promise to combat global warming. CCS works by collecting emissions from power plants, steel mills or cement factories and transporting them underground to be stored permanently within geological formations.
CO2 captured during this process is then stored underground, in either depleted oil reservoirs or saline aquifers using various techniques that prevent any escape.
Capture
CCS works to capture carbon dioxide (CO2) produced when fossil fuels are burned before it enters the atmosphere, with power plants as a major source of emission. But it could also help cut emissions from steel and cement factories as well as those producing ammonia and ethanol.
Huge fans guide air through machines that isolate CO2, leaving behind a liquid known as supercritical CO2. This liquid is then compressed at high pressure before being shipped via pipeline – an efficient, safe process with over 50 such pipelines stretching across 5,000 miles of US territory.
Most CCS strategies involve injecting CO2 deep underground, often into depleted oil fields or saline aquifers, under an impermeable layer of rock to ensure it does not rise towards the surface and cause harm. Long-term monitoring will be necessary to ensure safety. Alternatively, CO2 may also be stored by reinjecting it back into an active oilfield in an attempt to increase production through enhanced oil recovery (EOR), however this method remains controversial due to creating additional emissions into the atmosphere by burning excess oil produced.
Compression
Carbon capture and storage (CCS) refers to the process by which CO2 from power plants, steel production facilities and other industrial processes is separated and compressed before being stored permanently underground.
CCS systems must separate and compress CO2 produced from burning fossil fuels at pressures significantly higher than atmospheric conditions in order to function. This represents one of the major capital and operational cost penalties associated with CCS and requires high efficiency low emission compressors.
CO2 from power plants is usually stored in porous and permeable geological formations like saline aquifers or depleted gas fields that allow CO2 injection at large scale to safely be stored, including rock layers or faults that seal above storage sites and prevent leakage pathways; additionally, their permeability must allow CO2 storage at depth so as to be isolated from other underground fluids.
Transportation
Numerous technologies exist to remove CO2 from industrial flue gases and other emissions, either directly from the air (point source capture) or at large industrial facilities such as steel mills or power plants. Once collected, this carbon dioxide can either be sent for permanent underground storage or reused to help extract oil or make industrial materials.
Most carbon capture and storage strategies involve depositing CO2 deep underground in permeable rock formations like depleted oil reservoirs or saline aquifers, where its presence can be safely contained over long time periods. There are currently more than 5,000 miles of pipelines transporting the gas for permanent underground storage sites.
CO2 can be transported via tanks, rail, or ship depending on its source and destination. Trains offer significantly lower per ton mile costs compared to trucks while being more environmentally responsible than ships – future developments such as onboard carbon capture may reduce emissions at sea further still.
Storage
CCS can assist in meeting climate change goals by preventing emissions in the future and permanently storing them underground, as well as clearing away historic emissions from the air.
CO2 can be collected at its source – such as power plants, steel and cement production facilities and other industrial sites – before being transported for storage in geological formations underground like used oil and gas reservoirs or saline aquifers. Transportation options for CO2 include pipeline, ship or truck transport; pipelines provide the most cost-effective means, due to being built incrementally at scale.
Once at its storage site, carbon dioxide is injected into rock formations where it can be trapped using various mechanisms, including structural trapping and aquifer sealing. Once stored underground for years without leakage into surface water or drinking supplies – commercial projects like Norway’s Sleipner-Weyburn-Midale CO2 Storage Projects and Australia’s Zero Carbon Humber facility being developed on Barrow Island have already stored CO2.