Carbon Capture and Storage (CCS) is an emerging technology designed to reduce CO2 emissions from power plants and industrial activities like cement or steel manufacturing, before transporting and permanently storing the captured CO2 underground in geological formations.
Decarbonisation also allows the decarbonisation of hard-to-abate sectors such as heavy industry and transport that otherwise have few options available for mitigation.
What is CCS?
Carbon Capture and Storage (CCS) is an emerging technology designed to lower emissions of climate-warming carbon dioxide from power plants and other industrial processes, in three distinct steps. Capturing, transporting and storing are its key components.
CO2 can be captured after combustion before it escapes into the atmosphere using post-combustion capture technologies or pre-combustion capture technologies in power plants equipped with CCS.
CO2 collected is then transported to an underground storage location that meets these criteria, often depleted oil and gas reservoirs or saline formations.
At present, there are 77 commercial CCS projects operating worldwide that store up to 64 million tonnes of CO2 each year. But for CCS to become mainstream technology it will require government support through subsidies or carbon taxes that make fossil fuels more costly or legal restrictions on how much CO2 industries can emit. Furthermore, more cost-effective means must also be found of capturing it from the air, such as tree planting or direct air capture.
Capture
Carbon capture and storage (CCS) technologies use chemical process to capture carbon emissions at power plants, steel mills, cement plants, petrochemical facilities, coal or gas power plants or from the atmosphere for permanent storage in underground geological formations.
There are various techniques for extracting CO2 from fuels, including post-combustion capture where solvents are used to remove carbon dioxide from exhaust gases; pre-combustion capture, which involves extracting carbon from fossil fuels before burning to generate electricity; and direct air capture where pure CO2 is extracted directly from the air. Many research and commercial companies are also exploring creating low carbon products from captured CO2, including fuels, building materials like concrete and cement, and futuristic products like carbon fibres from captured CO2.
Carbon dioxide is transported via pipeline to a CCS site for injection into geological formations that will safely store it permanently, such as salt caverns. Each CCS site should be carefully chosen and secured so as to guarantee long-term storage safety of stored carbon dioxide.
Transport
CCS involves extracting CO2 from industrial exhaust gas or directly capturing it from the atmosphere and storing it deep underground for later release into our atmosphere. CCS is an invaluable technology that will enable us to reach net zero emissions while maintaining industrial production and growth without creating unacceptably large changes to our electricity grid infrastructure.
Capture technologies use chemical absorption, physical adsorption and membrane filtration to efficiently separate CO2 from other gases produced during power generation or industrial processes. They often combine this approach with cryogenic separation processes that operate at very low temperatures for maximum energy savings and purer outputs.
Once separated, CO2 is compressed into liquid form for transport to storage sites. Depending on its destination, transport options include pipeline (reinforced concrete pipe is often preferred over shorter distances), ship, or truck – many modern CCS plants feature shared infrastructure connecting to existing gas pipelines.
Storage
Captured CO2 is transported primarily via pipelines to onshore or offshore underground storage sites for long-term storage, often via compression and deep chilling to avoid damaging its surrounding pipes and surroundings. Furthermore, this part of CCS requires significantly more energy consumption in terms of maintaining high pressures and low temperatures throughout its transport system, making this part more expensive than renewables or efficiency improvements alone.
Once at its storage site, CO2 is injected into deep geological formations for permanent storage, including saline formations, depleted oil and gas fields or basalt layers. Key characteristics that make an appropriate location for carbon storage include porous reservoir rock (with lots of tiny spaces) with impermeable sealing rocks above it.
Saline formations provide the largest potential volume for storage, with extensive deposits located worldwide in sedimentary basins. Numerous commercial saline projects like Norway’s Sleipner facility have demonstrated that CO2 can be stored safely and securely at scale within these formations.