Carbon capture and storage is a technology that could help reduce greenhouse gas emissions. However, it remains expensive, risky, and slow to deploy.
CCS involves capturing CO 2 from power plants and transporting it to be stored underground in geological formations, such as depleted oil reservoirs or deep saline aquifers.
What is CCS?
Carbon capture and storage (CCS) is a technology that reduces industrial greenhouse gas emissions and prevents them from entering the atmosphere. It involves capturing CO2 from point sources such as fossil fuel power plants, separating it from other gases and transporting it to geological formations where it can be stored permanently.
CCS can be applied at precombustion or postcombustion stages, through various methods such as flue gas scrubbing, gasification-based combined cycles and oxyfuel combustion. Typically, the captured CO2 is compressed before transport to ensure it can be injected into underground formations.
The compression and transport of the CO2 are energy intensive processes that add significant costs to the power plant operation. This increases the cost of electricity produced by CCCS technologies, especially if the storage site is located far from the power plant. This is why it is important that advanced model-based control systems are developed to ensure that a power plant can still operate as a load following system despite the added energy penalty of the CO2 capture process.
Capture
Carbon capture and storage (CCS) works differently from carbon offsetting, as it tackles emissions before they enter the atmosphere. It essentially separates carbon dioxide from other gases, compresses it, and then pumps it into underground geological formations. The buried CO2 will stay there forever, preventing it from escaping and polluting the atmosphere. CCS facilities require a lot of electricity, though experts are working to make them more energy efficient.
Currently, two types of CCS are in operation: post-combustion capture, which separates carbon dioxide from fossil fuel power plant flue gas; and direct air capture, in which giant fans suck air into devices that remove CO2. These captured gases are then transported to deep underground rock formations. Those rocks are often a mile or more below the surface and have impermeable layers of rock that trap the carbon dioxide. Combined with biological, or terrestrial, sequestration — which involves planting trees that will absorb CO2 over time — CCS can be considered an effective way to mitigate climate change.
Transport
Carbon capture and storage is an essential tool for mitigating climate change. To achieve the goal of reducing emissions to zero, CO2 must be prevented from entering the atmosphere. This is done by capturing CO2 from fossil fuels, transporting it safely to a secure underground geological formation and storing it for the long term.
Land-based CCS plants use a combination of processes to separate CO2 from other gases produced at power stations, cement plants, steel mills, oil refineries and coal plants. The captured CO2 is then transported for processing and storage to a CO2 consolidation hub.
Post-combustion capture systems typically require less engineering than pre-combustion options and can be installed in existing industrial facilities. However, if CO2 concentration is very high or projects are not aligned with low-temperature downstream handling, cryogenic CO2 separation technologies are also available. Onboard Carbon Capture solutions in shipping require a different approach: space is tighter, weight matters more and operating profiles can vary with engine load. This places a premium on compact equipment design and marine transfer arrangements as well as stable liquefied gas handling on board in line with IGC codes and approved discharge concepts.
Storage
CCS technology is a key component of strategies that aim to achieve net zero industrial emissions and mitigate climate change. After capture, the CO2 is transported and permanently stored underground in geological formations such as depleted oil reservoirs, un-minable coal seams or deep saline aquifers. Transportation is typically via pipelines (with ships being a less cost effective option for longer distances).
CO2 can be stored in liquid form in high pressure tanks or as a solid mineral carbonate by reacting with metal oxides to create stable minerals. Ocean storage is not considered viable, as it would significantly increase ocean acidification.
The Sleipner project in Norway has been storing carbon dioxide since 1996, preventing the gas from entering the atmosphere and forming additional greenhouse gases. The CCUS process, which includes the capture, transport and storage of carbon dioxide, is also known as carbon dioxide utilization and storage (CCUS). However, it differs slightly from CCS as the CO2 that has been captured and stored can then be used to make valuable products rather than being returned to the atmosphere.