Carbon Capture and Storage (CCS) technology utilizes existing methods to mitigate industrial emissions that are difficult or expensive to eliminate, by extracting CO2 from air or flue gas from fossil fuel power plants and transporting it for permanent storage in deep underground geological formations.
CCS technology is currently limited to point source facilities like coal power plants or ethanol refineries; however, new approaches such as Direct Air Capture and Bioenergy with CCS could expand its potential.
What is CCS?
Carbon capture and storage (CCS) technology enables emissions from industrial processes utilizing fossil fuels to be removed and permanently stored underground geologic formations, as part of strategies intended to meet global climate targets and mitigate the risks of dangerous warming, according to leading energy agencies and the IPCC. It has emerged as a crucial element of these strategies.
Capturing and storing CO2 can be expensive, so CCS should only be employed at large-scale plants currently under development. Furthermore, its effect will only have limited success at reducing greenhouse gas emissions; CCS should be combined with cuts to fossil fuel use as well as rapid shift to renewables to have any lasting results.
The International Maritime Organization is working on ways to regulate onboard CCS technology that would enable ships to capture and store CO2 emissions while at sea. Such technology would fall under the purview of London Protocol regulations that regulate marine pollution from dumping activities.
Capturing CO2
Carbon capture and storage (CCS) is a three-step process involving the capture, transport, and permanent storage of CO2 emissions at power plants and industrial facilities such as saline aquifers, steel mills, cement factories etc. Most CCS installations employ post-combustion technologies which separate CO2 from flue gas produced during fossil fuel combustion; alternative options could include pre-combustion processes that partially oxidize fuel prior to combustion or even direct air capture of CO2.
Once captured, CO2 is typically stored in underground geological formations such as depleted oil and gas reservoirs or un-minable coal seams for easier transportation than solid storage methods. CO2 may also be released directly into ocean waters but this approach raises serious environmental concerns about impacts to marine ecosystems. However, its most promising use has so far been enhanced oil recovery (EOR), whereby heavy crude oils that would otherwise be difficult to extract can be extracted with its help.
Transporting CO2
Carbon capture and storage works by isolating greenhouse gases produced during industrial processes or fossil-fuel power plant combustion from other gases produced. Once separated, these are then transported underground where permanent injection occurs into porous geological formations.
CO2 can be captured through post-combustion CCS, which involves extracting it from flue gas using chemical solvents or adsorption technologies; pre-combustion CCS removes carbon dioxide before fuel combustion by gasification techniques; or direct air capture (DAC), which removes carbon directly from ambient air and draws CO2 directly out. Direct air capture may even serve as a negative emissions technology under certain circumstances.
Once it is separated and compressed, CO2 gas can be transported via pipeline, ship or tanker truck for injection sites. Pipelines provide the cheapest option and have long been in use across North America; for ship or truck transportation methods however, liquid form transportation of the CO2 must be chilled prior to being chilled down for travel to its final destination.
Storing CO2
Carbon Capture and Storage (CCUS), is an emission mitigation strategy used by power plants and other polluters to sequester greenhouse gas emissions permanently underground. There are currently around 30 CCS facilities operating worldwide (and another 153 under development), totalling about one tonne per year captured and stored.
CO2 can be safely stored underground using natural rock formations like depleted oil and gas reservoirs that contain porous material that traps CO2. Alternatively, the CO2 may be injected into underground oil wells for “enhanced oil recovery”, although this does not qualify as carbon capture and storage since it does not lower greenhouse gas levels.
Mineral carbonation can also provide an efficient method for storing CO2, reacting with certain types of rocks to form stable minerals that store carbon safely and cost-effectively. While this process is expensive and energy intensive, it may provide long-term storage solutions. Another possibility would be dumping CO2 directly into the ocean; however, this option can have negative impacts on marine life and might ultimately not work out well as planned.