Carbon capture and storage (CCS) is a set of technologies that remove CO2 from the atmosphere at large point sources such as power plants. It is a key technology for limiting global warming to below 2 degrees Celsius.
The process consists of several steps: capturing, transporting and storing carbon dioxide. The last step, storage, is what distinguishes CCS from other industrial processes.
Capturing Carbon
Carbon capture and storage involves capturing carbon dioxide from major point sources, like fossil fuel power plants or industrial facilities, transporting it to a storage site and injecting it into a geological formation where it can be permanently stored. This prevents the release of CO2 into the atmosphere from these sources and is a key technology in mitigating climate change.
Enbridge is involved in both pre- and post-combustion capture technologies as we advance world-class CCS projects across North America. During pre-combustion capture, pulverized coal power plants are scrubbed to remove the CO2 from the flue gas before it is sent up the smokestack. This is accomplished through a process known as amine-based absorption. The CO2 is removed from the flue gas by contacting it with solutions of water and amines in a gas absorber, then separated from the solution using heat.
This captured CO2 can then be transported to a storage site and injected into deep geological formations for permanent storage. The CO2 can also be reutilized, either in the form of pure carbon or by being used as a raw material for various applications, including cement and concrete, fuels, and futuristic materials like graphene and carbon fibers.
Transporting Carbon
Carbon Capture and Storage (CCS) is a set of proven technologies that can reduce greenhouse gas emissions from power plants and industrial facilities and then permanently store them underground. This technology helps us achieve net-zero emissions needed to meet climate goals.
CCS involves separating carbon dioxide from the exhaust gases of a power plant or directly from the atmosphere and transporting it to a storage site where it will be permanently stored in geological formations. This process requires CO2 pipeline networks.
To be cost effective, CCS needs to be applied widely across the energy sector and at scale. This will require new facilities using pre-combustion, oxy-combustion, or direct air capture (DAC) technologies and the development of robust, reliable CO2 transport systems to deliver them.
Depending on the location of the storage site, it may be necessary to transport the captured CO2 over large distances. The resulting transportation network will need to be integrated with the system at the power plant and the geological storage site.
Storing Carbon
Carbon dioxide from fossil fuel power plants and other stationary sources such as cement and steel production needs to be captured and stored in order to mitigate global warming and ocean acidification. Depending on the technology used, this can be done through pre-combustion capture, oxy-combustion or post-combustion capture and storage (CCS).
The carbon is stored in geological formations or in the ocean. These sites must be selected carefully to ensure that the CO2 does not leak into the atmosphere. Geological sequestration of CO2 is an expensive proposition, with long-term maintenance costs that disincentivize large scale implementation.
Some natural ecosystems such as wetlands, grasslands and forests can also store carbon. The carbon can also be stored in the form of saline water or mineral carbonates. The oceans are a huge carbon sink, storing the equivalent of billions of tons of CO2 in the form of calcium and magnesium carbonate sediments over geological time. This process is referred to as natural geological sequestration.
Utilizing Carbon
Carbon can be utilized in a range of ways. It can be combined with hydrogen to produce low-carbon fuels such as methane and methanol, or replaced as raw material in the manufacture of chemicals and polymers.
The most common and economical method of utilization is to combine it with a material such as gypsum or concrete. This is often done at CCS facilities that use biomass for energy, such as kilns in the cement and lime industries, or that operate natural gas processing plants.
Most conversion pathways are energy-intensive and thus a supplementary rather than a replacement for CCS, but a growing number of companies are exploring them. In the US, a USD 20 million global competition, the NRG COSIA Carbon XPrize, is supporting development of novel CO2 conversion opportunities. In addition, the US 45Q tax credit loosened restrictions in 2022 to encourage carbon capture and storage (CCS) and utilization projects. Nonetheless, it is important that carbon removal technologies complement, not replace, emissions reductions, minimize negative impacts on people and the environment, and utilize resources sustainably.