Carbon capture and storage

Carbon capture and storage (CCS) is a process in which a relatively pure stream of carbon dioxide (CO₂) from industrial sources is separated, treated and transported to a long-term storage location.^: 2221 For example, the carbon dioxide stream that is to be captured can result from burning fossil fuels or biomass. Usually the CO₂ is captured from large point sources, such as a chemical plant or biomass plant, and then stored in an underground geological formation. The aim is to reduce greenhouse gas emissions and thus mitigate climate change. The IPCC's most recent report on mitigating climate change describes CCS retrofits for existing power plants as one of the ways to limit emissions from the electricity sector and meet Paris Agreement goals.

CO₂ can be captured directly from an industrial source, such as a cement kiln, using a variety of technologies; including adsorption, chemical looping, membrane gas separation or gas hydration. As of 2022, about one thousandth of global CO₂ emissions are captured by CCS, and most projects are for fossil gas processing.^: 32 Current CCS projects generally aim for 90% capture efficiency, but a number of current projects have failed to meet that goal. Opponents argue that carbon capture and storage is only a justification for indefinite fossil fuel usage disguised as marginal emission reductions.

Storage of the CO₂ is either in deep geological formations, or in the form of mineral carbonates. Pyrogenic carbon capture and storage (PyCCS) is also being researched. Geological formations are currently considered the most promising sequestration sites. The US National Energy Technology Laboratory (NETL) reported that North America has enough storage capacity for more than 900 years worth of CO₂ at current production rates. A general problem is that long-term predictions about submarine or underground storage security are very difficult and uncertain, and there is still the risk that some CO₂ might leak into the atmosphere. Despite this, a 2018 evaluation estimates the risk of substantial leakage to be fairly low.

CCS is often considered to be a relatively expensive process yielding a product which is too cheap. Carbon capture makes more economic sense where the carbon price is high enough, such as in much of Europe, or when combined with a utilization process where the cheap CO₂ can be used to produce high-value chemicals to offset the high costs of capture operations. Some environmental activists and politicians have criticized CCS as a false solution to the climate crisis. They cite the role of the fossil fuel industry in origins of the technology and in lobbying for CCS focused legislation. Opponents also argue that carbon capture and storage is only a justification for indefinite fossil fuel usage disguised as marginal emission reductions. People already involved or used to industry are more likely to accept CCS, while communities who have been negatively affected by any industrial activity are also less supportive of CCS.

Globally, a number of laws and rules have been issued that either support or require the use of CCS technologies. In the US, the 2021 Infrastructure, Investment and Jobs Act provides support for a variety of CCS projects, while the Inflation Reduction Act of 2022 updates tax credit law to encourage the use of carbon capture and storage. In 2023 EPA issued a rule proposing that CCS be required order to achieve a 90% emission reduction for existing coal-fired and natural gas power plants. That rule would become effective in the 2035-2040 time period. Other countries are also developing programs to support CCS technologies, including Canada, Denmark, China, and the UK.