Carbon capture and storage

Carbon capture and storage (CCS) is a process in which carbon dioxide (CO₂) from industrial sources is separated before it mixes with the atmosphere, treated and transported to a long-term storage location.^[1]: 2221 In CCS, the CO₂ is captured from a large point source, such as a natural gas processing plant or coal power plant, and typically is stored in a deep geological formation. As of 2024, around 80% of the CO₂ captured annually is used for enhanced oil recovery (EOR), a process in which CO₂ is injected into partially-depleted oil reservoirs in order to extract more oil and then is left underground.^[2] Since EOR utilizes the CO₂ in addition to storing it, CCS is also known as carbon capture, utilization, and storage (CCUS).^[3]

American oil and gas companies developed the processes involved in CCS in the mid 20th century. Early versions of CCS technologies served to purify natural gas and to facilitate oil production. Subsequently, CCS was discussed as a strategy to reduce greenhouse gas emissions.^[4][5] Around 70% of announced CCS projects have not materialized.^[2] As of 2023, 40 commercial CCS facilities are operational and collectively capture about one thousandth of anthropogenic CO2 emissions. CCS facilities typically require capital investments of up to several billion dollars, and CCS also increases operating costs.^[6] Power plants with CCS are expected to require around 15-25% more energy to operate,^[7] thus they typically burn additional fossil fuel and increase the pollution from extracting and transporting fuel. Almost all CCS projects operating today have benefited from government financial support, usually in the form of grants.^{[8]: 156–160}

In strategies to mitigate climate change, CCS plays a small but critical role. CCS is expensive compared to other methods of reducing emissions such as renewable energy, electrification, and public transit and is much less effective at reducing air pollution. Given its limitations, CCS is most useful in specific niches, particularly heavy industry, plant retrofits, natural gas processing, and electrofuel production.^{[9]: 21–24} In electricity generation and blue hydrogen production, CCS is envisioned to play a role that complements a broader shift to renewable energy.^{[9]: 21–24} CCS is a component of bioenergy with carbon capture and storage, which can under some conditions remove carbon from the atmosphere.

The effectiveness of CCS projects in reducing carbon emissions depends on the capture efficiency, the additional energy used for CCS itself, leakage, and business and technical issues that can keep facilities from operating as designed. Many large CCS implementations have failed to meet their emission-reduction goals.^[10] Additionally, there is controversy over whether CCS is beneficial for the climate if the CO₂ is used to extract more oil.^[11] Fossil fuel companies have heavily promoted CCS, framing it as an area of innovation and cost-effectiveness.^[12] Some environmental activists and politicians have criticized CCS as a false solution to the climate crisis. Critics also argue that CCS is only a justification for indefinite fossil fuel usage and equate to further investments into the environmental and social harms related to the fossil fuel industry.^[13][14]

Globally, a number of laws and rules have been issued that either support or mandate the implementation of CCS. In the US, the 2021 Infrastructure Investment and Jobs Act provides support for a variety of CCS projects, and the Inflation Reduction Act of 2022 updates tax credit law to encourage the use of CCS.^[15][16] Other countries are also developing programs to support CCS technologies, including Canada, Denmark, China, and the UK.^[17][18]