Carbon capture and storage

Carbon capture and storage (CCS) is a process by which carbon dioxide (CO₂) from industrial installations is separated before it is released into the atmosphere, then transported to a long-term storage location.^[1]: 2221 The CO₂ is captured from a large point source, such as a natural gas processing plant and is typically stored in a deep geological formation. Around 80% of the CO₂ captured annually is used for enhanced oil recovery (EOR), a process by which CO₂ is injected into partially-depleted oil reservoirs in order to extract more oil and then is largely 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]

Oil and gas companies first used the processes involved in CCS in the mid 20th century. Early versions of CCS technologies served to purify natural gas and to enhance oil production. Subsequently, CCS was discussed as a strategy to reduce greenhouse gas emissions. Around 70% of announced CCS projects have not materialized,^[2] with a failure rate above 98% in the electricity sector.^[4] As of 2024 CCS was in operation at 44 plants worldwide,^[5] collectively capturing about one-thousandth of greenhouse gas emissions.^[6] 90% of CCS operations involve the oil and gas industry.^[7]: 15 Plants with CCS require more energy to operate, thus they typically burn additional fossil fuels and increase the pollution caused by extracting and transporting fuel.

In strategies to mitigate climate change, CCS could have a critical but limited role in reducing emissions.^[6] Other ways to reduce emissions such as solar and wind energy, electrification, and public transit are less expensive than CCS and also much more effective at reducing air pollution. Given its cost and limitations, CCS is envisioned to be most useful in specific niches. These niches include heavy industry and plant retrofits.^{[8]: 21–24} In the context of deep and sustained cuts in natural gas consumption,^[9] CCS can reduce emissions from natural gas processing. ^{[8]: 21–24} In electricity generation and hydrogen production, CCS is envisioned to complement a broader shift to renewable energy.^{[8]: 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 in reducing carbon emissions depends on the plant's capture efficiency, the additional energy used for CCS itself, leakage, and business and technical issues that can keep facilities from operating as designed. Some large CCS implementations have sequestered far less CO₂ than originally expected.^[10][6] 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 heavily promote CCS.^[12] Many environmental groups regard CCS as an unproven, expensive technology that will perpetuate dependence on fossil fuels. They believe other ways to reduce emissions are more effective and that CCS is a distraction.^[13]

Some international climate agreements refer to the concept of fossil fuel abatement, which is not defined in these agreements but is generally understood to mean use of CCS.^[14] Almost all CCS projects operating today have benefited from government financial support. Countries with programs to support or mandate CCS technologies include the US, Canada, Denmark, China, and the UK.