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.^[2]: 2221 For example, the burning of fossil fuels or biomass results in a stream of CO₂ that could be captured and stored by CCS. Usually the CO₂ is captured from large point sources, such as a chemical plant or a bioenergy plant, and then stored in a suitable geological formation. The aim is to reduce greenhouse gas emissions and thus mitigate climate change.^[3][4] For example, CCS retrofits for existing power plants can be one of the ways to limit emissions from the electricity sector and meet the Paris Agreement goals.^[5]: 16

Carbon dioxide can be captured directly from the gaseous emissions of an industrial source, for example from a cement factory (cement kiln). Several technologies are in use: adsorption, chemical looping, membrane gas separation or gas hydration.^[6][7][8] However, as of 2022, only about one thousandth of global CO₂ emissions are captured by CCS, and most of those CCS projects are for natural-gas processing.^[9]: 32 CCS projects generally aim for 90% capture efficiency,^[10] but most of the current installations have failed to meet that goal.^[11]

Storage of the captured CO₂ is either in deep geological formations or in the form of mineral carbonates. Geological formations are currently the favored option for storage. Pyrogenic carbon capture and storage (PyCCS) is another option.^[12] Long-term predictions about submarine or underground storage security are difficult. There is still the risk that some CO₂ might leak into the atmosphere.^[13][14][15] A 2018 evaluation estimates the risk of substantial leakage to be fairly low.^[16][17] CCS is so far still a relatively expensive process.^[18] Carbon capture becomes more economically viable when the carbon price is high, which is the case in much of Europe.^[9] Another option is to combine CCS with a utilization process where the captured CO₂ is used to produce high-value chemicals to offset the high costs of capture operations.^[19]

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.^[20] 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.^[21][22] With regards to public support, communities who have been negatively affected by an industrial activity in the past are less supportive of CCS.^[23] Communities that feel inadequately informed about or excluded from project decision-making may also resist CCS development.^[24]

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.^[25][26] Other countries are also developing programs to support CCS technologies, including Canada, Denmark, China, and the UK.^[27][28]