Carbon capture and storage
[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.
[6] However, other emission-reduction options such as solar and wind energy, electrification, and public transit are less expensive than CCS and are much more effective at reducing air pollution.
The Intergovernmental Panel on Climate Change (IPCC) defines CCS as:"A process in which a relatively pure stream of carbon dioxide (CO2) from industrial and energy-related sources is separated (captured), conditioned, compressed and transported to a storage location for long-term isolation from the atmosphere.
[16][17][18] In this article, the term CCS is used according to the IPCC's definition, which requires CO2 to be captured from point-sources such as a natural gas processing plant.
In 1977, the Italian physicist Cesare Marchetti proposed that CCS could be used to reduce emissions from coal power plants and fuel refineries.
[21][25] The first large-scale CO2 capture and injection project with dedicated CO2 storage and monitoring was commissioned at the Sleipner gas field in Norway in 1996.
[29]: 133 In 2020, the International Energy Agency (IEA) stated, “The story of CCUS has largely been one of unmet expectations: its potential to mitigate climate change has been recognised for decades, but deployment has been slow and so has had only a limited impact on global CO2 emissions.”[8]: 18 By July 2024, commercial-scale CCS was in operation at 44 plants worldwide.
Technological components are used to separate and treat CO2 from a gas mixture, compress and transport the CO2, inject it into the subsurface, and monitor the overall process.
[35][36][37] Impurities in CO2 streams, like sulfur dioxides and water vapor, can have a significant effect on their phase behavior and could cause increased pipeline and well corrosion.
[23] Dedicated geologic storage is generally less expensive than EOR because it does not require a high level of CO2 purity and because suitable sites are more numerous, which means pipelines can be shorter.
[42] In-situ mineral carbonation involves injecting CO2 and water into underground formations that are rich in highly-reactive rocks such as basalt.
[47] If very large amounts of CO2 are sequestered, even a 1% leakage rate over 1000 years could cause significant impact on the climate for future generations.
[6] Since liquid amine solutions are used to capture CO2 in many CCS systems, these types of chemicals can also be released as air pollutants if not adequately controlled.
Retrofitting CO2 capture equipment can enable the continued operation of existing plants, as well as associated infrastructure and supply chains.
[6] Often, community-based organizations would prefer that a facility be shut down and for investment be focused instead on cleaner production processes, such as renewable electricity.
[66] CCS implementations involve multiple technologies that are highly customized to each site, which limits the industry's ability to reduce costs through learning-by-doing.
[68] Options that have far more potential to reduce emissions at lower cost than CCS include public transit, electric vehicles, and various energy efficiency measures.
[51]: 38 The dramatic fall in the costs of renewable power and batteries has made it difficult for fossil fuel plants with CCS to be cost-competitive.
[66] In the literature on climate change mitigation, CCS is described as having a small but critical role in reducing greenhouse gas emissions.
[79][80] For instance, one study found that in the Petra Nova CCS retrofit of a coal power plant, the actual rate of emissions reduction was so low that it would average only 10.8% over a 20-year time frame.
[82]: 19 In one year of operation of the Gorgon gas project in Australia, issues with subsurface water prevented two-thirds of captured CO2 from being injected.
[3] A 2020 review found that scientific papers were roughly evenly split on the question of whether carbon capture with EOR increased or decreased emissions.
[84]: 16 Other observers see the slow pace of implementation as an indication that the concept of CCS is fundamentally unlikely to succeed, and call for efforts to be redirected to other mitigation tools such as renewable energy.
[11] Their statements typically position CCS as a necessary way to tackle climate change, while not mentioning options for reducing fossil fuel use.
[94] The IPCC considers fossil fuels to be unabated if they are "produced and used without interventions that substantially reduce the amount of GHG emitted throughout the life-cycle; for example, capturing 90% or more from power plants, or 50–80% of fugitive methane emissions from energy supply.
[101] The Internal Revenue Service relies on documentation from the corporation to substantiate claims on how much CO2 is being sequestered, and does not perform independent investigations.
[89] In 2020, a federal investigation found that claimants for the 45Q tax credit failed to document successful geological storage for nearly $900 million of the $1 billion they had claimed.
[3] In 2023 the US EPA issued a rule proposing that CCS be required in order to achieve a 90% emission reduction for existing coal-fired and natural gas power plants.
[109]: 20 This tax, combined with favorable and well-understood site geology, was a reason Equinor chose to implement CCS in the Sleipner and Snøhvit gas fields.
The utilization of CO2 in construction materials holds promise for deployment at large scale,[117] and is the only foreseeable CO2 use that is permanent enough to qualify as storage.
