Carbon capture and storage

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." Both terms have been used predominantly to refer to enhanced oil recovery (EOR) a process in which captured CO2 is injected into partially depleted oil reservoirs in order to extract more oil. These uses are forms of carbon capture and utilization. In some cases, the product durably stores the carbon from the CO2 and thus is also considered to be a form of CCS. To qualify as CCS, carbon storage must be long-term, therefore utilization of CO2 to produce fertilizer, fuel, or chemicals is not CCS because these products release CO2 when burned or consumed. 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. == History and current status ==

were cancelled in 2013. Over 98% of plans to use CCS in power plants have failed. |alt=Aerial view of the Belchatow Power Station site, with smoke coming from its smokestacks, and surrounding buildings. In the natural gas industry, technology to remove CO2 from raw natural gas was patented in 1930. This processing is essential to make natural gas ready for commercial sale and distribution. Usually after CO2 is removed, it is vented to the atmosphere. Subsequently, natural gas companies in Texas began capturing the CO2 produced by their processing plants and selling it to local oil producers for EOR. Small-scale implementations were first demonstrated in the early 1980s and an economic evaluation was published in 1991. 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. Governments spent an estimated US$30 billion on subsidies for CCS and for fossil-fuel-based hydrogen. Sixteen of these facilities were devoted to separating naturally occurring CO2 from raw natural gas. Seven facilities were for hydrogen, ammonia, or fertilizer production, seven for chemical production, five for electricity and heat, and two for oil refining. CCS was also used in one iron and steel plant. Collectively, the facilities capture about one-thousandth of global greenhouse gas emissions. Eighteen facilities were in the United States, fourteen in China, five in Canada, and two in Norway. Australia, Brazil, Qatar, Saudi Arabia, and the United Arab Emirates had one project each. As of 2020, North America has more than of CO2 pipelines, and there are two CO2 pipeline systems in Europe and two in the Middle East. == Process overview ==

CCS facilities capture carbon dioxide before it enters the atmosphere. Generally, a chemical solvent or a porous solid material is used to separate the CO2 from other components of a plant's exhaust stream. Most commonly, the gas stream passes through an amine solvent, which binds the CO2 molecule. This CO2-rich solvent is heated in a regeneration unit to release the CO2 from the solvent. The CO2 stream then undergoes conditioning to remove impurities and bring the gas to an appropriate temperature for compression. The purified CO2 stream is compressed and transported for storage or end-use and the released solvents are recycled to capture more CO2 from the facility. After the has been captured, it is usually compressed into a supercritical fluid and then injected underground. Pipelines are the cheapest way of transporting CO2 in large quantities onshore and, depending on the distance and volumes, offshore. Transport via ship has been researched. CO2 can also be transported by truck or rail, albeit at higher cost per tonne of CO2. == Technical components ==

CCS processes involve several different technologies working together. 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. There are three ways that CO2 can be separated from a gas mixture: post-combustion capture, pre-combustion capture, and oxy-combustion: • In post combustion capture, the CO2 is removed after combustion of the fossil fuel. • The technology for pre-combustion is widely applied in natural gas processing. 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. In instances where CO2 impurities exist, a process is needed to remove them. == Storage and enhanced oil recovery ==

Storing CO2 involves the injection of captured CO2 into a deep underground geological reservoir of porous rock overlaid by an impermeable layer of rocks, which seals the reservoir and prevents the upward migration of CO2 and escape into the atmosphere. Oil extracted through EOR is mixed with CO2, which can then mostly be recaptured and re-injected multiple times. This CO2 recycling process can reduce losses to 1%; however, it is energy-intensive. Around 20% of captured CO2 is injected into dedicated geological storage, In-situ mineral carbonation involves injecting CO2 and water into underground formations that are rich in highly-reactive rocks such as basalt. There, the CO2 may react with the rock to form stable carbonate minerals relatively quickly. Once this process is complete, the risk of CO2 escape from carbonate minerals is estimated to be close to zero. The global capacity for underground CO2 storage is potentially very large and is unlikely to be a constraint on the development of CCS. After injection, supercritical CO2 tends to rise until it is trapped beneath a caprock. Once it encounters a caprock, it spreads laterally until it encounters a gap. If there are fault planes near the injection zone, CO2 could migrate along the fault to the surface, leaking into the atmosphere, which would be potentially dangerous to life in the surrounding area. If the injection of CO2 creates pressures underground that are too high, the formation will fracture, potentially causing an earthquake. While research suggests that earthquakes from injected CO2 would be too small to endanger property, they could be large enough to cause a leak. According to the IPCC, well-managed storage sites likely retain over 99% of injected CO2 for more than a thousand years, where 'likely' means a 66–90% probability. 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. == Social and environmental impacts ==

Energy and water requirements Facilities with CCS use more energy than those without CCS. The energy consumed by CCS is called an "energy penalty". Depending on the technology used, CCS can require large amounts of water. For instance, coal-fired power plants with CCS may need to use 50% more water. Pollution Since plants with CCS require more fuel to produce the same amount of electricity or heat, the use of CCS increases the "upstream" environmental problems of fossil fuels. Upstream impacts include pollution caused by coal mining, emissions from the fuel used to transport coal and gas, emissions from gas flaring, and fugitive methane emissions. Since CCS facilities require more fossil fuel to be burned, CCS can cause a net increase in air pollution from those facilities. This can be mitigated by pollution control equipment, however no equipment can eliminate all pollutants. 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. Among the chemicals of concern are volatile nitrosamines and nitramines which are carcinogenic when inhaled or drunk in water. Studies that consider both upstream and downstream impacts indicate that adding CCS to power plants increases overall negative impacts on human health. The health impacts of adding CCS in the industrial sector are less well-understood. Pipelines and storage sites can be sources of large accidental releases of CO2 that can endanger local communities. A 2005 IPCC report stated that "existing CO2 pipelines, mostly in areas of low population density, accident numbers reported per kilometre of pipeline are very low and are comparable to those for hydrocarbon pipelines." While infrequent, accidents can be serious. In 2020, a CO2 pipeline ruptured following a mudslide near Satartia, Mississippi, causing people nearby to lose consciousness. About 200 people were evacuated and 45 were hospitalized, and some experienced longer-term effects on their health. High concentrations of CO2 in the air also caused vehicle engines to stop running, hampering the rescue effort. Jobs Retrofitting facilities with CCS can help to preserve jobs and economic prosperity in regions that rely on emissions-intensive industry, while avoiding the economic and social disruption of early retirements. While there is evidence that CCS can help reduce non-CO2 pollutants along with capturing CO2, environmental justice groups are often concerned that CCS will be used as a way to prolong a facility's lifetime and continue the local harms it causes. == Cost ==

Project cost, low technology readiness levels in capture technologies, and a lack of revenue streams are among the main reasons for CCS projects to stop. The cost of CCS varies greatly by CO2 source. If the facility produces a gas mixture with a high concentration of CO2, as is the case for natural gas processing, it can be captured and compressed for USD 15–25/tonne. In the United States, the cost of onshore pipeline transport is in the range of USD 2–14/tonne CO2, and more than half of onshore storage capacity is estimated to be available below USD 10/tonne CO2. == Role in climate change mitigation ==

Comparison with other mitigation options Compared to other options for reducing emissions, CCS is very expensive. For instance, removing CO2 in fossil fuel power plants increases costs by US$50–$200 per tonne of CO2 removed. Options that have far more potential to reduce emissions at lower cost than CCS include public transit, electric vehicles, and various energy efficiency measures. Priority uses In the literature on climate change mitigation, CCS is described as having a small but critical role in reducing greenhouse gas emissions. Excessive reliance on CCS as a mitigation tool would also be costly and technically unfeasible. According to the IEA, attempting to abate oil and gas consumption only through CCS and direct air capture would cost USD 3.5 trillion per year, which is about the same as the annual revenue of the entire oil and gas industry. Emissions are relatively difficult or expensive to abate without CCS in the following niches: The Global Cement and Concrete Association say that CCS could reduce carbon emissions by 36%. Cleaner industrial processes are at varying stages of development and some have been commercialized, but are far from being widely deployed.Although solar and wind energy are typically cheaper, power plants that burn natural gas, biomass, or coal have the advantage of being able to produce electricity in any season and any time of day, and can be dispatched at times of high demand. However, this approach may be more expensive. • Bioenergy with carbon capture and storage: Bioenergy with carbon capture and storage (BECCS) is the process of extracting bioenergy from biomass and capturing and storing the CO2 that is produced. Under some conditions, BECCS can remove carbon dioxide from the atmosphere. The IPCC stated in 2022 that "implementation of CCS currently faces technological, economic, institutional, ecological-environmental and socio-cultural barriers." However, industry representatives say actual capture rates are closer to 75%, and have lobbied for government programs to accept this lower target. The potential for a CCS project to reduce emissions depends on several factors in addition to the capture rate. These factors include the amount of additional energy needed to power CCS processes, the source of the additional energy used, and post-capture leakage. The energy needed for CCS usually comes from fossil fuels whose mining, processing, and transport produce emissions. Some studies indicate that under certain circumstances the overall emissions reduction from CCS can be very low, or that adding CCS can even increase emissions relative to no capture. 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. Some CCS implementations have not sequestered carbon at their designed capacity, either for business or technical reasons. 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. A 2022 analysis of 13 major CCS projects found that most had either sequestered far less CO2 than originally expected, or had failed entirely. As a result of the lack of progress, authors of climate change mitigation strategies have repeatedly reduced the role of CCS. == Political debate ==

, an advocacy group representing coal producers, utility companies and railroads.|alt=Photo of a crowd lining up outside a truck. The truck has "Clean coal technology. It works." painted on the side. , England|alt=Cloth banner being held up by two people. The banner has a picture of a tree with an arrow pointing to it saying "Carbon capture storage". The banner also has a picture of an industrial facility and an arrow pointing to it saying "Another big lie". CCS has been discussed by political actors at least since the start of the UNFCCC negotiations in the beginning of the 1990s, and remains a very divisive issue. Public statements from fossil fuel companies and fossil-based electric utilities ask for "recognition" that fossil fuel usage will increase in the future and suggest that CCS will allow the fossil fuel era to be extended. In these conferences, they have advocated for agreements to use language about reducing the emissions from fossil fuel use (through CCS), instead of language about reducing the use of fossil fuels. Many environmental NGOs such as Friends of the Earth hold strongly negative views on CCS. In surveys, environmental NGOs' importance ratings for fossil energy with CCS have been around as low as their ratings for nuclear energy. Critics see 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. The term abated is generally understood to mean the use of CCS, however the agreement left the term undefined. The intention of the IPCC definition is to require both effective CCS and deep reduction of fugitive gas emissions in order for fossil fuel emissions to qualify as being "abated." == Social acceptance ==

The public has generally low awareness of CCS. Another factor in acceptance is whether uncertainties are acknowledged, including uncertainties around potentially negative impacts on the natural environment and public health. Research indicates that engaging comprehensively with communities increases the likelihood of project success compared to projects that do not engage the public. Some studies indicate that community collaboration can contribute to the avoidance of harm within communities impacted by the project. == Government programs ==

Almost all CCS projects operating today have benefited from government financial support, largely in the form of capital grants and – to a lesser extent – operational subsidies. In the U.S., the 2021 Infrastructure Investment and Jobs Act designates over $3 billion for a variety of CCS demonstration projects. A similar amount is provided for regional CCS hubs that focus on the broader capture, transport, and either storage or use of captured . Hundreds of millions more are dedicated annually to loan guarantees supporting transport infrastructure. The Inflation Reduction Act of 2022 (IRA) updates tax credit law to encourage the use of carbon capture and storage. Tax incentives under the law provide up to $85/tonne for capture and storage in saline geologic formations or up to $60/tonne for used for enhanced oil recovery. The Internal Revenue Service relies on documentation from the corporation to substantiate claims on how much is being sequestered, and does not perform independent investigations. For natural gas power plants, the rule would require 90 percent capture of CO2 using CCS by 2035, or co-firing of 30% low-GHG hydrogen beginning in 2032 and co-firing 96% low-GHG hydrogen beginning in 2038. CO2 pipeline safety is overseen by the Pipeline and Hazardous Materials Safety Administration, which has been criticized as being underfunded and understaffed. Canada established a tax credit for CCS equipment for 2022–2028. The credit is 50% for CCS capture equipment and 37.5% for transportation and storage equipment. Saskatchewan extended its 20 per cent tax credit under the province's Oil Infrastructure Investment Program to pipelines carrying CO2. Europe In Norway, CCS has been part of a strategy to make fossil fuel exports compatible with national emission-reduction goals. In 1991, the government introduced a tax on CO2 emissions from offshore oil and gas production. 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. In 2022, Denmark announced up to €5 billion in subsidies for CCS, aiming to reduce emissions by 0.9Mt of CO2 by 2030. In the UK the CCUS roadmap outlines joint government and industry commitments to the deployment of CCUS and sets out an approach to delivering four CCUS low carbon industrial clusters, capturing 20–30 Mt per year by 2030. In September 2024 the UK government announced £21.7bn of subsidy over 25 years for the HyNet CCS and blue hydrogen scheme in Merseyside and the East Coast Cluster scheme in Teesside. Asia The Chinese State Council has now issued more than 10 national policies and guidelines promoting CCS, including the Outline of the 14th Five-Year Plan (2021–2025) for National Economic and Social Development and Vision 2035 of China. ==Related concepts==

CO2 utilization in products would sequester it indefinitely. CO2 can be used as a feedstock for making various types of products. As of 2022, usage in products consumes around 1% of the CO2 captured each year. As of 2023, it is commercially feasible to produce the following products from captured CO2: methanol, urea, polycarbonates, polyols, polyurethane, and salicylic acids. Methanol is currently primarily used to produce other chemicals, with potential for more widespread future use as a fuel. Technologies for sequestering CO2 in mineral carbonate products have been demonstrated, but are not ready for commercial deployment as of 2023. and is the only foreseeable CO2 use that is permanent enough to qualify as storage. Other potential uses for captured CO2 that are being researched include the creation of synthetic fuels, and various chemicals and plastics. In contrast to CCS, which captures emissions from a point source, DAC has the potential to remove carbon dioxide that is already in the atmosphere. Thus, DAC can be used to capture emissions that originated in non-stationary sources such as airplane engines. As of 2023, DACCS has yet to be integrated into emissions trading because, at over US$1000, the cost per ton of carbon dioxide is many times the carbon price on those markets. == See also ==