Carbon Dioxide Capture and Storage
IPCC, 2005 - Bert Metz, Ogunlade Davidson, Heleen de Coninck, Manuela Loos and Leo Meyer (Eds.)
Cambridge University Press, UK. pp 431.
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Summary for Policymakers (notes)

1. Carbon dioxide (CO2) capture and storage (CCS) is a process consisting of the separation of CO2 from industrial and energy-related sources, transport to a storage location and long-term isolation from the atmosphere. This report considers CCS as an option in the portfolio of mitigation actions for stabilization of atmospheric greenhouse gas concentrations.
2. The Third Assessment Report (TAR) indicates that no single technology option will provide all of the emission reductions needed to achieve stabilization, but a portfolio of mitigation measures will be needed.
3. Capture of CO2 can be applied to large point sources. The CO2 would then be compressed and transported for storage in geological formations, in the ocean, in mineral carbonates2, or for use in industrial processes.
4. The net reduction of emissions to the atmosphere through CCS depends on the fraction of CO2 captured, the increased CO2 production resulting from loss in overall efficiency of power plants or industrial processes due to the additional energy required for capture, transport and storage, any leakage from transport and the fraction of CO2 retained in storage over the long term.
5. There are different types of CO2 capture systems: postcombustion, pre-combustion and oxyfuel combustion (Figure SPM.3). The concentration of CO2 in the gas stream, the pressure of the gas stream and the fuel type (solid or gas) are important factors in selecting the capture system.
6. Pipelines are preferred for transporting large amounts of CO2 for distances up to around 1,000 km. For amounts smaller than a few million tonnes of CO2 per year or for larger distances overseas, the use of ships, where applicable, could be economically more attractive.
7. Storage of CO2 in deep, onshore or offshore geological formations uses many of the same technologies that have been developed by the oil and gas industry and has been proven to be economically feasible under specific conditions for oil and gas fi elds and saline formations, but not yet for storage in unminable coal beds8 (see Figure SPM.4).
8. Ocean storage potentially could be done in two ways: by injecting and dissolving CO2 into the water column (typically below 1,000 meters) via a fixed pipeline or a moving ship, or by depositing it via a fixed pipeline or an offshore platform onto the sea floor at depths below 3,000 m, where CO2 is denser than water and is expected to form a “lake” that would delay dissolution of CO2 into the surrounding environment (see Figure SPM.5). Ocean storage and its ecological impacts are still in the research phase13.
9. The reaction of CO2 with metal oxides, which are abundant in silicate minerals and available in small quantities in waste streams, produces stable carbonates. The technology is currently in the research stage, but certain applications in using waste streams are in the demonstration phase.
10. Industrial uses14 of captured CO2 as a gas or liquid or as a feedstock in chemical processes that produce valuable carbon-containing products are possible, but are not expected to contribute to signifi cant abatement of CO2 emissions.
11. Components of CCS are in various stages of development (see Table SPM.2). Complete CCS systems can be assembled from existing technologies that are mature or economically feasible under specific conditions, although the state of development of the overall system may be less than some of its separate components.
12. Large point sources of CO2 are concentrated in proximity to major industrial and urban areas. Many such sources are within 300 km of areas that potentially hold formations suitable for geological storage (see Figure SPM.6). Preliminary research suggests that, globally, a small proportion of large point sources is close to potential ocean storage locations.
13. CCS enables the control of the CO2 emissions from fossil fuel-based production of electricity or hydrogen, which in the longer term could reduce part of the dispersed CO2 emissions from transport and distributed energy supply systems.
14. Application of CCS to electricity production, under 2002 conditions, is estimated to increase electricity generation costs by about 0.01–0.05 US dollars16 per kilowatt hour (US$/kWh), depending on the fuel, the specific technology, the location and the national circumstances. Inclusion of the benefits of EOR would reduce additional electricity production costs due to CCS by around 0.01– 0.02 US$/kWh17 (see Table SPM.3 for absolute electricity production costs and Table SPM.4 for costs in US$/tCO2 avoided). Increases in market prices of fuels used for power generation would generally tend to increase the cost of CCS. The quantitative impact of oil price on CCS is uncertain. However, revenue from EOR would generally be higher with higher oil prices. While applying CCS to biomass-based power production at the current small scale would add substantially to the electricity costs, cofiring of biomass in a larger coal-fired power plant with CCS would be more cost-effective.
15. Retrofitting existing plants with CO2 capture is expected to lead to higher costs and significantly reduced overall efficiencies than for newly built power plants  with capture. The cost disadvantages of retrofitting may be reduced in the case of some relatively new and highly efficient existing plants or where a plant is substantially upgraded or rebuilt.
16. In most CCS systems, the cost of capture (including compression) is the largest cost component.
17. Energy and economic models indicate that the CCS system's major contribution to climate change mitigation would come from deployment in the electricity sector. Most modelling as assessed in this report suggests that CCS systems begin to deploy at a significant level when CO2 prices begin to reach approximately 25–30 US$/tCO2.
18. Available evidence suggests that, worldwide, it is likely19 that there is a technical potential20 of at least about 2,000 GtCO 2 (545 GtC) of storage capacity in geological formations21.
19. In most scenarios for stabilization of atmospheric greenhouse gas concentrations between 450 and 750 ppmv CO2 and in a least-cost portfolio of mitigation options, the economic potential23 of CCS would amount to 220– 2,200 GtCO2 (60–600 GtC) cumulatively, which would mean that CCS contributes 15–55% to the cumulative mitigation effort worldwide until 2100, averaged over a range of baseline scenarios. It is likely20 that the technical potential21 for geological storage is sufficient to cover the high end of the economic potential range, but for specific regions, this may not be true.
20. In most scenario studies, the role of CCS in mitigation portfolios increases over the course of the century, and the inclusion of CCS in a mitigation portfolio is found to reduce the costs of stabilizing CO2 concentrations by 30% or more.
21. The local risks24 associated with CO2 pipeline transport could be similar to or lower than those posed by hydrocarbon pipelines already in operation.
22. With appropriate site selection based on available subsurface information, a monitoring programme to detect problems, a regulatory system and the appropriate use of remediation methods to stop or control CO2 releases if they arise, the local health, safety and environment risks of geological storage would be comparable to the risks of current activities such as natural gas storage, EOR and deep underground disposal of acid gas.
23. Adding CO2 to the ocean or forming pools of liquid CO2 on the ocean fl oor at industrial scales will alter the local chemical environment. Experiments have shown that sustained high concentrations of CO2 would cause mortality of ocean organisms. CO2 effects on marine organisms will have ecosystem consequences. The chronic effects of direct CO2 injection into the ocean on ecosystems over large ocean areas and long time scales have not yet been studied.
24. Environmental impacts of large-scale mineral carbonation would be a consequence of the required mining and disposal of resulting products that have no practical use.
25. Observations from engineered and natural analogues as well as models suggest that the fraction retained in appropriately selected and managed geological reservoirs is very likely25 to exceed 99% over 100 years and is likely20 to exceed 99% over 1,000 years.
26. Release of CO2 from ocean storage would be gradual over hundreds of years.
27. In the case of mineral carbonation, the CO2 stored would not be released to the atmosphere (Sections 1.6.3, 7.2.7).
28. If continuous leakage of CO2 occurs, it could, at least in part, offset the benefi ts of CCS for mitigating climate change. Assessments of the implications of leakage for climate change mitigation depend on the framework chosen for decision-making and on the information available on the fractions retained for geological or ocean storage as presented in paragraphs 25 and 26.
29. Some regulations for operations in the subsurface do exist that may be relevant or, in some cases, directly applicable to geological storage, but few countries have  specifically developed legal or regulatory frameworks for long-term CO2 storage.
30. No formal interpretations so far have been agreed upon with respect to whether or under what conditions CO2 injection into the geological sub-seabed or the ocean is compatible.
31. The current IPCC Guidelines28 do not include methods specific to estimating emissions associated with CCS.
32. The few current CCS projects all involve geological storage, and there is therefore limited experience with the monitoring, verifi cation and reporting of actual physical leakage rates and associated uncertainties.
33. CO2 might be captured in one country and stored in another with different commitments. Issues associated with accounting for cross-border storage are not unique to CCS.
34. There are gaps in currently available knowledge regarding some aspects of CCS. Increasing knowledge and experience would reduce uncertainties and thus facilitate decision-making with respect to the deployment of CCS for climate change mitigation (Section TS.10).