In a CCS system, CO2 from power plants like this one in Kentucky would be captured and stored deep underground. Credit: EPA

Carbon dioxide capture and storage (CCS) encompasses the processes of capture and storage of carbon dioxide produced from human activities that would otherwise reside in the atmosphere for long periods of time. It involves separating pure CO₂ from the waste stream of facilities such as natural gas and oil processing plants and electricity generating stations, transporting the CO₂ to a disposal site, and then injecting it deep underground into stable geological formations such as depleted oil and gas wells, coalbeds (as part of enhanced coalbed methane recovery), or deep saline aquifers.

CCS is an attractive candidate technology to reduce carbon emissions from large stationary sources such as coal-fired power plants.  Coal is the predominant fuel for electricity and responsible for about 40% of global CO2 emissions. About 100 GW of additional coal-fired power capacity is currently built every year, and the use of coal is projected to increase in the future.

The Intergovernmental Panel on Climate Change (IPCC) Special Report on Carbon Dioxide Capture and Storage argued that CCS is needed achieve the large-scale reductions in CO2 that are required during this century. The IPCC report concluded that CO₂ CCS could contribute 15–55% to the cumulative mitigation effort until 2100 (for a range of stabilization scenarios between 450 and 750 ppmv CO₂) and that inclusion of CCS reduces the costs of stabilizing CO₂ concentrations by 30% or more.

Points sources of CO2 in the U.S. Credit: Vulcan Project, Purdue University.

The U.S. Department of Energy has identified the power plant and other stationary sources of more than 3.8 billion tons a year of CO2 in the United States and Canada and companion candidate storage capacity for more than 3,500 billion tons.  Emissions from those sources account for more than half of total CO2 emissions.

CCS faces many challenges, chief of which is that no fully integrated power plants with CCS have yet been built at scale.  Thus, we have no firm information regarding the impact of CCS on the cost of electricity. The IPCC report cited a possible 40 to 90% increase in the price of electricity from a pulverized coal-fired plant with capture and geological storage. In addition, some scientists are concerned the CO₂ could "leak" from storage sites and enter the atmosphere. Disposing of CO₂ in the ocean could significantly alter ocean chemistry.

CCS could become a critical component of an overall strategy to reduce carbon emissions. However, political dialogue on CCS has advanced faster than the actual technology.  Even if CCS is feasible and cost-effective, it will be decades before it removes substantial CO2 due to the long leads times associated with building new plants. Low-carbon energy sources and improved energy efficiency must be front and central in efforts to mitigate the effects on climate change.

Sources

• Heleen de Coninck, Jennie C. Stephens, Bert Metz, Global learning on carbon capture and storage: A call for strong international cooperation on CCS demonstration, Energy Policy, Volume 37, Issue 6, China Energy Efficiency, June 2009, Pages 2161-2165.
• IPCC Special Report on Carbon Dioxide Capture and Storage. Prepared by Working Group III of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA (2005) 442 pp.
• IPCC, Climate Change Mitigation. Working Group III's Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, UK (2007).
• Jacqueline D. Sharp, Mark K. Jaccard, David W. Keith, Anticipating public attitudes toward underground CO2 storage, International Journal of Greenhouse Gas Control, In Press, Corrected Proof, Available online 6 May 2009.
• National Renewable Energy Laboratory, Carbon Sequestration Atlas of the United States and Canada.