Carbon sequestration means putting carbon dioxide, the leading global warming pollutant, somewhere other than into the atmosphere. There are two basic methods of sequestering carbon: geologic sequestration and terrestrial sequestration.

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Geologic sequestration takes carbon dioxide from large emissions sources such as coal-fired power plants and pumps it in a nearly liquid state deep into the earth. The geologic formation then traps the carbon dioxide. As stated by the Intergovernmental Panel on Climate Change: “For well-selected, designed and managed geological storage sites, the vast majority of the CO₂ will gradually be immobilized by various trapping mechanisms and, in that case, could be retained for up to millions of years.”

Geologic sequestration has the most potential to help stabilize the concentration of global warming pollutants in the atmosphere. But it comes with certain hazards:

• Fractured rock formations, faults, and seismic activity could provide an avenue for CO₂ leakage.
• Pressure from CO₂ injection could trigger small earthquakes.
• The cement caps usually placed on the wells could deteriorate when exposed to carbonic acid, which can form when CO₂ interacts with saline formations.
• Abandoned oil and gas wells that were not sealed to today’s standards could leak. A sudden and large release of CO₂ could pose immediate dangers to people in the vicinity.
• Elevated CO₂ concentrations in the shallow subsurface could have lethal effects on plants and subsoil animals, and could contaminate groundwater.
• Carbon-laden liquids could mobilize toxic metals and organics and contaminate groundwater.

See Fact Sheet on the Potential Risks associated with Carbon Sequestration

Despite these hazards, and despite substantial talk on the part of the coal and electric utility industry saying it wants to start pumping carbon dioxide into geologic formations, there are no regulations defining geologic sequestration, and no guarantee that carbon dioxide will be pumped into the earth in a safe and effective manner.

Many people mistakenly say that geologic sequestration is the same things as enhanced oil recovery (EOR). EOR pumps carbon dioxide or other gases into an oil or gas field in order to access more oil and gas. If done properly, EOR can result in geologic sequestration, but the two terms are not synonymous. They are done for different purposes; the permanent storage of the CO₂ is not the priority of EOR. Additional modeling, monitoring, and verification will be necessary if an EOR well is to subsequently be used for the permanent sequestration of carbon dioxide.

In the News:

• Lawmakers plan bills to sequester, curb carbon dioxide (by JENNIFER McKEE, Missoulian State Bureau, December 2008)
  

 For more information:

• CO2 sequestration isn't practical (by MICHAEL J. ECONOMIDES - Perspective | February 20, 2010)
  

• Health and Safety Risks of Carbon Capture and Storage (by John Fogarty, MD, MPH and Michael McCally, MD, PhD, Journal of the American Medical Association, January 6, 2010—Vol 303, No. 1)

• View the PBS special Dark Energy: The Clean Coal Controversy (first aired July 29, 2008). This hour-long documentary examines both the potential for liquid coal to meet energy needs and the very real environmental and economic costs of the technology. It also scrutinizes proposals to capture carbon dioxide emissions and pump them deep into the ground in the hopes of trapping the CO2 there for hundreds of years. Interviews include Governor Brian Schweitzer, Assistant Secretary of the U.S. Air Force William Anderson, Congressman Henry Waxman, and MEIC Program Director Anne Hedges.
• Carbon capture and storage from Encyclopedia of Earth.  NOTE:  This article provides a good introductory overview and helpful diagrams of  geologic sequestration of carbon dioxide. However, some of its conclusions (e.g. that this is an effective solution to the global climate problem) are not supported by the evidence nor are they supported by MEIC.
  
• Carbon Sequestration Technology Roadmap and Program Plan 2007 A U.S. Department of Energy document that  (1) defines the current status of carbon dioxide (CO₂) capture and sequestration technology, (2) identifies research pathways that lead to achievement of the Carbon Sequestration Program goal, and (3) describes efforts that the DOE program is pursuing along priority pathways.
• Climate Change 2007: Mitigation of Climate Change, A Summary for Policymakers.  A report by the Intergovernmental Panel on Climate Change.
  
• "The Future of Coal: An Interdisciplinary MIT Study" (© 2007) This report, the future of coal in a carbon-constrained world, evaluates the technologies and costs associated with the generation of electricity from coal along with those associated with the capture and sequestration of the carbon dioxide produced coal-based power generation.