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Carbon Capture and Geologic Sequestration

What Is It? | How Does It Work? | More Information | Workgroup


Figure 1 - Simplified overview of the CCGS process
Source: http://www.co2crc.com.au/imagelibrary/

What Is It?

Carbon dioxide (CO2) capture and geologic sequestration is a process by which CO2 is separated from gases emitted by large stationary sources, collected (captured) and compressed to a supercritical state. Supercritical CO2 is then transported to a sequestration facility where it is injected underground into suitable deep geologic formations for long-term isolation (sequestration) from the atmosphere. Figure 1 above illustrates the components in the carbon capture and geologic sequestration process.

The Intergovernmental Panel on Climate Change (IPCC) identified CO2 capture and sequestration as one of several options for reducing greenhouse gas emissions.

 

How Does It Work?

Sources of CO2

Carbon Capture and Geologic Sequestration (CCGS) starts at the beginning – where carbon dioxide is emitted in large volumes. Stationary CO2 sources that meet this large volume requirement typically fall into one of the three following categories:

  1. Facilities that burn (combust) large quantities of carbon-based fossil fuels such as coal, petroleum, and natural gas.  Examples of this type of facility are: power plants, oil refineries, and large industrial facilities.  CO2 is formed by the combination of carbon and oxygen (oxidation) during the combustion of the fossil fuel.
  1. Industrial facilities that emit CO2 as a result of the physical, chemical, or biological transformation of materials.  Although some CO2 may be emitted from the combustion of fossil fuels at these facilities, most of the CO2 emitted is from the non-combustion processes above.  Examples of this type of facility are those that perform: petrochemical processes, metal production from ore, cement production, and fermentation of biomass.
  2. Natural-gas processing plants where naturally-occurring CO2 is removed from natural gas.

Of the large stationary CO2 sources, fossil fuel combustion facilities for electricity generation, especially coal-fired power plants, contribute the highest percentage of CO2 emissions.


Figure 2 - Percent CO2 Stationary Emissions by Category - North American Sources
Source:  http://www.natcarb.org/Atlas/sources.html

Methods for Capturing CO2

The three methods for capturing CO2 are classified as follows:

  1. Post-Combustion capture of CO2 involves the separation of CO2 from flue (stack) gases produced through the combustion of carbon-based fuels in air.
  2. Pre-Combustion capture of CO2 involves the pre-processing of carbon-based primary fuel to produce a synthesis gas (syngas) consisting of hydrogen and various carbon oxides including CO2 that can be separated and captured while the hydrogen is burned as fuel.
  3. Oxy-Fuel Combustion involves the burning of carbon-based fuel in pure oxygen, instead of air, to produce a flue gas consisting mainly of water and CO2 that can be separated and captured.

Transportation of CO2

Transportation of captured CO2 from a large stationary source to a geologic sequestration facility will occur through a pipeline.  Pipeline technology for transporting large volumes of gas is a mature technology that has been routinely employed in the transport of CO2 to enhanced oil recovery (EOR) projects through out the western US and Canada. The transport of CO2 via pipeline to a geologic sequestration site is not anticipated to pose unique challenges for implementation. Existing pipeline standards and regulations will generally dictate the composition of the CO2 stream to be sequestered.

Geologic Sequestration of CO2

Geologic sequestration of CO2 occurs by first compressing it to a supercritical state thereby reducing its volume significantly. It is then injected through a carefully constructed well into a suitable geologic environment that meets certain criteria for ensuring long term storage of the CO2 while protecting other natural resources. Geologic sequestration can occur under several scenarios illustrated in Figure 3 below.

Figure 3 - Methods for Storing CO2 in Deep Underground Geological Formations
* Click to view larger * (Source)

 

More Information

CCGS in Utah

U.S. Environmental Protection Agency

U.S. Department of Energy

Intergovernmental Panel on Climate Change (IPCC)

The Intergovernmental Panel on Climate Change (IPCC) was established to provide the decision-makers and others interested in climate change with an objective source of information about climate change. The IPCC does not conduct any research nor does it monitor climate related data or parameters. Its role is to assess on a comprehensive, objective, open and transparent basis the latest scientific, technical and socio-economic literature produced worldwide relevant to the understanding of the risk of human-induced climate change, its observed and projected impacts and options for adaptation and mitigation. View or Download the Intergovernmental Panel on Climate Change (IPCC) Special Report on Carbon Dioxide Capture and Storage at this site.

Research Centers

 

Contact

Candace Cady
Environmental Scientist
Utah Division of Water Quality
801-538-9260
ccady@utah.gov

Last updated: 09/03/2008