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CO2 sequestration, also known as CO2 capture and storage (CCS), uses a range of technologies and approaches that isolate, extract, and store carbon dioxide emissions from industrial and energy-related sources in order to prevent the release of it into the atmosphere.
Video courtesy of National Energy Technology Lab (NETL).
Carbon capture and storage technology involves the process of trapping and separating the CO2, transporting it to a storage location, and then storing it long-term so that it does not enter into the atmosphere. It is not a new technology and has been used by petroleum, chemical, and power industries for decades. In fact, carbon capture was first used in Texas in 1972 as a method to enhance oil recovery.
CO2 emissions from the burning of fossil fuels has been on the incline since the industrial era; and with more than 85% of the world’s energy coming from fossil fuels, it will remain an important energy source well into the future. As the demand for fossil fuels is growing, so is the volume of CO2 emitted each year. This has led to concerns over the impact of CO2 emissions on global climate change. CO2 sequestration is an option that is gaining interest to stabilize and reduce the concentration of CO2.
After CO2 is captured at the source, it then must be safely sequestered or stored away. There are three types of CO2 sequestration: terrestrial, geologic, and mineralization (Fig. 1). More than 150 CO2 sequestration projects are in progress in North America alone.
Fig. 1—Three types of CO2 sequestration.
Terrestrial sequestration is the removal and storage of CO2 from the atmosphere by vegetation and soils on the earth’s surface through tree-planting, no-till farming, wetland restoration, and forestation.
Geologic sequestration is permanently storing CO2 in subsurface structures such as oil reservoirs, natural gas deposits, unmineable coal seams, deep saline formations, shale rich in oil or gas, and basalt formations.
Mineral sequestration is the formation of stable carbonate salts by the reaction of CO2 with dissolved calcium and magnesium. It is a natural process that happens slowly and produces limestone. A process that occurs faster than a natural reaction is when “dunite, or its hydrated equivalent serpentinite, reacts with carbon dioxide to form the carbonate mineral magnesite, plus silica and iron oxide (magnetite).”
Geologic carbon sequestration stands out, in particular, as a viable option because of its substantial storage capacity, which is estimated to be between 800 and 3,000 billion metric tons; the technology of separating and injecting CO2 underground has been used for more than 30 years; and the large CO2 sources such as power plants and refineries are conveniently located near many potential geologic storage sites across the US and Canada (Fig. 2).
Fig. 2—Geologic potential storage in the US. Courtesy of US Department of Energy, National Carbon Sequestration Database and Geographic Information System (NATCARB).
CCS consists of two different yet connected steps. In the first step, CO2 from power plants and industrial plants is separated and concentrated, and then compressed and transferred through pipelines. In the second step, a dense, fluid state of the CO2 (known as supercritical) is injected into underground geologic formations. There are three methods for capturing and separating CO2 (Fig. 3):
- Precombustion capture: Before the fuel is burned, the fuel is converted to syngas, and then the syngas to hydrogen and CO2. Next, the hydrogen is separated from the CO2 so the hydrogen can be used as fuel.
- Post-combustion: After the fuel is burned, the CO2 is separated from the nitrogen using chemical sorbents such as monoethanolamine.
- Oxyfuel combustion: Burning fuel in pure oxygen so no nitrogen is present in the captured gases.
Fig. 3—CO2 capture overview of three optional processes.
The challenges that CCS needs to address are technical, regulatory, and economic in nature. Though some elements of CCS, such as CO2 transport and injection, have been in practice for several decades, the large-scale commercial deployment of the CCS process from beginning to end—from capture to long-term storage—is relatively new and requires increased support for continued research, development, and practice.
- CO2 Capture Project. 2008. What Is CO2 Capture & Storage?, http://www.co2captureproject.org/what_is_co2_capture_storage.html (accessed 2 September 2014).
- Ronca, D. 2014. How Carbon Capture Works, http://science.howstuffworks.com/environmental/green-science/carbon-capture1.htm (accessed 25 September 2014).
- Carbon Sequestration Leadership Forum. 2011. CO2 Capture—Does It Work? inFocus http://www.cslforum.org/publications/documents/CSLF_inFocus_CO2Capture_DoesItWork.pdf.
- Richey, S. 2013. Carbon Sequestration: Myth or Hope?, http://www.steverichey.com/writing-samples/climate-change/carbon-sequestration-myth-or-hope/ (accessed 23 September 2014).
- Ramharack, R.M., Aminian, K., and Ameri, S. 2010. Impact of Carbon Dioxide Sequestration in Gas/Condensate Reservoirs. Presented at the SPE Eastern Regional Meeting, Morgantown, West Virginia, USA, 13–15 October. SPE-139083-MS. http://dx.doi.org/10.2118/139083-MS.
- The University of Utah, Department of Civil and Environmental Engineering. 2011. Carbon Capture and Sequestration, http://co2.egi.utah.edu/ (accessed 4 September 2014).
- Cuff, D. and Goudie, A., eds. 2008. The Oxford Companion to Global Change. New York: Oxford University Press.
- Global CCS Institute. 2014. CO2 Capture Overview, http://www.globalccsinstitute.com/sites/default/files/pages/92241/4-co2-capture-overview.jpg (accessed 29 September 2014).
- Logan, J., Venezia, J., and Larsen, K. 2007. Opportunities and Challenges for Carbon Capture and Sequestration. WRI Issue Brief (No. 1), http://pdf.wri.org/opportunities-challenges-carbon-capture-sequestration.pdf.
Noteworthy papers in OnePetro
Barrufet, M.A., Bacquet, A., and Falcone, G. 2010. Analysis of the Storage Capacity for CO2 Sequestration of a Depleted Gas Condensate Reservoir and a Saline Aquifer. J Can Pet Technol 49 (8): 23–31. SPE-139771-PA. http://dx.doi.org/10.2118/139771-PA.
Bilardo, U. and Panvini, F. 2007. Carbon Sequestration: Key Features and Issues. Presented at the Offshore Mediterranean Conference and Exhibition, Ravenna, Italy, 28–30 March. OMC-2007-036.
Flanery, S.O. and McCarty, S.C. 2008. Recent Legal Developments in Carbon Sequestration. Presented at the SPE Eastern Regional/AAPG Eastern Section Joint Meeting, Pittsburgh, Pennsylvania, USA, 11–15 October. SPE-116231-MS. http://dx.doi.org/10.2118/116231-MS.
Kheshgi, H.S., Thomann, H., Bhore, N.A. et al. 2012. Perspectives on CCS Cost and Economics. SPE Econ & Mgmt 4 (1): 24–31. SPE-139716-PA. http://dx.doi.org/10.2118/139716-PA.
Lucci, A., Demofonti, G., Tudori, P. et al. 2011. CCTS (Carbon Capture Transportation & Storage) Transportation Issues. Presented at the Twenty-First International Offshore and Polar Engineering Conference, Maui, Hawaii, USA, 19–24 June. ISOPE-I-11-162.
Pawde, C. and Parekh, R. 2013. A Discussion of the HSE Aspects of Carbon Dioxide Sequestration. Presented at the SPE Asia Pacific Oil and Gas Conference and Exhibition, Jakarta, 22–24 October. SPE-165781-MS. http://dx.doi.org/10.2118/165781-MS.
Schembre-McCabe, J.M., Kamath, J., and Gurton, R.M. 2007. Mechanistic Studies of CO2 Sequestration. Presented at the International Petroleum Technology Conference, Dubai, 4–6 December. IPTC-11391-MS. http://dx.doi.org/10.2523/11391-MS.