Carbon capture and sequestration effects on geologic formations
Carbon capture and storage (CCS), (carbon capture and sequestration), refers to technology attempting to prevent the release of large quantities of CO2 into the atmosphere from fossil fuel use in power generation and other industries by capturing CO2, transporting it and ultimately, pumping it into underground geologic formations to securely store it away from the atmosphere. It is a potential means of mitigating the contribution of fossil fuel emissions to global warming. The process is based on capturing carbon dioxide (CO2) from large point sources, such as fossil fuel power plants, and storing it where it will not enter the atmosphere. It can also be used to describe the scrubbing of CO2 from ambient air as a geoengineering technique. Although CO2 has been injected into geological formations for various purposes, the long term storage of CO2 is a relatively new concept. The first commercial example was Weyburn in 2000.
Also known as geo-sequestration, this method involves injecting carbon dioxide, generally in supercritical form, directly into underground geological formations. Oil fields, gas fields, saline formations, unmineable coal seams, and saline-filled basalt formations have been suggested as storage sites. Various physical (e.g., highly impermeable caprock) and geochemical trapping mechanisms would prevent the CO2 from escaping to the surface.
Danger of Leaks: Carbon dioxide may be stored deep underground. At depth, hydrostatic pressure acts to keep it in a liquid state. Reservoir design faults, rock fissures and tectonic processes may act to release the gas stored into the ocean or atmosphere.
Financial Costs: Some argue that the cost of carbon sequestration would actually increase over time. The use of the technology would add an additional 1-5 cents of cost per kilowatt hour, according to estimate made by the Intergovernmental Panel on Climate Change. The financial costs of modern coal technology would nearly double if use of CCS technology were to be implemented.
Energy requirements: The energy requirements of sequestration processes may be significant. In one paper, sequestration consumed 25 percent of the plant's rated 600 megawatt output capacity.
A major concern with CCS is whether leakage of stored CO2 will compromise CCS as a climate change mitigation option. For well-selected, designed and managed geological storage sites, IPCC estimates that risks are comparable to those associated with current hydrocarbon activity. Although some question this assumption as arbitrary citing a lack of experience in such long term storage. CO2 could be trapped for millions of years, and although some leakage occurs upwards through the soil, well selected storage sites are likely to retain over 99% of the injected CO2 over 1000 years. Leakage through the injection pipe is a greater risk.
Although the injection pipe is usually protected with non-return valves to prevent release on a power outage, there is still a risk that the pipe itself could tear and leak due to the pressure. The Berkel en Rodenrijs incident in December 2008 was an example, where a modest release of CO2 from a pipeline under a bridge resulted in the deaths of some ducks sheltering there. In order to measure accidental carbon releases more accurately and decrease the risk of fatalities through this type of leakage, the implementation of CO2 alert meters around the project perimeter has been proposed.
For More Information:
Carbon Capture and Storage
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