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CO2 sequestration is the storage of carbon dioxide (usually captured from the atmosphere) in a solid material through biological or physical processes.[1] CO2 can also be captured as a pure by-product in processes related to petroleum refining (upgrading) and power generation.[2] CO2 sequestration can then be seen as being synonymous with the storage part of carbon capture and storage, a term which refers to the large-scale, permanent artificial capture and sequestration of industrially-produced CO2 using subsurface saline aquifers, reservoirs, ocean water, or other sinks. It has been proposed as a way to mitigate the accumulation of greenhouse gases in the atmosphere released by the burning of fossil fuels. In September 2008, a coal-fired power plant in Spremberg eastern Germany, became the world's first coal using plant to capture and store carbon dioxide.[3] A detailed technical survey of the technology, the issues and existing plants is contained in [4] [edit] MethodsMethods of CO2 sequestration include :
The RCRS on the space shuttle Orbiter uses a two-bed system that provides continuous removal of CO2 without expendable products. Regenerable systems allow a shuttle mission a longer stay in space without having to replenish its sorbent canisters. Older lithium hydroxide (LiOH)-based systems, which are non-regenerable, are being replaced by regenerable metal-oxide-based systems. A system based on metal oxide primarily consists of a metal oxide sorbent canister and a regenerator assembly. It works by removing carbon dioxide using a sorbent material and then regenerating the sorbent material. The metal-oxide sorbent is regenerated by pumping air heated to around 400°F at 7.5 scfm through its canister for 10 hours.[9]
On February 9, 2007 Sir Richard Branson offered a $25 million prize to anyone who develops a workable means to remove a billion (109) tonnes of carbon dioxide per year from the atmosphere.[14] According to the Wallula Energy Resource Center in Washington state, by gasifying the coal, it is possible to capture approximately 65% of Carbon dioxide embedded in coal and sequester them into the solid form. [edit] Benefits of CO2 sequestrationIt was recently noted that the CO2 from fossil fuel emissions is almost entirely depleted in radiocarbon, or 14C, and so could be used to produce food products containing little or no radiocarbon. [15] Humans and animals raised on such food could be spared billions of lifetime chromosomal damage events normally caused by radiation in food and the environment. This could reduce rates of spontaneous cancer or birth defects, or even slow their aging. This use for CO2 could increase incentives for carbon capture in general, and particularly in those methods which would allow the recovery and reuse of low radiocarbon CO2 for sequestration in soils for producing safer food.[citation needed] This would have the added advantage of inducing terra preta formation, one of the richest soils on the planet and the only one known to regenerate itself. CO2 has been used extensively in enhanced crude oil recovery operations in the United States beginning in 1972[16]. There are in excess of 10,000 CO2 wells in the state of Texas alone. The gas comes in part from anthropogenic sources, but principally from large naturally-occurring geologic formations of CO2. It is transported to the oil-producing fields through a large network of over 5,000 kilometers of CO2 pipelines. The use of CO2 for enhanced oil recovery (EOR) methods in heavy oil reservoirs in the Western Canadian Sedimentary Basin (WCSB)has also been proposed.[17] However, cost of transport remains an important hurdle. A similar CO2 pipeline system to that of Texas does not yet exist in the WCSB that could connect most of the sources for CO2 in Canada associated with the mining and upgrading operations in the Athabasca oil sands, with the subsurface heavy oil reservoirs that could most benefit from CO2 injection hundred's of km to the south. [edit] References
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