evaluates opportunities for capture, and considers how the CO2 might be transported at the scale required.
Figure 7.14 shows estimated cost as a function of the total quantity of CO2 that could be captured and stored with current technologies at existing U.S. CO2 sources. It indicates that if all the CO2 emitted from stationary sources that could be stored at costs below about $50 per tonne were captured, the total emissions reduction would be about 1.5 billion tonnes CO2, or about 20 percent of current emissions (Dooley et al., 2006). The storage cost shown as negative in Figure 7.14 stems from the use of CO2 for EOR, which may make use of sources of CO2 other than power plants (ammonia plants or natural gas purification, for example) in which CO2 is already separated. About 28 million tonnes CO2 per year is presently injected for EOR in oil fields in west Texas, though most of that CO2 comes from natural underground sources.
Significant growth in the amount of CO2 captured from anthropogenic sources would likely be put to use for EOR in regions where oil fields are within reasonable distance from a source. The existence of a CO2 price would favor expansion of EOR in such locations as the magnitude of present EOR operations is constrained by the availability of CO2 for injection. Thus combined EOR and CO2 storage has the potential to lead to a significant expansion of EOR production from the 200,000 barrels per day produced now.
Long-term geologic storage of carbon dioxide appears to be technologically feasible, but it has yet to be demonstrated at the scale of a large power plant in a variety of geologic repositories.
A suite of projects can be designed to clarify the costs, risks, and environmental impacts of carbon storage. This would enable a determination of whether such plants can become significant contributors to the U.S. power system in a carbon-constrained world. Successful demonstration will require projects spanning the many types of coal, using several capture strategies, at a variety of storage sites, at both power and synfuel plants, and with storage both in deep saline aquifers and in hydrocarbon-bearing seams.