testing of all three settings have been done. Use of basalt formations and organic-rich shales has been proposed, but neither has been tested in the field (Dooley et al., 2006; NETL, 2007b). And while sedimentary rocks that might be suitable for CO2 injection are widespread, not all locations would be appropriate. Storage in saline formations and coal beds will also require seal formations above the storage formation that prevent vertical migration of the CO2 to the surface. Appropriate sites will have to be selected that have sufficient pore space available and that have rock properties that allow the CO2 to be injected at a reasonable rate.
Figure 7.A.6 shows estimates of the cost components of CCS for various sources, sinks, and geographic distances between them. Note that there is no single homogeneous “CCS technology” or situation; economic viability will depend on specific source and sink characteristics. For situations in which the CO2 is already separated (natural gas processing, H2 production, or ammonia production, for example), the incremental separation cost is zero. About 6 percent of U.S.