Abstract
Carbon dioxide capture and sequestration (CCS) in deep geological formations has quickly emerged as an important option for reducing greenhouse emissions. If CCS is implemented on the scale needed for large reductions in CO2 emissions, a billion of tonnes or more of CO2 will be sequestered annually�a 250 fold increase over the amount sequestered annually today. Sequestering these large volumes will require a strong scientific foundation of the coupled hydrological-geochemical-geomechanical processes that govern the long term fate of CO2 in the subsurface. Methods to characterize and select sequestration sites, subsurface engineering to optimize performance and cost, safe operations, monitoring technology, remediation methods, regulatory oversight, and an institutional approach for managing long term liability are also needed.