The reaction of a mineral carbonate, such as limestone, with water and CO2 to form bicarbonate in solution, is explored as a CO:! mitigation strategy. Initial cost estimates for such a process range from $18 to $128 per tonne CO2 sequestered, with an energy penalty of about 8% and with relatively low environmental impact. The regional availability and transport of water and mineral carbonate appear to be the primary determinants of the strategy＇s cost and applicability. The bicarbonate-rich waste effluent would be released into rivers or coastal waters, ultimately adding a small amount to the existing, very large bicarbonate reservoir in the ocean. For many applications, this form of ＇marine＇ carbon sequestration appears to be less costly, less affected by national and international regulations, more environmentally friendly and more effective over the long term than direct CO2 injection into the ocean.