The volume of carbon dioxide associated with the use of fossil fuels to produce electricity is enormous. For example, in the United States alone, approximately 1.8 Gtons of CO2 was emitted in 1999, and for comparison, water withdrawn in 1990 in the U.S. for public supplies was approximately 55 Gtons. The scale of CO2 production is central to any viable method to store captured CO2 in order to reduce emissions. Consequently, most methods being considered as options for CO2 storage exploit one of the major natural carbon reservoirs, such as the oceans, subsurface reservoirs (such as brines or depleted oil & gas fields), or the terrestrial carbon pool. Related to subsurface reservoirs are carbonate rocks, which are the dominant natural pool for oxidized carbon. Carbonate rocks develop largely from the interaction of aqueous fluid with silicate rocks enriched in calcium and magnesium, either through weathering, ground water flow, or hydrothermal activities: each of these fluid-rock interactions can lead, essentially, to the release of the alkaline-earth metals from the silicates via dissolution, leaching, or other mineral-alteration reactions. Once released to the aqueous fluid, the alkaline-earth metals can react with dissolved CO2 to precipitate carbonates. The net result is the conversion of carbon dioxide to a thermodynamically stable and immobile form.
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