Carbon, in the form of CO2 can be removed from the atmosphere by chemical processes, and stored in stable carbonate mineral forms. This process is known as ‘carbon sequestration by mineral carbonation’ or mineral sequestration. The process involves reacting carbon dioxide with abundantly available metal oxides–either magnesium oxide (MgO) or calcium oxide (CaO)–to form stable carbonates. These reactions are exothermic and occur naturally (e.g., the weathering of rock over geologic time periods).
CaO + CO2 → CaCO3
MgO + CO2 → MgCO3
Calcium and magnesium are found in nature typically as calcium and magnesium silicates (such as forsterite and serpentinite) and not as binary oxides.
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The use of the technology would add an additional 1–5 cents of cost per kilowatt hour, according to estimate made by the Intergovernmental Panel on Climate Change. The financial costs of modern coal technology would nearly double if use of CCS technology were to be required by regulation. The cost of CCS technology differs with the different types of capture technologies being used and with the different sites that it is implemented in, but the costs tend to increase with CCS capture implementation. One study conducted predicted that with new technologies these costs could be lowered but would remain slightly higher than prices without CCS technologies.
The energy requirements of sequestration processes may be significant. In one paper, sequestration consumed 25 percent of the plant’s rated 600 megawatt output capacity.