Using rock formations, really, to reduce greenhouse gases

In a prior post I noted that the IEA was pitching the construction of 10,000 carbon capture and storage projects in order to keep GHG emissions to a level that may limit the increase in global temperature to 3 degrees C or less over the next century. Costs could be in the range of 1013 dollars spread over 50 years. An alternative strategy has been proposed by researchers in a recent paper, http://www.pnas.org/content/early/2008/10/31/0805794105.abstract. The researchers note that peridotite [http://en.wikipedia.org/wiki/Peridotite], the predominant rock in the Earth’s mantle (the region below the crust) can absorb very large quantities of CO2; the reaction forms carbonates such as limestone and marble. Although the rock generally is found about 12 miles down, there are regions where plate tectonics have forced this layer to the surface (e.g., Omani desert, some Pacific Islands , along the coasts of and , and in small deposits in N. America ). Some scientists have suggested in the past that the rock be ground up and used at power stations to absorb CO2, an expensive process if only because of transportation costs. In the article the researchers suggest that CO2 be pumped from the locale where it is produced into underground strata of peridotite. The researchers have shown that the Omani peridotite absorbs much more CO2 than previously believed, and speculate that by drilling and fracturing the rock the absorption rate can be increased by many orders of magnitude. The researchers note that if their estimate is correct, such action on the Omni outcrop alone would allow it to absorb 4 billion tons of CO2 per year, which is roughly 13% of the CO2 currently produced by humans, mostly by burning fossil fuels. When some of the more conventional CCS strategies are guesstimating costs as large as that noted above, it is certainly worth taking a look at alternatives, even if they seem a bit out-there at first blush, particularly if there is some hard science at their foundation.