Coal is the largest fossil resource available to us and the most problematic from an environmental standpoint. From all indications, coal use will continue to grow for power production around the world because of expected increases in China, India, Australia, and other countries. From an environmental point of view, this would be unsustainable unless advanced "clean coal technology" (CCT) with carbon sequestration is deployed.

Clean coal technology is based on an integrated gasification combined-cycle (IGCC) that converts coal to a gas that is used in a turbine to provide electricity with CO2 and pollutant removal before the fuel is burned (Hawkins, Lashof, and Williams 2006). According to R.C. Kelly, President and Chief Executive Officer of Minneapolis-based Xcel Energy, the company is about to build such a plant in Colorado, U.S.A. The plant will capture CO2 and inject it underground, possibly in depleted oil fields. According to Kelly, an IGCC plant can cost 20% more to build than a conventional coal plant, but is more efficient to operate (Associated Press 2006). According to an Australian study (Sadler 2004), no carbon capture and storage system is yet operating on a commercial scale, but may become an attractive technology to achieve atmospheric CO2 stabilization.

According to BP, the proven recoverable world coal resources were estimated to be 909 billion tons at the end of 2004 with a reserve to production ratio (R/P) of 164 years. The BP data also shows that coal use increased at an average rate of 6% from 2002 to 2005, the largest increase of all fossil resources. Because China and India are continuing to build new coal power plants, it is reasonable to assume that coal use will continue to increase for at least some years in the future. Therefore, the R/P ratio will decrease from the present value of 164 years. This R/P ratio will decrease even more rapidly when clean coal technologies such as coal gasification and liquification are utilized instead of direct combustion.

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