Clean coal technology is any energy production method which is used to lessen the environmental pollution of traditional coal burning. President George W. Bush's Clean Coal Technology Initiative pledged $2 billion to clean coal energy resources over a 10 year span. There are numerous proposed methods fro reducing the environmental impact of coal burning. These include removing minerals and impurities from the coal by chemical washingFree Patents: Process for removing mineral impurities from coals and oil shales, gasificationPopular Mechanics: Clean Coal: How to Make Rock into Biofuel and carbon captureAmerican Progress: Global Warming and the Future of Coal A certain amount of controversy continues around the debate on clean coal and skeptics' arguments have been reinforced by the toxic sludge spill in Tennessee in December 2008.The Christian Science Monitor: Tennessee spill revives coal ash controversy