It is no secret that coal is dirty and that generating electricity from coal causes pollution.

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Coal is the dominant energy source for generating electricity in China, with Coal-fired power plants account for nearly three quarters of electricity produced in China, and the most intense demand is along the coast in Eastern Chinese provinces.

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Gas has become so cheap that it can be substituted for coal as an electricity-generating fuel.

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Why not simply convert coal-fired electricity-generating plants to natural gas?

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Cheap US gas is already driving down the price of the biggest substitute for generating electricity, coal, freeing it up for export to Europe, where it is displacing Europe's relatively highly-priced gas.

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The total amount of coal sold to utility customers was not significantly impacted during the economic downturn as utility coal is used in power plants for generating electricity, the demand for which is largely inelastic.

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Coal-fired power plants are now generating just 36 percent of U.S. electricity, versus 44.6 percent just one year ago.

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