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There are huge resources of coal in the world—probably enough for hundreds of years of use, and, per unit of energy produced, coal is a significantly cheaper fuel than either oil or gas.
On the other hand, the environmental effects of burning coal are obvious and considerable. Combustion of coal produces more carbon dioxide per unit of energy than other fossil fuels. It also produces more sulphur dioxide and nitrous oxide, plus a lot of smoke and ash. The sulphur dioxide contributes significantly to acid precipitation. While some of these environmental effects can be reduced by applying new technologies, they cannot be eliminated.
Coal also has high levels of many trace metals, including mercury, arsenic, selenium, lead, vanadium and uranium. For many of these elements the amounts released through the combustion of coal are greater than those from any other industrial source.