Coal, oil and gas are called "fossil fuels" because they have been formed from the organic remains of prehistoric plants and animals. Coal provides around 28% of our energy, and oil provides around 40%. Burning coal produces sulfur dioxide, and acidic gas that contributes to the formation of acid rain.This could be avoided using "fuel gas desulphuration" to clean the fossil fuels before they are released into the atmosphere.
Photo used under Creative Commons from Timitrius