Coal
Coal formed from the dead remains of trees, ferns and other plants that lived 300 to 400 million years ago. In some areas, coal was formed from swamps covered by sea water. The sea water contained a large amount of sulphur, and as the seas dried up, the sulphur was left behind in the coal.
The sulphur trapped inside coal, along with nitrogen, is released into the air when coal is burned. While floating in the air, these substances can combine with water vapour and contribute to acid rain. Coal – like all fossil fuels – is made up of carbon and when burned, combines with oxygen to produce carbon dioxide, a major contributory to global warming.
When coal's burning properties were discovered hundreds of years ago, it was originally found on the ground. However man found that by mining deep into the ground, there was an abundance of coal. But that is running out now.
Coal is no longer used in modern homes for heat, it is now generally used for firing power stations to produce electricity.