5. Coal

Coal is the most abundant fossil resource, but also the most polluting . The younger the coal, the greater the pollution. For example, lignite, formed in the Tertiary period, is more polluting than anthracite, formed in the Carboniferous, at the end of the Primary period.

One third of the world's coal comes from open-cast mines. These are easier and more profitable to operate than underground mines. Their operation generates noise and visual nuisance, and can...