About 80 per cent of the world's energy is currently supplied by fossil fuels such as coal, oil and gas. Present estimates suggest that, at current consumption rates, there are over 200-years' worth of coal left, 60-years' of gas, and 40-years' of oil. Clearly, reliance on these finite or, ‘non renewable’, resources is unsustainable and new sources of energy are required.

A second problem with fossil fuels is that they are hydrocarbons, and their combustion releases carbon dioxide into the atmosphere, one of the main causes of the human-induced greenhouse effect, that we examined in chapter 2.

Above text sourced from OpenLearn under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence
http://openlearn.open.ac.uk/mod/oucontent/view.php?id=397916&section=3
 

Above image sourced from Flickr under a Creative Commons Attribution-NonCommercial-NoDerivs 2.0 Generic License
http://www.flickr.com/photos/barwell/83724642/sizes/m/in/photostream/