They are non-renewable sources of energy as they are derived from pre-historic fossils and are no longer available if once used. Their source is limited and they are depleting at a faster rate. When extracted it poses a severe damage to the landscape as they are to be dig out from underground wells. - See more at: http://www.conserve-energy-future.com/Disadvantages_FossilFuels.php#sthash.ngNhRrEI.dpuf