Every stage in the process to extract and process fossil fuels can harm the environment. Coal is mined, either from the surface in huge open cast mines (also called strip mines) or by underground tunnels. Open cast mining eats up hectares of countryside, leaving behind huge holes that have little use and produce dust and other discharges into the atmosphere. Lignite is a poor quality coal that is taken from open cast mines. When burnt, it releases a lot of sulphur dioxide, which creates acid rain. Mining produces large quantities of waste, which is usually dumped in piles called spoil heaps. Water runs off these heaps, and the drainage from these areas can carry pollutants into rivers and lakes.
Wells are dug into the ground to bring the oil to the surface. There can be local damage from spills, but most of the damage occurs during its transportation. Some of the largest tankers carry up to 500,000 tonnes of crude oil and many only have a single hull. Any damage to the hull results in an oil spill. In the past, there have been numerous tanker accidents in which hundreds of thousands of tonnes of crude oil have been spilt into the sea. The oil causes widespread damage to local populations of birds, mammals and invertebrates, and also damages coastlines. Large quantities of oil also enter the water every year when tankers clean out their tanks, or from minor spills in ports.