So thick layers of peat built up over thousands of years. These then became covered in sands or muds as the land subsided. As more material accumulated above the peat, the water was squeezed out leaving just carbon-rich plant remains. 100 tonnes of CO 2 is released by burning coal to generate a given amount of electricity. Until recently, most coal came from underground mines.
Coal mines are notorious killers due to roof falls and explosions.
Many single accidents have resulted in hundreds of deaths. Huge cranes strip off the soils and rocks covering the buried coal seams. Much coal also contains other minerals which yield pollutants when you burn the coal. Sulphur is the worst of these and causes severe damage to buildings, forests and lakes due to acid rain. Acid rain forms when the sulphur dioxide-rich plumes from power station smokestacks mix with water vapour in ordinary clouds.