Millions of years ago, trees and other plants grew rapidly in a tropical climate, and when they died they fell into swamps. The water in the swamps prevented the plant material from decaying completely and peat was formed. As time passed, layer upon layer of peat build up. The pressure from these layers and heat from below the Earth’s crust gradually changed the material into coal. Coal can be found in parts of the world that were once covered with swampy forest, such as the UK about 250 million years ago. There are large deposits in China, USA, Europe and Russia. South Africa also has relatively large deposits.
When coal burns, it produces mainly carbon dioxide, some carbon monoxide and soot (which is unburned carbon). Many coals when burned produce smoky flames. Their energy content weight for weight is not as great as oil. When coals burns it produces more carbon dioxide than oil.
Click Arivan Issue 5/2013 to read more.