Fossil fuels Main article: Fossil fuel Most electricity today is generated by burning fossil fuels. This results in high temperatures, which move some kind of heat engine, often a steam turbine. Such systems allow electricity to be generated where needed, as the fossil fuel can be transported quickly. Also take advantage of the vast infrastructure designed to serve customers cars. Fossil fuel reserves are large, but finite. The depletion of low cost fossil fuels will have significant implications for both energy sources and for the manufacture of plastics and many other items. Estimates have been made to calculate exactly when depletion occurs, but are still discovering new fossil fuel sources.More serious are the concerns about the emissions resulting from fossil fuel burning, which is a significant repository of coal buried below ground. When burned it produces carbon conversion of that carbon dioxide, which is diluted in the atmosphere, resulting in increased levels of atmospheric carbon dioxide, which increases the greenhouse effect and contributes to global warming of the Earth. The relationship between increased carbon dioxide and global warming is almost universally accepted, although fossil fuel products vigorously replicate these results. Depending on the type of fossil fuel burning and the method also can produce other emissions. They often emit ozone, sulfur dioxide, NO2 and other gases and fumes. Sulfur oxides and nitrogen oxides contribute to smog and acid rain.In the past, factory owners attacked this problem through the construction of tall chimneys smoke, so that items could dilute pollutants in the atmosphere, which, while it helps to reduce local pollution, it does with the global . Fossil fuels, especially coal, also contains radioactive material in solution, therefore, to burn in very large quantities, show this material to the environment, causing local radioactive contamination levels and overall low but real. The coal also contains toxic heavy trace elements such as mercury, arsenic and others. The vaporized mercury in power plant can be suspended in the atmosphere and move throughout the world. While in the environment there exists a substantial amount of mercury, of which from other human activities is better controlled, from power plants is a significant fraction of the remaining emissions.Mercury emissions from power plants in the United States are estimated at 50 tons per year by 2003, and several hundred tonnes per year for China. The designers of power plants can provide special equipment to reduce emissions. The coal mining practice of the United States also include mining excavation and destruction of the mountaintops. The removed material remains are left uncovered and are thrown into the local river beds, causing most of all the rivers run red coal areas throughout the year with sulfuric acid that kills the entire life of the rivers .