Description: The various types of resources currently used for energy production are discussed. Energy is primarily used for heating, transportation, and generating electricity. Coal is burned largely to produce electricity and is a major contributor to air pollution with coal power plants emitting carbon dioxides and nitrous oxides. Another major resource used for energy is oil. It is projected that each country either has reached or will reach a peak oil use, after which oil use will decrease. Natural gas is now being obtained from shale using the extraction technique of fracting which is a recent discovery. Nuclear power gained popularity worldwide through the 1970s, however very few new power plants have been built in the last three decades following the Three Mile Island and Chernobyl episodes. Hydroelectric power is generated by forcing water flowing from high terrain through a turbine to produce electricity. There are many hydroelectric dams operating globally.