By Damon van der Linde - Exclusive to Coal Investing NewsFor thousands of years coal has been used as an important source of energy, including playing a crucial role as a driving force in the Industrial Revolution. Today, coal is the largest source of energy for electricity generation in the world. Coal provides 27 percent of global primary energy needs and generates 41 percent of the world's electricity. World coal consumption was about 6,743,786,000 tons in 2006 and is expected to increase 48 percent to 9.98 billion tons by 2030, according to the U.S. Energy Information Administration.The World Coal Association predicts that coal reserves should last 116 years following the current consumption trends. A 2008 estimate lists the top five holders of proven coal reserves as: the United States, Russia, China, Australia and India. Japan, Taiwan, and South Korea are among the five largest importers, along with China and India. Coal is classified at varying contents of volatiles, which determines the amount and quality of energy it produces. The most commonly mined classifications are sub-bituminous coal, used primarily as fuel for steam-electric power generation, and bituminous coal, also used primarily as fuel in steam-electric power generation, but with substantial quantities also used for heat and power applications in manufacturing as well as the production of coke - an important component of steel fabrication. Coal has been the subject of numerous environmental concerns, both in its mining and its burning for energy production. Two main environmental concerns associated with the use of coal are pollution, caused by emissions of contaminants such as sulfur dioxide, nitrogen oxides and mercury, which effects human and environmental health, and greenhouse gases emissions which contribute to global warming. The leaders of the G-20—the world's top industrialized nations—as well as key countries with developing economies, have agreed to phase out their subsidies for fossil fuels, including coal. The agreement plans to ultimately phase out nearly $300 billion US in global subsidies for fossil fuels. The Organization for Economic Cooperation and Development and the International Energy Agency estimate that eliminating fossil fuel subsidies worldwide would cut global greenhouse gas emissions by 10 percent or more by 2050.