This was the fuel that launched the industrial revolution and has continued to grow in use; China, which already has many of the world's most polluted cities,[4] was in 2007 building about two coal-fired power plants every week.[5][6] Coal is the fastest growing fossil fuel and its large reserves would make it a popular candidate to meet the energy demand of the global community, short of global warming concerns and other pollutants.[7] According to the International Energy Agency the proven reserves of coal are around 909 billion tonnes, which could sustain the current production rate for 155 years,[8] although at a 5% growth per annum this would be reduced to 45 years, or until 2051. With the Fischer–Tropsch process it is possible to make liquid fuels such as diesel and jet fuel from coal. In the United States, 49% of electricity generation comes from burning coal.[9]