In the series of carbonaceous fuels that ranges from peat to anthracite, bituminous coal is of middle rank, containing intermediate amounts of fixed carbon, volatile material, and moisture in comparison with the other materials to which it is related. Bituminous coal also exhibits a relatively high heat value, which along with its abundance, is responsible for its common use in a number of important practical applications. The material is, for instance, utilized to generate steam in industrial plants and to produce coke for the smelting of iron ore, two functions that are central to modern civilization. Unfortunately, however, burning sizable quantities of sulfur-containing bituminous coal can have an adverse effect on the environment, leading to such detrimental effects as air pollution and acid rain. Due to these considerable problems, some electric power plants have begun utilizing the less environmentally damaging subbituminous coal instead, and scientists are in constant pursuit of even better sources of fuel.