More than 50% of the energy produced in the United States is generated from coal combustion. This process creates energy and generates coal combustion products (CCPs) in the form of fly ash, bottom ash, boiler slag, and flue gas desulfurization (fgd) products. In 1998, 97.8 million mt of CCPs were generated by electric utilities in the United States. Only 29% of this total is used in other products with the remaining 69.4 million mt landfilled. Fly ash is the major constituent of total CCP's produced (57 million mt) and 33.5% of the total is predominantly used in cement and concrete, waste stabilization, structural fill, road base, and mining applications.
Wyoming is the leading coal producer in the US and Montana, Colorado, New Mexico, North Dakota, Utah, and Arizona are among the major coal-producing states in the US. Most of these states rely heavily on coal for electrical generation. With the exception of Arizona and Montana, greater than 85% of the energy produced in these western states is from coal. Some of these coals are high in ash, particularly those from New Mexico, and produce significant amounts of CCPs. Both Type C (high calcium) and Type F (high silica) fly ash is produced from western coals. In many western states, transportation departments require Type F to be used to counteract alkaline aggregate in the concrete. It is estimated that 9 million mt of fly ash were produced in these states in 1998. About 23% is used mostly in cement and concrete applications, waste stabilization, and mining applications. Market area and transportation are important factors influencing the use of fly ash in these states. With relatively few large population centers, the potential markets are limited and haulage distances and variable rail infrastructure restrict the market area.