Fueling the Inferno

As cement producers continue to search for alternative fuels, many people wonder what types of fuel can be used in the combustion process.

The high temperature needed for cement manufacturing makes it an energy-intensive process. The average energy input required to make one ton of cement is 4.7 million Btu—the equivalent of about 418 pounds of coal. The U.S. cement industry uses energy equivalent to about 16 million tons of coal every year. According to the Department of Energy, U.S. cement production accounts for 0.33 percent of energy consumption—lower production levels than steel production at 1.8 percent and wood production at 0.5 percent. From the PCA publication: U.S. and Canadian Labor-Energy Input Survey 2001, the cement industry has improved energy efficiency by over 33 percent from 1972.

Finding ways to reduce both energy needs and reliance on fossil fuels is a top priority for cement companies. Although coal, petroleum coke, and other fossil fuels have been traditionally burned in cement kilns, many cement companies have turned to energy-rich alternative fuels. Today, many plants meet between 20-70% of their energy requirements with alternative fuels. And many of these alternative fuels are consumer wastes or byproducts from other industries. Recovering their energy value in cement making is a safe and proven form of recycling.

Fuels like coal and coke contain carbon and release tremendous quantities of heat when they’re burned. But coal and coke aren’t the only fuels that contain carbon. Tires are also a great source of hydrocarbons (carbon and hydrogen). Using tires for combustion in a cement kiln produces 25% more energy than coal and it can also result in lower emissions. In fact, any material with high carbon content could be used as a fuel. Paper, packaging, plastics, saw dust, solvents… all are suitable for use as alternative fuels. Because of the extremely high temperatures (well above 3,000 °F), these materials burn quickly and extremely efficiently.

Burning alternative fuels in cement kilns offers several environmental benefits. This type of energy recovery conserves valuable fossil fuels for future generations while safely destroying wastes that would otherwise be deposited in landfills. From the PCA publication: 2002 U.S. and Canadian Portland Cement Industry:Plant Information Summary, 15 plants used waste oil, and 40 plants in 23 states used scrap tires. Solvents, unrecyclable plastics, and other materials are used as well.

The information in this article was taken primarily from PCA’s Report on Sustainable Manufacturing. To view the entire report click here.