The United States annually generates about 235 million tons of hazardous waste. Cement kilns are an ideal national resource to recover the energy from hazardous waste. Raw materials require large amounts of fuel to heat them to 2,700 degrees Fahrenheit in the kiln to make cement clinker. The select fuel-quality hazardous wastes from which energy is recovered in cement kilns include spent solvents, paints, residues from chemical manufacturing and other flammable wastes.

The cement industry has used a technology since the late 1970s to help fulfill the 1976 U.S. Congress mandate to recover energy from spent industrial materials and preserve resources. Congress recognized that the United States must not waste energy by failing to conserve natural resources or recovering energy from industrial wastes.

In 1976, Congress passed the Resource Conservation and Recovery Act (RCRA) and authorized the U.S. Environmental Protection Agency to administer it. It was an environmental legislation landmark.

Resource Conservation and Recovery Act

RCRA was a sweeping package of legislative initiatives that overhauled the Solid Waste Disposal Act and built a framework for a national policy on hazardous waste management. The RCRA objectives are to promote protection of health and the environment and to conserve valuable material and energy resources.

Cement Kilns: An Environmental Solution

It takes about 470 pounds of coal to make one ton of cement. In the United States today, cement kilns annually burn an amount of fuel-quality hazardous waste equal to one million tons of coal or four million barrels of oil. Instead of this energy being wasted by other thermal treatment processes, cement kilns recover the energy from wastes and nonrenewable fossil fuel like coal is conserved. In the process, the wastes are destroyed and cement, a valuable product, is made.

In addition, energy recovery in cement kilns:

• Reduces sulfur dioxide emissions because fuel-quality hazardous wastes have low sulfur content (0.5 percent) compared to coal (2 to 3 percent).
• Reduces greenhouse emissions by more than 3.4 million tons (net) of carbon dioxide a year.
• Helps make cement plants more competitive by reducing fossil fuel expenditures. Fuel costs are 30 to 40 percent of the variable cement production expenses.

Fifteen cement plants in the U.S. use fuel-quality hazardous waste to supplement fossil fuel.

Scrap Tires as Fuel

Thirty-five other plants use non hazardous scrap tires as a fuel substitute. In addition to the benefits to these 35 plants, using scrap tires helps reduce the unwanted inventory of two billion of these tires in the U.S.

All these factors together mean that energy recovery in cement kilns makes good environmental and business sense.