The Process

Each year, the United States generates millions of tons of secondary materials that have significant energy value. To recover this energy and avoid simple disposal, the cement industry uses these materials as alternative fuels, which replaces a portion of the non-renewable traditional fossil fuels used to provide energy for the manufacture of cement. This beneficial use of alternative fuels is a significant sustainability component incorporated in cement manufacturing operations throughout the U.S. and worldwide.

The U.S. consumes over 90 million tons of cement every year, a rate of use that tends to grow when the economy strengthens. Cement is the active ingredient in concrete, the most widely used construction material in the world. Cement is produced in huge rotary kilns by heating a mixture of minerals to over 2600°F. This is a very energy intensive process and cement manufacturers have developed technology that allows them to use energy-rich secondary materials created by other industrial processes to replace non-renewable fossil fuels. These wastes can be both hazardous and non-hazardous waste fuels.  Hazardous waste fuels may include things like paint solvents, inks, and cleaning solvents.  Non-hazardous alternative fuels can be a wide variety (or mixture) of energy-bearing materials such as tires and similar rubber-related materials, carpet, paper and plastics, fibers and fabrics, and much more.

The benefits of energy recovery are important for the environment. When cement kilns use alternative fuels derived from secondary materials, substances that would otherwise be regarded as waste, and simply discarded, are removed from the environment and handled and re-used in a safe and responsible manner. In addition, the amount of fossil fuels needed to produce cement is reduced, thereby conserving non-renewable energy resources and reducing emissions of greenhouse gases. For example, as EPA has noted, “both GHG and PM emissions have
been reduced as a co-benefit of the use of secondary materials.” “For example, the GHG rate associated with the combustion of scrap tires is approximately 0.081 MTCO2E per MMBtu of scrap tires combusted, while the GHG emissions rate for coal is approximately 0.094 MTCO2E per MMBtu. Combined with the avoided extraction and processing emissions 0.006 MTCO2E/MMBtu for coal, the total avoided GHG is 0.019 MTCO2E per MMBtu.” EPA has also noted additional benefits: “The use of secondary materials, such as use as a fuel in industrial processes [cement kilns] may also result in other benefits. These may include reduced fuel imports, reducing negative environmental impacts caused by previous dumping (e.g., tires), and reduced methane gas generation from landfills.” [Proposed Rule, Identification of Non-Hazardous Secondary Materials That are Solid Waste, 75 FR 31844, 31849 (June 4, 2010)]