The traditional fuel used to heat the kiln was gas, oil and coal. In recent years, the industry has been switching to alternative fuels around the globe.
The alternative fuels being tested, and in many cases being used for full production, include waste oils, plastics, auto shredded residues, waste tires, sewage sludge and all kinds of slaughterhouse residues. The industry is also using liquid waste such as tar, chemical wastes, distillation residues, paint waste and asphalt slurry. Solid waste includes petroleum coke, paper waste, battery cases and even domestic refuse.
One of the challenges in switching to waste instead of gas, oil or coal is that not all of the different waste matters burn the same, and even if one form of waste is used, the waste does not burn consistently. The fuel burning process must be adjusted accordingly.
Yet even with the inconsistencies in the burning of waste, the cement industry has widely adopted alternative fuels. A number of cement plants in Australia are now using alternative fuels for 50 percent of their kiln heat. The benefits include reductions in fuel cost, lower emissions, and the ability to use waste that otherwise would end up in landfills.