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Alternative Fuels

Author: Dr Johan Schoonraad - Holcim, South Africa

( Article Type: Explanation )

Waste-derived fuels in the cement industry
The cement industry worldwide is a major consumer of thermal energy for the kilns used in the manufacture of cement. From the early 1800s, this thermal energy demand has usually been met by using wood, coal or, more recently, other traditional fossil fuels such as natural gas or heavy fuel oil (HFO).

With the increasing demand on fossil fuels, the dwindling natural reserves, and the subsequent rising energy prices, the cement industry globally began searching for alternative sources of thermal energy. A synergistic solution was found when it was realised that energy containing waste (both hazardous and nonhazardous) could be safely used in cement kilns as a replacement for fossil fuels. From this early beginning has developed a sophisticated waste-management solution whereby increasing volumes of calorific containing wastes that would normally be disposed of to landfill are now used as waste-derived fuels in cement kilns.

Extensive evaluation of a diverse range of wastes has shown that materials such as scrap tyres, spent solvents, paint sludges and glues, plastics, and other wastes typically generated by modern society can be cleanly combusted in modern cement kilns without undue fear of pollution or risk of impacting the quality of the cement so produced. Extended trials by many of the leading cement manufacturers in the world, often under the scrutiny of the United States EPA (Environmental Protection Agency), the United Nations Environment Programme (UNEP) or other such organisations, has proven time and again that ‘the emission factors for cement kilns co-processing hazardous wastes are among the lowest of all source categories‘.

True to their commitment to Sustainable Development (SD), the global cement industry has moved increasingly toward the use of waste-derived fuels and away from the use of non-renewable fossil fuels. By doing so they have developed and now offer to waste generators in many countries an environmentally acceptable, safe, permanent disposal option for many of the energy-containing wastes that were previously disposed of to landfill and that would otherwise have remained as legacy issues for centuries to come. In many countries around the world, this ‘co-processing’ of waste in cement kilns is now viewed as the most acceptable way of solving many waste problems facing society.