Alternative fuel and raw materials
Cement manufacturing requires a number of minerals and lots of thermal energy, traditionally sourced from limestone, clay and sands, and coal and gas. There are a number of by-products that can equally supply these requirements, reducing the need to extract resources from the environment.
Using by-products provides a whole of life waste management option that can be economically viable, regionally available and environmentally sound.
What are alternative fuels and raw materials (AFRs)?
Alternative fuels are energy-rich materials such as used tyres, waste wood, used oil, spent solvents and other by-products and wastes that can be used to replace coal or gas as a source of thermal energy in the cement manufacturing process.
Alternative raw materials are by-products or wastes rich in iron, silica, alumina or calcium carbonate, which can be used to supplement traditional limestone and clay input materials.
Since 1999, alternative fuels are estimated to have reduced the cement industry’s dependency on coal by over 800,000 tonnes. In our Gladstone and Railton plants, calcined spent cell liner (a by-product of aluminium smelting), and blended solvents are being co-processed to create a new alternative fuel for cement manufacture. Used tyres, demolition timber and tallow have also been used safely as alternative fuel due to the high combustion temperatures and long residence times inherent in cement kilns.
The use of AFRs reduces the impact of potentially harmful items being disposed of as landfill while reducing the burden on non-renewable energy sources. The use of alternative raw materials also provides substantial reductions in greenhouse gas emissions from the cement manufacturing process. These benefits are important considerations when evaluating the true environmental cost of our building materials.
Independent studies have shown that the cement kiln process is efficient and effective when using alternative fuels. High temperatures (about 1,400°C) and long residence times (typically 6 seconds) ensure that all harmful organics are completely converted to energy. The use of AFRs does not result in increased emissions of organics including dioxins and furans. Nitrogen oxide (NOx) emissions can also be reduced by using alternative fuels, while utilising bag filters on kilns ensures that there is no increase in particulate emissions.