The versatility of the cement making process enables the safe use of by-products from other industries as raw materials, fuels or constituents of cement. These by-products meet strict quality specifications to ensure the cement meets customer performance specifications, and their use contributes to sustainability by reducing both landfill and emissions and preserving valuable natural and non-renewable resources.
Use of alternative fuels such as demolition timber results in a GHG benefit because the emissions from combustion are lower than would otherwise be released if the material went to landfill.
Other alternative fuels-such as tyre chips or used oils-also reduce landfill and are lower emitters of GHG than their fuel equivalent in coal.
A cement kiln using waste materials retains ash and other residual constituents incorporating them into the clinker. Using by-products provides a whole-of-life waste management option that can be economically viable, regionally available and environmentally sound.
The industry’s viability is dependent upon minimising costs, utilising less expensive alternative raw materials and fuels, and advancing the industry toward greater sustainability.
Steel slag, mill scale, fibre board waste and spent catalysts from the petroleum industry are used at Blue Circle Southern Cement’s Berrima plant to substitute for 21 000 tonnes of natural materials. The company’s Waurn Ponds plant has been using waste oil for fuel since 1990. Tyres followed and the plant now consumes 1.2 million a year, about half of Victoria’s annual tyre dump. Some 45 per cent of Waurn Ponds conventional fuel needs are being met using alternatives.
Other cement companies are using these and other materials. At Cement Australia’s Gladstone plant spent solvents provide fuel, while at Adelaide Brighton’s Birkenhead plant, wood from the construction and demolition waste stream will replace 30 per cent of the fuel requirement by 2007.
The Australian cement industry will continue to work with regulators and local communities to improve sustainability by using alternative fuels and materials in cement manufacturing.
At its Gladstone plant, Cement Australia is using spent cell liners (SCL) from Comalco’s aluminium smelter. SCL is a carbon-based waste from the electrolytic cells that convert alumina to aluminium. It is a valuable fuel replacement for coal, and its silica and aluminium content are needed for making clinker. The use of calcined SCL as an alternative fuel has been positive; Cement Australia has seen no change in cement strengths with only benefits .owing to local industry and the environment.
Demolition timber as an alternative fuel
In an effort to reduce its reliance on fossil fuels and cut energy costs, Adelaide Brighton’s Birkenhead plant trialled a number of alternative fuels before .finding a solution, demolition timber. Traditionally reliant on natural gas, Birkenhead developed a strategic plan which had a focus on alternative fuels. The plan had plenty of clout, not only including both plant and management resources, but was driven and monitored by the Managing Director and Board of Adelaide Brighton. Through modelling and researching the effects of demolition timber in the Birkenhead plant, it was decided that the proposal could meet the specific requirements of the calciner and environmental standards. Discussions were conducted with the EPA and community to ensure that the burning of demolition timber was not only within government health guidelines, but met with the approval of local residents.
Trials were conducted and emissions monitoring found there was no increase in heavy metals or organics, which include dioxins. In fact a drop in nitrogen dioxide emissions proved an environmental win for all involved. Birkenhead’s use of demolition wood as an alternative fuel means that the 75 000 tonnes available in South Australia no longer end up as landfill.
The industry is proactive in using alternative raw materials and fuels to reduce the use of fossil fuels and natural materials