The use of alternative fuels and raw materials is common practice in the European cement industry. In this excerpt from MVW Lechtenberg & Partner’s Alternative Fuels & Raw Materials Handbook, the company gives an overview of scrap tyres as an alternative fuel highlighting the economic value for usage in cement plants, the impact on clinker quality as well as considerations and recommendations. By Dirk Lechtenberg, MVW Lechtenberg & Partner, Germany.
Scrap tyres are end-of-life tyres that are no longer safe or suitable for road use due to damage or brittleness or if the tread depth is below the sufficient limit. By the time a tyre has reached its end of life, it has generally lost around 20 per cent of its weight from the tread.
The main raw materials of a tyre are natural and synthetic rubber, carbon black and oil while the rest consists of various kinds of reinforcing materials. Around half of the rubber is natural from a rubber tree. These trees are grown in the tropics, in countries such as Malaysia and Indonesia. Most of the synthetic, oil-based rubber comes from European manufacturers. Around one-third of the compounds consists of filler substances. The most important of these is carbon black which gives tyres their black colour. An important filler is oil which is used as a plasticiser in the compound. Furthermore, hardening or vulcanising agents, various booster chemicals and protective agents are used in the rubber compounds.
