The cement industry is very energy intensive. Its energy bill represents a significant part of total production costs and a good deal of uncertainty in view of fluctuating energy prices. It is for this reason that the European cement industry has, over the last 40 years, made considerable efforts to reduce energy consumption. Through technological change and investment, the European cement industry has significantly reduced its specific energy needs (i.e., the energy required to produce one tonne of cement). Nonetheless, already in 1993, the cement industry was close to the limit of what could be achieved through technical improvements and rationalisation, with an independent study commissioned by the European Commission assessing the potential for further improvements at 2.2%[1]. Information recently published by the Cement Sustainability Initiative (CSIi)[2] confirms that existing clinker[3]-making technologies do not provide further potential for significant improvement in terms of energy-efficiency. More details on this report can be found on the website of the World Business Council for Sustainable Development.
In order to safeguard its competitiveness, the European cement industry began some 20 years ago to look for new forms of energy. This move has expanded at the same time as the cement industry has been trying to combine energy efficiency and the need to preserve non-renewable energy and non-energy resources. This is where the use of waste, both as alternative fuels and raw materials, comes as a major breakthrough.
In 2006, the European cement industry used an energy equivalent of about 26Mt of coal, a non renewable fossil fuel, for the production of 266Mt of cement. Alternative fuels constituted 18% of this across Europe, saving about 5Mt of coal and reducing the need for mining a non renewable resource. In terms of the co-processing of waste as an alternative fuel in the cement industry, many different types of waste are burnt in a cement kiln including waste oil, waste wood, sewage sludge, wastes tyres, plastics, animal meat & bone meal, solvents and impregnated saw dust. There are two characteristics of particular importance: burning conditions (high temperature with a long residence time and oxidising atmosphere) and a natural alkaline environment of the raw materials. Co-processing offers a high potential for the cement industry to reduce global CO2 emissions. Without co-processing, the waste and by-products which make up these materials would have to be incinerated or landfilled with corresponding greenhouse gas emissions.
In February 2009, CEMBUREAU, the European Cement Association, launched a publication on the ‘Co-processing of alternative fuels and raw materials in the European cement industry’. The launch coincided with the European Union’s Sustainable Energy Week.
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[1] “Energy Technology in the Cement Industrial Sector” Final Report for Directorate-General for Energy (XVII) Contract NO XVII/4.1000/E/91-6
[2] The Cement Sustainability Initiative (CSI) launched its “Getting the Numbers Right” (GNRi) project to obtain current and robust data for CO2 and energy performance of clinker and cement production at regional and global levels across cement companies worldwide.
[3] Clinker, one of the main constituents of cement, is produced from raw materials (mainly limestone and clay) which are heated by a 2000°C flame in rotary kilns.
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