The role of cement in the
2050 Low Carbon Economy

ANNEX 2: Sustainable Cement Production

Co-processing of alternative fuels and raw materials

Cement plants are an essential part of Europe’s industrial landscape and are increasingly important partners in innovative waste management solutions, called co-processing. Co-processing waste in this way consists of using both the calorific potential to heat the kiln and the material component from the fuel ash as a raw material, thereby reducing our requirement for natural resources.

Many different types of industrial by-products, waste and biomass can be used as fuel in a cement kiln, including refused derived fuel, waste oil, waste wood, sewage sludge, waste tyres, plastics, bone meal, solvents and impregnated sawdust. Once the calorific potential of this waste has been recovered, what is left over (i.e. ashes) will be bound in the clinker during the burning process, and thus used as a raw material to produce cement. This cannot be done in an arbitrary way however, as the chemical composition of the fuel ash must fit the overall raw meal composition. Therefore a good knowledge of the calorific and chemical composition of any fuel used in cement production is mandatory.


The use of waste materials and by-products offers a win-win-win situation. The cement sector helps other industries or municipalities dispose of their waste and, in exchange, gains access to cost-effective fuel sources or raw materials. Moreover, co-processing decreases dependency on fossil fuels, reduces the need for quarrying, and prevents waste ending up in landfill. It also has a direct impact on lowering CO2 emissions, since it reduces the quantity of natural raw materials needed for clinker production.

Co-processing in Europe varies from country to country because of different national regulations and/or waste management practices or local markets specificities. Acceptance by local authorities and communities or the vested interests of other economic actors can reduce the uptake of waste materials by the cement industry. Use of alternative resources in certain European countries is low and there is a clear potential for increased co-processing to benefit the environment, industry and society.

Principles of co-processing at a glance

Co-processing offers a solution to use both waste and industrial by-products in a way that maximises their potential, i.e. by extracting the energy potential and using what remains as a raw material. Co-processing is effective because it is based on sound principles.

Co-processing respects the waste hierarchy:

  • Co-processing does not hamper waste reduction efforts.
  • Co-processing does not replace recovery nor recycling but is a waste management solution that can reduce the amount of waste that is landfilled or incinerated without energy and material recovery.
  • Co-processing is regarded as a flexible and integral part of modern waste management, as it provides an environmentally sound resource recovery option.
  • Co-processing must remain in line with relevant international environmental agreements1.

Controlled emissions and no health effects:

  • Due to the inherent features of cement kilns, i.e. high temperatures, stable operation, long residence time and high volumes of alkali raw materials, co-processing is a safe waste recovery option.
  • Emissions from cement kilns using alternative fuels can be lower than those from cement kilns with traditional fuels.
  • Co-processing has even proven very useful in specific cases, such as safe utilisation of meat and bone meal in Europe.

Cement and concrete quality remains unchanged:

  • Product quality (clinker, cement, concrete) must remain controlled and fully within standards.
  • Concrete must fulfil environmental norms e.g. leaching tests, enabling it to be used for uses including water reticulation.
  • The quality of cement should allow end-of-life recovery.

Companies engaged in co-processing must be qualified and able to:

  • Show good environmental and safety compliance track records and provide relevant information to the public and appropriate authorities.
  • Ensure adequate personnel, processes and systems to demonstrate commitment to the protection of the environment, health and safety.
  • Ensure all activities comply with applicable laws, rules and regulations.
  • Control inputs and process parameters required for effective co-processing of waste materials.
  • Maintain good relations with the public and other stakeholders in local, national and international waste management schemes.

Implementation of co-processing has to consider national circumstances:

  • Country-specific requirements and needs must be reflected in regulations, procedures and implementation.
  • Stepwise implementation will allow for the build-up of required capacity and set-up of institutional arrangements.2
  • Countries can maximise the use of waste materials for alternative fuels to avoid the depletion of local fossil fuels and/or to minimise the need to import fuels, thereby reducing  national energy costs as well as the emissions associated with transportation.
  • Co-processing has to take into account specific national circumstances. However, country -specific requirements, should ideally aim to be as homogeneous as possible at EU level, in order to avoid different treatments between countries.

Substituting clinker with other suitable materials

Part of the clinker used in certain types of cement can be replaced with alternative materials. Two main examples are granulated blastfurnace slag, a by-product of the steel manufacturing process, and fly ash, one of the materials resulting from the combustion of coal in traditional coal fired power plants.

The use of these by-products in cement production is not new; it has been common practice for decades and has led to several innovative cement types sometimes with different and beneficial characteristics. By using these products in cement manufacturing, millions of tonnes of alternative raw materials are put to good use, do not end up in landfill sites, reduce the need for virgin raw materials and lower the  CO2 content of the resulting cement

In numbers

Cement manufacturing is a volume business and the volumes of waste and by-products used are important. In 2010, the European cement industry recovered or recycled:

  • Over 13 million tonnes of granulated blastfurnace slag.
  • Close to 5 million tonnes of fly ash.
  • Over 7 million tonnes of waste materials such as tyres, sewage sludge, saw dust.

Using waste or industrial by-products in cement plants also makes sense from a financial point of view for local or regional governments because these materials are recovered using existing infrastructure without the cost of building an incinerator.