Cement, concrete & the circular economy IN BRIEF s The raw materials used to produce cement and concrete, primarily limestone and aggregates, are abundantly available. However, our industry makes strong efforts to reduce its recourse to these primary raw materials, both in its manufacturing process and in the use of its products, and this through the use of different types of waste streams from a variety of other industries. The cement industry is a key example of industrial symbiosis. s When manufacturing clinker, the cement industry is able to use waste as a fuel instead of coal and petcoke. At the same time, the mineral content of waste is recycled as a raw material. We, in the cement industry, refer to this use of waste as an energy source and/or a raw material in industrial processes as ‘co-processing’. s Material recycling also occurs when making cement. Here, we replace part of the clinker with by-products from other industries. One example is fly ash from coal combustion. s In concrete production, material recycling also occurs, thanks to the use of recycled aggregates. s Not only is concrete a durable construction material, it is also 100% recyclable as either a recycled concrete aggregate or in other applications (as road base, for example). 3 4 SETTING THE POLITICAL SCENE Circular economy & the Energy Union Strategy The cement industry is friendly energy. With this in supportive of the aims of mind, the energy recovery the European Commission from waste through co- concerning the circular processing in the cement economy1 and welcomes industry has a relevant role the recognition afforded to to play across the EU-28 the material recycling which Member States, as by using occurs at the same time as waste as a fuel, the cement energy recovery in cement industry contributes towards production. The sector also security of energy supply, supports the promotion of which is fully in line with industrial symbiosis and the the Energy Union Strategy. recognition of energy recovery Against this backdrop, as a waste management the following publication solution for non recyclable provides an overview of why waste. The need for sorting the cement and concrete systems for construction & industry is central to the demolition waste, is another circular economy and what area welcomed by the cement can be done to leverage industry. Furthermore the the opportunities. It also cement industry welcomes demonstrates how the sector the Energy Union Strategy2 fits perfectly with many of which aims to ensure that the European Union’s policy Europe has access to secure, objectives, in terms of affordable and climate- security of energy supply. THE STORY OF CEMENT 5 & CONCRETE MANUFACTURE What is cement? Cement is a fine, soft, powdery-type substance, mainly used to bind sand and aggregates together to make concrete. Cement is a glue, acting as a hydraulic binder, i.e. it hardens when water is added. Everyone knows the word cement, but it is often confused with concrete or mortar. Cement is a key ingredient in both concrete and mortar, and it is always mixed with other materials before use: ss Cement mixed with water, sand and aggregates forms concrete, which is what the vast majority of cement is used for. ss Cement mixed with water, lime and sand forms mortar. Cement and concrete have been used to build durable structures for quite some time. The Coliseum in Rome, completed in 80 AD, is a good example of how a concrete structure can withstand time. The cement used by the Romans was produced using locally available raw materials, chalk and volcanic ash heated in open fires. The modern version of cement, called Portland cement, was developed back in the early 19th century and has been improved ever since. Common cements in Europe are specified by the European standard EN 197-1. There are also a number of special cements, such as supersulfated cements, very low heat cements and calcium aluminate cements. Cement manufacture The cement-making process can be divided into two basic steps: ss Clinker (the main constituent of cement) is first made in a kiln with gas up to 2000°C, which heats raw materials such as limestone (calcium carbonate) with small quantities of other materials (e.g. clay) to 1450°C. During this process, known as calcination, the calcium carbonate (limestone) is transformed into calcium oxide (lime), which then reacts with the other constituents from the raw material to form new minerals. This near-molten material is rapidly cooled to a temperature of 100 - 200°C. ss Clinker is then ground with gypsum and other materials to produce the grey powder known as cement. What is concrete? Concrete is a mixture of cement, water, aggregates and a small amount of ingredients called admixtures. It is the most commonly used manmade material in the world, its production equivalent to almost three tonnes of concrete per person, per year, twice as much as all other materials put together, including wood, steel, plastics and aluminium. Aggregates make up approximately 60-75% of the mixture by volume and cement and water make up the rest. Aggregates are usually inert materials like gravel, crushed stone, sand or recycled concrete. The type of aggregate selected depends on the application of the concrete. Thanks to the special binding properties of cement, concrete is a very resilient, durable material that can bear heavy loads and resist environmental extremes. The vast majority of cement is used to make concrete. ¹ Closing the loop - An EU action plan for the Circular Economy 2 A European Energy Union 6 CLINKER PRODUCTION & CO-PROCESSING From waste management to resource management The European cement industry is committed to ensuring that society has sufficient cement to meet its needs, whilst at the same time reducing its fuel and raw material requirements and subsequent emissions. The use of waste materials in the cement industry, also referred to as co-processing, contributes towards achieving these objectives. Co-processing is the use of waste as raw material, or as a source of energy, or both to replace natural mineral resources (material recycling) and fossil fuels such as coal, petroleum and gas (energy recovery) in industrial processes. The co-processing of waste in the cement industry provides a maximum substitution of non renewable materials. The cement industry uses waste which is, in principle, non recyclable due to a number of factors, including: ss Recycling it is not always economically viable ss There can be an insufficient market for the recycled product ss Recycling could, in fact, not be the best ecological option (eg, it could increase the CO footprint) 2 The main raw materials used in cement production have traditionally been limestone and clay, both of which are abundantly available. However, as mentioned, it is possible to replace part of the raw materials used in cement production with waste and by-products from other industrial processes. Selected waste and by- products containing useful elements such as calcium, silica, alumina and iron can be recycled as raw materials in the kiln, replacing natural substances. In recent years, about 5% of raw materials used in the production of clinker in Europe consisted of recycled materials and ashes from fuel, totalling about 5.5  million tonnes per year. Examples of recycled materials include contaminated soil, waste from road cleaning and other iron-, aluminium-, and silica- containing wastes or by-products, such as coal fly ash and blast furnace slag. The chemical suitability of recycled materials is important to ensure that they provide the necessary constituents for the formation of clinker. The use of alternative raw materials offers numerous benefits, including a reduced need for quarrying and lower CO emissions if the alternative materials are 2 already decarbonated, as in the case of ashes from lignite or coal, blastfurnace slag, concrete crusher sand, aerated concrete meal and fractions from demolition waste. 7 The decision on what type of waste can be used in a certain plant cannot be answered uniformly. As a basic rule, waste accepted as an alternative fuel and/or raw material must give an added value for the cement kiln in terms of the calorific value of the organic part and the material value of the mineral part. Some alternative materials will often meet both of these requirements. Due to the characteristics of the production process, the cement industry is capable of co-processing: ss alternative fuels, which have a significant calorific value (e.g. waste oils) ss materials which have a significant mineral component (e.g. industrial slags) ss materials that have both a calorific value and provide mineral components (e.g. used tyres and industrial sludges) Breakdown of fuels Breakdown of alternative fuels Thermal Energy Consumption by fuel type 2013 Alternative fuels breakdown 2013 Biomass impregnated dried sewage waste oil 6% saw dust 3% sludge 2% 2% solvents5% other biomass 5% wood, non impregnated saw dust1% plastics 37% other fossil based wastes 8% Alternative fossil fuels33% tyres 14% Conventional fossil fuels 61% animal bone meal, mixed industrial waste meal & fats (biomass) 5% 18% It has been estimated that by 2050, 40% of kiln energy will come from traditional sources, i.e. coal (30%) and petcoke (10%), while 60% of kiln energy could potentially be provided by alternative fuels of which 40% could be biomass. This fuel mix would lead to an overall decrease of 27% in fuel CO emissions. 2 Source: Getting the Numbers Right 8 However, not all waste materials can be co-processed in the cement industry. Several factors must be taken into consideration when deciding on the suitability of the materials. These include the chemical composition of the final product (cement) as well as the environmental impact of the clinker production process. Examples of waste which is not suitable for co-processing in the cement industry include nuclear waste, infectious medical waste, and entire batteries. An adequate quality control system is strictly adhered to for all the materials used. This ensures that they are co-processed in an environmentally safe and sound manner, safeguarding the: ss health & safety of the workers in the plant and the people living in the neighbourhood ss high quality of the final product ss correct and undisturbed functioning of the production process ss environmental impact of the production process. Characteristics of co-processing in the cement industry Clinker is manufactured by heating raw materials inside the main burner of a kiln to a temperature of 1450°C, which is hotter than lava flowing from a volcano! The flame reaches temperatures of 1800°C. The material remains at 1200°C for 12-15 seconds at 1800°C for 5-8 seconds (also referred to as residence time). These characteristics of a clinker kiln offer numerous benefits and they ensure a complete destruction of organic compounds, a total neutralization of acid gases, sulphur oxides and hydrogen chloride. Furthermore, heavy metal traces are embedded in the clinker structure and no by-products, such as ash of liquid residues, are produced. What makes co-processing unique? 9 In addition to combining both energy recovery and material The legislative framework recycling, co-processing in the cement industry is unique needs to recognise these new in that dedicated waste pre-treatment facilities have been waste management options, established in order to treat the waste prior to sending it as such as material recycling a fuel to cement plants. The alternative materials used by in the cement industry, as the cement industry are derived exclusively from selected contributing to the EU and waste streams. They usually require pre-treatment (e.g. Member State recycling drying, shredding, blending, grinding or homogenisation) and targets. an appropriate Quality Assurance. Pre-treatment is, therefore, an integral part of the “recovery” operation. Waste is often prepared for use as an alternative fuel by outside suppliers. On the one hand, these facilities provide a constant supply of waste which allows the cement industry to control the clinker production process and ensure clinker quality. At the same time, these pre-treatment facilities also separate the waste and ensure that any waste which can be recycled is sent for recycling. Why is energy recovery important? By using waste as a fuel, the cement industry contributes towards security of energy supply, which is fully in line with the recently published Energy Union Package. In the cement industry, energy recovery: ss contributes to the lowering of CO emissions 2 ss makes the cement industry less dependent on imported fossil fuels ss reduces the amount of waste sent to landfill In 2013, the European cement industry used an energy equivalent of about 15Mt of coal, a non renewable fossil fuel, for the production of 157.5Mt cement. Alternative fuels, including waste biomass, constituted 39% of this total across Europe, saving about 6Mt of coal. Furthermore, co-processing offers a high potential for the cement industry to reduce global CO emissions. In 1990, 2 the percentage of non-renewable energy gained by the use of waste as a fuel was 3%. In 2013, it stood at 33%, resulting in a reduction of 16Mt of CO emissions each year. CO 2 2 emissions from waste biomass are climate neutral. 14% of the alternative fuels used by the European cement industry consist of biomass from waste, such as meat & bone meal and sewage sludge. This could be developed further provided biomass remains accessible. 10 Why is material recycling important? There is a large amount of waste which cannot be recycled back into the same product category. Fortunately, there are several other solutions available for this waste - and co-processing in the cement industry is one of them! Thanks to material recycling in the cement industry, the mineral content of waste used as an alternative fuel serves as a raw material for the production of clinker, the main constituent in cement. It should be borne in mind that the level of co-processing in Europe varies from country to country as a result of: ss national regulation/waste management ss experience (in the cement industry) ss market and local conditions. The use of alternative resources in certain European countries is low and has a clear potential for growth. The European cement industry, is, therefore, keen to collaborate in developing this further and become an integral part of Member States waste management systems, thereby contributing to the EU Energy Union goals with steady and cost-effective energy security of supply from waste diverted from landfills. Co-processing: A combination of energy recovery and material recycling The cement industry specialises in the treatment of difficult waste streams and supports a ban on the landfilling of recyclable and recoverable waste. ss On the one hand, the cement industry is able to use waste as an alternative fuel (Energy Recovery), which reduces our recourse to primary fossil fuels – as well as reducing CO emissions! 2 ss On the other, the cement industry can recycle the mineral content of the waste as a raw material (Material Recycling) – thus reducing our dependence on virgin raw materials! In accordance with the Waste Framework Directive, ‘recycling’ includes any operation by which waste materials are reprocessed into products, materials or substances whether for the original or other purposes. Given the above, material recycling in the cement industry is clearly a recycling operation. The material recycling component of co-processing contributes towards Member States compliance with EU recycling targets and should be recognised as such.