According to the World Business Council for Sustainable Development’s (WBCSD) Tire Industry Project (TIP), the world is projected to generate approximately one billion end of life-tyres each year. Though as they are, end of life-tyre waste poses a challenge in our strive for a circular economy and away from landfills. But there are many ways in which tyres can be reused or recycled. Worldwide, laws and regulations differ considerably, aiming to encourage or discourage various ways of dealing with end of life-tyre waste, but generally it makes sense to reuse and recycle tyres.
One way of dealing with worn tyres is retreading tyres by replacing the worn tread with a new one. This process reuses approx. 90 % of the tyres material and is as such a good way to avoid waste. But for safety reasons, this process can only be done if the rest of the tyre is in good enough condition. End of life-tyres that are unfit for retreading must be disposed of in another way.
Since tyres are not biodegradable, governments globally encourage recycling of end of life-tyres unfit for retreading in different ways. One way is to de-bead the tyre (removing the steel bead), cutting it, and stamping it into products like shims or belts. Another is downsizing the whole tyres, thus opening many other recycling opportunities.
Shreds, chips, and granules
End of life-tyres can be cut into various sizes, typically named shreds (50-300 mm), chips (10-50 mm) and granules (1-10 mm). The type of equipment you need depends on the range of sizes you want to produce.
Cutting tyres to shreds in a shredder like the Super Chopper is useful. Not only are shreds the ideal size for transporting end of life-tyres as they can be compacted more than whole tyres. The material has a high burning value, and shreds are often used as tyre derived fuel (TDF) within the cement and paper industries as a supplement to traditional fossil fuels. Another use for shreds is as tyre derived aggregate (TDA). Depending on shred size, it is a low-cost material intended for use in civil engineering applications like lightweight fill for embankments or vibration reduction under light rail tracks, etc.
Tyre chips can be made from hole tyres or tyre shreds in a shredder with a build-in screen, like the Multi Purpose Rasper. They can be used for the same TDF applications as tyre shred with the additional benefit of a lower steel content. Tyre chips are also used for Equestrian, which is rubber mixed with sand or sawdust used in the horse industry in stables or at the tracks. Equestrian protects the legs of the horses and is a big industry in countries like the UK.
Rubber granulate can be used in production of rubber mats and moulded products such as rubber tiles. It is also used in sports fields and artificial turfs for soccer, golf, athletic tracks, etc. Recently, rubber granules have also been popular for pyrolysis, the process of extracting oil and solids from the rubber for use in new products or as fuel. Making high quality rubber granules from whole tyres requires a versatile tyre recycling solution since the size of rubber granules often depends on customer requirements – e.g., 0.8 to 1.6 mm or 1.6 to 3.2 mm. A high-quality rubber granule is characterized by low textile content, low steel content, and high consistency in size.
Powder and other products
Rubber powder <1 mm is typically made by processing granules in a Cracker Mill. It is used much like granules, but for products that need an even smaller material size, like shoe soles. The use of rubber powder is currently gaining momentum in the asphalt industry as well, where major projects with rubberized asphalt have been conducted in countries like USA, Poland, Sweden, and Australia.
Apart from rubber, tyres contain both steel and textile – approx. 20 % steel and 10 % textile by weight. The steel wire is of high interest for recyclers since it is of good quality. Steel works worldwide regularly use recycled steel from tyre recycling plants and pay a good price, especially if it has been cleaned from rubber and textile in a steel cleaning plant.
The liberated textile is mostly burned, prized for its very high effective burning value. It can be mixed with other materials to increase that material’s effective burning value, i.e., in the cement industry. Some cement plants also use it for cleaning out the sludge from the rotation ovens, since the temperature while burning cause the sludge to burn too. This way, the oven does not need to be cooled down for manual cleaning. Another use for textile is as noise insulation and to reduce vibration in industrial plants.
Prospects
These are just some of the areas in which end of life-tyre waste is recycled into new products, and only the future knows what it will be used for in 10 or 20 years. There are, however, already projects looking into the future use and a truly circular economy: tyre companies launching new tyres with recycled rubber, experiments with efficient de-vulcanisation of rubber, and pyrolysis as a rapidly developing industry. As more and more innovation and funding are changing the industry, flexibility and know-how will be increasingly important. And in these areas, the ELDAN tyre recycling solutions truly excel.
