Materials
There are an estimated 800 million cars and commercial vehicles in use worldwide, with almost 70 million units being added to that number every year. The explosive growth in the automobile sector in recent decades has been accompanied by a substantial increase in volume of end-of-life tyres. Significant developments by the recycling industry can now guarantee the adequate recovery of the millions of tyres that are disposed of daily.
Mainly composed of rubber, textiles and steel, tyres are an ideal product for recycling. Recycling tyres translates into lower energy consumption, a reduction in emissions and most importantly, a reduction in the amount of raw rubber needed for manufacturing which ultimately contributes to preserve natural resources like crude oil.
Tyres are built to last. However, the very same properties that make them durable also make them difficult to break down. Disposing of tyres in landfills or stockpiles can cause severe environmental and health concerns:
- In many cases, tyre stockpiles end up being burned, releasing toxins and pollutants into the air, water and soil.
- Stockpiled tyres hold water very efficiently, creating an ideal breeding environment for insects, rodents and other parasites that can transfer diseases to humans.
Recycling Processes
Rubber powders are used to provide a resilient surface on children's playgrounds
Remoulding gives tyres a new life
Granulated rubber for recycling
- Sorting: Tyres are sorted by size and composition.
- Shredding: When producing tyres, the vulcanisation process makes the rubber more durable and flexible. Unfortunately, this makes the melting process difficult, so tyres must be broken down and shredded into strips.
- Steel removal: Shredding machines use rotors to further shred the material and to remove steel fibres from tyres. Magnets are used to separate the steel from the rubber.
- Grinding: Once the steel is removed, the strips are placed into granulators. Different applications are employed to determine the desired consistency of the recycled rubber, which can be grounded into granules, shreds, chips, crumbs or powder.
Special processes
- Cryogenic process: Shredded tyres are frozen using liquid nitrogen to facilitate the grinding and the removal of steel.
- Pyrolytic process: This innovative process is currently being developed. It involves heating the tyres in an oxygen-free environment and decomposing them into oils, gases and char.
Retreading
- Recycling tyres does not always involve shredding and melting the rubber. They can also be retreaded, which means that a new tread and sometimes a sidewall veneer are applied. Afterwards, vulcanization and curing can be carried out to increase tyre resistance.
Applications
Tyres are one of the most versatile recycled materials and are used as fuel or for numerous innovative applications, such as construction and civil engineering.
- Granulated scrap tyres are used in cement kilns, pulp and paper factories, as well as in power plants.
- In civil engineering works, shredded tyres are used as filling to stabilise weak soil and also as insulation for roads, walls and bridge abutments.
- Rubber powder and granulates are extensively used in asphalt applications. They improve road performance by adding extra traction, reducing noise levels and lowering maintenance costs.
- Granulated rubber is employed in building sports facilities. Its shock-absorbing properties are ideal for surfaces of running tracks and playgrounds.
- Rubber improves drainage when used underneath grass playing fields.
Tyres also contain significant amounts of steel wiring which can be fully recovered and used as raw material by the steelmaking sector.
Recycling Facts
- The oil required to retread a tyre is 20 litres less than the oil needed to manufacture a new tyre. With commercial vehicle tyres, the savings are even greater, estimated to be about 68 litres per tyre.
- Retreading a tyre costs anywhere from 30% to 70% less than manufacturing a new tyre.
- Over 90% of all aircraft tyres are retreads.
- Scrap tyres used as fuel can produce the same amount of energy as oil and 25% more than coal.
Our Experts
For further information on technical issues, contact our experts working on the Tyres Commodity Committee: