Where do all the old car tires go? Before answering that question, let’s take a look at the composition of modern rubber tires. Just under half of a tire consists of natural and synthetic polymers, the most common of which is styrene-butadiene rubber (SBR). Tires also contain carbon black, metal, textile weave, zinc oxide, sulphur and various additives.
|Composition of tires produced in the EU|
About 20% of the weight of a tire is worn away by the time tread depth falls below legal requirements for road driving, and the bulky carcass that remains constitutes a serious solid waste disposal problem. Each year, about 250 million tires are replaced in Europe, and several billion are piled up awaiting final disposal.
European Union “producer responsibility” legislation requires manufacturers, importers and retailers of tires (and all other motor vehicle components) to take responsibility for the financial and physical requirements of final disposal or recycling of products. For consumers, producer responsibility law means that old tires can be returned to the manufacturer or retailer without charge, and since 2003 it has been illegal throughout the EU to dispose of tires in landfills. Since 2006 even shredded tires may not be mixed with other municipal waste.
Where tires go
The EU has identified five main avenues for dealing with worn-out tires from autos, trucks and busses:
- Export to developing countries. Tires are retreaded or used as-is in countries with less stringent road safety requirements. This export is expected to decline.
- Retreading. The worn-out tread is replaced. The environmental impacts of manufacturing retreads are of course substantially lower than production of new tires.
- Recycling. The rubber material is finely chopped (granulated) for use in a number of industrial and consumer products, including roadway embankments, riding trails and all-weather outdoor sports fields.
- Energy Recovery. The most common fate for used tires is to reclaim the relatively high energy content through incineration in ovens for cement production and district heating.
- Landfill. No longer permitted in the EU, but probably still occurring in many places.
With the landfill option closed off and only limited applications for energy recovery, the focus is now on using shredded tires as a raw material. The main obstacle, however, is achieving desired product characteristics and quality levels. One promising avenue is creation of a hybrid material composed of pulverised rubber bound to a plastic polymer.
EcoRub AB, based in northern Sweden, holds a European patent on a technology for creating such copolymers for use in manufacturing thermoplastic rubber that it calls “eco-rubber”. EcoRub is currently refining the product and developing a process for mass production. Åke Paulsson, the company’s primary shareholder, hopes to establish a factory in Piteå, Sweden for recycling used tires into finished products, including components for the auto industry.
Paulsson’s method is already in use by licensees in the United States, where some 15,000 tons of eco-rubber are used each year. Paulsson says market acceptance of the recycled material is growing fast. The European market is estimated at several hundred thousand tons of recycled rubber, not least because the European auto industry is required by EU law to steadily increase its use of reclaimed raw materials.
EcoRub AB has developed a unique method for recycling used tires. After first shredding the tires into small pieces, EcoRub separates the rubber from metal and fabric fractions and mills the rubber down to a powder. This rubber powder is mixed with plastic (which may also be from reclaimed sources), and the two polymers are bound and strengthened through a patented chemical reaction. The resulting rubber-like material, which is wear-resistant and has a homogenous surface, can be treated with methods and equipment used for conventional thermoplastics. EcoRub’s business concept is based on manufacturing ecological rubber sheets and composite boards.
Article published in May 2009