57% of the 260,000 tonnes of used tires estimated to be discarded every year in Brazil were consigned to cement ovens in Brazil. In the United States, that figure is around 73%, or 685,000 of the 940,000 tonnes of tires thrown away each year.

In 2002, Brazil produced 41 million tires and 45 million in 2003. The US generates 275 million used tires per year and has a stock of around 3 billion.

Figures are unavailable for other ways of recycling tires in Brazil. Nevertheless, tire remolders say that they collected almost 3.8 million old tires in 2002, which were mainly sent to the Petrobras gas production plant in Paraná state.

Brazil produces around 45 million tires per year. Almost one third of these are exported to 85 countries and the remainder is used on the country’s vehicles. Despite the high incidence of recapping in the country, prolonging the tire’s useful life by 40%, most of them, once used, end up in dumps, at the side of roads and rivers, and even in backyards, where they accumulate rainwater, forming breeding grounds for disease transmitting insects. Tires and inner tubes consume around 70% of Brazilian rubber production and their recycling returns to the productive process a raw material regenerated at less than half the cost of natural or synthetic rubber. In addition, this saves energy and the oil that would be used as virgin raw material and even improves the properties of the materials made from the rubber.

In Rio de Janeiro, tires and rubber articles in general account for 0.5% of urban refuse and in São Paulo, less than 3%. In the US, tires account for 1% of waste.

After the American Charles Goodyear discovered the vulcanization process in the 19th century, by accidentally dropping rubber and sulfur on the stove, demand for the product spread around the world. Later, Germany began to market synthetic rubber made from petroleum oil. Energy recovery and recapping were the first ways in which they were recycled. With advances in technology, new applications arose, such as mixture with asphalt in a concentration of from 15% to 25%, seen today in the US as one of the best solutions to the mountains of used tires.  

Pollution

The burning of tires to heat boilers is regulated by legislation stipulating that the smoke produced must fall within standard 1 of the Reingelmann scale for all kinds of smoke. The principal users of tires in boilers are the pulp and paper industry and manufacturers of lime and cement, which use the whole tire and also some of the oxides contained in the metal of radial tires. Burning in the open air, which produces a black smoke with a strong odor (sulfur dioxide) is prohibited in various countries, including Brazil.

Reduction at source

Over the last 40 years, improved manufacturing techniques have greatly increased the average useful life of tires. Recapping or retreading, which in Brazil affects 70% of passenger and freight vehicles, is another important way of reducing this waste.

Composting

Tire scrap cannot be transformed into organic fertilizer. However when cut into 5cm strips the rubber can help in aerating organic compost. These pieces must be removed from the fertilizer before it is marketed.

Incineration

Tires are highly combustible, with a calorific power of from 12,000 to 16,000 BTUs per kilo, higher than that of coal.

Landfill

Left in dumps, landfills or other outside locations, tires attract rodents and disease transmitting mosquitoes. Sometimes, due to problems with compacting, small pieces of buried tire can return to the surface. Some cities prohibit the burial of whole tires in landfills.

Back to the origins

Cut into strips, old tires are transformed into rubber powder and purified by a system of sieves. The powder is then ground until the desired degree of granulation is achieved and then undergoes a chemical treatment to allow the vulcanization of the rubber. The material receives oxygen, heat and high pressure in rotating sterilizers, causing its molecular chain to break. The rubber is now ready to be reformulated. It is mechanically refined to increase viscosity and then pressed. At the end of the process, the material takes the form of baled regenerated rubber. This is then mixed with other chemical ingredients to form a dough of rubber which is then put through a mangle and a mold. The rubber is vulcanized in a battery of presses to form final products such as car carpets and shoe soles.