Disposing Of 800 Million Tires
Over 800 million of on and off road tires are replaced every year in North America and Europe alone. The problem of how to deal with these millions of tons of tires piling up in landfills everywhere has posed a significant ecological challenge.
In the summer of 1999, the world was spurred into action when a dump containing over 25 million tires in the U.S. state of Ohio caught fire. The smoke from the fire was visible up to 60 miles away and resulted in an ecological disaster for the area. While the Ohio fire was still smouldering, another similar fire broke out in Stanislaus County, California.
Fires in large tire piles can take several months to burn themselves out and cannot readily be extinguished. They produce heavy thick smoke and extremely toxic liquid runoff that can pollute surface and groundwaters.
The first steel belted tires were invented by Michelin in 1948 but did not come into general use until the world switched from the earlier bias ply tires to the more modern steel belted radials in the late 1970s and onwards. Steel belted radial tires deliver longer service life, lower fuel consumption due to reduced rolling resistance, better handling and fewer flats. The problem that steel belted tires present is that the recycling process is significantly more difficult as the metal which is embedded within the rubber has to be separated and recycled separately, which is a complex and extremely costly process.
Tire recyclers such as Colway Tires in Durham, England, have developed a process to recase existing used radial tires, eliminating the requirement to separate the metal from rubber. The first step in this process is to remove the old rubber from the casing treads and sidewalls in a very coarse buffing process. Then the critical area of the tire bead where it adheres to the wheel is cleaned and refurbished. The casings are then treated with a chemical which prepares the surface for retreading.
The next step is to literally rebuild the tire by thrusting out rubber in the precise dimension and form for the sidewall and tread. At this point the tire is balanced and cured under 200 psi of pressures at temperatures up to 150 degrees C for around half an hour, depending on the size and other inherent qualities of the tire.
Excess rubber is trimmed, the tire is inflated to check for leaks and imperfections, and subjected to rigid quality control standards before they are allowed to be shipped out from Colway Tires to retailers.
More than 50% of all on and off road tires submitted for the process of retreading to Colway Tires are found to be unsuitable thus are shredded into crumb rubber and turned into various products including carpet underlay, playground and landscaping mulch, engineering construction site fills, athletic track surfaces, railroad ties, automotive acoustic insulation, or even mixed with asphalt to make road surfaces.
There is no question that the problem of on and off road tire disposal must be resolved. It is of the foremost importance to support these various recycling and refurbishing processes to avoid further ecological tire fire disasters.