How Tires Get Recycled

Tire waste is a mounting problem and states have taken action to give consumers options for the proper disposal and recycling of tires.

Many municipalities have tire “amnesty” days where residents can bring a limited number of tires without charge for proper disposal. Additionally, some tire retailers and manufacturers offer take-back programs where customers have the opportunity to return used tires. You can search for local retailers and drop-off points in your area using Earth911’s recycling locator.

Rubber is difficult to recycle due to the procedure known as “vulcanization,” which it undergoes to attain its springy, flexible nature. Vulcanization is a curing process that involves adding sulfur to rubber, which creates stronger bonds between the rubber polymers. Due to the vulcanization method, tires are difficult to melt for reuse and are therefore typically broken down by a mechanical process.

Initially, whole tires are shred into strips using rugged machines. The shredded material is then placed in grinding machines that use rotors to further shred the material and remove the steel fibers from the tire. Some processors also use powerful magnets to further draw metal from the rubber.

Once the bulk of the steel is removed, the strips are placed into granulators. Depending on the consistency desired by the end user of the shredded tires, the rubber can be milled into assorted sizes of granules that are useful in a number of industries.

While less common, some tires are recycled through a freezing process using liquid nitrogen. After being frozen, the tires are crushed and then milled in a similar process described above.

Another process that is still being researched is “pyrolysis.” Pyrolysis involves heating materials in an oxygen-free environment, decomposing the tire into oil, gases and char. Pyrolysis has yet to be proven to be commercially viable in the U.S., but is an intriguing future prospect.