The process of vulcanizing rubber was discovered by Charles Goodyear (yes, you read that right) in 1839, and the development of rubber tires followed not long after (Source: Continental Truck). From there, it didn’t take long for worn-out tires to start piling up, and finding good ways to recycle them has been a pressing concern for over a century, though initially it was because rubber was so expensive that throwing it away was like throwing away silver (Source: The Balance).

As soon as synthetic rubber hit the market a few years before World War I, production skyrocketed and recycling dropped off everyone’s priority list, which led to enormous stockpiles of end-of-life tires, both in landfills and out.

Now, we might think of tires as being harmless, if unsightly—after all, we use old tires to make swings for children, and rubber is an excellent insulator against electricity, right? While this is true, it doesn’t mean they’re flame-proof. Quite the opposite, in fact. According to John T. MacDermid, CEO and owner of the MacDermid Group, which worked hard to find better ways to recycle tires in the early ‘80s, each tire contains two gallons of oil, which is why large piles of abandoned tires present such a serious fire hazard (Source: New York Times). And, as we’ve discussed in previous entries, abandoned tires can also provide prime breeding grounds for disease-carrying mosquitoes.

After decades of attempts at recycling tires to minimize the chances for tire fires and the spreading of disease, a new invention in the early ‘70s finally introduced a far more efficient way to recycle them: tire shredding.

The Evolution of Tire Shredders

In February of 1970, Stanley J. Burwell of Maryland filed a patent for his “Apparatus for Disintegrating Tires and the Like” with the U.S. Patent Office (Source: US Patent 3,658,267). The object of his invention was to efficiently reduce end-of-life tires to powdered form without causing pollution, and it did so via a cylindrical chamber which would lower tires one at a time onto rotating cutters. The small pieces would then be removed by a vacuum system. While possibly the first tire shredding machine invented, it certainly wasn’t the most efficient or versatile, and no future versions would remotely resemble it.

Seven months later, Raymond W. Willette of Minnesota filed a very different patent for a machine that would grip individual tires and rotate them while a stationary cutting apparatus shredded the rubber, with a mechanism for feeding tires into it (Source: US Patent 3,693,894). Willette, like Burwell, saw the need for efficient tire recycling after burning them to dispose of them was banned due to pollution. His machine, which he considered a new and unique invention, was modeled somewhat after tire buffers, taking no inspiration from Burwell’s design. It could be adjusted for different sizes of tires, but couldn’t process high volumes of tires quickly and couldn’t handle tires with metallic bead.

Less than two years later, Clarence A. Krigbaum of Texas came up with a much more effective style of tire shredder, involving counter-rotating bladed discs that would pull tires into them and cut them into pieces, then drop them onto a second series of counter-rotating discs that would cut the rubber into even smaller pieces (Source: US Patent 3,817,463). This style more closely resembles modern tire shredders and is capable of handling a greater volume of tires.

Tire shredder designs continued to increase in both complexity and effectiveness from there, with John and Stanley Ehrlich of Oregon patenting a noteworthy evolution of the machine in ’79, specifically designed to improve upon Krigbaum’s version and others that followed, including an earlier design of their own, which used oscillating knives to shred the tires into diamond-shaped pieces (Source: US Patent 4,134,556). The Ehrlichs’ second tire shredder patent added removable teeth to the cutting discs to make maintenance much easier. It also incorporated a screening drum that would allow small pieces to fall onto a discharge conveyor while large pieces cycled back through the counter-rotating blades. In order to keep the machine from overloading, it was designed to alternate between shredding whole tires and re-shredding the larger pieces.

Michael Rouse and Robert Thelon of Oregon realized that you can’t always bring the tires to the shredder. Sometimes you need to bring the shredder to the tires, so they patented a portable tire shredder in ’83 (Source: US Patent 4,374,573). Their tire shredder mounted onto a gooseneck trailer, but portability wasn’t the only improvement. They noted and corrected several flaws with earlier designs, such as inconsistent feeding and alignment mechanisms that required a great deal of manual labor and risk of injury to compensate for and the shredders not being strong enough to handle larger, thicker tires with metallic bead. Their design wasn’t the first portable one, but it was the first that didn’t simply drop tire shreds on the ground.

Since the ‘80s, inventors have continued to streamline the machines, increasing efficiency and durability or coming up with more elaborate portable systems, but tire shredders have largely replicated the general mechanisms of the Ehrlichs’ and Rouse and Thelon’s designs up until the present.

Modern Tire Recycling with EcoGreen

Recycling tires is still a serious concern today—possibly even more so than in previous decades, with one billion tires reaching the end of their usefulness worldwide per year and as many as four billion scrap tires sitting in landfills and illegal stockpiles (Source: The Balance). Over the years, more and more people own cars, and more and more families own multiple cars. Add to that the growth of commuting, and that’s a lot of tires being worn through each year.

Tire shredding vastly increases the possibilities for recycling tires, and EcoGreen’s tire shredders are the best in the industry. We can answer all your questions about tire shredding, and we invite you to learn more by contacting our experts today.