Because they’re really hard to recycle. The whole point of a tire is to be *really* durable. They’re full of fibers and steel so they’re very hard to cut up. The rubber is molded around the fibers so they’re almost impossible to separate. And the base components (rubber, steel, carbon) are incredibly cheap so there’s almost no market value to the materials you’d recover.
The cheapest option is to just leave them in a pile.
Very large tires (trucks) can be retreaded several times and are reused.
Most tires do get recycled, “tire graveyards” are just where they go to wait.
Also, burning tires to dispose of them isn’t really a thing. Yes, tire fires happen sometimes and can be incredibly difficult to extinguish, but it’s a myth perpetuated by the Simpson’s that we just infinitely burn tires instead of recycling them.
Most of your used tires are recycled when you purchase from a large box retailer (Costco, Firestone, Americas Tire/Discount Tire). Hence to scrap recycling fee.
I have been in a few Manufacturing plants at this point in my career and speaking specifically about Bridgestone, the tires that are re-collected are generally made into building materials, roofing products, asphalt and even tires once more.
Early 1900’s, Harvey Firestone, Henry Ford and Thomas Edison were on a ten year road trip titled “The Vagabonds” where they ultimately learned that recycling that Mr. Firestone was producing would lead to paving a roads for not only them but truckers across America.
So how much of an old shredded tyre do you want, and what are you going to pay for it? Come on? There are literally stacks of them there, and people will give them to you for basically nothing.
What are you going to use it for? Playground material? Well I hope you removed all the metal supports, all the gravel, all the things puncturing it, every sharp edge, and ground it all down fine enough to make… what? Some squidgy polluted rubber gravel? How much you gonna pay for that, per square metre? And how much is the liability insurance going to cost for if you mess up and a kid injures themselves on it?
Once rubber is galvanised, it’s undergone a pretty irreversible process. Yes, you can feed a small percentage back into other tyres or rubber items, but you can’t just remould it 100% and off you go again. There are very few materials in the world you can do that for (glass, paper, metal, that’s about it – even clay you have to recycle in small proportions mixed with lots of fresh clay if you want things to hold together).
Whenever you think about recycling, consider what you’re asking: You effectively want someone to take something that’s so worthless that we have to pay to landfill it, we have to PAY people to take it away!, and – by some process – turn it into a product that people will pay money for, and in doing so make a desirable quality product, equal to or superior to its rival products from new material, that costs roughly the same or less as them.
That process will involve chemicals, pollution, heating, pressure, not to mention manpower, collection, stripping, moulding, filtering, purity testing, materials testing (nobody is gonna pay if the new tyres you make just shred apart in ten minutes), product creation and distribution, plus the general costs of doing business (wages, insurance, legal, and a bit of profit). And you need to do it all cheaper than, or about the same price as, new rubber would cost.
This applies not just to rubber but to almost all materials. Very few of them are worth recycling at all, even with subsidies (read: free money to run your business, because it’s unprofitable trying to do so without it).
If you could unbake a cake and get an egg back, if that’s even possible, that egg is going to be inferior quality and far more expensive to obtain – even from a free cake – than just buying a new egg – or even a whole chicken.
Toward the end of manufacturing, the rubber goes through a process called “vulcanization”.
This basically fuses the rubber molecules into one giant tire-shaped molecule. After vulcanization, it’s not as simple as melting the rubber back down, since the rubber no longer melts, which makes it basically impossible to recover the rubber in a usable form.
(Some tires do get ground up and used for track surfaces or playgrounds, but that rubber couldn’t be used in tires again)
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