The title of this post is taken from a question we received about the source of recycled rubber used for a parking-bumper and speed-bump manufacturer. It motivated me to do some digging to get a better understanding of the scrap tire industry. As it turns out, it's actually kind of fascinating. The following is unverified single-pass research, and any thoughts, additions, or corrections are welcome.
The Rubber Manufacturers Association (RMA) provides a bunch of info on domestic scrap tires in a 2006 report titled Scrap Tire Markets in the United States. According to their data, in 2005 almost seven-eighths of domestic scrap tires were finding their way to end-use markets — about 259 million tires. Nearly seven-eighths, or 87%, is an exceptionally respectable rate of reuse. (The EPA estimated an 80.4% end-use market rate in 2003, two years earlier.) For comparison, a reclamation fact sheet from the The Aluminum Association shows that just 52% of aluminum cans were recycled in 2005 (down from a 1997 high of 66.5%).
The RMA estimate appears to be based on U.S.-manufactured tires only, however. Their report says that "about 299 million tires were generated in the U.S. in 2005" — seven-eighths of that number is right in the neighborhood of the number of scrap tires generated. It's not clear, however, that the scrap tire number excludes tires of non-domestic origin, which would change the figure some. A 2006 article in the Toledo Blade titled U.S. tire maker betting on China reported, "Nearly 102 million passenger tires were imported into the United States last year, estimates the Rubber Manufacturers Association. And although $7.7 billion worth of rubber tires and tubes were imported into the United States last year, only $2.8 billion worth were exported, according to the U.S. Census Bureau." It's a little frustrating that they switched from units to dollars in mid-stream, but we can derive that in 2005 we imported about 36% more new tires than we exported, and it appears that something over 25% of the tires sold in the U.S. came from somewhere else. (In 2005, anyway. In 2006, Tire Business magazine ran an article titled Off-shore tire influx deepens amid slumping domestic production that reported, "Every other replacement market passenger tire sold in the U.S. today is made outside the U.S. Three out of five replacement light truck tires sold in the U.S. are made elsewhere. Two out of three replacement medium truck tires sold in the U.S. are made outside the U.S.")
One more little complication: In addition to not counting "retreadable casings" as scrap tires, the RMA also doesn't count "used tires" that are either resold in the U.S. or — more significantly — exported for sale in other countries. RMA notes that "there is a significant likelihood that more tires are exported than have been reported." The EPA chimes in, "Many scrap tires are exported to foreign countries to be reused as retreads, especially in countries with growing populations of automobile drivers such as Japan and Mexico. According to Mexico's National Association of Tire Distributors, as many as 20% of tires sold in Mexico are imported as used tires from the US and then retreaded for reuse. The downside of exporting scrap tires is that the receiving countries may end up with a disproportionate amount of tires, in addition to their own internally-generated scrap tires."
An argument seems to be shaping up that scrap tires, like just about every other complex manufactured thing, generally aren't very local to anywhere. The constituent materials of tires include natural rubber (a.k.a. polyisoprene — 95% of which comes from Asia... and tires and tubes account for over half of total global use); synthetic rubbers such as styrene-butadiene co-polymer (SBR), polybutadiene, and halobutyl (crude oil is the principal raw material of synthetic rubber — RMA indicates that it takes about five gallons of oil to make a tire, and two more for the energy of the manufacturing process... which accounts only for the onsite manufacturing part of the lifecycle); carbon black (a nanomaterial used for coloration and reinforcement, it's generally produced by the incomplete combustion of 'sour' natural gas); and smaller amounts of other reinforcing, cross-linking, accelerating, activating, and antioxidant compounds and materials.
But it remains that reducing the transportation energy along any part of the lifecycle of tires is to be applauded. And even when mitigating factors like how things are counted or not counted are considered, the reuse ratio is still nothing short of inspiring.
So to what markets are these scrap tires going? Mostly, they're getting burned at cement factories. According to the RMA report, 52% were burned as fuel for cement kilns, pulp and paper mills, and industrial and utility boilers. 16% were used for civil engineering and construction purposes — such as using shreds in road projects, septic fields, and landfill construction (which is evidently different than putting shredded tires in a landfill). Ground-rubber applications including playground and sport surfacing, rubber-modified asphalt, and feedstock for new products had a 12% share... which, unfortunately, is still catching up with the 14% "land disposed" slice of the scrap tire pie. (Only two years earlier, however, 25% were being landfilled.)
This brings me to an uplifting note to close on: tire dumps — that is, "stockpiles" — are being rapidly and significantly depleted... over 80% since 1990. Which sets the imagination looking toward the future, when demand for dead tires exceeds supply.
One last tidbit: Waste reduction fast facts: Tires and rubber
We installed these in our new house and they work great. Excellent product.
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