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volume 10 issue 3 .
human interest
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What happens after a tire retires from the road?

After years of faithful service, when the rubber from its last retread wears away, it's time to retire the tire. But what happens after it's hauled away?

Decades ago, most tires were 'put out to pasture,' abandoned in fields and landfills.

In 1990, the Rubber Manufacturers Association (RMA) stepped in to help organize and support scrap tire markets.  Fifteen years later, new ways to recycle and re-use scrap tires are still being developed.

To learn more about tire "retirement," we spoke with John Sherrin, environmental manager for BFS Retail & Commercial Operations. In his spare time, he serves as chairman of the RMA Scrap Tire Management committee.




The cement industry burns about 53 million whole scrap tires as fuel in kilns each year.



Gyms with workout equipment need a durable surface that can withstand heavy loads per square inch. Plus rubber flooring is easier to walk on and is much less painful to knees and other sensitive joints.
(Photo compliments of Dinoflex
Manufacturing LTD)

Recycled truck and bus tires are used as tough, durable fenders on tugs, barges and other marine workboats. Recycled tires offer a "softer bounce" than solid rubber for faster and safer ship docking.
(Photo courtesy of Schuyler Rubber
Company, Inc.)



In Memphis, Tennessee, the Allen Fossil electric plant supplements coal burning with tire-derived fuel. The plant has burned almost 112,000 tons of tires in the past seven years.

 


How many tires are recycled each year?

 "In 1990, 223 million tires were used, but only 24.5 million were recycled. In 2003, Americans used 290 million tires and 233 million were recycled.  That means the industry is re-using four out of five tires scrapped in the U.S."

How are recycled tires being used?

"Dozens and dozens of ways, from tire-derived fuel to exercise mats.  It all depends on the local market."

How so?

"Hauling tires is not a profitable business. Dealers and manufacturers pay someone to take the tires away, but it's too expensive to haul the tires more than 250 to 300 miles.

"The number of facilities - as well as the processing capabilities of those facilities - determine how active and dynamic that market is for recycled tires."

What do you mean by processing capabilities?

"A majority of tires have to be processed in order to be recycled. Some facilities coarsely shred the tire - that's considered a low-quality product. Others grind the tires over and over again so the end result is a fine powder, similar in consistency to sugar."

Are there any uses for whole tires?

"The agriculture industry cuts OTR tires in half and uses them for feeding stations.  But the most interesting use is as a fuel source.

"Almost 45% of all recycled tires are used whole as tire-derived fuel in cement kilns and pulp and paper mills. It's a cleaner and cheaper alternative to coal."

Is burning tires more efficient than coal?

"A passenger car tire burns hotter - in fact, it's equivalent to 20 to 25 pounds of coal.  But remember the industry has a seemingly never-ending supply of scrap tires, while coal is a natural resource that has to be mined."

Any other industries use whole tires?

"Electric arc furnaces use whole tires to manufacture steel. Essentially the whole tire is used as the raw material to manufacture the steel. The carbon black replaces the coke and the steel cord is melted to make new steel."

Do electric arc furnaces consume a lot of tires?

"Not yet. The process was invented only two years ago, so it uses a very small percentage of scrap tires. Considering the global demand for steel, this will be a very interesting industry to watch in the next few years."

You mentioned the grinding process earlier. What are the uses for a low-quality mix?

"The low-quality product has gone through the shredder once. It's in large chunks and there are wires hanging out of it.

"This type of shred goes to the landfill."

Isn't this in conflict with keeping scrap tires out of landfills?

"Today, landfills are managed smarter both in usage and how the land interacts with the environment.

"One thing any healthy eco-system needs is proper drainage. The large chunks of recycled tires are layered to form channels so the water has a chance to get out.

"And that's another benefit to scrap rubber - it stays where it's put so water can drain properly on a long-term basis."

Is that beneficial for other uses?

"Civil engineers use scrap rubber to prevent erosion and landslides because it doesn't compact and it stays where it's put.

"Scrap rubber is also becoming popular as garden mulch for those same reasons. Wood chip mulch floats on puddles and by the next spring, it's gone and has to be put down again. Not so with rubber garden mulch."

But isn't it expensive?

"Rubber mulch has been shredded several times so the end product is about one inch square. And if you look closely at the mulch, you won't find any wires - the steel cord has been removed. This level of processing yields a higher quality product, which accounts for its cost."

Is this the same type of product that's used for playgrounds?

"Yes, sometimes it's a little smaller, and the newer playground materials are pieced together to look like a giant mat. But the important thing is there are absolutely no wires that could poke a child.

"Rubber has always been an ideal product for cushioning. Rubber mulch - shredded to about 3/4 inch - is used for equestrian arenas, athletic surfaces, indoor rock-climbing areas and running tracks.

"And speaking of cushioning, scrap rubber is used in a lot of flooring products."

How small is the grind?

"The scrap is shredded into 1/4-inch chunks. Most consumers never know the floor tiles are made from scrap rubber tires because it's underneath the decorative surface.

"Not only is rubber flooring easier to walk on, it absorbs noise. It's terrific in condominiums and apartments because the people aren't bothered by footfalls and other noises from the occupants who live above."

What kinds of products are made from finely ground rubber?

"Most consumer products are made from this expensive end product. And because the rubber has the consistency of sugar, it offers manufacturers the most flexibility in their design. That's why you can find the biggest variety in this segment. There's everything from flip-flops, mouse pads and pet toys to marine bumpers and automotive gaskets. 

"By the way, this segment uses the most scrap truck tires."

At this point, why does it matter where the original rubber comes from?

"Passenger car and light truck shredded scrap has white flecks in the rubber mixture - from the white lettering and white sidewalls on the tires.

"Truck tires are all black, so the rubber mixture is all black. That's important if appearance is part of the product's appeal."

Any predictions for the future?

"The RMA predicts scrap tire markets for playgrounds, sports and athletic surfaces, as well as civil engineering, will continue to grow. And, not surprising, more industries will be examining how they can use tire-derived fuel as an energy source."

 

 

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