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Scrap tire recycling can be viewed as a success story as scrap tire stockpiles have steadily declined throughout the past few decades, according to the U.S. Tire Manufacturers Association (USTMA), Washington. The association released its “2017 U.S. Scrap Tire Management Summary” July 18, 2018, which reveals that about 60 million tires are left in stockpiles.

“I would say that scrap tire recycling in this particular report demonstrates a real environmental success story,” John Sheerin, USTMA’s director of end-of-life tire programs, says. “In 1991, over 1 billion scrap tires [were] in stockpiles, now it’s at 60 million. So, it’s a 94 percent decrease—a positive story to tell.”

With fewer scrap tires left in stockpiles, more are being recycled and used by various end markets. According to USTMA’s 2018 report, tire-derived fuel (TDF) continues to be the largest end market for recycled scrap tires. USTMA reports that about 43 percent of scrap tires were recycled for TDF use, while ground rubber serves as the second largest end market (25 percent). The USTMA also reports, however, that 16 percent of scrap tires generated in 2017 were landfilled.

Although TDF serves as the largest end market for scrap tires, TDF demand is steadily declining every year. While many scrap tires are being recycled, Sheerin says USTMA’s 2017 report notes a slight decline in the recycling of tires overall compared with its 2015 report, “predominantly due to a decrease in TDF.”

According to USTMA’s report, the largest end-market decline was in TDF, with 9.7 percent less demand in 2017 compared with 2015. With a decline of 22.7 percent, TDF experienced the most demand loss in the utility boiler sector. Demand from the pulp and paper sector also dropped 18.4 percent.

While TDF demand from the cement kiln sector grew 7 percent, Sheerin says it wasn’t enough to offset the declines experienced overall.

“So, TDF went down, and overall that’s 43 percent of the end market,” he says. “There’s a shift in much of the country where a TDF market might disappear [and] landfilling might increase.”

Doug Carlson, vice president of asphalt products at Liberty Tire Recycling, Pittsburgh, attributes the declines in TDF demand to competition from other fuels, such as natural gas. “There’s a lot of pressure on [the TDF] market now due to inexpensive natural gas,” Carlson says. “Natural gas is very cheap and abundant everywhere. So, it burns much cleaner and has more favorable requirements. It’s easier to burn gas than coal. So, a lot of facilities are switching fuel sources to natural gas, which is putting pressure on TDF.”

Terry Gray, president of T.A.G. Resource Recovery, Houston, adds that pulp and paper mill closures also are having an adverse impact on TDF demand. He says TDF demand is undoubtedly decreasing overall, but he estimates it will continue to remain the largest end market for at least the next five years.

“TDF is still the largest market and will continue [to be] for the foreseeable future,” Gray says. “Nothing else can rise and take its place. But you have declines occurring in two of the three major market segments within [the TDF sector]. I don’t see much that will reverse that.”

With TDF steadily declining as an end market, other end markets for scrap tires may see a boost. Industry experts say they are hopeful to see increased demand for scrap tires in rubber-modified asphalt applications. Also, crumb rubber could serve as a stable, steady-growth market. As TDF demand declines, the industry may see these other segments as more viable end markets for recycled scrap tires, sources say.

Rubber meets the road

Some industry experts have expressed optimism when looking to rubber-modified asphalt as an end market. Neal Frey, vice president of market development at Entech, Middlebury, Indiana, says this end market for scrap tires has potential for growth. “This is an end market with the most potential,” he says. “It could use enormous, enormous volume [of scrap tires].”

Frey says it’s a difficult market to get into—state departments of transportation (DOTs) are still testing the application to gauge its effectiveness. Also, he says some contractors have been resistant to use rubber-modified asphalt because it would require slightly different equipment than traditional asphalt.

However, industry experts overall say this end market could likely grow down the road. Carlson of Liberty Tire says opportunity in this end market has been expanding in several pockets of the U.S.—he says the market is the most developed in Arizona, and it is also growing in states such as California, Massachusetts, New Jersey, New York, Rhode Island and Texas.

“I think this market segment is emerging with great potential,” Carlson says. “The asphalt industry is conservative and slow moving, but as a nation we’re on the cusp of change and moving toward this end-product mixed testing.”

Although some state DOT offices restrict rubber-modified asphalt use, Sheerin says USTMA is working with DOT offices in various states to try to expand their application.

“Rubber asphalt is less prone to rutting [and has] less cracking [and] lower life cycle costs,” Sheerin says. “We’re seeing potential, especially as states review and update their standards, and this becomes more accepted in the construction industry.”

Grounded in crumb rubber

Ground or crumb rubber serves as another alternative end market that may help with declining opportunities in TDF, according to industry experts. Based on USTMA research, it’s also the second largest end market for scrap tires (consuming 25 percent of them).

Gray says this end market is growing, and he thinks it could grow further—provided some “myths” are addressed.

While the use of crumb rubber in sports fields is growing in popularity, the end market has experienced some setbacks because of media reports that athletes who have come in contact with crumb rubber sports fields have developed health issues, including cancer. Gray says many of these claims have come from the Northeast and California.

“There was a newscast about five years ago now where a soccer coach in Washington had a player on her team who got cancer,” Gray says. “They drew the conclusion through anecdotal data that crumb rubber caused cancer. I’m not a toxicologist, but I can read the data, and I don’t see factual basis for [these claims]. It’s an emotional claim I don’t think any technical argument can overcome.”

Aside from some of these claims, Gray adds this end market is generally stable and even growing slightly. But he says the industry needs to clear up the facts with the general public in some regions on crumb rubber’s safety.

“I think we need to continue resolving crumb rubber market issues, getting people to realize they do not represent a risk to our children,” Gray says. “It’s a perception thing. People are going to have to stop listening to the emotional, unfounded cries and look at the data and say this is not an issue and it is safe for our kids.”

Advancing technologies

Industry experts say a handful of technologies for recycling scrap tires are still in the testing stages, such as devulcanization. Yet, some are hopeful about pyrolysis—a way to reprocess scrap tires by breaking down their chemical chains through thermal degradation in the absence of oxygen. Gray says the carbon black end product from pyrolysis is highly valuable—up to 50 cents per pound or more if recovered.

However, he adds that the technology may still need some improvements. “If you can recover it, it’s a great story,” Gray says. “But historically, [pyrolysis] has been a better story than a reality.”

He says this scrap tire processing technology is closer to becoming normalized than others, though.

Sheerin says he thinks the technology could be ready to apply on a broader scale in the U.S. in the near future. “[Pyrolysis] plants are under construction,” he says. “Some plants, we believe, are operating at full scale in North America. As a result, the technology is becoming proven.”

While some variations of the technology experienced difficulties in the past, Sheerin says many of these concerns have been resolved. The only issue, he says, is ensuring commercial viability for pyrolysis processing.

“The most clever pyrolysis companies are finding markets for their product,” Sheerin adds. “Even with relatively low- to midrange prices for oil, some pyrolysis companies are making a go at commercial viability.”

He estimates that by the next USTMA study, pyrolysis could very well be listed as an end market. “The markets we list are consuming more than 1 percent,” Sheerin says. “I would foresee that pyrolysis could consume greater than 1 percent after 2019, and we see [it] as a growing market in the near future.”

The author is managing editor of Recycling Today and can be contacted via email at msmalley@gie.net.