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Tire Recovery

Introduction

Americans generate 250 million scrap tires each year—one for every citizen. In 1995, 69% of all tires generated were recovered; a 26% increase from 1994. Fewer tires were sent to landfills or stockpiled in 1995 largely resulting from a growing technology known as Tire Derived Fuel (TDF), which burns shredded tires for energy that can be used by electric utilities, pulp and paper mills, and cement kilns. Increased demand for scrap tires provides a promising outlook for tire reuse and recovery, which will help decrease the number of tires illegally dumped and stockpiled.
 

The Challenge

Despite significant strides in recovery rates, tires are still stockpiled or illegally dumped. Tire piles can create many problems. (Disease-carrying rodents and mosquitoes thrive in the standing water of tire piles and use them as breeding sites, creating a public health hazard.) Tire piles are also a hazard because, if set afire, they are difficult to extinguish and under uncontrolled conditions, create air, ground and water pollution.

In response to the health and environmental hazards associated with stockpiled and illegally dumped tires, 47 states have passed scrap tire regulations mandating the proper management of tires. Many states also charge disposal fees of $1-$3 when replacement tires are purchased to eliminate stockpiles and help fund alternative management methods. Since tires often rise to the surface of a landfill due to the resiliency of the rubber, many states require tires to be shredded or split before they are landfilled. Though they take up less space when shredded, tires can be difficult and expensive to shred due to their steel belts and tough design. Some states completely ban tires from their landfills to encourage other uses.
 
 
 

Tire Derived Fuel

Scrap tires have historically been a big challenge for solid waste management. Tire-Derived Fuel (TDF), however, is playing a large role in meeting the challenge. In 1995, 130 million tires were burned for energy according to the Scrap Tire Management Council (STMC). As a petroleum by-product, tires have an energy value nearly equal to oil, and 25% higher than coal. Recent reports have shown that TDF is comparable to fossil fuel and, in many cases, burns cleaner and cheaper than coal. It also has a higher heating value.

Industry is seeing the opportunities in TDF and the market for scrap tires continues to expand. Shredded tires are used as a fuel in dedicated tire-to-energy facilities, in pulp and paper mills, and in cement kilns. Today, approximately 38 cement kilns burn tire-derived fuel; only 2 cement kilns used TDF in 1990. The high temperature inside a cement kiln provides for the complete combustion of tires, without black smoke and odors that are normally associated with uncontrolled burning tires, according to the STMC.

Tire Derived Fuel Markets

80 million consumed as fuel 38 cement kilns burn TDF (only 2 in 1990)
14 kilns are testing
15 paper mills burn TDF
16 industrial plants including utilities burn TDF
2 whole-tires-to-energy plants
Other areas of research and development include pyrolysis and gasification. The goal of both technologies is to convert tires into fuel gas and oil with a marketable residual char (carbon black) and steel. Research has been conducted in this area since 1965, but there has been no successful commercial application for the technology to date. While the char is not as suitable in the tire industry, it is suitable as a solid powder fuel.
 
 
 

Reuse of Tires

Scrap tires are extending their lives through a variety of uses. Product research and business development will continue to increase the number of scrap tires diverted from the waste stream. According to the Recycled Products Guide newsletter, a company in North Carolina takes worn racing tires and makes everything from doormats to jewelry. Another in Washington state has designed products made from used tires to maintain hiking trails and reduce soil erosion. Its products are being used in a number of national forests around the nation.

There are many other examples of practical, effective uses for discarded tires, including:

Highway and road applications is another use that states are using to manage scrap tires. "Rubber asphalt" is made by blending crumb rubber with asphalt, with the rubber comprising up to 25% of the mix. California, Arizona, and Florida use crumb rubber in many of their road projects.
 
 
 

Conclusion

As markets for scrap tires continue to expand across the country, communities and tire retailers will find it easier to manage tires generated in their community. Innovative ideas for the reuse of scrap tires indicate the potential for diverting an increasing number of tires from the waste stream and recovering the millions of illegally dumped and stockpiled tires.

References

"Recycled Products Guide 'Reporter'," 1995
The Goodyear Tire & Rubber Company
The Scrap Tire Management Council
"Scrap Tire Users Directory," Scrap Tire Management Council, 1995
"Burning Tires for Fuel and Tire Pyrolysis: Air Implications," EPA - 450/3-91-024, 1991
"Scrap Tires: A Resource and Technology Evaluation of Tire Pyrolysis and Other Selected Alternate Technologies," EGG-2241, U.S. Dept. of Energy, 1983

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