March/April 1991
There’s more than one way to recover scrap tires, and a recent conference reviewed the processes that can help the nation eliminate its used tire stockpiles.
By Ben Warner
Ben Warner is a freelance writer based in Sacramento, Calif.
Scrap tires may be an unusual commodity in the scrap industry, but if just a few of the ideas broached at the recent International Tire Recycling Conference in San Jose, Calif., become fact, the estimated 2 billion to 3 billion scrap tires stockpiled in the United States better look out. Something's coming--and it could be a whole new arm of the scrap business.
Approximately 300 tire dealers and manufacturers, scrap processors, waste management representatives, government officials, and utility executives attended the 2 1/2-day meeting, sponsored by the American Retreaders' Association Inc. (Louisville, Ky.) in late January. The conference presented an equally diverse group of speakers, who discussed how the mountains of scrap tires around the country that attract mosquitoes, arsonists, and outraged citizens are facing legislative, business, and technical attacks.
The result? It's still too early to tell, but it's clear that the more than 170 million tires currently discarded in U.S. landfills, illegal dumps, and unsightly and hazardous stockpiles every year can be transformed into useful products, perhaps at a profit.
Legislating Tire Recycling
Rep. Esteban Torres (D-Calif.), author of the Tire Recycling Incentives Act, legislation introduced (but not passed) during the last session of Congress, presented the keynote address. Torres's bill, which will likely be reintroduced this year, would establish a tire recycling credit system.
Under the system, tire makers and importers would have to use scrap tires in the manufacture of a certain percentage of new tires or buy credits from others. One credit would be earned for every tire recycled into a tire product, for every two tires recovered for fuel, and for every four tires shredded for disposal. Torres said he believes the credits would become marketable items and produce extra income for tire recyclers. Responding to a question, he estimated that the bill's effects might add $1 to the total cost of a single tire.
Edward J. Wagner, Tire Technical Services (Louisville, Ky.), provided a statistical review of the tire industry. He projected that by 2000 there will be a 20- to 30-percent increase in the more than 39 million cars traveling the world's streets and highways, with a similar increase in trucks. This translates to an astronomical total of approximately 860 million tires. Since low-cost radials have substantially decreased passenger car retreading (it's still a common practice for tires on trucks, aircraft, and miscellaneous vehicles), he noted, the 2 billion to 3 billion scrap tires now stockpiled will also grow by at least 20 percent in the next 10 years.
Processing Guidelines Offered
Michael H. Blumenthal, executive director of the Scrap Tire Management Council (Washington, D.C.), offered suggestions on scrap tire storage and safety measures. To prevent used tire piles from becoming health hazards due to stagnant water and mosquito infestation, he said, tires should be shredded or cut to prevent them from catching and holding rainwater. If shredding is not possible, he suggested, stack the tires and cover them to prevent rainwater from filling them. He advised against spraying tire piles with insect repellent because mosquitoes usually breed at the bottom of piles, where the spray cannot reach.
Reviewing fire prevention methods, Blumenthal pointed out that while most tire stockpile fires are set by arsonists, this threat can be reduced by enclosing the tire area inside a 10-foot industrial fence. If a fire does start, it is best to extinguish it with an inert material such as soil or sand, he said. If water is used, pay attention to the runoff because it may contain oil that could contaminate adjacent soil and water. To keep tire from spreading, processors should create fire-break lanes between tire piles, with about 50 to 75 feet between large stacks. Blumenthal also advised limiting scrap tire piles to no larger than 100 feet wide by 100 feet long by 20 feet tall.
Equipment manufacturers offered other processing suggestions:
Scrap tire processors must work closely with their end users to make certain that specifications are thoroughly understood by both parties in advance of processing, said Charles G. Astafan, Carthage Machine Co. (Carthage, N.Y.). In particular, he pointed out, processors should clarify the size of the particles needed, whether the wire and fiber in the tires is to be removed, and what variation from specification is acceptable to the customer. It would also be helpful, Astafan suggested, for the processor to ascertain how and for what purpose the customer will use the material.
Donald G. Morgan, Applied Magnetic Systems (Milwaukee), looked at the use of permanent and electromagnets to separate bead wire and steel belt material from scrap tires. Processors can choose from many options, including magnetic pulleys, suspended magnets, magnetic drums, and plate and grate magnets, depending on their needs. Rare earth magnets are particularly good at attracting material with low magnetic traits, Morgan said. Such magnetic equipment typically costs from $3,000 up, he noted, which represents a fraction of the total cost of a processing system.
Matthew Mayo, Triple/S Dynamics Inc. (Dallas), described the primary, intermediate, and final processing steps involved in producing crumb rubber, which is used m rubber-modified asphalt and applications requiring fine mesh material from which all fiber and metal have been removed. Processing systems can produce everything from basic shredded tire material to ground rubber to an almost powderlike material. Each processor's system needs will vary, depending on its end markets, Mayo said.
Examining Asphalt Applications
The conference included a three-person panel discussion titled "The Use of Rubber in Pavement Surfaces," which looked at both public- and private-sector initiatives. On the public side, 35 states reportedly have enacted legislation regulating scrap tire disposal, while another 7 states are considering similar programs. Furthermore, the Environmental Protection Agency is currently reviewing a federal scrap tire management study, panelists noted.
Robert Eaton, U.S. Army Corps of Engineers, cold regions research and engineering laboratory (Hanover, N.H.), described his facility's development of a new compound called chunk rubber asphalt concrete (CRAC), which shows promise in road uses, particularly on structures such as bridges and overpasses that are subject to icing. Early tests indicate that not only are CRAC's costs comparable with conventional asphalt but it can last up to twice as long as ordinary asphalt.
Smaller rubber particles are employed in rubber-modified asphalt concrete, now being used in a demonstration project of the Oregon Department of Environmental Quality. Although the project could take several years to complete, Deanna Mueller-Crispin reported that preliminary results indicate that early contact and coordination with various public and private agencies with an interest in such projects may be advantageous to processors. She estimated that rubberized asphalt could cost $10 to $20 more per ton than conventional material and that some changes would be required in the paving contractor's procedures regarding mixing, application, and compaction.
Michael Rouse, president of Rouse Industries (Vicksburg, Miss.), a scrap rubber processing firm, asserted that paving could become the major use of rubber from scrap tires. Such use represents a middle-of-the-road use between burning used tires for energy, which recovers only 10 percent of a tire's original content value, he said, and using scrap rubber in retreads or new tires, which uses up to 95 percent of the material's value.
Rouse said there is currently potential to use 132 million to 160 million pounds of scrap rubber annually (8 million to 10 million tires) in such applications, with the volume possibly jumping to 750 million to 950 million pounds by 2000. In fact, he claimed, if the nation's stockpile of 2 billion to 3 billion scrap tires were used exclusively in road paving, it would be cleaned out in only eight years.
The benefits of rubberized asphalt include improved roadway elasticity, noise reduction, longer life, improved traction and deicing characteristics, and, possibly, lower cost, Rouse said.
Other Markets Offer Promise
Fernley G. Smith, Midwest Elastomer (Wapakoneta, Ohio), and other speakers detailed other prospective and actual uses of scrap rubber. Smith agreed that road paving is probably the most promising use, but his company has found that tire manufacturers can use a small but significant percentage of scrap rubber in new tires. He cited field tests validating the performance and safety of new tires containing scrap rubber and said there is enough of a cost benefit to manufacturers to encourage them to use the recovered material. Smith estimated that 185 million to 375 million pounds of scrap rubber from 15 million to 30 million scrap tires could be used annually in new tire production.
C.J.H. Houtackers, Envicon B.V. (Roemond, Netherlands), discussed his firm's scrap rubber processing plant, which furnishes processed scrap rubber as foundation material for artificial turf, carpet backing, insulation, floor tile, piping, and other molded rubber products. The company also produces a mixture of polymers and ground rubber for a variety of applications. Houtackers said that the "tipping" fees his company charges scrap tire suppliers have helped to make his operation profitable within four years. The company's products sell for half the price of new materials, he claimed, and he has had no problem securing a steady supply of scrap tires.
Recovering Fuel and Energy
The conference's final session looked at various approaches to burning tires to produce energy or for use as fuel for specific industries. The Scrap Tire Management Council, in a study distributed at the conference, asserts that burning scrap tires as fuel is environmentally acceptable, economically feasible, and capable of reducing a significant volume of the nation's scrap tire stockpiles.
Two officials from California's Integrated Waste Management Board discussed the state's tire recovery efforts. Ronald McLaughlin, acting chief of the research branch, reviewed the state's tire recycling act, which regulates scrap tire storage and supports studies to evaluate the benefits of using scrap tires as supplemental fuel. The act is funded in part by a 25-cent-per-tire disposal charge. The state's goal is to reduce its scrap tire backlog--estimated at 100 million tires--by 25 percent by 1995.
Robert Boughton, with the board's advanced technologies staff, described the use of scrap tires as supplemental fuel for cement kilns. He pointed out that three such facilities in California use tires for 10 to 15 percent of their fuel supply. Scrap tires are less expensive than coal or oil, partially due to lower Deportation costs, he said. In addition, he noted, emissions seem manageable and there are no other waste disposal requirements since the residual ash is incorporated into the final cement product. The cement kiln operators have found the energy content of scrap tires to be higher than the equivalent amount of coal, he said. Two of the plants use shredded tires, while the third consumes both whole tires and chips.
Currently, about 6 million scrap tires are burned for energy or as supplemental fuel in California, out of an estimated 30 million discards each year, Boughton said. He asserted that expanding the use of scrap tires for fuel could help the state recover more of its yearly scrap tire volume and help buy time while other processes are implemented to attack its stockpile.
The burning of scrap tires in power-generating facilities was also considered at a one-day conference, hosted by the Electric Power Research Institute (Palo Alto, Calif.), just prior to the tire conference. Representatives from state agencies, private and public power utilities, and waste disposal firms and electric-power-generating specialists reviewed a wide range of field tests, research programs, and design concepts for supplemental fuel and energy production facilities using scrap tires.
ISRI Assembles Scrap Tire Group
In response to increasing scrap processor interest in “nontraditional” scrap commodities, the Institute of Scrap Recycling Industries (ISRI) (Washington, D.C.) has formed an ad hoc tire/rubber committee to examine issues related to recycling scrap tires.
The committee, chaired by Barry Shapiro, National Metals Co. (Phoenix), held its first meeting in December in New York City. A follow-up meeting is scheduled to take place in conjunction with the association’s convention at the Mirage in Las Vegas. It will be held on March 20, 2-3:30 p.m., in the Trinidad room.•
There’s more than one way to recover scrap tires, and a recent conference reviewed the processes that can help the nation eliminate its used tire stockpiles.