Funding Innovative Uses For Scrap Tires

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Courtesy of BioCycle Magazine

Many States are cleaning up their stockpiles of scrap tires, but more roll in every day. According to the industry, each person in the United States generates one used tire annually. A number of states like North Carolina and Illinois are providing grants to stimulate markets for products made from scrap tire rubber, while states like Texas and New York are developing new civil engineering applications for the material.

CART WHEELS IN NORTH CAROLINA

The North Carolina Division of Waste Management offers grants to companies manufacturing products such as fuel, tires, mats, auto parts, gaskets and flooring material from scrap tires. Funding comes from a disposal tax of one to two percent, depending on the size of the tires, which is collected when tires are purchased. The grant program began last year, using funds originally slated to clean up nuisance tire sites. Forty percent of the disposal taxes collected now can be used to promote scrap tire market development.

Three grants were awarded last year. Roll-Tech Inc. in Hickory, a subsidiary of Roll-Gom SA of France, received a grant of $102,420 to double its capacity to manufacture solid rubber wheels made from 100 percent recycled crumb rubber. Continental General Tire Co. in Charlotte obtained $380,000 to develop technology to make new automobile tires with increased recycled crumb rubber content. International Paper of Riegelwood, North Carolina secured a grant of $500,000 to purchase metering equipment that determines the allowable percentage of tire chips that can be burned for tire derived fuel (TDF).

Roll-Gom is the largest manufacturer of recycled rubber products in Europe, according to the company. In 1996, it founded Roll-Tech as a distributor of its products and manufacturer of recycled rubber wheels and castors for industrial applications, including carts and hand trucks. Many of the wheels are used for garbage containers and refuse carts by the U.S. operations of Roll-Gom’s European customers. Now employing about 40 workers, Roll-Tech already had a secure client base when it began and could take its products straight to market.

The company used almost one million auto and truck tires in 1998 in manufacturing three million wheels. Granular rubber sized between 12-inch to 20-inch mesh is purchased from a tire processor. The rubber is mixed with bonding agents and chemical accelerators. A press molds the material under high pressure into wheels.

Six to 16 inches in diameter, the wheels are designed for carts sized up to 95 gallons, carrying weights ranging from 250 to 600 lbs/wheel. “These will last until they are destroyed,” says Patrice Bertrand, operations manager for Roll-Tech. “For roll-off containers and carts, these perform better than natural rubber — they have more hardness.” The wheels cost up to $6/each, but the price drops as the volume of an order increases.

The state grant was used to construct 32 tire molds. “We have a plan to make wheels from six to 12 inches for the materials handling industry,” adds Bertrand. “We’re already selling those, but they’re imported from our parent company. We would like to bring production here for American customers.”

RUNNING TRACKS IN ILLINOIS

For the past three years, the Illinois Department of Commerce and Community Affairs has been providing grants to nonprofit organizations to help build running tracks containing scrap rubber. The grants pay 50 percent of the cost of materials and labor. Ed Hosey, the department’s energy and natural resources specialist, says almost all of the tracks have been installed at public and private high schools, and the remainder at colleges, universities and middle schools. So far, 135 tracks have been funded through the program, although not all have been built yet. The Department awarded $2,155,000 in grants in FY 1997, $772,780 in FY 1998 and to date, $875,380 in 1999.

Different types of running tracks use various types of rubber. “Tracks that have a latex binder use buffings rubber,” Hosey explains. “Buffings are the rubber that is ground off from the treads of old tires by tire retread shops. When polyurethane is the binder, granulated tire rubber is used.” The tracks generally have a cinder or gravel sub-base on which an asphalt base is laid. The asphalt base is then covered with the running surface, which is made from either used tires or EDPM rubber (not from tires). Buffings can be used as the layer between the asphalt and EDPM.

The nonprofits select a company to install the track. “Any company is acceptable as long as it is willing to follow the guidelines of the program, which include using tire rubber generated in Illinois,” notes Hosey. Eleven companies from around the U.S. have laid down tracks in Illinois through the grant program, but 75 to 80 percent of the installations are being done by four companies. One is RDF Inc. of El Dorado, Illinois, which has provided buffings for more than 20 of the running tracks. RDF sells buffings for a variety of applications, including horse arena surfaces, floor mats, dock bumpers, hoses and safety tiles for gymnasiums. Last year, the company processed 6,500 tons of recycled tire rubber.
 
 For running tracks, RDF collects the buffings and sifts them through Rotex screens to remove any impurities. “Retread shops aren’t hospitals, so when the buffings are scooped up from a shop’s floor with a Bobcat, other items like cigarette butts can get mixed in,” says Jim Tasso, RDF’s sales and marketing manager. The rubber then is ground to one-quarter-inch particles with Cumberland grinders. It is packaged in 50-lb. triple-lined bags to keep out moisture and delivered in pallets containing 40 bags.

The vast majority of the state’s scrap tires are burned as TDF, Hosey notes, but the running track program has utilized a significant amount. For the tracks, contractors used 1,342 tons of scrap rubber in FY 1997, 535 tons in FY 1998 and for the first 28 tracks in FY 1999, 648 tons.

TEXAS AND NEW YORK DOT PROJECTS

Texas’ scrap tire management program ended in December, 1997. The state no longer charges a fee on scrap tires, but it is still promoting new uses for them. The Texas Department of Transportation (DOT) has designated 1999 as the Year of Recycled Roadway Materials. DOT features a different material each month and tire rubber’s turn will be in December. “We have chosen materials that are generally available throughout the state in high volumes and that have shown a potential for use as roadway materials, such as crushed concrete, glass and tire rubber,” notes Rebecca Davio of the DOT. Each month, the DOT is distributing an information packet about the featured material to road construction contractors and generators of recycled roadway materials. Included are a list of the DOT’s specifications for the material, summaries of research, case studies and sources. Over the past five years, the DOT has spent $73.6 million on asphalt products containing crumb rubber such as asphalt crack sealers, including $18.4 million in the last fiscal year, notes Davio.

Recently, the Texas DOT used roughly 2,500 tons of scrap tires to make a “tire chip burrito” as fill for a bridge embankment in El Paso. Two sizes of shreds were used — 12-inch minus with a single pass through the cutting blades, and three-inch minus with multiple passes. The tire chips compacted to six inches thick and then wrapped in a geotextile fabric. A dozen feet of dirt were piled on top.

For comparison, about 2,000 tons of scrap tires were mixed with an equal proportion of soil for another overpass area, while soil alone was used at a third site. Various equipment was placed at the two tire chip areas to measure temperature, vertical and horizontal displacement, air flow and leachate. Conditions will be monitored by the University of Texas-El Paso for the next three years to assess performance and hazards such as tire chip fires and groundwater contamination.

Bids are being processed for a similar project in Binghamton, New York, where shreds from 450,000 tires will be used as embankment fill for a highway off-ramp. Four different sizes of chips will be used, with a maximum size of 12 inches. Compaction will be accomplished by at least eight passes of a smooth steel roller.

After laying down a thin strip of geotextile fabric, the New York State DOT will place the tire chips in a section about 200 meters long, compacting them to a maximum height of three meters. To complete the fill, the tire shreds will be covered with 1.5 meters of soil. The layer will be topped off temporarily with another 1.25 to 2.5 meters of soil to eliminate long-term settlements. After an estimated three months, when a measurement tool indicates the tire shreds have settled, the extra soil will be removed.

Like the Texas project, the New York experiment is designed to develop a further understanding of how tire shreds perform as an engineering material. Settlement gauges will be placed under and within the pile of tire chips and temperature monitors installed. Two sampling collection points will be arranged to test leachate from water trickling through the embankment, while wells will be observed above and below it to monitor natural groundwater levels. Construction of the tire shred portion of the project is expected to take place this spring and last a month.

“Quite honestly, dirt is the cheapest material,” says Todd Dickson, civil engineer with the New York DOT. “When we get into recycled materials like rubber, glass or concrete, we have to look at those and see how the costs compare with each other.” In some circumstances, savings in disposal costs can make tire shreds economically competitive if a source is nearby. “Right now, using tire chips is more expensive because workers are not used to it,” adds David Head, the Texas DOT’s director of construction. “The contractor was worried about placement of the burrito, but there really wasn’t much of a problem with it.”

Economics aside, both DOT officials see benefits to using tire shreds. “We normally would use soil,” explains Head. “This stuff is quite a bit lighter. In terms of civil engineering, there are advantages for some applications, such as places where lightweight fill is needed because traffic is going over a swamp, or there are problems with soil due to weight. It also can be used as backfill for retaining walls and bridge abutments. It can relieve earth pressure because the tire shreds absorb.” Adds Dickson: “In applications where we have to use lightweight material, this probably will be very competitive. It also is very permeable and can move water through very well.”
By Molly Farrell and Dave Block

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