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Scrap Rubber: Tires / Tyres

Introduction: The average passenger car tire measures about 26 inches across, but take away just a quarter-inch of tread and it becomes an accident waiting to happen.

The United States, like the rest of the industrialized world, goes through a lot of tires. Approximately one tire is discarded per person each year. The U.S. Environmental Protection Agency estimates that 250 million scrap tires are generated in the United States each year, not counting another 45 million scrap tires that are used to make 34.5 million automobile and truck tire retreads every year.

Until the 1960s, rubber from scrap tires was routinely recycled, but that started to change as cheap oil imports — the raw material behind synthetic rubber — made reclaimed rubber less valuable, and the spread of steel belted tires made tire recycling more expensive, difficult and time-consuming.

As so often proves true when waste makes short-term economic sense, the long-term consequences of wasting scrap tires began to accumulate.

Scrap tires not only waste landfill space, they can damage the linings put in place to keep groundwater and surface water from mixing with landfilled contaminants. Tires discarded illegally — individually as litter or collectively in clandestine tire dumps — are an eyesore and a drag on surrounding property values. They also pose threats to public health and safety.

Tire dumps provide excellent breeding grounds for mosquitoes, and elevated incidents of mosquito-borne diseases have been noted near large tire piles.

Tire pile fires have been an even greater environmental problem. Tire pile fires can burn for months, sending up an acrid black plume that can be seen for dozens of miles. That plume contains toxic chemicals and air pollutants, just as toxic chemicals are released into surrounding water supplies by oily runoff from tire fires. Fighting a tire pile fire is not only futile in some cases, it can actually make the pollution problem worse.

In Ohio, the last straw came in 1999, when a 140-acre tire dump in northeastern Ohio burned for five days, disgorging a column of toxic smoke that could be seen 60 miles away and releasing oil into a nearby creek, killing thousands of fish in the Sandusky River system. The state legislature ordered government agencies to clean out existing tire piles and to develop recycling markets extensive enough to accommodate all of Ohio's newly generated scrap tires. These were ambitious goals but part of a national trend, and the efforts have progressed well.

In 1989, only 10 percent of the scrap tires generated in the United States were reclaimed through recycling or other uses. Today, more than 80 percent of scrap tires are pulled from the waste stream and reused in some way.

These pages offer a quick look at the history of tires and tire recycling, uses for scrap tires and steps any motorist can take to reduce tire waste

Automotive tires are made from synthetic rubber derived from petroleum, the development of which was inspired by interest in improving on the performance of natural rubber.

Natural natural rubber Though grown on plantations in Southeast Asia, the rubber tree plant is native to the Amazonian lowlands of South America, where it is still harvested from wild trees.

Natural rubber is obtained from the liquid latex secreted by certain plants, primarily the Para rubber tree plant — Hevea brasiliensis — native to the jungles of the Amazon. Pre-Colombian people in South and Central America used rubber to waterproof fabrics and to make balls, containers and shoes. Europeans did not show much interest in rubber until the 18th Century, and then it was used almost exclusively to make elastic bands and pencil erasers. Joseph Priestley, a founder of the modern study of chemistry, named the substance "rubber" for its use as an eraser.

In 1819, a Scottish industrialist with an interest in chemistry, Charles MacIntosh, used a mix of rubber and a solvent to glue two sheets of fabric together to create a rainproof cloth. He worked with another chemist, Thomas Hancock, to improve the product. Investors were about to lose millions in the "rubber fever" that followed.

Natural rubber's potential for making waterproof fabrics and a wide range of other consumer and industrial goods was best appreciated at room temperature. In cold weather rubber products froze stiff and cracked. In the high heat of summer, rubber products melted down to a useless, glue-like goo. While some older rubber product manufacturers survived through the 1830s, none of the new companies that sprung up in response to "rubber fever" lasted more than five years.

It was at the scene of one such corporate calamity that Charles Goodyear, a bankrupt hardware merchant from Philadelphia, was inspired to dedicate his career to making rubber stand up to the elements.

Problems with wasting scrap tires: Fire

Scratch that plan Letting scrap tires accumulate in "stockpiles" until some future use could be identified backfired dramatically. In Ohio's Wyandot County, approximately 5 million tires in a 25-million scrap tire heap burned for days, poisoning the soil and nearby waterways after some teenage boys torched them in August 1999.

Even before the tire recycling business collapsed during the 1960s and early 1970s, scrap tires began accumulating in landfills, illegal dumps, vacant lots, abandoned buildings and roadsides around the nation.

The Rubber Manufacturers Association estimates that between two and three billion scrap tires are in landfills or are otherwise "stockpiled" across the United States. The Ohio EPA estimates that over 40 million scrap tires in large dumps around the state, with perhaps another 60 million more in roadside dumps, rural lots and warehouses around the state.

Even those that were dumped in sanitary landfills created environmental problems. Sometimes landfilled tires work their way back to the surface, causing expensive damage to liners and liquid collection systems and compromising their ability to keep landfill contaminants from mixing with local groundwater and surface water. Like most states, Ohio has banned the landfill disposal of whole tires.

Scrap tires illegally dumped in abandoned buildings and on the landscape present even greater public and environmental health risks.

"The most obvious hazard associated with the uncontrolled disposal and accumulation of large amounts of tires outdoors is the potential for large fires that are extremely detrimental to the environment," notes Kurt Reschner, a University of Nebraska-educated chemical engineer working in scrap tire recycling in Germany.

Not to be outdone A month after Ohio's big tire fire, another broke out in Stanislaus County, CA.

Fires in large tire piles are hard, if not impossible, to extinguish. Some have taken months to burn out, producing heavy smoke and toxic liquid run-off that can foul local groundwater and surface water. Air, water and soil pollution can actually be made worse if water or foam is used to put out the fire, so some have been consciously left to burn out.

This hazard became undeniable in Ohio shortly after August 21, 1999, when arsonists torched one of Ohio's largest tire piles — 26 million tires piled over 140 acres at the Kirby Tire Collection and Storage Facility in western Wyandot County.

The fire burned five days, sending up a black column of smoke that could be seen more than 60 miles away. Oil released from the burning tires ran into a nearby creek, killing thousands of fish in the Sandusky River system. State officials estimated that five million tires burned in the blaze. More than 250 firefighters from 21 fire departments battled the blaze, finally bringing it under control by dumping topsoil on it.

Even putting out the fire created environmental problems, according to the Ohio EPA. The 750 tons of topsoil dumped on the Kirby fire became contaminated with oils from the burning tires, according to an article in the July 11, 2003, issue of Solid Waste Report. Ohio is paying a clean-up firm $837,000 to remove the soil and to treat contaminated water.

If some good can be said to have come from the Kirby fire, it moved the Ohio Environmental Protection Agency (Ohio EPA) and the state legislature to accelerate efforts to clear out the state's illegal tire dumps.

Since 1996, the state legislature had been levying a fee of 50 cents on each tire sold in the state. Most of the money raised by the fee was spent by the Ohio EPA on inspections, regulatory enforcement and clean-up efforts at scrap tire dump sites. Another $1 million went to a Department of Development grant program that helped Ohio schools purchase running track pavement made from recycled tires.

A year and a half after the Kirby fire, Ohio's legislature doubled the fee. The $1 million-per-year grant program was transferred to the Division of Recycling and Litter Prevention for a program to help Ohio businesses conduct the research and purchase the equipment needed to integrate scrap tires into their production processes. The rest — now around $11 million a year — is focused on the clean-up process. The state's goal is to have all its major tire piles cleared out by 2010, when the fee expires. By then, the state also hopes to have end-use markets for every newly scrapped tire generated in Ohio.

As of the fall of 2003, the Kirby site was down to about 13 million of the tires, and it remains the largest scrap tire pile in Ohio by far. The next largest are estimated to contained 1.2 million tires each.

State officials believe it will take another three to five years to finish the Kirby clean-up, which has cost the state $14.1 milllion so far. Then they will turn their attention to some of the state's other large tire dumps.

The clean-up at Kirby was well underway when another health risk associated with discarded tires started making headlines in Ohio in 2002.

West Nile Virus is not the only mosquito-borne virus in Ohio, but it has proved to be one of the most deadly in living memory. Its rapid spread across the continent put new urgency on efforts to eliminate scrap tires as a breeding place for mosquitoes.

Problems with wasting scrap tires: Disease

Deadly mosquito-borne infections were not new to Ohio in 2002. As far as most people were concerned, they were history.

Disease on board Public health officials have long known that scrap tires provide breeding grounds for mosquitoes. In the mid 1980s — according to a National Public Radio report — Paul Reiter, an inspector for the Centers for Disease Control and Prevention, was the first to figure out that species of mosquitoes and strains of tropical diseases previously unknown in the United States were coming here in container shipments of scrap tires from Asia.

Now primarily confined to tropical and subtropical regions of the world, mosquito-borne diseases such as yellow fever and malaria once raged across temperate zones as well.

Springfield, Ohio, was established in the early 1800s by a band of settlers fleeing the malarial swamps they found around the central Ohio settlement of Franklinton. From 1826 to 1832, 500 of the men working on the Rideau Canal in Ontario, Canada, died of blackwater fever, one name for malaria. The disease raged up and down the Mississippi and Ohio Valleys through much of the late 19th Century.

Improvements in medicine, public sanitation, public health and the general health of Americans since then have contributed to the virtual elimination of mosquito-borne disease in the temperate regions of the United States. A mosquito bite might be an itchy nuisance, but hardly a thing for most people to fear.

West Nile Virus (WNV) reawakened America's appreciation of the potential dangers of mosquito-borne disease.

It is not a particularly deadly virus. According to the Ohio Department of Health, most people bitten by an infected mosquitoes shown no sign of disease at all. For those who do exhibit symptoms of the infection, West Nile fever is relatively mild — fever, headache and body aches, sometimes a skin rash or swollen lymph glands.

But a small number of people who contract WNV suffer from West Nile encephalitis or West Nile meningitis, a severe infection marked by the rapid onset of a high fever, severe headaches, neck stiffness, nausea or vomiting, confusion, muscle weakness or paralysis, seizures, coma and — though rarely — death.

WNV's rapid spread across North America was also cause for concern. First detected in New York City in 1999, it was found in birds and mosquitoes in Ohio in 2001, and by 2002 it had spread to the West Coast, detected in 44 states. There were 441 cases of West Nile Virus infection in Ohio that year, 31 resulting in death. More than 4,000 cases were reported across the United States in 2002, 263 ending in fatality.

The emergence of WNV inspired even greater interest in cleaning up scrap tires because scrap tires make excellent breeding grounds for mosquitoes.

Trouble besides tires Mosquitoes that feed on human blood like to live and breed near us. During spring cleaning, check your property and your neighborhood for scrap tires and other features that can hold water, where mosquitoes can lay their eggs: Children's wading pools Clogged gutters Clogged drains Dirty birdbaths Junk piles Puddles Underchlorinated pools SOURCE: Aladdin Pest Control

Mosquitoes lay eggs in standing water, such as can accumulate inside a discarded tire. The tires both protect the trapped water from the elements, and insulate the puddles as well. A single tire can be the source of thousands of mosquitoes over the course of a summer.

Though mostly in warm-weather areas, increased incidents of mosquito-borne illnesses have been documented around tire piles.

Other animals which become pests when they invade human space — rodents such as rats among them — also use tire piles to nest. Even a relatively vermin-free tire pile is an eyesore and a drag on nearby property values and community self-image.

Problems like fire, mosquito-borne disease and neighborhood blight are arguments for proper disposal of scrap tires. The arguments for recycling scrap tires center around energy and resource conservation and economic development.

Scrap tire management alternatives

A variety of means exist for reusing scrap tire rubber, each with their own drawbacks and benefits.

Economists and engineers examining the issue have drawn up hierarchies of scrap tire management. Their rankings may vary slightly, and new information may change these rankings. Presented here is the ranking outlined by chemical engineer Kurt Reschner.

Scrap Tire Disposal and Recycling Methods Ranked by environmental and economic preference 1. Use PRODUCT for its originally intended purpose as long as possible Design rubber compound and tire geometry for maximum durability. Keep tire properly inflated at all times to ensure maximum service life. Reuse partly worn tires. Regroove or retread tire casings. 2. Use MATERIAL to make new products Grind scrap tires into crumb rubber, separate steel and fiber. Sell rubber as raw material. 3. Use whole scrap tires for energy recovery Burn whole scrap tires as fuel supplement in cement kilns. 4. Use mechanically processed tires for energy recovery Tire chips added to coal as fuel supplement in power plants, paper mills, cement kilns, etc. 5. Alter the chemical structure of scrap tires and use the products for energy recovery Pyrolysis, Supercritical Extraction. 6. Storage for possible recovery at a later time Monofilling (Depositing tires or tire chips in a tires-only landfill or landfill cell). 7. Disposal without any current or future use Landfilling.

 Uses for scrap tires: Crumb rubber

Saving resources and kids' knees Attractive and with obvious safety benefits, the use of rubber mulch as play area groundcover can also be cheaper in the long run than using gravel and wood chips.

The best management strategy for scrap tires that are worn out beyond hope for reuse or retreading is recycling.

While very little rubber from used tires goes into the production of new tires, a host of other products made from recycled tire rubber have come on the market. Chips of shredded tire rubber are used as fill in engineering projects. More finely chipped and screened tire rubber is used is playground and landscaping mulch. Crumb rubber is used to make better asphalt, while rubber mixed with urethane is used to make athletic track surfaces and a variety of molded products.

Tire shredding is a mature technology. Tires are first shredded, cut into chunks approximately two-inches long. These tire chips are often then fed through a series of granulators which reduce the chips further, often down to about 3/8" across.

Tire shredding is often performed on the site of a large tire dump. Shredding reduces the volume of a tire by 75 percent, reducing storage and shipping costs.This process also loosens steel and fibers from the rubber. Steel is lifted out with magnets. The fibers are shaken or blown out of the granulated rubber.

Where the rubber is the road The stretch of interstate near Flagstaff, AR, on the left was paved with a mix of asphalt and crumb rubber. The stretch on the right was paved about the same time using conventional asphalt.

There has been an enormous growth in the demand for recycled tire rubber — "crumb rubber" — since the early 1990s, particularly in North America. These newly rubberized products are often superior to similar products made of conventional materials, and using recycled rubber over virgin rubber reduces manufacturing costs.

Crumb rubber markets 2001 U.S. and Canada market summary Application Millions of pounds used Rubber Modified Asphalt (RMA) 292 Widespread commercial applications of rubber modified asphalt (RMA) pavements started in Arizona in the 1960s. Usage nearly doubled from 1995 and 1999. Adding tire crumb rubber to the hot bitumen improves the performance, as proven over thousands of highway miles. Advantages include decreased rutting, reflective and thermal cracking, better de-icing properties and reduced traffic noise. Lower maintenance costs and significantly increased service life translate to a lower lifecycle cost for RMA.   Molded Products 307 Increasing supplies of crumb rubber and a newly developed moisture-curing urethane binder has led to a rapid increase in the number of products made by simple compression molding. Typically used to produce high-volume, low-tech products, such as livestock mats, railroad crossings, removable speed bumps and athletic mats, this process is not good for products that must resist abrasion or that require elasticity.   Athletic Surfaces 141 Playgrounds and athletic surfaces are frequently covered with a layer of rubber granules, and many stadiums have running tracks that consist of recycled material. The surface, a mix of urethane and crumb rubber, is applied much like other poured pavements, but provides superior protection against injuries. Crumb rubber is also used in a loose, mulch-like form as ground cover in landscaping and playgrounds. In playgrounds, rubber mulch offers protection from injuries superior to wood mulch, gravel or other traditional materials and can actually be less expensive to maintain than other surfaces. Scrap tire rubber is even integrated right into turf. Research has shown this to be particularly beneficial in high-use areas, as the rubber helps reduce soil compaction, improving drainage and reducing the need for water, fertilizer and pesticides for between 25 and 50 years.   Tires/Automotive 112 The tire industry consumes 65 percent of all rubber compounds produced worldwide, but it is not a candidate for extensive re-use of recycled tire rubber with today's technology. Because of speed, safety and other performance requirements of tires, they need to be made mostly using virgin rubber compound. But mixing five to 15 percent recycled rubber into the virgin rubber provides a few advantages in the production process, including better mixing properties and an increase in plant efficiency due to reduced curing times. Some tire manufacturers routinely use crumb rubber as a filler, especially to make treads on passenger car tires, farm equipment tires and solid rubber tires.   Devulcanized and Surface Modified Rubber 36 These methods of recycling rubber are similar in that they are comparatively experimental and expensive processing methods. Devulcanization involves breaking the sulfur bond that helps rubber hold its shape in extreme weather. Early methods involved exposing cured rubber to elevated temperatures for extended periods of time, but there are problems with the process. It not only severs the sulfur bond, but breaks polymer chains and causes a degradation of quality. There are economic and environmental concerns as well. Research with ways to use ultrasound to break sulfur bonds or mechanical means to essentially chew them up show promise. Experimental methods using bacteria to eat away the sulfur bonds are complex and therefore too expensive, so far. Surface Activation involves treating crumb rubber particles so they stick together better, a compromise between using recycled rubber strictly as a filler and wholesale devulcanization. The economic viability of the process is in question.   Plastic/Rubber Blends 38 Combining crumb rubber with a plastic binding agent is a very cost effective way to produce a material that can be processed like plastic, but retains some of the elasticity of rubber. It is used to produce high-volume products like pallets, railroad ties and acoustic insulation for cars.   Construction and Miscellaneous 70 Larger and requiring less processing than crumb rubber, tire chips are being used in place of conventional construction material such as road fill, gravel, crushed rock or sand in a variety of construction and civil engineering projects. Tire chips are successfully used as fill for embankments and retaining walls, drainage material and daily cover at solid waste landfills and as an insulating layer beneath roads and behind retaining walls. Tire chips can be an improvement on traditional materials because they are not as dense, are easier to install, provide better drainage and better thermal insulation. Developers in Clark and Geauga counties are taking part in an Ohio Department of Development-funded study to see if tire chips are useful in leaching beds of residential septic systems. South Carolina has allowed tire chips to be used in leach beds for 10 years, and they have been found to be easier to install, more effective and less expensive than traditional materials.   Total 996

Reducing tires to crumb rubber is not the only way tires can be recycled into new products. The Federal Office of Energy Efficiency and Renewable Energy estimates that nearly 8 million scrap tires are cut, stamped, or punched into hundreds of different products every year in the United States.

Scrap tires as fuel

The single biggest use of scrap tires in the United States and the European Union is as fuel. Environmentally or even economically speaking, it is not the best method of reclaiming scrap tires, but it beats the alternative of disposing or dumping unused tires.

What a tire's made of The Goodyear P195/75R14 all season passenger tire, the most popular size, weighs about 21 pounds and contains: Material Pounds 30 different types of synthetic rubber 5 Eight types of natural rubber 4 Eight types of carbon black 5 Steel cord for belts 1 Polyester and nylon 1 Steel bead wire <1 40 different kinds of chemicals, waxes, oils, pigments, etc. 3 Approximate Composition Percentages: Carbon 85% Ferric material 10-15% Sulfur 0.9 to 1.25% Source: Texas Natural Resources Conservation Commission

Whole tires and rough tire chips are used at cement kilns, pulp and paper mills, power plants, waste-to-energy plants and industrial boilers. In 2000, approximately 47 percent of the 273 million scrap tires generated in the United States were burned for fuel.

Ohio lags far behind the rest of the nation and much of the industrialized world in burning tires for fuel, so-called "energy recovery." In 2000, only 11 percent of Ohio's 14 million newly scrapped tires were burned for fuel, mostly outside Ohio.

Ohio and its industries sat out on a national wave of tire-derived fuel (TDF) development that started in the mid-1980s. Uncertainty about air emission standards and questions about pending deregulation of the electric utility industry made Ohio utilities slow to integrate scrap tires in their fuel mix.

That cautionary approach has had its benefits. Ohio actually recycles a much higher percentage of its tires than the national average. In 2000, Ohio recycled 61 percent of its tires into new products, compared to the national average of 26 percent that year. Recycling is environmentallly and economically preferrable to combustion as a way of managing scrap tires.

But there were drawbacks as well, such as a severe lack of markets for the other 39 percent of Ohio's scrap tires.

Ohio is pushing ahead to make up for lost time. In 2002, the state restructured a tire recycling grant program to help utilities and industries fund the research and equipment purchases necessary to use TDF. The program gives out approximately $1 million in grants each year.

While it may seem counterintuitive to anyone who's seen an uncontrolled tire fire, there actually can be environmental benefits to controlled burning of scrap tires or TDF chips for energy. TDF produces slightly more heating value than coal with similar emissions. Terry Gray, a TDF consultant, says coal mixed with TDF produces less ash, greenhouse gases and metal emissions than burning coal alone.

Cement kilns are considered good places to use TDF because the ash is incorporated into the final product, there is no waste to dispose of, according to the Texas Natural Resource Conservation Commission.

Energy-intensive pulp and paper mills and metal foundries are also strong candidates for using TDF, in part because TDF is often cheaper than coal.

Such industrial users of TDF can often burn whole tires, a practice that cuts down the expense of shredding tires, but that increases storage and shipping costs.

Though using TDF reclaims some of the energy that went into making a scrap tire, it remains the second most wasteful alternative after disposal for managing scrap tires. That fact puts "energy recovery" near the bottom of the hierarchy of scrap tire management alternatives, just above dumping them.

For one thing, a tire is more than just a petroleum product. A 21-pound tire contains only five pounds of petroleum-based synthetic rubber. The rest is natural rubber, steel belts and bead wire, carbon black, cloth and a mix of other chemicals which do not contribute significantly to the heating value of an incinerated tire.

Burning tires for fuel also reclaims only a small portion of the energy it takes to produce a tire.

Energy lost in tire-derived fuel Measurement: Kilowatt-hours per kilogram of synthetic rubber Energy needed to manufacture a tire 32.0 Energy needed to produce tire rubber compound 25.0 Thermal energy released when incinerating scrap tires 9.0 Energy consumed in the process of grinding scrap tires into crumb rubber 1.2 Sources: W. Dierks: Incorporating the Use of Recycled Rubber, Robert Snyder: Scrap Tire Disposal and Reuse, compilation by Kurt Reschner.

Burning a tire for fuel also precludes further recycling.

Reschner points out that reusing, retreading or recycling tires is preferrable to burning them for economic reasons as well as environmental ones. The global traffic in used tires and retreadable tire casings show a strong market interest in reuse and retreading. Crumb rubber prepared for recycling also sells for $200 to $400 a ton, as much as 10 times the price paid for TDF chips.

But in the absence of viable recycling alternatives, Reschner writes, tire-derived fuel "is a perfectly reasonable use for scrap tires."

Other ways to recycle scrap tires

Recycling tires by grinding them down to crumb rubber — whether it is to be used as fuel or as feedstock for new production — is a mature technology with proven markets, and promising new products and markets are in development.

"Photographing old things such as cars, buildings, tools, and decaying things of 'times gone by' brings me great joy. They seem to speak to me and say 'Let me tell you my story'." — Steve Bingham    A Different View

Research continues on other ways to recycle tires, some more promising than others.

Most involve some form of devulcanization — breaking the sulfur bonds that help vulcanized rubber hold its shape, a characteristic that also prevents recyclers from melting tires down and remolding them into new products.

Another promising process — pyrolysis — involves breaking tires down beyond the rubber, to the hydrocarbon gases, carbon black and oil that the rubber is made from. The process also liberates the steel in tires for recycling. The hydrocarbon gases can be sold, but they are usually burned to fuel the pyrolysis process.

Devulcanization technologies

Thermal reclaim process: The oldest form of devulcanization — patented in 1858 — is also the least promising. Thermal devulcanization involves exposing rubber to high temperatures for an extended period of time to break the sulphur bonds. The process also breaks the polymer chains themselves, severely degrading the value of the rubber. The process also presents environmental and public health risks and is rarely used today.

Mechanical devulcanization: This process used rollers, mixers and extruders to mechanically "chew" away at the sulfur bonds. It produces good results but is not yet economically viable.

Devulcanization with ultrasound: Early efforts using ultrasound to break the sulfur bonds in vulcanized rubber were encouraging.

Bacterial devulcanization: Rubber is ground to a powder, then suspended in a liquid full of sulfur-eating bacteria such as thilbacillus, rodococcus and sulfolobus. The process is technically viable but complex, and therefore too expensive.

Pyrolysis

The technique uses heat, in the absence of oxygen, to speed up the decomposition of organic material. Theoretically, the oils, carbon black and scrap steel can be sold, and the hydrocarbon gases released through pyrolysis can either be sold or used as fuel at the pyrolysis plant.

But the tire pyrolysis techniques used today produce mixed quality oils and carbon black that can be difficult to market. The gas is a low to moderate BTU methane that is difficult to store.

Because of those quality issues, no tire pyrolysis plants have been in sustained production in the United States or anywhere else in the world. Research continues, however, for a technology that will make tire pyrolysis commercially viable.

17.04.2007. 07:34

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