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Recycling Options

Tire dumps are a growing problem as established in previous sections. However, scrap tires are also a valuable resource. Many people have become interested in innovative ideas to capitalize on this cheap abundant material. Several states have established grants or some form of funding to support the research and use of new technologies using scrap tires. These programs have generated many practical ideas. Some of these have been put into use and have achieved various levels of success. The following table is a compiled list of some of the uses, we found for scrap tires.

table 1:

coral reefs


homes or building material


live stock fencing

water filter

shoe soles


ground surfaces

stereo components

carpet overlay

computer accessories

automotive seals

sound barriers

golf courses


Tire Processing Technology

These ideas involve using the tires in various forms from whole to finely powdered. To process the tires , new technology has been developed. Machinery has been built to produce the consistency needed. For example crumb rubber has become a popular material. In order get get from a whole tire to crumb a process must be followed. One example of this process is called ambient grinding. ³Ambient grinding involves shredding tires at ambient temperatures into four inch by four inch pieces and then grinding the pieces with a comminuter into a rubber crumb.²(envirosense) Another technique used to crumb rubber is cryogenic cracking. This technique has been patented by the GreenMan technology, which is a new company based on selling recycled rubber products. This company is also a good example of how rubber recycling can be profitable. The cryogenic crumbing technique involves freezing the slit tires with liquid nitrogen and then shatters the frozen rubber to produce crumbs. Other techniques have been developed using chemical and mechanical measures however ambient grinding, cryogenic cracking, and slitting are the most popular.

Tire Derived Fuel and Advantages

The two most successful reuse techniques for scrap tires are TDF and rubberized asphalt. To define success we considered the advantages, disadvantages, cost, practicality, and effectiveness at removing the problem of stockpiles. TDF, or tire derived fuel is now widely used. The most popular uses are in pulp/paper mills, cement plants and electric plants. Many of these plants use TDF as a percentage or even full portion of their fuel requirements. There are several advantages to using tires as a fuel source. Such as their potential for lower pollution emission levels. In a study done by Toronto based Proctor & Redfern, emission rate data with TDF were similar to those of plants using only conventional fuels, and below accepted values for air emission standards drafted by the Canadian Council of Ministers of the Environment (CCME). The study was done using five Canadian and two U.S. cement plants using TDF in cement kilns. The survey measure the emission for metals (Zn, Thallium, Cadmium, lead, Nickel, Chromium), Co, SOx, NOx, HCL, dioxin, fuerons. The results showed no significant difference in emission. Another advantage to TDF is a potential for lower fuel cost. . Government incentive programs and Œtipping fees¹ , allow TDF to become a competitive alternative. For example in Wisconsin, incentives have led to the use of 95% of the states scrap tires produced yearly. (scrap tires) Other states have developed similar programs, Illinois being one of them. Illinois Power & Waste Recovery Inc., make use of inch tire chips to produce 5% of the electrical power generated by the company. (rain trap)ŒTipping¹ fees for the disposal of scrap tires can subsidize the processing fees of the tires. Tipping fees make this a more appealing option for private companies. However, currently without government incentives many of the plants using TDF would not survive the competitive markets. There is hope for TDF because scrap tires have the highest BTU, energy content, of all the alternative fuel sources. Per million BTU produce the cost using scrap tires would be between $.25- $.75, compared to $2.00 for equal amount of gas fueled electricity(rain trap). Two other advantages of TDF worth mentioning are that tire burning is publicly favorable, and that the waste ash can be used as a traction agent in the winter.

Disadvantages to TDF

There are three disadvantages to using tires as a fuel source. Two of the disadvantages are cost related. The first is that only certain types of boilers are suited for burning tires. Comment kilns are the best right now. Existing boilers can be modified to meet the requirement for such high temperatures. These modification can be expensive depending on the model. The second disadvantage is the processing processing fees. The tire must first be prepared to fit the specific boiler to be used, this could mean burning the whole tire or a finely ground powder. Finally, unless the whole tire is burned, there is a certain percentage of waste created. Until the cost of processing and equipment are lowered the use of TDF will be limited.

Using Recycled Rubber in Asphalt

The Other popular option, currently being employed, is using scrap tires in production of asphalt. Research for using rubber in asphalt was first started by Charles H. McDonald in the 1960¹s. Since then several processes have been developed using this idea. For example the McDonald process which uses 25% crumb and 75% asphalt, or the Arco process which uses 18-22% crumb rubber in hot asphalt cement, and Exxon process composed of 18% finely pulverized rubber. Advantages to Rubberized Asphalt The advantages of rubberized asphalt is based its improved performance over normal pavement. The asphalt containing rubber is more resistant to fatigue and resistant to wear. It also has strong adhesive and cohesive quality for better traction. Rubberized asphalt also reduces the noise level produced. Finally, using scrap tires in the production of pavement on average consumes 1000 tires per mile of one lane. Disadvantages of Rubberized Asphalt The disadvantages to using rubber in asphalt are also cost related. The overall cost of production is 2.4 times greater then regular pavement. It also requires specialized spraying and surfacing equipment, which lead to more expense. There has been a growing use of this product throughout the U.S. despite the cost. The city of Phoenix has a very high percentage of their road system utilizing this technique. The Government has also added to the incentive through funding and a Federal Mandate for the use of crumb rubber in 10% of all federal paving projects in 1996. This is supposed to be increased to 20% by 1997.

Rain Trap System

Of the other ideas we found for recycling tires we research two that had the best chance of success based on their practicality and usefulness. The first idea was developed by a private company and is targeted for private investment. Their product is call the rain trap system. This system involves the use of slit tires to form a barrier under the soil of a golf course. This would reduce the amount of irrigation by keeping the water within reach of the grass roots. I t would also prevent fertilizers from entering the ground water. In addition the system reduces the quantity of fertilizer required because it would be only be dissipating from use not run off. This solution is aim at private companies building golf courses, it is not a practical option for government involvement. The purposed plan would consume 1,231,166 tires per course. In 1994 alone 381 golf courses were built. This ideas is economically feasible and a practical solution to problems face by golf courses, especially in arid regions, however it is a limited use for a growing problem.

Sound Barriers

The second idea we research as a practical solution was using scrap tires in the production of sound barriers along highways to reduce noise to neighboring residential areas. Carsonite International has developed a hollow fiberglass wall supported by concrete or steel beams and filled with rubber crumbs.The rubber crumbs are purchased from scrap rubber companies and are less a half inch in diameter. An average wall of tongue-and-groove panels would consume about 20,000 scrap tires. (May,20) There this system boast three main advantages. The first being cost, on average the usual sound barrier can cost between $15-$17 dollars per square foot.. In contrast carsonite barrier can be produced at as little as $12 per square foot. The second advantage to using carsonite barrier, is repairability. When a concrete wall is hit, it takes many of man hours to fix it. The carsonite barrier can be fixed by replacing or mending the individual panel in very little time. Not only are the barriers easier to fix, their projected life span is comparable to that of concrete. Finally, the most impressive advantage of the carsonite barriers is their effectiveness. In a study done by Riverbank Acoustical Laboratory in Geneva Ill. , found a noise reduction between 24-42 decibels. The carsonite company indicated the success of their product and future plans for installation in highways in California, Illinois, Nevada, Oregon and Virginia. (May,21)

Summary for Recycling

There are many ideas for how to use the mountains of scrap tires existing and being produced. Government and private funding is sparking the development of new ideas every day. However the major stumbling block to most of the projects is cost and effectiveness. Until the cost of recycling is lower then the cost of dumping tires, people will continue to dump. Recycling tire involves not only putting the rubber to use it requires transport and processing. The ideas explored above are currently in use . The results of their effectiveness are still questioned. However stockpiling is should not be an option therefore we must continue to support the recycling efforts.

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