Minggu, 08 April 2012

Factors Affecting Both the Costs and Benefits of Increasing the Recycled Content in New Tires by Nevada Automotive Test Center Carson City, Nevada

A number of crumb rubber production technologies are available on the market. While an effort is underway to develop a sound technology that is cost-competitive, the tire industry has not yet accepted a technology for wide use in production of new tires.

There is an increasing need for waste tire rubber powder of 60-80 mesh and finer to create parts with smoother surfaces. Finer powders also improve the physical properties of rubber compounds and allow for faster mixing times when rubber powder is used as a partial substitute for virgin rubber. However, few techniques have been found that can produce fine tire rubber powder in a manner that meets current cost objectives [44]. To substantially increase the use of crumb rubber in new tires, several factors must be considered:

• A reliable source of crumb rubber with consistent physical characteristics such as
size, shape, and surface texture. Equally significant is the consistency in the chemical
composition of the ground rubber. Because of the great differences in rubber
compounding between all of the tires in the waste stream, this remains a significant
challenge.

• Waste tire recycling involves tire collection, transportation, and processing of waste tires, raw materials, blend treatment, and separation technology. The logistics of collecting and transporting waste tires to processing plants—or transporting processed rubber to tire manufacturing plants—in a timely manner is considered one of the cost determinants. Identifying new-tire sellers as the turning point for tires to be recycled helps close the transportation loop. Tire sellers, already familiar with tire requirements can support the grading and identification of tires, which are appropriate for recycling to new tires as opposed to tires, which are more appropriately used for fuels or other uses.

• Maintaining consistency in crumb rubbers for use in new tires has been difficult, primarily because of the many compounds used in tires.

• The processing methods must be consistent in the way the crumb rubber is produced. The same is true for the mixing of ingredients and tire building. The performance characteristics of the crumb rubber compounds must be equivalent to the virgin compounds they are replacing or be able to be integrated in a manner which does not adversely impact the overall system performance of the tire.

• Economic incentives need to be in place, particularly in the development of new technology, to produce high-quality crumb rubber. High-value products that are competitive in pricing and performance must be derived as a raw material from the waste tires. 1 8

• The low price of virgin rubber, its availability, and many years of utilizing virgin rubber materials determines the maximum cost that can be charged for crumb rubber. Significant capital investments have been made by tire manufacturers to process virgin rubber in their manufacturing plants. The processing costs are not eliminated by using recycled rubber.

• Development of new tire designs that can accommodate a higher percentage of recycled content without sacrificing tire performance or reliability. The factors listed above need to be considered in developing a feasible approach to increasing recycled content in new tires. Most ongoing research is focused on addressing the technical feasibility at a development level and does not address the commercialization aspect of the methods and processes developed. Commercial processes are highly proprietary and therefore additional efforts with tire manufacturers and recycling companies will be required to implement effective solutions. Ford and Michelin estimate that recycling waste tires back into new tires (with the use of recycled rubber at a rate of 10 percent) could cut the number of tires going into the landfills by approximately 33 million tires annually, or 12 percent of the approximately 281 million waste tires generated in 2001 (nationwide annual waste tire generated is assumed as approximately one tire per capita).

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