Scrap tires have many potential recycling and reuse applications, but marketing them can be a hard sell. The costs of processing scrap tires vs. the value of the end-product, its replacement potential and the unwanted constituents inherent in rubber tires make the economics questionable.
However, the Center for Integrated Waste Management at the State University of New York (SUNY) at Buffalo and Empire State Development are studying a promising use for scrap tires - as a replacement for stone in septic system leach fields.
As part of the project, which includes pilot-scale leaching studies and a field-scale demonstration project, a questionnaire was sent to all 50 states to find out how many of them currently allow scrap tires to be used in septic systems, and whether this use is regulated on a statewide or case-by-case basis. The questionnaire, which was sent to the state agency responsible for solid waste management, specifically asked whether shreds or chips were used. It also surveyed which states have attempted demonstration projects, how many states are interested in using scrap tires in septic systems and which states have no interest in this application.
SUNY Buffalo compared its results to a survey the state of Florida conducted in 1997. While comparing the results of the two surveys was difficult, one important observation was made - the number of states using scrap tires in septic systems is on the rise. Additionally, 13 states are investigating the potential of using tire chips in studies or demonstration projects, and some are seeking regulatory approval for their use. This suggests that the issue of scrap tires is becoming more prominent for regulators and that beneficial use is seen as a genuine alternative.
However, these views are tempered with concerns about the environmental impacts associated with using scrap tire chips, including:
* Groundwater contaminants. The long-term immersion of tires in water creates two main contaminants - iron and manganese. But in most cases, states considered these contaminants as secondary issues that could affect the color and taste of drinking water. The respondents appeared divided over whether the two contaminants would cause a significant groundwater problem (in septic system leach fields).
* Approvals. The permission method varies from state to state. While some states were satisfied that the application is environmentally safe and gave statewide approval, most reviewed applications case-by-case. Some indicated that as a "track record" was developed, the approval process would be more efficient.
* Potential users. Interest in this application varies. It is unclear whether home builders or subcontractors that construct septic systems, who were not interested in using scrap tires were not interested in the application because they found natural aggregate to be cheaper and more available, or because they weren't aware of the application. For the most part, when states had an interest in using tire chips, the regulatory agency reviewed the concept first.
* Wire. Respondents who approved tire chip use expressed concerns that the exposed wire belting in tires would be a source of leachable metals and an impediment to material placement, as well as affect the long-term integrity of the top geotextile.
* Chip size. Respondents said they preferred 2-inch to 4-inch chips.
* Value. Some states indicated that aggregate material still was plentiful and fairly inexpensive. Thus, some questioned the need for tire material if there wasn't a shortage of natural resources.
While mixed feelings continue about the use of tires as a replacement for natural resources, in general, the survey found that tire chips have potential use in septic system leach fields. Although only one-third of the states have approved some level of septic system application, interest from scrap tire regulators and managers continues to grow. This especially is true where scrap tires have few markets or where stone is at a premium.
Data from state solid waste managers suggest that automobile tires are discarded at the rate of about one tire per person each year. If not for tire-derived fuel projects, municipal solid waste (MSW) landfill leachate collection projects and civil engineering applications, the size and number of waste tire piles would continue to grow and present greater environmental, safety and aesthetic problems.
As an alternative to scrap tire disposal, state consultants and industry professionals, in conjunction with universities, are exploring engineering applications for tires that would offer both environmentally safe uses and conserve natural resources such as stone aggregate. Using tire chips in leach fields may be one option.