board products, industrial boiler fuel, landscaping and hydraulic mulches, sludge bulking
media, and animal bedding.
The predominant source of rubber in municipal solid waste is scrap tires. There are
approximately 2-3 billion scrap tires currently stockpiled across the U.S., and over 240
million more are generated annually. Improperly operated stockpiles can create serious
health and environmental threats from fires and insect- or rodent-borne diseases. Most states
now have scrap tire management legislation creating alternatives to tire stockpiling and
disposal. One of these alternatives is tire retreading, which is the focus of EPA's 1988 tire
procurement guideline. Another alternative is to use crumb rubber, either alone or mixed
with plastics, to produce new products. Several of the items designated in the CPG contain
recovered crumb rubber from tires.
Crumb rubber, a fine granular or powdered material capable of being used to make
traffic cones and other products, is currently recovered from whole scrap tires using thermal,
chemical, and/or mechanical processing techniques. Crumb rubber is also derived from the
tire retreading process, when a worn tire tread is removed from a retreadable tire casing
during a buffing process before a new tread surface is affixed. Rubber materials derived
from this process are frequently referred to as "buffings" or "buffing dust." Approximately
200 million tons of tire buffings are generated each year by the tire retreading industry in the
7. Engine Coolants
Annually, more than 200 million gallons of engine coolant are sold in the United
States. After purchase, engine coolant is diluted 50 percent with water before placement in
the engine. If the majority of engine coolant sold annually is replacing spent engine coolant
(rather than refilling leaking radiators), then 400 million `gallons of spent engine coolant
mixtures require disposal each year. Engine coolant is disposed by discharging it into a
sewage treatment system, dumping it on the ground, recycling it, or managing it as a
Some sewage treatment systems are designed in such a manner that they can treat
spent engine coolant without a problem. Increasingly, sewage treatment plants require
notification prior to or even restrict the discharge of spent engine coolant to their systems.
In addition, engine coolant can cause damage to a septic treatment system if it is flushed into
the system, and can cause harm to the environment if it is dumped on the ground.
Used engine coolant may become contaminated by heavy metals (predominately lead)
to such a degree that it is a hazardous waste according to EPA's regulations. Some engine
coolant has failed the Toxicity Characteristic Leaching Procedure (TCLP) test because of