Sixty percent of the rubber consumed in the United States is used to make tires. Raw materials used to make tires include - rubber (41 percent), carbon black (28 percent), steel (15 percent) and other materials (16 percent).

In 1998, 270 million scrap tires were generated. Cars supply 84 percent of scrap tires, trucks supply 15 percent and heavy equipment, aircraft and off-road vehicles supply 1 percent. The biggest market for scrap tires is tire-derived fuel (TDF), which is a low-sulfur, high-heating value fuel.

Scrap tires also can be recycled as whole or split tires, or as crumb (ground) or shredded rubber, but they present a recycling challenge because they are made from many materials.

Whole tire uses include artificial reefs and playground equipment. Split tire uses include floor mats and dock bumpers. Crumb rubber uses include products, such as mudguards, carpet padding, tracks and athletic surfaces, and rubberized asphalt. Shredded uses include road embankment or roadfill.

In 1998, approximately 500 million scrap tires were in stockpiles. This is a 30 percent stockpile reduction since 1994.

Scrap Tire Municipal Solid Waste (MSW) Facts: Generated: * 4.5 million tons or 2% of generated MSW by weight.*

* Almost one scrap tire is generated per person per year.

* The average weight of a passenger car scrap tire is 20 pounds.

* A truck scrap tire will weigh 40 pounds or more.

* A steel-belted radial passenger tire will have 2.5 pounds of steel.

Recycled: * 1.06 million tons for a 23.5% recovery rate.*

Recycled Content: * New tires generally contain 1% to 3% ground (recycled) rubber. A tire with 5% ground rubber now is available.

* Retreads contain 75% recycled content.

Composted: * Scrap tires do not compost, but shredded tire chips can be used as a bulking agent in composting wastewater treatment sludge.

Incinerated or Landfilled: * 3.45 million tons or 2.2% of discarded MSW by weight.*

* Scrap tires have a 15,000 Btu fuel value per pound, which is slightly higher than coal.

* Unlandfilled scrap tires can create a public health problem as a mosquito breeding area.

* Landfilled single tires can pose problems if the tires fail to compress within the landfill and then rise up and resurface.

* 35 states ban whole tires from landfills.

* 8 states ban all scrap tires from landfills.

Scrap Tire Stockpiles: * Less than 2,800 scrap tire stockpiles remain in the United States.

* Almost 73 million tires were removed from stockpiles from 1996 to 1998.

Landfill Volume: EPA landfill volume data does not include tires.

Source Reduction: * Purchasing longer tread-life tires, rotating and balancing tires every 4,000 miles, and keeping tires at their recommended air pressure levels are the best ways to reduce the number of scrap tires.

* Reuse of used (but usable) tires and retreading are the primary source-reduction options. Approximately 30 million to 33 million tires are retreaded yearly.

* The used tire market is probably about 30 million tires. Half of those tires are exported.

* Improved manufacturing techniques have doubled the useful life of tires since 1955, with 40,000 mile tires now commonplace.

Scrap Tire Markets: * Tire-derived fuel (TDF) is by far the largest market for scrap tires. A net decline in the number of TDF facilities between 1996 and 1998 led to a tire recovery rate net decline during this period

* Using scrap tires to replace other materials used in construction (such as soil, clean fill or drainage aggregate) is the next largest market, followed by exports and ground rubber markets.

Scrap Tire Market Specifications: Each market for scrap tires has its own unique specification.

Scrap Tire Value: Scrap tires usually have low to negative value. In many cases, generators pay a tip fee to scrap tire markets.

TDF markets generally are linked to the price of coal.

"Municipal Solid Waste Generation, Recycling and Disposal in the United States: Facts and Figures for 1998," U.S. Environmental Protection Agency (EPA), Office of Solid Waste 2000, Washington, D.C., Website: www.epa.gov/osw

Markets for Scrap Tires, U.S. EPA, October, 1991

"Scrap Tire Management Council,

Scrap Tire Use/Disposal Study, 1996 Update," Scrap Tire Management Council Website: www.rma.org/ tiresn.html

Rubber Manufacturers Association, Washington, D.C. Website: www. rma.org

Tire Retread Information Bureau, Pacific Grove, Calif. Website: www. retread. org

* 1998 U.S. EPA estimates.