Page 188 - Materials Chemistry, Second Edition

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Recycling Solid Wastes 159

FIGURE 6.17 Illegal tire dumps pose hazards from fires and insect breeding, and are unsightly.

TABLE 6.10
Typical Chemical Composition of a Tire
Synthetic rubber
Natural rubber
Sulfur and sulfur compounds
Silica
Phenolic resin
Oil: aromatic, naphthenic, paraffinic
Fabric: polyester, nylon, etc.
Petroleum waxes
Pigments: zinc oxide, titanium dioxide, etc.
Carbon black
Fatty acids
Inert materials
Steel wire
Source: Rubber Manufacturers Association, no date. Reproduced with kind permission of the
Rubber Manufacturers Association.

Since 1996, the use of scrap tire monofills (i.e., a landfill dedicated to one type of material) has
become more prominent in some locations as a means to manage scrap tires. In some cases,
monofills are used where there are no other markets available and were MSW landfills are not
accepting tires. In other cases, monofills are portrayed as a management system that allows long-
term storage of scrap tires without the problems associated with above ground storage. In theory,
monofilled processed scrap tires can be “harvested” when markets for scrap tire material improve.
Using monofills for scrap tires is preferable to above ground storage in piles, especially if a pile is
not well managed (Scrap Tire Management Council, 1999).
Markets for waste tires recovered an estimated 66% (177.5 million out of 270 million scrap tires)
in 1999 (Table 6.12). The conversion of scrap tires into fuel increases every year, and is currently the
largest single use of scrap tires (Scrap Tire Management Council, 1999). The use of tires as a fuel
material is discussed in Chapter 9. Overall 12.7% of rubber and leather in MSW was recovered in
1999 (U.S. EPA, 2001).