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140 Waste Management Practices: Municipal, Hazardous, and Industrial

FIGURE 6.3 Cullet stored outdoors and unprotected will inevitably become contaminated.

● If stored outdoors place the cullet on a concrete pad, not on the ground or asphalt, to avoid
contamination from dirt or gravel during loading (Figure 6.3). Cover the cullet during
inclement weather.
● When storing multiple loads of colored cullet, keep the cullet separated so that no inter-
mingling of colors can occur.
● Prior to loading cullet shipments, wash the truck bed. Inspect the truck bed and the tarp
used to cover the previous load for any residue.

6.8.8 OTHER USES FOR RECYCLED GLASS
In addition to serving as feedstock for manufacturing new glass containers, recycled glass is used
to make other products. Fiberglass, a common alternative market for cullet, is predominantly used
in the form of glass wool for thermal and acoustical insulation. Recycled glass used in the manu-
facture of fiberglass now constitutes the second highest volume of postconsumer glass. Industry
standards for product quality and consistency are very high. Another promising alternative market
is glassphalt, a road-paving material, which is a mixture of crushed low-grade, mixed-color cullet
and asphalt. Some glassphalt mixtures may contain ground glass, sand, gravel, and limestone (Liu
and Liptak, 2000). Given the comparatively low costs for road building aggregate, however, the
demand for glassphalt is modest. Cullet is also used to produce highway reflectors and signs,
sandblasting materials, decorative glass, and drainage aggregate. Cullet has been used in the man-
ufacture of some wastewater plumbing. As glass is a relatively inert material, it can readily with-
stand the corrosive agents within wastewater. Some of the more innovative uses of recycled glass
are listed in Table 6.4.

6.8.9 BENEFITS OF GLASS RECYCLING
Whereas some industrial sectors have been reluctant to utilize scrap material in routine production
because of concerns over retooling and excessive costs, glass recycling, particularly that of con-
tainers, is an integral component of the glass production industry. Recovered glass waste has a lower
melting point (1370°C [2500°F]) than the standard silica, soda ash, and limestone mixture; in con-
tainer manufacture, each 10% increase in cullet reduces the melting energy by about 2.5%. Less