Page 103 - Materials Chemistry, Second Edition

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74 Waste Management Practices: Municipal, Hazardous, and Industrial

TABLE 4.10
Rubber and Leather in MSW

Product Category Generation
(thousands of tons)
Durable goods
Rubber in tires a 2,890
Other durables b 2,430
Total rubber and leather
Durable goods 5,410
Nondurable goods
Clothing and footwear 540
Other nondurables 250
Total rubber and leather
Nondurable goods 790
Containers and packaging 20
Total rubber and leather 6,220

a Automobile and truck tires. Does not include other materials in tires.
b Includes carpets and rugs and other miscellaneous durables.
Source: U.S. EPA, 2001. With permission.

4.4.10 YARD WASTE

Yard waste includes grass clippings, leaves, and tree trimmings from residential, institutional,
and commercial sources. The average composition by weight is estimated to be about 50% grass,
25% leaves, and 25% tree trimmings (U.S. EPA, 1999). Quantities and relative proportions will vary
widely according to geographic region and climate. Yard waste is the second largest component of
MSW, at 12.1% of total generation.
In the past, the generation of yard waste increased steadily as the U.S. population and amount
of residential housing grew, although per capita generation remained relatively constant. In recent
years, however, the amounts of yard waste have declined substantially in many areas, as a result of
local and state legislation (usually in the form of bans) on the disposal of such wastes in landfills.
With such so-called “flow control” in place, homeowners are adjusting by establishing backyard
composting and using mulching lawnmowers that allow grass clippings to remain on the lawn sur-
face. In 1992, 11 states had legislation banning or discouraging yard waste disposal in landfills. By
1999, 23 states and the District of Columbia, representing more than 50% of the nation’s popula-
tion, had legislation affecting the disposal of yard waste (U.S. EPA, 2001).

4.4.11 HOUSEHOLD HAZARDOUS WASTES
The portion of MSW referred to as “household hazardous waste” (HHW) refers to those hazardous
materials occurring in MSW regardless of their source. Most hazardous material in household waste
occurs either as heavy metals, organic compounds, or asbestos. These items are considered haz-
ardous because they may contain materials that are ignitable, corrosive, reactive, or toxic. Metallic
wastes such as lead, cadmium, and mercury are hazardous due to direct toxicity. Many of the
organic wastes are deemed hazardous solely because they are flammable, although some pose
inhalation hazards (e.g., paint strippers and other solvents) and others may damage or penetrate the
skin (solvents and pesticides). Most of the asbestos occurring in solid waste occurs as old vinyl-
asbestos floor tiles and asbestos shingles. Since the primary asbestos hazard is in the form of res-
pirable particles, asbestos tiles and shingles are typically not a significant hazard. Table 4.11 lists