nondurable products and packaging. Figure 2-1 illustrates the composition of municipal waste in the United States in 1997. Almost 40% of the municipal waste stream is composed of paper and paperboard, about 10% plastics, about 13% metals and glass, and about 13% yard trimmings. The remainder consists of miscellaneous materials (wood, rubber, textiles, and so on). Municipal solid waste does not include segregated medical waste, but does include some medical waste that is mixed in.

The quantity of municipal solid waste in the United States has been increasing (see Table 2-2) despite government attention to the practices of waste reduction at the source and to recycling. Factors that contribute to the rate increase include the following: the U.S. population is growing (from 180 million in 1960 to 249 million in 1990 to a projected 276 million in 2000); per capita generation of waste has increased because of increasing consumption of nondurable, disposable items, and durable items, as well as extensive use of packaging.

As shown in Table 2-2, the per capita generation of municipal solid waste in the United States increased from 1960 to 1990, but decreased from 1994 to 1996. The decrease in per capita generation is attributable to increased on-site composting of organic materials from 1990 to 1996. Despite the results of recycling and composting, the nation faces the challenge of increased total waste generation as long as population continues to increase (Figure 2-2). The amount of discards after recovery was higher in 1996 than in 1970, which indicates that the

FIGURE 2-1 Municipal solid-waste composition by weight, 1997. (Total weight = 217 million tons.) Source: Franklin Associates 1998.

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