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Recycling Solid Wastes 157
bottles were recovered at a rate of 22.8% in 1999. Milk and water bottles (HDPE) were recovered at
an estimated 23.8% in 1999. Significant recovery of plastics from lead-acid battery casings and other
containers was also reported (APC, 2002). According to the U.S. EPA (1999), however, the plastics
industry recycled 5.2% of postconsumer polymers in 1997 and that rate was expected to increase
marginally at best over the next few years. The same report ranks plastics recycling at the bottom of
all recycled materials listed. The plastics industry has recently launched an intensive public relations
campaign and research program to enhance the image of plastic as an easily recycled material.

6.12 YARD WASTE
The U.S. EPA (1999) defines yard waste as grass, leaves, and tree and brush trimmings from resi-
dential, institutional, and commercial sources. There are limited data on the composition of yard
wastes; however, it is estimated that the average composition is about 50% grass, 25% leaves, and
25% brush on a weight basis. These numbers will vary as a function of climate, region of the coun-
try, and season of the year.
Due to the huge volumes of yard wastes produced, along with concerns over diminishing land-
fill space, many states have enacted legislation to divert these wastes away from landfills. By 1998,
22 states and the District of Columbia, representing more than 50% of the U.S. population, had
enacted legislation banning or discouraging yard waste disposal in landfills. Such legislation has led
to an increase in the use of mulching lawnmowers and backyard composting. Many municipalities
have also established compost programs near waste transfer stations or landfills.
About 3500 composting facilities for yard waste exist in the United States (U.S. EPA, 2001).
These vary in size and sophistication as well as in terms of quality and quantity of finished product.
Based on sampling studies at landfills and transfer stations, a total of 11.5 million tons of yard
wastes were recovered for composting in 1997, the second largest fraction of total recovery of the
waste stream. The percentage of yard waste composted (41%) has more than doubled since 1992.
This is due to increased numbers of yard waste composting facilities, more material being handled
at facilities, and bans of yard waste from landfills by states (U.S. EPA, 2001). Within the past few
years, however, composting has increased by lesser amounts, suggesting that much of the impact of
the states’ bans of yard waste from landfills has taken place.
Details of the composting process are discussed in Chapter 8.

6.13 FOOD WASTE
Food wastes include uneaten food and food preparation waste from residences, commercial estab-
lishments (restaurants, etc.), institutional sources (school cafeterias, hospital cafeterias), and indus-
trial sources (factory lunchrooms). Food waste generated during the preparation and packaging of
food products is not included in the U.S. EPA estimates for food waste. Food waste generation from
residential and commercial sources was estimated using data from sampling studies from parts of
the country combined with demographic data, grocery store sales, and restaurant sales. The esti-
mated food waste production was 24.6 million tons in 1999 (U.S. EPA, 2001).
As mentioned in Chapter 2, a substantial portion of food wastes generated during the 1940s and
1950s was fed to hogs. Today, however, “recycling” of food waste primarily refers to its incorpora-
tion into the composting process for later use as a soil conditioner or landscaping material. The U.S.
EPA (1999a) estimates that approximately 285,000 tons of food wastes are recycled (i.e., com-
posted) annually.

6.14 TIRES AND RUBBER

It is estimated that between 2 and 3 billion tires have been disposed in the United States alone, and
another 270 million tires (weighing 3.4 million tons) are added to the waste stream every year