Environmental Engineering Reference
In-Depth Information
4.6
Mixed Paper
Mixed paper includes discarded mail (third-class mail), telephone directories,
catalogs, books, and magazines. Mixed paper may include all types of paper
generated in offices and houses. Packages coated with plastics, such as frozen
food and tissue containers, are not acceptable for recycling. Usually mixed papers
may include other types of paper that are normally collected separately, such
as office paper or old magazines. In 2006 10.3 million tons of mixed papers
were generated in MSW. Out of these, 3.74 million tons, or 36.4 percent, were
recovered and 6.53 million tons were discarded. In general, the private sector
was responsible for more than 80 percent of the recovered quantity. Mixed paper
is the fastest-growing recovered paper category in the past several years. This
growth means that the industry is recovering a wide range of papers, but some
paper grades may reach their maximum achievable levels quickly. Magazines
and catalogs are collectively referred to as old magazines, since they are made
of the same materials and are equally useful for end users. Old magazines, like
other mixed paper, have traditionally been used as a low-grade paper supply
for production of paperboard and tissue paper. Recently they have emerged as a
valuable ingredient for recycled newsprint production, which has resulted in its
collection separately from the recovered paper.
4.7
Plastics
The amount of plastics consumed annually in the United States has been growing
steadily. Its generation in the MSW increased from less than 1 percent in 1960
to 11.7 percent in 2006, as can be seen in Table 5.1. In 2006, the United States
generated 29.5 million tons of all plastics. Its improved strength, low density,
user-friendly design and fabrication capabilities, and low cost are the drivers to
such growth (Subramanian 2000). Plastics are a small but significant compo-
nent of the waste stream. There are seven types of plastics coded from 1 to 7,
but the major types of plastics now recycled in most communities are type 1,
polyethylene terephthalate (PET), and type 2, high-density polyethylene (HDPE).
4.7.1 PET Plastic
One of the most popular resins used by the plastics industry is polyethylene
terephthalate (PET), also known as polyester. It is extensively used in different
variety of applications (e.g., plastic soda bottles). It is heavily used as polyester
fiber in the manufacturing of clothing and carpeting. PET usage has grown rapidly
due to the growth of soft drink container business recycled. The single-serve
container is the fastest-growing market for PET bottles. According to U.S. EPA
(2007), 3.06 million tons of PET were generated in MSW in 2006. Out of those,
0.62 million tons were recovered and 2.44 million tons were discarded. Soft drink
bottles represent more than 30 percent of the PET generated (0.94 million tons) in
the MSW. Recovery (0.29 million tons) would therefore target the largest portion
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