RECYCLING WASTE MATERIALS 1059
that these containers were returned to the place of purchase.
Imposition of deposits effectively kept much of the glass
from the waste stream. The plastics have, however, added
significantly to the volume of waste and have made waste
management more difficult.
A controversial subject is “Beverage container deposit
legislation” (BCDL), commonly called bottle bills. It has
been found that such bills are effective in controlling litter.
The US Environmental Protection Agency estimates that
the weight percentage of plastics in municipal solid waste is
about 7–9% but this material occupies 25–30% of the total
waste volume.
Many plastic containers today are stamped with symbols
as an aid to recycling. These are shown in Figure 1 and are
described in Table 1. Only PET and HDPE are commonly
collected for recycling.
In 1989 plastics were a part of 800 state and local waste
management related bills. This was indicative of the “green-
ing” of consumer buying patterns and more stringent waste
disposal regulations. Many major industrial users of plastics
are now looking closely at further uses of plastics as a part
of “design for disassembly” for ease of separation and reuse.
Public attitudes seem to have changed. Once recycled mate-
rials in products were regarded as shoddy. Now recyclability
is seen as a good selling point. Prices for recycled plastics
are now close to those for virgin materials. It is expected that
recycled plastics prices will stabilize at 80–90% of those for
virgin materials. Major plastics manufacturers have become
involved in plastics recycling efforts. In Europe, petrochemi-
cal producers have joined to form recycling research units.
It is felt that industry must become actively involved in
recycling. If it does not, legislation curbing applications and
seriously affecting producers may be introduced. In Japan,
which incinerates much of its municipal solid waste, indus-
trial plastics producers have also become deeply involved
in plastics recycling research. Much work is being done on
conversion of plastics to fuel oil.
A major problem in plastics recycling is the low weight-
to-volume ratio. It is unprofitable to transport uncrushed
containers over long distances. As mentioned earlier, sepa-
ration at the end user level is most important. Also, different
types of plastics are mixed in the waste stream and their sim-
ilar characteristics make them difficult to separate. Material
recovery facilities (MRF), sometimes called municipal recy-
cling facilities, have been established to address the latter
problem.
Plastics for reuse are ground or chopped, washed and
dried prior to use in extruding machines. Ground plastics
may be remelted. This allow additional purification and
assists in obtaining a more uniform color. Plastic pellets as
the end product can be molded or extruded the same as virgin
material. Plastic chips are separated by density differential
in liquid flotation processes. Water is commonly used but
hydrocarbon liquids have been tried. PET and HDPE are
the plastics most commonly collected for recycling from
municipal solid waste and inclusion of polyvinyl (PVC)
bottles is not desirable. PVC melts and decomposes at repro-
cessing temperatures. Methods for automatic detection andseparation are under development. One company, requiring
consistent container color, has sandwiched recycled polyeth-
ylene between layers of virgin material. It is generally recog-
nized that supply and regulatory problems must be solved in
order to make plastics recycling a viable industry. At present
the overall recovery rate for plastics is about 1–2%.
The majority of the paper recycling market is newsprint
and corrugated paper. However, more valuable grades of
paper are found among the 70 commercial grades of waste-
paper. Many of these are now incinerated or landfilled.
By the end of the 1990’s about one quarter of the pulp
supply in the US came from recycled sources. It is expected
that capacity for “secondary” fiber (including recycled and
byproduct material) will grow at a rate twice as great as that
for virgin (primary) fiber. Chemicals used in making paper
products are being reformulated or used differently in order
to assist recycling efforts.
The European Economic Community (EEC) averages a
recycle rate of about 35% for paper, about the same as that of1 2 3 4 5 6 7PSOTHERPPLDPEVHDPEPETFIGURE 1C018_003_r03.indd 1059C018_003_r03.indd 1059 11/18/2005 11:05:15 AM11/18/2005 11:05:15 AM