Reduced Use and Recycling

There is growing concern about the excess use of plastics, particularly in packaging. This has been done, in part, to avoid the theft of small objects. The use of plastics can be reduced through a better choice of container sizes and through the distribution of liquid products in more concentrated form. A concern is the proper disposal of waste plastics. Litter results from careless disposal, and decomposition rates in landfills can be extremely long. Consumers should be persuaded or required to divert these for recycling or other environmentally acceptable procedures. Marine pollution arising from disposal of plastics from ships or flow from storm sewers must be avoided. Disposal at sea is prohibited by federal regulation.

Recycling of plastics is desirable because it avoids their accumulation in landfills. While plastics constitute only about 8 percent by weight or 20 percent by volume of municipal solid waste, their low density and slowness to decompose makes them a visible pollutant of public concern. It is evident that the success of recycling is limited by the development of successful strategies for collection and separation. Recycling of scrap plastics by manufacturers has been highly successful and has proven economical, but recovering discarded plastics from consumers is more difficult. It is well recognized that separated plastics can be recycled to yield more superior products than possible for mixed ones.

Labeling plastic items with symbols has been employed, which enables consumers to identify them easily for placement in separate containers for curbside pickup. However, success depends on how conscientious consumers are in employing such standards and the ability of collectors to keep various types of plastic separate. Even a small amount of a foreign plastic in recycling feedstock can lead to the appreciable deterioration of properties, and it is difficult to achieve a high degree of purity. Manual sorting at recycling centers helps, but even trained sorters have difficulty identifying recyclables. Furthermore, manual sorting is an unattractive task and retaining labor willing to be trained for this is problematic. Automatic sorting techniques have been developed that depend on various physical, optical, or electronic properties of plastics for identification. Such methods prove difficult because of the variety of sizes, shapes, and colors of plastic objects that are encountered. Although in principle it is possible to create devices that can separate plastics with varying degrees of success, the equipment generally becomes more expensive with increasing efficiency. Technology for this continues to improve, and it is becoming possible to successfully separate mixed plastics derived from curbside pickup using such equipment.

To separate plastics, it is first necessary to identify the different types as indicated in the table. One must also distinguish between thermoplastics and thermosets. The latter, as found in tires and melamine dishes, has molecules that are interconnected by "crosslinks" and cannot be readily melted for recycling unless they are chemically reduced to low-molecular-weight species. For tires, recycling has not proved economical so disposal has involved grinding them up as asphalt additives for roads or burning in cement kilns.

Over 1.5 million pounds of plastic bottles were recycled in 2000, representing a four-fold increase in the amount of plastic recycled the previous decade. Nonetheless, the capacity to recycle bottles appreciably exceeds their supply by about 40 percent, so local governments and environmental groups need to encourage greater participation in this practice among consumers.

Profitable operations are currently in place for recycling polyethylene terephthalate (PET) from bottle sources and converting it into products such as fibers. One persistent problem, though, is obtaining clean enough feedstock to avoid the clogging of orifices in spinnerets by foreign particles. This has limited the ability to produce fine denier fibers from such sources. PET recycling is also constrained by regulations limiting its use to produce items in contact with food because there had been concern about contamination in consideration of improved recycling techniques.

A leading candidate for recycle feedstock is carpets because replacement carpets are usually installed by professionals able to identify recyclables and who serve as a ready source for recycling operations. They face the problem, however, of separating the recyclable carpet components from other parts such as jute backing and dirt. Such recycling operations have been only marginally profitable.

Polystyrene (PS) is another potentially recyclable polymer, but identifying a readily collectable source is problematic. One had been the Styrofoam "clamshells" fast-food chains use to package hamburgers. Recyclers were able to profitably collect polystyrene from such sources and produce salable products. However, largely because of public pressure, this use of polystyrene has

MAJOR TYPES OF PLASTICS BY S.P.I. CODES

SPI Code Type of Resin Example Products % of Plastic

1

PET - Polyethylene terephthalate

Soft drink bottles, medicine containers

0.5%

2

HDPE - High-density polyethylene

Milk and water bottles, detergent bottles, toys

21%

3

PVC - Polyvinyl chloride

Pipe, meat wrap, cooking oil bottles

6.50%

4

LDPE - Low-density polyethylene

Wrapping films, grocery bags

27%

5

PP - Polypropylene

Syrup bottles, yogurt tubs, diapers

16%

6

PS - Polystyrene

Coffee cups, "clamshells"

16%

7

Other

8.5%

TYPES OF PLASTIC PACKAGING

By Type of Use
By Type of Resin

• A one gallon plastic milk container that weighed 120 grams In 1960 now weighs just 65 grams.

• The average 1992 American car contains 300 pounds of plastic made from about 60 different resins.

• Every year, we make enough plastic film to shrink-wrap the state of Texas.

• 10% of the average grocery bill pays for packaging (mostly paper and plastics)—that's more than goes to the farmers.

• In 1993, plastics accounted for 11.5% of the U.S. municipal waste stream by weight (23.9% by volume). In 1994, plastics comprised 9.5% (by weight) of the waste stream.

• The rate of plastic soda bottle recycling rose from 33% in 1990 to 50% in 1994.

• 0.9 million tons of plastics (4.7%) were recycled in the U.S. in 1994.

• Products made from recovered plastic bottles include drainage pipes, toys, carpet, filler for pillows and sleeping bags, and cassette casings.

source: Modern Plastics, January, 1992

declined, so related recycling practices have largely disappeared too. Cafeteria items from school lunchrooms are another potential, but the collection of such objects involves the development of an infrastructure, often not in place. In these cases, it is necessary to separate the polystyrene from paper and food waste, but washing and flotation techniques have been developed for this purpose.

Increasing amounts of plastic components appear in automobiles, and their recovery from junked cars is a possibility. Its success depends on the ability of a prospective "junker" to identify and separate the plastic items. Three efforts may aid in this accomplishment:

1. The establishment of databases to enable junkers to learn what kinds of plastic are used in what parts of what model cars.

2. A reduction in the number of different plastics used for car construction.

3. The design of cars such that plastic parts may be removed easily (this would require special types of fasteners).

This illustrates a general need—the design of plastic-containing products with the ability to recycle in mind. As a consequence of public concern about the environmental problems arising from plastic use, industry is responding to these needs. The effort continues to use fewer different kinds of plastics and to adopt designs that allow for easier recycling but still retain desirable properties.

There are, however, some worthwhile products that can be produced from mixed plastic, such as "plastic lumber" used for picnic benches and marine applications such as docks and bulkheads that successfully replace wooden lumber which often contains toxic preservatives and arsenic. But, the market for such a product is limited, so efforts to obtain separated plastics are preferred.

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