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The strain plastics put on solid-waste disposal systems, and how to improve plastics-recovery efforts.
The strain plastics put on solid-waste disposal systems, and how to improve plastics-recovery efforts.
Uses of Plastics in the United States Economy
Plastics constitute one of the fastest-growing categories of materials used–and disposed of–in our economy. In 1970 plastics comprised less than 3 percent of the municipal solid-waste stream by weight; in 1986 the figure had risen to 6 percent (see figure 1); recent figures indicate that plastic waste comprises about 8 percent of the stream by weight and nearly 30 percent by volume. Projections for the year 2000 estimate that plastics will comprise at least 10 percent of the stream by weight. However, due to new efforts to reduce packaging size, volume may increase more slowly.
The increase in plastics use, which is a national trend, may pose serious problems to waste-disposal operations, almost all of which are managed by local governments. As landfill space–long the most common disposal method–diminishes, and new landfills are becoming nearly impossible to site, solid-waste planners must look to other methods of waste management. Resource recovery through mass-burn incineration, the alternative most frequently mentioned, is often cited as an acceptable method of "recycling" waste plastic (due to the high energy content of plastics), but serious concerns over health issues have been raised. Recycling, more and more considered the most acceptable method of disposal, is firmly established for materials such as glass, paper, and metals, but is in its infancy in regard to plastics.
Currently, the two largest market areas for plastics in the United States are packaging and the building and construction industries. The use of plastics in packaging increased from 6.7 billion pounds in 1974 to 12.4 billion pounds in 1984. Projections indicate that use will increase to 16.1 billion pounds in 1990 and to 19.1 billion pounds by 1995. Because plastic packaging materials have a life span of less than one year, consumption by the industry for this purpose is nearly equal to the amount of waste. Approximately 29.4 billion pounds of postconsumer plastic wastes were discarded in 1984; over one-third of this came from packaging that was quickly discarded.
The use of plastics in building and construction materials increased from 4.3 billion pounds in 1974 to 9.7 billion pounds in 1984. Use is projected to increase to 12 billion pounds in 1990 and to 14.5 billion pounds in 1995. Since these materials generally have a life span of 25 to 50 years, substantial amounts of plastic wastes from building and construction undertaken in the 1960s and 1970s are expected to enter the waste stream in the late 1990s and into the next century. If plastic becomes more widely used for these applications, disposal problems may accelerate far into the future. Thus, planning should begin now to address this situation.
Consumer and institutional goods represent the third largest use of plastics. This category includes all carryout packages; disposable plastic serviceware in institutions such as schools, hospitals, and prisons; and throwaways such as razors, lighters, pens, watches, and cameras. Other areas of use include electrical and electronic equipment, furniture and furnishings, transportation, and industrial applications.
The projected growth in all categories of postconsumer plastic wastes in the United States is shown in table 1.
It is estimated that packaging materials account for more than one-third of municipal waste, by volume, in the United States. By weight, the percentages of packaging materials in the municipal waste stream in 1986 were: 14.5 percent paper, 7.6 percent glass, 1 percent aluminum, 4 percent plastic, and 2 percent steel.
The packaging industry is the largest consumer of plastics, accounting for over one-third of all plastic resin use annually. Plastics are used as films for flexible packages, for barrier material on bottles and rigid containers, for soft-drink containers, and for coating on many other items. Packaging is also the largest single source of plastic waste, reaching approximately 13 billion pounds a year, or 40 percent of all plastic waste. Most of the waste plastics are thermoplastics (see Appendix A), and waste plastics are expected to increase as packaging manufacturers continue to switch from other packaging materials. More new materials are developed in this area of the economy than in any other area. The two largest categories of current use are rigid containers and packaging film, accounting for 51 percent and 35 percent of plastics, respectively (see figure 2).
Plastic packaging materials are composed of a variety of different resins and resin combinations. (See Appendixes A through D.) The most common are low-density polyethylene (LDPE), high-density polyethylene (HDPE), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polypropylene (PP). The amounts of plastics used in packaging in 1987 are summarized in table 2 and illustrated in figure 3.
Polyethylene (HDPE and LDPE) makes up over 60 percent of the plastic packaging waste stream. LDPE packaging film, the most prevalent plastic film, is used in applications such as grocery sacks and bread wrap. HDPE containers, which comprise over 50 percent of all plastic containers, are used to package items such as milk, water, laundry detergent, and bleach, and for the basecups of soft-drink bottles. Common packaging and disposable uses of various plastics are listed in table 3.
Polyethylene terephthalate (PET), primarily used in soft-drink bottles, constitutes approximately 14 percent of plastic containers overall. PET is now the most widely used soft-drink container, based on the total volume of soft drinks sold in the United States in 1986: 43 percent of all soft drinks are packaged in PET bottles, compared to 34 percent in 12-ounce cans. In 1988 an estimated 7.5 billion PET bottles were discarded after use in the U.S.; usage is anticipated to double by 1995 to 15 billion bottles a year, or over 2 billion pounds of resin.
Other materials used in packaging, to a lesser extent, include ethylene vinyl acetate (EVA) copolymer, polyvinyl acetate as an adhesive, and ethylene vinyl alcohol (EVOH) as an oxygen barrier. The use of these materials reflects an important recent development in plastic packaging–the use of composite, or multilayer, packaging. These packages contain layers–sometimes as many as 12–of different types of resins and other materials. For example, the squeezable ketchup bottle, now replacing glass, consists of a layer of polypropylene (PP), an adhesive layer, an oxygen barrier layer (EVOH), another adhesive layer, and another layer of PP. The use of EVOH as an oxygen barrier allows manufacturers to package in plastic many foods they previously could not, because of possible contamination. Another example of a composite package now in wider use is the aseptic juice box, or "brick-pack." The package combines plastic and adhesive layers with paperboard and metal foil.
Many such composite packages are now replacing packaging materials with high recycling histories, such as glass and paperboard. The reasons cited for these changes include increased convenience to the consumer, longer shelf life, and lighter weight. But the disposability of the packages and the environmental impacts of disposal have been largely overlooked. As complex combinations of plastic become more common in packaging, the potential recyclability of the solid-waste stream will decrease, since there is no recycling mechanism for these combination packages.
Building and Construction Materials
In 1985 the building and construction industries consumed about 10 billion pounds of plastics. It is expected that by the year 2000 the industry will consume almost 15 billion pounds of plastics in the form of pipes and fittings, plumbing and bathroom fixtures, interior/exterior building materials, and air-supported structures. Unlike packaging, these uses of plastics do not immediately impact the waste stream, but their eventual disposability must be considered in waste management planning for the intermediate and long term.
The largest building/construction use of thermoplastics is for pipe and conduit applications. Almost one-half of the polymers consumed in building and construction is used for piping. PVC, HDPE, LD/LLDPE, and PP are used in potable water pipe, irrigation pipe, drainage pipe, gas pipe, and various other constructions. PS is used for products such as light fixtures and ornamental profiles. PVC is used for window profiles, flooring gutters, foam moldings, and weather stripping, and is the major plastic used in construction. Uses of plastics in durable construction and consumer products are listed in table 4.
Postconsumer plastic waste from the building and construction industries totaled approximately 710 million pounds in 1984, or 2.4 percent of all postconsumer plastic wastes. About 80 percent of these materials were thermoplastics, with PVC and LDPE the most common (46.5 percent and 10.1 percent, respectively); PS was present at 6 percent. Thermosets comprised approximately 20 percent of postconsumer plastic wastes, the most common being phenolics (13 percent) and polyester (6.5 percent).
Postconsumer plastic wastes for the building/construction sector are projected to be 3.9 billion pounds, or 8.9 percent of all postconsumer plastic wastes, by 1995. The growth in the use of plastics for building/construction is projected to be large through the year 2000–surpassed only by the use of plastics in the packaging industry. The building/construction uses of plastics have a life span of 25 to 50 years, the longest of all categories of use. This means that plastic construction wastes present in the waste stream in 1984 were primarily from products manufactured in the 1950s. Thus the "revolution" in the use of plastics for building/construction that began in the 1960s will begin to impact the waste stream in the 1990s and in the next century.
Consumer and Institutional Goods
A wide variety of consumer products use plastics: toys, housewares, disposable cutlery, sporting goods, footwear, medical and health care devices, laboratory supplies, lawn and garden instruments, serviceware, and luggage (see table 4). In 1984 about 4 billion pounds of plastics were used in consumer products; projections show this figure rising to 4.4 billion pounds in 1990 and 4.8 billion pounds in 1995.
Consumer and institutional products are estimated to have a life span of five years. In 1984 this segment accounted for 12.3 percent of the postconsumer waste stream, or 3.6 billion pounds. Ninety-five percent of these materials were thermoplastics. PS, the most common material, constituted an estimated 20.6 percent of waste from this category, or 740 million pounds. Other plastics in the waste stream from consumer goods included LDPE (16.3 percent), HDPE (13.1 percent), PP (13.3 percent), and PVC (11.8 percent). Projections for 1995 estimate that consumer products will account for nearly 10 percent of postconsumer plastic wastes, or 4.4 billion pounds.
The electrical/electronic market includes home and industrial appliances, electrical and industrial equipment, business machines, computers, records, tapes, and batteries. Resins commonly used in this market include polyethylene, PVC, PS, and PP. In 1984 some 2.8 million pounds of plastics were used for these applications; consumption is projected to increase to approximately 2.9 million pounds by 1995.
Products in this area generally have a life span of about 15 years. Therefore, materials used in the manufacture of electrical and electronic equipment in the mid 1980s can be expected to appear in the waste stream around the year 2000. During 1984 this category of economic activity accounted for roughly 8 percent of all postconsumer plastic wastes, or 2.4 billion pounds. By 1995, this category of waste is projected to increase to 2.8 billion pounds.
Furniture and Furnishings
The furniture and furnishings market consists of residential, office, commercial, and institutional furniture, as well as carpets, rugs, wall coverings, bedding, curtains, and blinds. The principal plastic materials in this market are polyurethane foams and PP, used in upholstery and carpets. Wood still dominates the furniture market, but there is an increasing trend toward the use of PVC laminates, particularly for unassembled furniture such as home entertainment centers, shelving, and computer stands.
In 1984 furniture and furnishings manufacturers used roughly 2.2 billion pounds of plastics. Consumption is projected to increase to about 2.4 billion pounds in 1995. These products have an approximate life span of ten years. Postconsumer plastic wastes from this category comprised 7.4 percent of the total postconsumer plastic waste stream, or 4.4 billion pounds, during 1984. Of this, 35 percent was PP and 28 percent polyurethane foam; other materials included PVC (7.3 percent) and urea and melamine (7.8 percent).
Projections for 1995 estimate that products from this category will comprise 7.2 percent of the postconsumer plastic waste stream, or 6.3 billion pounds. Polyurethane foam and PP are expected to continue their dominance.
The transportation market includes automotive, marine, railroad, recreational, and military applications. The use of plastics in the transportation sector is expected to decrease slightly from its 1984 level of 2.1 billion pounds to 2 billion pounds by 1995. Although plastics are anticipated to constitute a larger portion of the typical automobile's weight in the future, recent trends in the use of plastics in automobiles and the production index for transportation equipment indicate that the use of plastics in overall domestic transportation equipment will not increase in the coming decade.
In 1984 postconsumer plastic from the transportation sector totaled roughly 1.9 billion pounds, or 6.7 percent of the nation's postconsumer plastic waste. Fifty-two percent of these waste materials were thermoplastics, including PP (17 percent) and PVC (12 percent); 30 percent were thermosets, with polyester the most common (24 percent); and polyurethane foam accounted for the remaining 18 percent. Projections for 1995 estimate plastic wastes from the transportation sector to be 5.2 percent of postconsumer wastes, or 2.2 million pounds.
Plastics use continues to increase in automobile manufacturing, where new grades of plastics are being introduced for use in body panels, bumpers, and interior components. Thermoplastics are becoming increasingly common in automobile design. The use of plastics for bumper systems in North American–made vehicles is expected to increase by at least 60 percent in the next decade. Nearly 90 percent of the cars sold in the U.S. in 1990 are expected to have one or more major plastic components in their bumpers. By 1992 the typical U.S. car is likely to contain at least 400 pounds of plastics and composites, up from 200 pounds in 1984.
The industrial machinery market includes signs and displays, farm and construction equipment, machine tools, marine supplies, and engine parts. In 1984 this sector of the economy used 0.4 billion pounds of plastics; usage is expected to decrease to 0.3 billion pounds in 1995. In 1984 postconsumer plastic wastes from this category comprised 1.2 percent of total postconsumer plastic wastes, or 360 million pounds. HDPE, PP, nylon, and phenolics were the predominant materials. In 1995 this sector is estimated to comprise 1 percent of postconsumer plastic wastes, or 433 million pounds.
Adhesives are used as alternatives to mechanical fasteners in automotive, aerospace, and other structural applications; for bonding dissimilar materials in multilayer constructions; and for lamination and coextrusion of polymeric building materials and weatherable thermoplastic panels.
Use of plastics in the manufacture of adhesives reached 2.5 billion pounds in 1985, with the majority being vinyl (34 percent), thermosets (30 percent), and styrenics (23 percent). Usage is expected to grow to nearly 3.6 billion pounds by 2000, with thermosets comprising a 32 percent share, vinyl 29 percent, and styrenics 24 percent.CHAPTER 2
Focus on Packaging
Although the use of plastics is increasing in almost all sectors of the U.S. economy, the most rapid growth is occurring in the manufacture of packaging materials. The packaging portion of the municipal waste stream has become the focus of attention for solid-waste planners, legislators, and environmentalists because it is from packaging that major gains in recycling must occur if the nation is to have an effective integrated waste-management system.
Excerpted from Plastics by Nancy A. Wolf, Ellen D. Feldman. Copyright © 1991 Environmental Action Coalition. Excerpted by permission of ISLAND PRESS.
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