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Update on plastics and the environment: progress and trends.

Longer term basic research in the field of polymer compatibilization is being addressed by many academic and commercial research facilities. In theory, compatible polymers need not be separated before reprocessing. However, most polymers are thermodynamically immiscible and thus incompatible when mixed. Most research on polymer blend compatibilization focuses on specific combinations of polymers and attempts to develop compatibilizers or compatibilization techniques for these subgroups.

Resin by Resin: PE, PET, PP, PS, PVC, Other Engineering Thermoplastics, PUR and Thermosets PART ONE

Recycling of clean industrial plastic scrap has been practiced since commercial-scale plastics processing began. Post-consumer plastics recycling was first addressed during the energy crunch of the early 1970s. Research at that time was motivated by a desire to reduce foreign oil and petroleum dependence, and may also have been influenced by post-Earth Day interest after the first Earth Day in 1970. After the energy crises passed, the issue of recycling post-consumer plastics faded away until the 1980s, when the onset of the "green revolution" got the public actively concerned about solid waste disposal in general and recycling in particular. In order to meet marketing and legislative demand for green products and processes, there has been extensive development in plastics recycling and plastics additive reformulation over the last few years. The manufacturer has been forced to think about the cradle-to-grave life cycle for every product. Some practices have cost money while some have helped increase profits, just as some are here to stay while others are not.

This article updates the reader on recent actions taken by both the public and the industry that have helped advance plastics recycling and related technologies. It gives an overview of a) current legislation and solid waste issues affecting plastics, b) current recycling practices and programs that involve items made with plastics, and c) related developing technologies. The material presented here focuses primarily on activities in the U.S. and, to a lesser extent, Europe, and it encompasses the period between 1990 and 1992. It is not intended to be exhaustive, but rather to give the reader an idea of the type and extent of activities being pursued.

REGULATIONS AND ENVIRONMENTAL CONCERNS RELATED TO PLASTICS AND PACKAGING

General Recycling Legislation

Historically, deposit laws were set up as anti-litter measures. Nine states have adopted them, and collection of aluminum cans and polyethylene terephthalate (PET) beverage bottles from those states has helped recycling efforts progress, especially in the case of PET. As of January 1991, Maine put more forms of packaging under its deposit system, other than just PET bottles and aluminum cans for soft drinks. Containers now to have deposits include soft drink, beer, liquor, and wine bottles, and juice containers (1).

Not everyone, however, considers deposit legislation as something positive. Recycling officials often object to bottle bills. They raise concerns that deposit systems remove the most valuable, revenue-generating materials from the recycling stream. It is the sale of aluminum, glass, and PET that helps subsidize curbside programs. On the other hand, advantages to a combined curbside/deposit system are that an increased amount of material is removed from the waste stream, collection costs are reduced, and disposal costs are avoided. The National Container Recycling Coalition developed a model to look at collection costs, tons of materials diverted, and revenues derived from sale of materials in both curbside and combined curbside/deposit programs. Figures for the curbside only system were based on successful Rhode Island recycling programs. The combined system is predicted to divert 31% to 47% more material from landfills, largely because of the consumption of soft drinks away from home that never get into residential waste streams. Some recycling revenue loss is definitely predicted because of reduced amounts of aluminum, glass, and PET, but it can be made up by removing deposit containers from curbside pickups and redeeming them. A pilot project of this type exists in Connecticut. Alternatively, legislation can be set up to return unclaimed deposits to localities. At present they are kept by the beverage industry. In 1990, Michigan and Massachusetts enacted legislation for unredeemed deposits to go into a state fund, with the majority of the fund paying for environmental programs (2). New York State proposed a similar bill in 1991 (1).

Waste haulers have complained at times that they can't get rid of green and brown bottles, newspapers, milk jugs, and even aluminum that accumulated at recycling collection centers, especially in the Northeast and Midwest. Some haulers have dumped or burned separated recyclables when they ran out of storage space. The problem is that the supply side has grown through curbside recycling programs, but the demand side has not (3). Relying on consumer "good will" to buy recycled products is not enough. Consumers often say they will pay more for products with recycled content, but when it comes down to purchasing, they are reluctant, especially during a recession (4).

Proposed solutions to the lack of markets include instituting legal incentives to stimulate demand. The Resource Conservation and Recovery Act (RCRA) of 1976 requires the Environmental Protection Agency (EPA) to set guidelines for government procurement of recycled products, and it mandates federal agencies and contractors to implement affirmative procurement programs. Forty-one states and at least 35 local governments have established programs to procure recycled materials and set standards to define the term "recycled" (5). President Bush issued an executive order that requires "federal agencies (to) promote cost-effective waste reduction and recycling of reusable materials from wastes generated by federal government activities." The order encourages "the recycling of recyclable materials such as paper, plastic, metals, glass, ... and used oil." It establishes a forum for developing and studying policy options and procurement practices that will promote environmentally sound and economically efficient waste reduction. The General Services Administration will issue the implementing regulations necessary to comply with the directive (6).

According to environmental groups, the EPA procurement guidelines have not been successful because they do not specify post-consumer recycled content, they provide little incentive to seek secondary materials, cover only a limited number of materials, and are not seriously enforced. Instead, these groups advocate "Recycled Content" legislation to stimulate demand, mandating use of recycled materials in production. An example is the recycled content newsprint legislation signed in Arizona, California, Connecticut, Maryland, and Missouri in 1990 (5). California's law stipulates that newspapers must use at least 50% recycled paper by the end of the decade. Laws exist in about nine states that require minimum percent of recycled content in certain products including newsprint, aluminum and glass and plastics packaging, tissue; and other paper goods. If government programs for paving with glassphalt (asphalt blend with 5% glass as aggregate) would be instituted, markets for surplus glass, especially colored glass, would be created. Alternatively, a few states offer low interest loans, grants, or tax credits to companies that make products from recycled materials (3).

Plastics Coding and Recycling Labeling

The Society of the Plastics Industry (SPI) first proposed a resin coding plan in 1965 (7). By now, many states have adopted plastic bottle coding laws using the SPI labeling system (8). This type of labeling can assist in operations that utilize hand-separation of resins.

A different labeling problem has recently evolved. With the growth of consumers' environmental awareness, manufacturers have been making claims and labeling their products so as to convey the idea that their products are "environmentally friendly." Many of these claims are misleading and even false. California law now makes it illegal to represent a consumer product in advertising as "ozone-friendly," "biodegradable," recyclable, recycled, etc., without meeting criteria laid down by the U.S. Federal Trade Commission (FTC). "Recycled" is defined by the FTC as an item containing a minimum 10% by weight of reclaimed post-consumer material and can be recycled in every county having a population of at least 300,000. Other states are adopting different and sometimes conflicting definitions (9). The Northeast Recycling Council, representing state officials and legislators from ten states, recently adopted model standards for labeling packages and products in regard to reusability, recyclability, and recycled content (10).

From Plastics Bans to Packaging Bills

The first round of battles against plastics and plastics packaging came in the form of proposed bans, especially bans against expanded polystyrene (PS) for packaging. A survey in 1990 showed that approximately 84% of the U.S. public backed bans on PS in fast-food packaging. Forty-two laws to ban or restrict PS use were in place in the U.S. by September 1990, and more were proposed (11, 12). The Vermont Senate narrowly defeated a ban on all PS food packaging by a vote of 15-14 (13). Multilayer aseptic drink boxes, which are composed of paper, foil, and low- density polyethylene (LDPE), were banned in Maine in 1991 (12). In a hotly contested case, the New York State Court of Appeals upheld Long Island's Suffolk County's landmark ban on plastic grocery bags and many plastic containers (14).

More than 500 solid waste management proposals affecting the plastics industry were introduced in 48 state legislatures in the U.S. in 1991. Of these, 80 of were enacted. The level of state legislative activity in 1991 equaled the previous year's pace, but pressures on industry shifted from product bans to proposals to impose strict recycling and recycled content requirements on entire categories of packaging. One hundred five (105) bills were introduced requiring that plastics meet a recycling standard; 42 bills mandated recycled content in packaging (6). Recycled content legislation is usually set up with a scaled percentage requirement to allow industry time to create recycling infrastructures and to ensure increased use of recycled materials over time. Enforcement provisions include taxes, fines, or bans for noncompliance (5).

The legislature in Massachusetts has been working on a packaging initiative with the Massachusetts Public Interest Research Group (MassPIRG) in a number of forms since 1989. MassPIRG's bill in 1990 called for all packaging to be either a) reusable five times for the original purpose, b) have 50% recycled content, or c) have a recycling rate of 35% by 1996 and 50% by 2000. Industry battled the MassPIRG bill and offered a more lenient version for which only rigid packaging (8-oz to 1-gal bottles and containers) was to be targeted. The industry bill called for such packaging to be either a) refilled five times or demonstrated to be repeatedly reused by the consumer, b) have 25% recycled content, c) have a recycling rate of 25%, or d) have 5% reduction in size or volume from five years previous. Penalty for noncompliance in the MassPIRG bill is a ban, and in the industry bill it is a fine of up to $100,000, with revenues generated dedicated toward development of a recycling infrastructure.

The MassPIRG bill unduly targeted plastics since each individual resin is targeted for a given rate, whereas recycling rates of other materials do not target packaging alone. For example, paper could easily reach its rate target through existing levels of cardboard carton and newspaper recycling--without the need to recycle paper packaging such as paper milk cartons. An example of a potential result of such legislation is that presently unrecyclable paper milk cartons will be on the store shelves while recyclable high-density polyethylene (HDPE) milk jugs will not (15). On the other hand, the original industry bill for Massachusetts may have been too lenient, especially with respect to a five-year 5% source reduction stipulation. Rather than draw up a compromise bill together with industry, MassPIRG ultimately withdrew their bill and offered it as a referendum in the November 1992 balloting. In the end, the majority of the public's votes was against MassPIRG's referendum.

Legislation modeled on the MassPIRG bill was defeated by state legislatures in Florida, Illinois, and Maine in 1990.(16) In 1991, California and Oregon passed bills that more closely reflect the industry's proposed bill in Massachusetts. California approved bill SB235 requiring that 8-oz-5 gal size rigid plastic containers have a 25% recycling rate, unless they are made from PET, for which the rate is 55%. Alternatively, they must be reusable, refillable, or source-reduced by 10% (17). Oregon's bill (SB 66) requires rigid plastic containers to achieve a 25% recycling rate or have 25% recycled content by 1995, and also calls for mandatory resin coding of plastic containers as of January 1992, using the SPI number system (18). Also, both bills reflect the industry's position that an infrastructure must exist before recycling rates or content goals can be enforced; thus the laws go into effect only if 60% of the homes in the states have curbside recycling programs by January 1, 1995. In addition to the California and Oregon bills, twelve similar proposals were enacted in 1991 (6).

The German government has also been determined to make headway to reduce packaging waste. They issued a mandatory $0.03 deposit for all beverage, liquor, soap, detergent, and paint containers (9,19). By January 1993, a 50% (by weight) recycle rate for all packaging must be collected, with 30% of the plastics, 70% of glass, 65% of tinplate, and 60% of aluminum, paper, and cardboard recycled. By July 1995, the requirement rises to 80% of packaging materials to be collected, with reprocessing of 80% of plastics, and 90% of glass, tinplate, and aluminum (20). Also, all secondary (transport) packaging, including blister packs and exterior cartons and films, can be returned to the point of sale as of April 1992. Thus, shops must take back plastic bags, wrapping paper, and boxes from consumers (9,19). Those taking part in the recycling scheme can mark their products with a green dot. The Environmental Ministry sees the packaging laws as pilot regulation for possible similar legislation on printed matter, cars, and electronics. The point that is being made is that manufacturers should take responsibility for the waste management of their products (21). Industry claims that the recycling quotas are too harsh, and that the laws emphasize collection over recycling, ignore the potential role of incineration (which is not accepted in the definition of disposal under this law), and remove all responsibility for packaging recovery from municipal authorities, placing it instead on manufacturers and retailers (9). In any case, they are setting up recycling systems to collect and sort packaging in order to reuse or recycle it. The German plastics suppliers' trade association has announced plans, together with plastics-collection organization DSD, to increase recycling capacity from the current 50,000 (metric) tons/yr to 300,000 tons/yr (22).

France followed Germany's lead and drafted legislation mandating that producers take back packaging waste. According to the decree, beginning in 1993, packers, fillers, and importers must "provide for or contribute to recovery of packaging waste from their products by direct collection from consumers or through an organization that takes back waste from municipal authorities." An operation called Eco-emballage is being developed for the latter scheme. In its current draft, the decree sets a recovery target of 75% by weight by 1997. Of this, 90% must be material or energy recycled. This decree is in line with general European Community thinking as set out in a recent directive on packaging waste (23). In Sweden, 40% of all plastics packaging that is not burned must be recycled. (Sweden incinerates more than 55% of its household waste in energy recovery facilities.) The nonreturnable PET bottle was banned in Sweden in July 1991, and a returnable/refillable PET bottle program for 1.5 liter soft drink bottles was mandated (17).

Durables

Durable goods are items designed to last three years or more. They encompass electronics, vehicles, appliances (including business machines and white goods such as refrigerators and washing machines), construction materials, and furniture. Over 10 billion lbs of plastic go into such items every year (11). Building-site construction waste may soon be regulated in Europe (24). At least twelve states in the U.S. have outlawed appliance disposal in landfills (25). Other bills were introduced in Congress on the subject of recycling appliance parts (26).

A number of proposals on the subject of automobile disposal and recycling have been introduced by the government in Germany. Proposed legislation would levy a tax on new cars to pay for their eventual disposal. Tires already carry such taxes (1). Another proposal from Germany's Environmental Minister is that by the end of 1993, car manufacturers, or their representatives in the case of imported cars, will be responsible for the final disposal of their cars. This proposal also mandates that auto makers recycle 20% (by weight) of plastics in cars by 1996 and 50% by 2000 (27,28). Draft legislation was submitted in 1991 stipulating that by 1993, plastics in new cars produced in Germany would also be required to contain 25% by weight recycled materials. Plastics were the only raw materials specifically mentioned. It also required automobile manufacturers to set up systems for accepting, sorting, and recycling parts from old automobiles (29).

Incineration and Polyvinyl Chloride (PVC)

In Japan, municipal solid waste (MSW) is presorted to separate combustibles from noncombustibles for incineration. About 50% of total MSW there, including 67% of plastics waste, is disposed of by incineration via 2000 municipal incinerators (though most of them do not have waste-to-energy integration at present). Landfilling accounts for only 16% of MSW and 23% of plastics disposal in Japan (30). In Europe, 30% of MSW is incinerated on average (31). Switzerland processes about 72% in waste-to-energy plants, compared to only 2% in the United Kingdom (32).

In the U.S., 320 incineration units, of which approximately 130 include waste-to-energy capability, handle less than 15% of total U.S. MSW (33). But the suggestion of incineration on the part of the plastics industry is opposed by environmental activists. Their main objections with regard to incineration are air emissions and cost. Efficient pollution controls make up 20% to 30% of the cost of the incineration system (11). Compared to landfilling, incineration is competitive in cost only in landfill-scarce areas such as the Northeast (34). Under the U.S. Clean Air Act, the EPA set new emissions standards for MSW incinerators that were to have become effective in August 1991. The new standards affect emissions of chlorinated dioxins and furans, nitrogen oxides, metal, sulfur dioxide, and hydrogen chloride, among others components, and are applicable to incinerators with capacities of more than 250 tons/day (35).

About 18% of all PVC sold in Europe is in the form of packaging. Controversy still exists regarding whether PVC contributes significantly to HCl and dioxin and furan emissions from municipal waste incinerators. PVC packaging has thus been the target of bans in Western Europe (31). The Swiss parliament, for example, passed a law banning PVC bottles for beer, soft drinks, and mineral water (36).

In addition to PVC, chlorine from paper, wood, and other waste also contributes to formation of HCl in incinerated MSW. Industry sees PVC as a minor contributor to chlorine in MSW, but a 1989 study by Denmark's EPA showed that when the amount of PVC fed to municipal incinerators was doubled, HCl emissions increased by 62%. PVC was found to be responsible for 90% of the HCl at eleven incinerators, while bleached paper contributed less than 10% of chlorine emissions. With scrubbers, HCl emissions could be negligible at all Danish sites and such equipment was made mandatory by 1992. According to a Scottish study, only 3% of total atmospheric HCl is due to PVC given modern incinerators, while coal-burning contributes 93%. Sulfur dioxide (SO2) and nitrogen oxide (NOx) are the main components in acid rain and result from the burning of fossil fuels, such as from auto exhaust (31).

As for a possible link between PVC and dioxin formation, results from the Danish study suggest that PVC does play a role in forming dioxins at municipal incinerators. However, a 1987 study by the New York State Energy and Development Authority at the Pittsfield, Mass., Vicon incinerator showed opposing results. In the Danish study, when the amount of PVC fed to municipal incinerators was doubled, dioxin emissions increased by 34%. The Pittsfield study compared emissions of typical MSW to a waste stream with no PVC. Results showed no correlation between the amount of PVC in MSW and dioxin formation. Obviously more testing is needed to verify the results of both tests (31).

Heavy Metal-Containing Additives

Lead and cadmium-based stabilizers are not used in disposable PVC packaging materials (11), but they are present in most non-packaging applications of PVC. PVC stabilizers are the source of about 15% of the cadmium found in MSW in the U.S. (31). All plastics contribute approximately 28% of all cadmium in U.S. MSW and 2% of all lead. Data are too limited to determine whether these and other additives contribute significantly to heavy metal content in landfill leachate (37). Some research shows that the amount of cadmium leaching from landfills, measured on a parts per million basis, is considered too small to be a health concern (31). The European Economic Community proposed a ban on cadmium-containing pigments and stabilizers conforming to existing bans in Switzerland, Sweden, Denmark, and Holland. In the U.S., New Hampshire and Connecticut signed into law bans on cadmium, lead, mercury, and hexavalent chromium in packaging products (38), and New York passed a "toxics reduction bill" to lower levels of these components in packaging (39).

Industry is quickly developing alternatives to heavy metal-containing additives. Cadmium-containing heat stabilizers are being replaced by barium-zinc and calcium-zinc products (11). For example, Baerlocher USA, Ferro Co., and Witco's Argus Division all recently introduced lines of cadmium-free heat stabilizers for PVC using liquid barium-zinc formulations (40). Currently, there is no alternative to lead-based stabilizers for wire and cable (11). As for pigments and colorants, a large array of organic replacements for lead chromate and cadmium compounds have hit the market. Currently, organic colorants are 25% to 300% more expensive, but they are rapidly being commercialized. Many suppliers are offering full lines of new organic pigments, and some are discontinuing many or all of their metal-based pigments (11,40,41).

Some organics have been shown to degrade into undesirable products when subjected to processing heat and shear; thus, technology is still very much under development for these materials (11,42).

Chlorinated Compounds

Chlorofluorocarbons (CFCs) are rapidly being phased out. A worldwide ban on CFCs for non-insulation use is scheduled for 1994 (9). Depending on the application, pentane, carbon dioxide (CO2), and hydrochlorofluorocarbons (HCFCs) are the current replacements of choice for CFCs. HCFCs have only 2% to 10% of the ozone depletion potential of CFCs, but they are considered only to be transitional agents since they still have some ozone depleting potential (11).

Prior to 1989, CFC gases were used for about 35% of extruded expanded PS (EPS) food service products, but in 1988, the industry voluntarily agreed to discontinue CFC use. Most EPS manufacturers switched to pentane or to HCFC-22 (43). Dow Plastics now licenses PS foam sheet extrusion technology based on 100% C|O.sub.2~ blowing agent. The C|O.sub.2~ dissipates into the atmosphere in about 24 hours, whereas pentane or HCFCs can linger in a product for weeks, leading to possible variation in stiffness of thermoformed parts with time (9). Partial replacement of CFC-11 with C|O.sub.2~ for rigid PUR foaming has been reported by Miles Inc. Other reported CFC replacements include organic liquids such as methyl or ethyl formate or endothermic blowing agents rather than exothermic ones. But replacing one agent with another is not a simple matter. For example, urethane reaction catalysts are affected by replacement of CFC blowing agents. Changing the blowing system requires changing processing conditions and product formulations (11).

Substitutes for other chlorinated agents are being developed as well. Miles Inc. replaced halogenated flame retardants with non-halogenated ones. Chlorine-free mold releases and cleaners, especially for PUR systems, have been introduced by Air Products, Texaco, and Percy Harms (11,40).

Dow Chemical will halt production and sale of 1,1,1,-trichloroethane (TCE) solvent for most uses by December 1995. (TCE is among the group of ozone-depleting substances targeted for phaseout under the Montreal Protocol and the 1990 Clean Air Act Amendments) (44). Dow and Domtar Packaging scrapped a planned project to recover PET and HDPE with technology involving chlorinated solvents, including TCE) to separate PET from aluminum and to "ultra clean" the PET of residual glue, labels, and base cup remnants (31).

Carcinogens

Regarding dioxins, the National Institute for Occupational Safety and Health (NIOSH) reported that workers exposed to high levels of 2,3,7,8, tetrachlorodibenzo-p-dioxin (TCDD) for more than a year have an increased risk of dying of cancer than unexposed persons. However, those with lower exposures do not have an increased risk. These conclusions were drawn from epidemiological studies of 5172 male workers at twelve chemical plants that had made products that were contaminated with TCDD (45).

In 1987, styrene was classified as a possible human carcinogen by the International Agency for Research on Cancer (France). However, reviews of data on human and animal exposure to styrene gave rise to the conclusion that styrene poses no significant health risk to workers in manufacturing plants and to surrounding communities (46). The EPA's Office of Drinking water thus decided to classify styrene as a compound that is "not considered to have sufficient carcinogenic potential" to be listed as a carcinogen (47).

The problem of residual vinyl chloride monomer in PVC resin has been eliminated, but di-2-ethylhexyl phthalate plasticizer, a common plasticizer for flexible PVC, has been shown to be carcinogenic in animals in laboratory tests. Whether or not it is carcinogenic to humans has yet to be determined (31), but it has been labeled a potential carcinogen by the EPA (11).

MSW and Landfills

EPA data signify that annual U.S. MSW generation is at least 180 million tons and that approximately 13% is recovered (but not necessarily recycled), 14% is incinerated, and 73% is landfilled (48). At about 4 lb/person/day, the U.S. has one of the highest per capita waste levels in the western world. Plastics account for approximately 8% by weight and 20% by volume of landfill content (49). Packaging materials in general account for about one third of landfill weight and volume (50).

Although plastic wastes are very slow to degrade in landfills, other wastes such as paper and food are also slow to degrade (51,52). Degradation of waste, therefore, has little effect on landfill capacity. There are at least 32 variables influencing material degradation rates in a landfill, such as moisture, temperature, and pH, and thus rate and extent of degradation varies greatly from location to location within a landfill. By making a material "biodegradable," you adjust only one of those parameters (53). Because of increased waste compaction, use of daily cover, and other management techniques (for example, siting landfills on hills), degradation occurs at a slower rate in newer land fills than in older landfills (54). Yet some combination of aerobic and anaerobic degradation is occurring. Degradation has been estimated to lead to about a 7% total volume change in 10 years (53). One report claims that 44.1 million tons of methane is released annually to the atmosphere from landfills, accounting for about 10% of the total amount of methane produced on the planet. Approximately fifty landfill operators in the U.S. collect enough methane to convert it to electricity (54).

The EPA recently issued the first U.S. federal standards for municipal solid waste landfills. The standards cover location, design, operation, and closure requirements, and mandate cleanup of existing contamination. The main object of the guidelines is groundwater protection. Forty-five organic chemicals and 15 metals are listed as requiring monitoring from groundwater at all landfills. Only about 25% of existing landfills monitor ground water. Over the next the five years, the standards are expected to cause closure of about half of the existing landfills (55). (The number of legal landfills was approximately 6,000 as of 1991 (53), 9,000 in 1989 and 18,000 in 1976 (56).) Annual cost of compliance is estimated at $330 million, mostly for closing old landfills and constructing new ones (55).

Life Cycle Analysis

Waste buildup is obviously not a simple problem of buildup of one component, such as plastics. Reduction or replacement of one material may cause an increase in another and possibly the entire waste stream. Thus life cycle evaluations are recommended when deciding the merits of one material over another. Such evaluations need to take into account all stages of raw materials acquisition, production, shipment, and disposal, and must include analysis of energy and resources used and emissions created "from cradle to grave." Such studies often show that the overall impact of plastics (given present technology for production and recovery) is less detrimental than replacements (57).

In an article entitled "Paper versus Polystyrene: A Complex Choice," a life cycle analysis of uncoated paper cups versus EPS cups is presented. PS uses one sixth the material by weight compared to the paper cup. On a per cup basis, production of the paper cup consumes 12 times the steam, 36 times the electricity, and two times the cooling water of the PS cup. The volume of waste water for the pulp process is 580 times that of the PS process, and residual wastewater contaminants are 10 to 100 times that of the PS process. The price per cup is 2.5 greater for the paper cup. Emissions to the air are 23 kg/metric ton bleached pulp versus 53 kg/metric ton PS, but one needs six times as much paper by weight to give the same number of cups. Forty-three kilograms of pentane are used as a blowing agent per metric ton of PS, but ultimate paper degradation produces methane, a gas with worse greenhouse gas effects. Both are recoverable with proper technology, however, at present, paper cups are not included in any recycling programs (58).

Franklin Associates performed life cycle evaluations to compare polyethylene (PE) grocery sacks to kraft paper bags and PS foam food-service "clamshell" containers to paper containers. Results reported by the plastics industry include the following: PE sacks use 20% to 40% less energy than the unbleached paper equivalent, assuming zero-percent recycling. PE sacks create 74% to 80% less solid waste by volume and have 63% to 73% less atmospheric emissions. PS food-service containers lead to 29% more solid waste by volume than paper containers but give 46% less emissions Both PE and PS resin production processes emit fewer particulates and less NOx, SO2 and CO than the paper processes. They also give less total waterborne waste of dissolved solids, suspended solids, acids, and O2 depleting effluents than paper. Compared to paper, waterborne wastes are 90% less for the production of PE bags, and 42% less for PS containers. Paper, however, emits lower total levels of hydrocarbons (51).

Criticisms of these studies have been noted as well. McDonald's switched from PS clamshells to wax-coated paper wraps, not to paperboard. According to the Franklin Associates report cited above, wax-coated paper wraps come out ahead of the PS containers in terms of manufacturing energy, air and water discharge, and solid waste (59). Paper wraps give a 90% volume reduction over the PS clamshells and greatly reduce transport packaging (60). The Environmental Action Foundation (EAF) points out that in most life cycle studies to date, "environmental impact" is based on quantities of materials used and emissions released but not on relative toxicities and ultimate fate of the particular releases and resources. No attempt is made to measure the relative risk or toxicity that the various pollutants impose on the environment. The studies assume that the paper products will not be recycled and ignore the possibility of composting them. Also, they provide no analysis of the markets or potential use of the recycled materials (61).

What about a life cycle analysis for diapers? Nine out of ten American mothers surveyed in a recent Gallup poll use disposable diapers. They cite health and convenience as the reasons for their preference (62). According to an Arthur D. Little, Inc., life cycle analysis of disposable diapers versus cloth diapers, the disposables generate 90 times the amount of post-use solid waste as reusable cloth diapers, however, washing and reusing the cloth consumes three times the amount of nonrenewable energy and generates 10 times as much water pollutants (34). Therefore, if landfill volume is scarce, it may be better to use the cloth diapers. On the other hand, if water conservation is a greater priority, then disposables are the better choice.

The bottom line is that when deciding what the "better" product for the environment is, we are typically faced with a tradeoff between various factors. We must not only consider total product impact, but also risk/benefit analyses and resource priorities.

References for Part One

1. Resource Recycling, Feb. 1991, 10, 76.

2. Wastelines 2(2), Nov. 1990, Environmental Action Foundation, Washington, D.C.

3. Wall Street Journal, 17 Jan. 1992, 1.

4. C&EN, 1 Jun 1992, 14.

5. Solid Waste Action Paper, "Legislation for Market Creation," prepared by the Solid Waste Alternatives Project, Environmental Action Foundation, Washington, D.C. (1990).

6. Plastics Engineering, Feb. 1992, 4.

7. Chemical & Engineering News (C&EN), 12 Nov. 1990, 43.

8. Modern Plastics, July 1990, 85.

9. Modern Plastics, May 1991, pp. 29, 44, 47.

10. Plastics Engineering, Apr. 1991, 8.

11. Modern Plastics, Sep. 1990, pp. 11, 53, 89.

12. BioCycle, Jan. 1991, 28.

13. Reuse/Recycle, May 1990.

14. Modern Plastics, June 1991, 42.

15. Private communications, May, 1991: Anne Wilcox, MassPIRG; Kim Vollbrecht, Council for Solid Waste Solutions.

16. Plastics Engineering, Aug. 1991, 6.

17. SPE Plastics Recycling Division Newsletter, Spring 1992.

18. Plastics Engineering, Sep. 1991, 6.

19. Reuse/Recycle, May 1991.

20. C&EN, 27 July 1992, 12.

21. Jerusalem Post, 11 Feb. 1992, 12.

22. Modern Plastics International, June 1992, 142.

23. Modern Plastics International, May 1992, 94.

24. Modern Plastics International, Sept. 1992, 166.

25. Popular Science, July 1992, 32.

26. Modern Plastics, Nov. 1990, 16.

27. Reuse/Recycle, Oct. 1990.

28. Modern Plastics International, Oct. 1992, 56.

29. Modern Plastics, Feb. 1991, 13.

30. Modern Plastics, July 1991, 32.

31. Modern Plastics, June 1990, pp. 20, 60.

32. V. Mathews, World Plastics and Rubber Technology, 154 (1991).

33. Reuse/Recycle, Nov. 1990.

34. New York Times, 26 Feb 1991, C1.

35. C&EN, 18 Feb. 1991, 24.

36. Modern Plastics, Jan. 1991, 77.

37. EPA Executive Summary, Report to Congress: Managing and Controlling Plastic Wastes (1990).

38. Plastics Engineering, Aug. 1990, 5.

39. Plastics Engineering, Oct. 1990, 3.

40. Plastics Engineering, June 1992, 22.

41. Plastics Engineering, Jan. 1991, 35.

42. Wall Street Journal, 13 Aug. 1990, B5.

43. "Plastic Foam and the Environment," pamphlet from the Scott Paper Co., Philadelphia (1990).

44. C&EN, 20 Apr. 1992, 7.

45. M.A. Fingerhut, W.E. Halperin, D.A. Marlow, L.S. Piacitelli, P.A. Honchar, M.H. Sweeney, A.L. Greife, P.A. Dill, K. Steenland, and A.J. Suruda, New England J. Med., 324, 212 (1991); C&EN, 28 Jan. 1991, 7.

46. Modern Plastics, Jan. 1990, 140.

47. Modern Plastics, Mar. 1991, 13.

48. C&EN, 9 July 1990, 23.

49. Reuse/Recycle, Aug. 1990.

50. Franklin Associates, Ltd., Estimates of the Volume of Municipal Solid Waste and Selected Components, Executive Summary, 19 Oct. 1989.

51. Plastics Engineering, Sept. 1990, pp. 5, 9.

52. J.M. Suflita, G.R Gerba, R.K. Ham, A.C. Palmisano, W.L. Rathje, and J.A. Robinson, Env. Sci. Tech., 26(8), 1486 (1992).

53. C&EN, 25 June 1990, 7.

54. Resource Recycling, Jan. 1991, 106.

55. C&EN, 16 Sep. 1991, 6.

56. N.P. Cheremismoff and P.N. Cheremismoff, Pollution Engineering, Aug. 1989, 58.

57. Modern Plastics, Apr. 1990, 43.

58. M.B. Hocking, Science, 251, 1 Feb. 1991, 504.

59. C&EN, letter to the editor from T.P. Silverstein, 29 Apr. 1991, 3.

60. Modern Plastics, Dec. 1990, 43.

61. Solid Waste Action Paper, "Science or PR?," prepared by the Solid Waste Alternatives Project, Environmental Action Foundation, Washington, D.C. (1990).

62.American Baby, Feb. 1991, 24.

PART TWO

RECYCLING, SOURCE REDUCTION, AND OPPORTUNITIES FOR BIODEGRADABLES

General Curbside Collection, and Aluminum, Paper, and Glass Recycling

The number of curbside collection and recycling programs in the U.S. grew from 600 to more than 3700 between 1988 and 1991 (1,2). Collection programs are now reaching about 15 million households and thousands of office buildings, with about 40% of curbside programs mandatory (1). Mandatory programs divert a little more than 20% of municipal MSW volume from landfills, while voluntary programs divert about 12% (3).

Most curbside collection programs are in the Northeast, California, and Minnesota (1). Collected mixed recyclables are typically transported to Materials Recovery Facilities (MRFs) where they are sorted and processed for market. Prior to 1988, only six MRFs were operating in the U.S., compared to 126 in operation and 18 under construction by mid-1991. The only part of the country not well represented is the Rocky Mountain region. Nearly 75% of MRFs handle two streams--paper and mixed containers from separated curbside receptacles. New facilities also being developed for recyclables collected primarily from commercial sources. On average, gross MRF operational and maintenance (O&M) costs average $45.67/ton. In planned facilities, O&M costs are expected to run $42.03/ton (4).

After subtracting revenue from sale of reusable material, the cost of recycling programs ranges from $35 to $199/ton. Nationwide, average landfill costs are about $30/ton,(1) with the highest in the nation being in certain parts of New Jersey (5). Tipping fees ranged from $36 to $102 in five New Jersey communities in 1990. Thus in many cases, the expenses of running recycling programs are higher than the costs of landfilling (6). Because they aren't profitable, a number of collection projects are in jeopardy (3).

Aluminum recycling is successful because it costs significantly less to recycle it than to produce it from bauxite ore(5) and because deposit legislation in certain states allows for high collection rates of aluminum beverage cans. In 1990, 54.9 billion aluminum beverage cans were recycled in the U.S., giving an aluminum beverage can recycling rate of 63.6% (7,8).

Most of the paper material that is recycled comes from newspaper and cardboard carton, and it primarily gets recycled into corrugated boxes, paperboard, egg cartons, wall board, and roofing felt and insulation (9). The recovery rate of old newspapers in North America in 1988 was 33%, and it is expected to rise to 65% by the year 2000 as a result of an estimated seven-fold increase in newspaper de-inking capacity (8) that will allow more newsprint to be recycled back into newsprint. Currently, about 40 de-inking plants are being built or have been planned in the U.S. and Canada (5). The price of newsprint is fickle, however. Throughout 1990, old newsprint was bringing negative prices--in parts of New York for example, collectors had to pay dealers $35/ton to haul old newspapers away (5). By mid-1991, prices turned positive and newsprint sold at $25/ton (4). During 1992, prices dropped once again (10).

A major criticism of the paper packaging industry is that it does not recycle paper packaging for liquids (e.g., milk cartons). The industry has developed only an occasional program for collecting and recycling this type of paper packaging. One complication is that paper liquid packaging is typically wax or PE-coated. International Paper initiated pilot programs to recycle used milk and juice cartons into new cartons. Cartons were collected, washed, separated into paper and PE components, repulped, and reused. The PE residue was sold. Champion International, a major competitor, was not interested in putting paper back into food containers because of the poor economics of repulping and technical problems involved with sufficiently cleaning the material (11).

Prices of post consumer glass cullet have been decreasing as curbside collection increases (12). Throughout 1991, there was an oversupply of cullet in the U.S. Northwest (5). A glass recycling plant that opened in Seattle in 1991 was expected to ease the oversupply situation in that region (13). Meanwhile in Rhode Island, about 30% of all glass from curbside collections was being sent to the dump because of breakage with mixed color. Colored glass is nearly worthless, whereas clear glass has sold in the past for $45 to $50/ton (5).

Public Perception of Plastics and the Plastics Industry

A 1990 opinion poll conducted by the Council for Solid Waste Solutions (CSWS) showed that 51% of Americans rated plastics as "unfavorable." Thirty-one percent rated plastics as the "most threatening" material in the environment. Just 6% classified cigarettes and 4% automotive emissions as "most threatening." Sixty-one percent said the risks associated with plastics outweigh the benefits (1). The public is prejudiced toward what it sees as "natural" materials, as opposed to "synthetic" materials, and assumes that products made from renewable resources or from materials with a long history of recycling are inherently more compatible with the environment than plastics are. Another complaint against plastics is the low rate of recycling compared to aluminum, glass, and paper. This feeling may change when plastics recycling has had more of a chance to mature and develop its own long history. In the meantime, the excuse that plastics recycling is new and needs time to develop is not accepted by environmentalists. They claim that the need for recycling--whether aluminum, paper, glass, or plastic--has been recognized for a long time and that the plastics industry should have had enough foresight to see an environmental problem and come up with a solution. In other words, "no industry is entitled to a grace period where it is absolved of responsibility to solve the problem it creates" (14).

Industry points out that critics of plastics ignore manufacturing economy, distribution and use efficiency, product quality, safety, and source reduction of plastics relative to alternative materials (14). Nevertheless, industry has admitted that "perception is reality" from the business standpoint (15). Issues of public opinion must be addressed. Recycling is necessary not only for good citizenship but also to remain competitive and efficient. Executives and managers from 27 of the largest U.S. plastics producers formed the Partnership for Plastics Progress in 1991 to respond to public concerns about plastics. This is a joint program of the Chemical Manufacturers Association and the Society of the Plastics Industry, Inc. The group's stated goals are to coordinate and improve recycling, conservation, resource recovery, and public relations programs. The Responsible Care program is a broader coalition from the whole chemical industry with similar goals (16). Such goals are great in theory; the question is to what extent they will be acted on.

Dow Chemical committed $1 million in 1992 for plastics recycling messages to consumers (17) and is actively forging links between resin producers, plastic product manufacturers, and local community groups. Among other projects, Dow was instrumental in establishing programs to collect and recycle mixed plastics, aluminum, and glass at seven National Parks(15,18) and PS beverage cups at Chicago's Comiskey Park, and developed a plastics recycling curriculum for grade school students (17). (In addition, Dow recently introduced a line of PE and PS resins containing 10% to 100% recycled resin under the trade name Retain.) (19,20)

Long range public relations needs more attention. The idea of introducing school children to plastics recycling is a good one. Teachers and parents need to be educated as well, perhaps by having industry schedule local plant tours for neighboring residents. By allowing access to and observation of manufacturing processes and the people who run them, plastics production and processing is demystified, and the public is able to see that responsibly managed industries are not an environmental enemy (14).

Dropoff programs that involve return of packaging to stores where the item originated get good feedback from the public. This concept is in line with the recent German legislation requiring manufacturers and retailers to take back unwanted packaging from the consumers. Popular and successful dropoff programs in North America involve PE grocery sacks, HDPE and PET containers (21,22), and LDPE dry cleaning garment covers. The supermarket chain Bread and Circus installed "Box Bank" collection receptacles near store entrances to collect empty aseptic drink boxes (these are the multi-material packages comprising paper, foil, and PE that were banned in Maine). Collected boxes from Bread and Circus are combined with similar boxes from Long Island curbside collection programs and schools in Rhode Island. Theoretically, recovered paper fiber can be recycled into corrugated medium, and the recovered plastic and aluminum foil can be sold to plastics and aluminum recyclers, or the whole container can be combined with mixed plastics waste to make commingled plastic lumber (13).

Plastics Collection Programs

In 1991, CSWS put out a document entitled "Blueprint for Plastics Recycling." It is a how-to for implementing municipal recycling programs that includes plastics. Its primary goal is to optimize public participation in plastics recycling programs. The council developed a computer model to help communities predict and manage financial aspects of plastics recycling programs (23). CSWS set up six different Model Cities Programs across the U.S. to determine the best methods of collecting and processing plastics for recycling. At each location, slightly different methods of collection, compaction, or processing were used. Gathered data are shared with other communities to help launch successful recycling programs (2).

According to one survey, at least 1800 U.S. curbside programs currently include plastics. An additional 2900 programs involve collection of plastics through dropoff or buy-back centers. The most commonly collected plastic is unpigmented HDPE--more than 96% of the survey respondents collect it. PET is collected in 89% of the programs and pigmented HDPE in 82%. More than 56% collect only PET and/or HDPE. The others report collecting additional types of plastic including PVC, PP (polypropylene), and PS (2). Allentown, Pa., decided not to pick up plastics as part of its curbside recycling program after it estimated that including plastic bottles would have raised yearly operating costs by $4.10 per household (24). In contrast, a study that examined the extra costs and benefits of adding plastics to curbside programs in five New Jersey communities showed that the money saved from avoided landfill costs outweighed costs borne for adding plastic bottles to curbside collection (6).

Nine out of the U.S.'s ten most populous cities (New York, Los Angeles, Chicago, Houston, Philadelphia, San Diego, Dallas, Phoenix, Detroit, and San Antonio) have established curbside collection programs. The exception is Detroit, which relies more heavily on incineration. New York City has the biggest single program the world has ever seen. As for plastics, PET is collected in all of these programs, HDPE and mixed rigid plastic containers are collected in some (3). Because of a city ordinance that required all packaging to be degradable, returnable, or recyclable, or otherwise be subject to a ban, CSWS worked with city officials in Minneapolis and a surrounding county to establish a comprehensive collection program that included all rigid plastics containers (25).

Among the 19 MRFs that were operating in 1988, it was hard to find one that sorted and processed plastics. By mid-1991, 120 of the 126 MRFs in operation processed at least one type of plastic. Most--110--handled both PET beverage bottles and HDPE bottles. A few handled either all plastic bottles or all plastic rigid containers, and at 4 MRF's, anything made of plastic was accepted (4).

Most of the major resin producers in the U.S. have been involved in setting up municipal collection programs and reprocessing facilities for plastics (13,17,26,27,28). PET and HDPE are primarily targeted for reclamation in these operations, while a few recover other resins as well. One of the largest plastics reprocessing facilities was recently opened in New Jersey by Union Carbide. It has the capacity to reclaim 54 million lbs/yr of plastics, including post-consumer PE film, HDPE, PET (29,30).

The level of plastics recycling in Europe exceeds that of the rest of the world (31). The Netherlands leads western Europe in plastics recycling with 10% recovery of post-use plastics (3). Reko, a recycling subsidiary of DSM, recently opened a new plastics recycling plant that doubles its capacity to 30,000 tons/yr. Eighty percent of capacity is devoted to PE, 20% to PET (30). Ecoplast (Belgium), the recycling division of Cabot Plastics, will build two recycling plants, one in France and one in Germany. The facility in France will initially reprocess plastics from commercial sources but will later add municipal streams. They also acquired an existing plant in The Netherlands that reclaims PS, and a plant in France that handles agricultural film, bags, and industrial waste (32).

Plastics recycling is not significant in Japan because of high levels of incineration. However, plastics recycling is gaining attention there, and the Ministry of International Trade and Industry recently sponsored a committee to promote plastics recycling. Most interest in plastics recycling focuses on PET, which is rapidly replacing glass in Japan, and on auto shredder residue (33). The Japan PET Bottle Association plans to build a number of 5000 tons/yr recycling plants for used PET bottles, and the Expanded Polystyrene Sheet Industry Association intends to recycle EPS (34).

Amnir (Hadera, Israel) is Israel's principal paper and plastics recycler. Amnir collects plastics primarily from agricultural and commercial sources. Following the Gulf War in 1991, they collected and recycled PE sheeting that the public had used to seal their rooms against potential gas attacks from Iraqi Scud missiles. Polyziv (Kibbutz Gesher Haziv, Israel) recycles scrap polyolefins into industrial pallets and is now also working with GE Plastics in The Netherlands to make pallets from scrap and post-consumer engineering resins.

The Environmental Defense Fund acknowledges that the U.S. plastics industry has relatively successfully promoted plastics collection, but warns that without stronger markets for the recycled resins, many initiatives will fail. They cite as examples the collapse of curbside collection in Nashville, Tenn., and the withdrawal of Waste Management from the PRA partnership with Du Pont. Unless legislation mandates the purchase of recycled resins, buyers who can potentially use recycled resins will choose between recycled versus virgin based on price. At present, the price of some high-grade recovered resins is higher than that of the virgin material.

Technology

Reuse of industrial thermoplastic scrap--which is generated during polymerization, compounding, processing, shipment, and storage--has been in place for decades. Products such as bottles with handles and thermoformed trays can generate up to 40% waste. Some waste can be reused easily by regrinding and adding to virgin material; for example, injection molding waste from sprues and runners are routinely reground and added to virgin in amounts of 5% to 20%. Other waste that has undergone more extensive molecular damage cannot be readily reprocessed (35).

The ability to reprocess a plastic after it has already been exposed to high processing temperatures is limited if the molecular structure has undergone extensive thermal or thermo-oxidative reaction. Such reactions lead to molecular weight reduction, crosslinking, and/or formation of unsaturation or cyclization because of side chain reactions. Melt viscosity increases in the case of crosslinking and decreases in the case of molecular weight reduction. Physical properties such as strength, impact resistance, stiffness, color, and chemical resistance are generally affected as well (35).

Oxidation is the mode of breakdown of HDPE and LDPE. PP recycling gives increased melt flow and falloff in impact strength. PP and PS are sensitive to contamination and exhibit property reduction and color shift upon extensive high temperature processing. Prolonged recycling of PVC depletes the stabilizers and the material begins to yellow and emit odors. Nylons can be easily reprocessed but are sensitive to contamination and tend to "brown" with repeated reprocessing. During processing of reinforced thermoplastics, degradation of properties can occur as a result of degradation of the polymer, degradation of the polymer/reinforcement interface, and/or breakdown of reinforcement. The primary mode of defense against thermal and thermo-oxidative reactions is by the addition of appropriate stabilizers and/or antioxidants. Stabilizers such as hindered phenols or aromatic amines trap or remove freed radicals. Antioxidants extend induction period of autoaccelerating thermo-oxidative processes (35).

Post-consumer plastics recycling technology got its earliest boost by DSM (The Netherlands), which entered the plastics recycling business in 1976 and established its recycling subsidiary Reko in 1980 (3). Reko technology allows separation of HDPE, LDPE, LLDPE (linear low-density polyethylene), PET, PP, PS, ABS (acrylonitrile butadiene styrene), and polyamides (36). Reko-designed plants are typically built by Sorema (Italy) and account for nearly half the plastics recycling in The Netherlands (3). They have also built at least 33 installations in Europe, South America, and Asia, and two in the U.S. Finished pellets are suitable for any application other than food contact. Reko has also developed a wide range of cleaning systems that include recycle of the wash-water (36). In the U.S., makers of plastics processing equipment are also developing equipment specifically designed for the waste reclamation market (37). In addition, manufacturers and recyclers are working together to redesign packaging to facilitate recycling. For example, Reko convinced Coca-Cola Germany to adopt a PET bottle design that got rid of non-PET contaminants such aluminum lids, PE coated labels, and PVC liners (3). Du Pont developed a polyolefinic label to replace paper labels on PE and PP textile and fiber packaging (38).

In general, technology is available to sort plastics by density, color (transparency or reflectivity), glass transition (Tg), melting point (Tm), size or shape, hardness, flexibility, electrical or magnetic properties, or encoded information (39). Most commercial plastics separations processes involve density separation technology for polyolefins and PET in the form of water-based sink/float processes. Despite technological ability, there is still a large degree of hand-sorting from conveyor belts in most recycling facilities (40). Automated separation is considered crucial for expanding plastics recycling beyond PET and HDPE (41).

One of the biggest sorting problems is removal of PVC from PET. At temperatures suitable for processing PET, i.e., at or above 250|degrees~C, PVC degrades and leaves black particles in an otherwise clear PET resin (40). Even as little as 20 parts-per-million PVC can ruin recycled PET (42). These two materials have very similar densities (approximately 1.3 g/cm3); thus they cannot be separated by conventional sink/float technologies. A number of alternative technologies have been developed to sort PET and PVC bottles. Most involve detection of the chlorine atom in PVC via X-ray analysis (34,40,41,43). Eastman Chemical is developing technology that incorporates low concentrations of an organic compound marker into resins that can be detected with an electronic scanner (44).

A completely automated system for sorting virtually any plastic in the solid waste stream by resin type and color was developed at Rutgers University's Center for Plastics Recycling Research (New Jersey) (34). CSWS is funding development for at least two other automated sortation systems. The first is a modular system in which detection components can be added on the basis of the number of sorts required. Bottles are separated into three streams: PET and PVC, unpigmented HDPE and PP, and mixed color HDPE and other opaque bottles. Modules may be added to separate these three groups into subcategories. The first stream can be sorted into PVC, clear PET, and green PET by the addition of a PVC detector and a color detector. The unpigmented resins can be separated into PP and HDPE, and the mixed color and opaque stream can be sorted into as many as seven colors by means of a second color detector. In the second system, separation is accomplished at a rate of three containers per second via two detectors at one station, where one determines the resin type and one identifies the color. This system is capable of detecting and separating most resins, including PS and polycarbonate (PC) (45).
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Author:Nir, M.M.; Miltz, J.; Ram, A.
Publication:Plastics Engineering
Date:Mar 1, 1993
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