Modern Plastics Handbook 2011 Part 16 pdf

resin and fiber companies, and some is used by United Recycling, a subsidiary of Environmental Technologies USA, to make “grey felt” which is used for padding installed under commercial floor coverings, as well as for sound insulation in automobiles. 145 Collins & Aikman Floorcoverings, of Dalton, Ga., uses vinyl-backed carpet to make solid commingled plastic products such as car stops and highway sound-wall barriers. They are now using up to 75% reclaimed carpet materials to make a nylon-reinforced backing for new carpet for modular tile products. 143 DuPont is investigating the use of ammonolysis to depolymerize mixed nylon 6 and nylon 6/6 from used carpet. The company is also using reclaimed fiberized material from nylon carpet to make nylon building products for use in wet environments such as kitchens and bathrooms. 143 Researchers in Georgia are investigating an unconventional use of carpet fibers, incorporating them into the surface of unpaved roads to improve road performance. 146 To simplify the task of carpet material identification, the Carpet and Rug Institute has developed a seven-part universal coding system where a code on the carpet backing can be used to describe the components of the carpet, including facing, backing, adhesive, and fillers. As of 1997, it was estimated that 85% of the carpet now being made in the United States uses this code. However, the average 10-year life span of carpet means that for the next several years, most carpet entering the recycling stream will not be so labeled. 143 Thus, as for automobile parts, equipment for identifying carpet materials will continue to be needed. 12.4.16 Other plastics While the major types of plastics recycling have been addressed, there are a variety of other types of plastics recycling going on, often on a small-scale or experimental basis. For example, Arco Chemical Company has a process for recycling glass-reinforced styrene maleic anhydride from industrial scrap. 147 The University of Nottingham has a project for developing recycling techniques for thermoset materials, including polyesters, vinyl esters, epoxies, phenolics, and amino resins along with glass and carbon-fiber reinforced resins. 148 The Fraunhofer Institute in Teltow is developing a process for recycling thermosets using an amine-based reagent in a one-step process which requires little added heat. The process is said to be applicable to almost all thermosets. 149 Imperial Chemical Industries plc and Mitsubishi Rayon Company Ltd. are developing technology for recycling of acrylics by chemical depolymerization and repolymerization. 150 The introduction 12.70 Chapter Twelve 0267146_CH_12_HARPER 2/24/00 4:40 PM Page 12.70 of polyethylene naphthalate (PEN) in U.S. packaging markets was delayed by the perceived need to develop processes for automatic separation of PEN from PET as well as technology for recycling of PEN. Other examples could also be cited. The field of plastics recycling is constantly evolving, in response to changing demands and opportunities, as well as the emergence of new resins and new applications. 12.5 Overview of Plastics Degradation Until the early 1970s, attention to plastics degradation, including biodegradation, was focused primarily on ensuring that the plastic materials being used were resistant to such degradation so that they could maintain their usability. Biodegradation and other types of degradation, such as photodegradation, were not always clearly differ- entiated. Further, the extent of degradation was frequently measured based on loss of useful properties, such as tensile strength, rather than on chemical changes in the polymer structure. In the mid-1980s, when concerns about solid waste disposal were increasing rapidly, there was again a flurry of interest in biodegradation, stemming from a perception that disposal problems could be alle- viated substantially if we stopped filling up our landfills with nonbiodegradable plastics and instead switched to biodegradable materials. As information increased about both the composition and the behavior of solid waste in landfills, it became clear that this was a misperception. First, the majority of material in landfills was, in fact, biodegradable, consisting of paper, food waste, and yard waste. Second, conditions in modern landfills, designed to keep materials dry to reduce problems with groundwater contamination, were not con- ducive to rapid biodegradation. Pictures of grass clippings, vegetables, and hot dogs, still recognizable after 10 to 20 years in a landfill, reinforced this reality, as did the statement by landfill researchers such as William Rathje of the University of Arizona that landfill waste was often dated simply by reading the dates on the still-legible newspapers contained in the garbage. Additionally, it became clear that the “out of sight, out of mind” approach to plastics degradation could not be justi- fied. In other words, mechanical disintegration of a plastic product into plastic dust was not equivalent to chemical breakdown and return of the carbon and other elements to global cycles. Nonetheless, during the time when biodegradability was perceived as a potent selling attribute for products such as merchandise sacks and garbage bags, a number of products were introduced which were composed of a mixture of starch, usually about 6% by weight, and low- density polyethylene. Manufacturers of these materials claimed they were biodegradable, based on the fact that the starch component Plastics Recycling and Biodegradable Plastics 12.71 0267146_CH_12_HARPER 2/24/00 4:40 PM Page 12.71 would be consumed by microorganisms if the materials were buried in soil and the argument that the then-fragmented plastic would also be biodegraded. Some manufacturers added pro-oxidants to enhance the further degradation of the materials. The discovery that even materials such as food wastes often biodegraded very slowly under landfill conditions cast doubt on the claims, since even if the materials were biodegradable, it was not clear that this degradability would serve any useful purpose. Further, evidence suggested that the mere increase in exposed surface did not materially increase the biodegradability of the polyethylene remnants. The value of pro-oxidants in the anaerobic environment of a landfill was also questionable. As a result, some environmental organizations began calling for boycotts of these products. Finally, some manufacturers of these products were charged by some state attorneys general with misleading consumers, under statutes related to fair trade practices, and ordered to pay fines and cease making such claims. Ultimately, these products disappeared, having suc- ceeded primarily in giving biodegradable plastics a bad name. Since that time, two important changes have occurred. First, a variety of truly biodegradable plastics have been formulated, and their usefulness in niche markets, such as where plastics are likely to become a litter problem, particularly in bodies of water, has been rec- ognized. Secondly, the use of composting as a waste management practice has grown dramatically. Composting is designed and managed to promote rapid biodegradation, so biodegradable products have assets in this scheme that they do not have where landfill or incineration are the usual approach to solid waste disposal. This, then, is the motiva- tion for an examination of biodegradable plastics. 12.5.1 Definitions and tests Biodegradability of a plastic means that living organisms can use the plastic as a food source, transforming its chemical structure within a reasonable period of time. In practice, the organisms which we rely on to accomplish this task are microorganisms, and the transformation of chemical structure results in conversion of most of the carbon in the polymer to carbon dioxide, methane, or other small molecules, along with some incorporation of the carbon into the cell mass of the microorganisms as they grow and reproduce. The time period involved is usually several weeks to several months. Unfortunately, as indicated earlier, there has been abundant misuse of the terms “biodegradable” and “biodegradability,” with considerable confusion resulting. One of the main points of confusion has been the misidentification of photodegradable polymers as biodegradable. Photodegradation refers to loss of physical properties induced by expo- 12.72 Chapter Twelve 0267146_CH_12_HARPER 2/24/00 4:40 PM Page 12.72 sure to light. A significant part of polymer research in the decades since these materials were introduced into commerce has been in the deter- mination of ways to minimize loss in strength in polymers which are exposed to sunlight. Virtually all polymers have some tendency to pho- todegrade, so outdoor use of many polymers depends on the inclusion of appropriate stabilizers to extend the plastic’s lifetime. On the other hand, it is sometimes desirable to hasten this light-induced degradation. Appropriate modification of the polymer’s chemical structure or the use of additives can accomplish this accelerated degradation. Such plastics are properly termed photodegradable, but have been misiden- tified in many instances as biodegradable. Photodegradable plastics are outside the scope of this chapter. Another point of confusion has been the amount of chemical change needed to classify a plastic as biodegradable. Early work in this area followed the practice initiated by those who were seeking to conserve the performance attributes of plastics and who measured degradation by loss of physical properties such as tensile strength. If one is interested in using a plastic for some purpose, the end point is clearly the point at which the plastic no longer has useful properties. In this con- text, defining degradation in terms of loss of strength is perfectly reasonable. However, if one is interested in total decomposition of the polymer, it is not reasonable, since relatively few bond cleavages in a polymer backbone can destroy the polymer’s strength, while still pre- serving most of its chemical structure. Many of the early discussions of biodegradable polymers failed to clearly make this crucial distinction. Another point of confusion has been the “reasonable time” part of the definition. As is also true for photodegradation, the time required for biodegradation is a function of exposure conditions (as well as a function of the extent of degradation defined as the end point). Time to reach the defined end point after disposal can be markedly different if the object degrades in sewage sludge, in a compost pile, or in a landfill, even under the same climatic conditions. To this variation, then, must be added differences in ambient temperatures, rainfall, etc. Faced with a proliferation of environmental claims about products and packaging, several state attorneys general produced guidelines for environmental claims, culminating in the issuing of the Green Report II, and took legal action against companies which they saw as making misleading claims. In 1992, the U.S. Federal Trade Commission (FTC) issued 16 CFR Part 260, “Guides for the Use of Environmental Marketing Claims,” which was modified in 1996 and 1998. It includes guidelines for the use of degradability claims. 151 The FTC guidance on the use of degradable, biodegradable, and photodegradable is that such claims can be made only if there is “compe- tent and reliable scientific evidence that the entire product or package Plastics Recycling and Biodegradable Plastics 12.73 0267146_CH_12_HARPER 2/24/00 4:40 PM Page 12.73 will completely break down and return to nature, i.e., decompose into elements found in nature within a reasonably short period of time after customary disposal.” Unqualified claims about compostability can be made only if “all materials in the product or package will break down into, or otherwise become part of, usable compost (e.g., soil-conditioning material, mulch) in a safe and timely manner in an appropriate composting program or facility, or in a home compost pile or device.” 151 There has also been activity in the area of definitions, environmental claims, and testing of such materials by standards-setting organizations on both national and international levels. The American Society for Testing and Materials has issued several standards relating to degradability in a variety of environments. For example, ASTM D5338-92, “Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials Under Controlled Composting Conditions,” provides for measuring evolution of carbon dioxide after inoculation with composting microorganisms. The percent of biodegradation relative to a cel- lulose reference is reported. 152 In Germany, the Fraunhofer Institute for Process Engineering and Packaging (IVV) formulated a standard in 1998 for the compostability of biodegradable plastics, Standard DIN V 54900. 153 The European Committee for Standardization (CEN) has “Requirements for Packaging Recoverable through Composting and Biodegradation—Test Scheme and Evaluation Criteria for the Final Acceptance of Packaging” in draft form. 154 In Japan, the Biodegradable Plastics Society has developed several standards for testing biodegradability in different environments. 155 The Degradable Polymers Council of SPI adopted definitions of biodegradable and compostable for plastic collection bags in 1998. Their standard is that “biodegradable” and “compostable” bags “should, at a minimum, satisfy ASTM D5338 and D6002 tests showing conversion to carbon dioxide at 60 percent for a single polymer and 90 percent for other materials in 180 days or less, and leave no more than 10 percent of the original weight on a 3/8″ screen after 12 weeks.” 156 Some early studies of biodegradation of packaging materials which used growth of microorganisms as a measure came to misleading con- clusions. For example, PVC was incorrectly determined to be biodegradable since it supported growth of microorganisms. However, later studies showed that it was the plasticizers in PVC which were being metabolized, not the PVC itself. Care must be taken to avoid such misleading assessments. In particular, a limited amount of degradation in a short time cannot be extrapolated to a conclusion of substantial degradation at a later time. In addition to the problem of additives, some parts of the structure of a polymer may well be more resistant to degradation than other parts. For example, crystalline regions in a semicrystalline polymer will be more resistant to degra- 12.74 Chapter Twelve 0267146_CH_12_HARPER 2/24/00 4:40 PM Page 12.74 dation than amorphous regions. Also, chain ends are typically less resistant than middle regions. 12.5.2 Effects of environment/exposure conditions As was mentioned earlier, rates of biodegradation are very sensitive to environmental conditions. One result of this sensitivity is that degradation rates in modern municipal solid waste landfills tend to be quite slow. A key factor is the amount of water. When landfills were found to often be the source of pollutants entering groundwater systems, regu- lations were tightened to ensure that landfills would not generate substantial amounts of liquid effluent which could make their way into water systems. Liners at the bottom of landfills and caps on the top were added to the requirements, and it was no longer possible to build landfills in some high-moisture areas. The caps, in particular, are designed to create a barrier to the ingress of water. In addition, leachate (the liquid effluent from a landfill) must be pumped out and treated before it is discharged. Thus, relatively little water enters a modern landfill, and what does enter is routinely removed, so the landfill environment is relatively dry. Microorganisms do not grow as rapidly in such environments as they do when moisture is plentiful. In addition to the moisture factor, landfills within a few years become largely anaerobic. Trapped oxygen is used up, and cannot be replaced rapidly enough to maintain aerobic conditions. Therefore, the types of organisms predominating in an oxygen-rich environment will not be identical to those which predominate in an oxygen-poor environment, and growth rates in general will be lower. In addition to differences in the amounts and types of microorganisms, some change their metabo- lism in response to oxygen availability. The end result is slower rates of decay, and a change from generation of carbon dioxide to generation of methane. While the methane can be collected, concentrated, and used as an energy source, it is also a potentially explosive gas and an air pollutant. A modern landfill will continue to generate methane for a substantial length of time after it is closed and capped. Slow biodegradation occurring over many years results in sinking and set- tling of the landfill area as well as generation of methane. In addition, the leachate from a landfill can contain a variety of undesirable chem- icals. Therefore, biodegradation in a landfill environment can have negative environmental consequences. If it is desired to speed up decomposition in a landfill environment, leachate recirculation can be used. In such systems, instead of pump- ing out, treating, and discarding any liquid effluent which reaches the top of the landfill liner, the liquid which is pumped out is reintroduced Plastics Recycling and Biodegradable Plastics 12.75 0267146_CH_12_HARPER 2/24/00 4:40 PM Page 12.75 into the top of the landfill, creating an environment much richer in water than is otherwise the case. In such circumstances, biodegradation will occur more rapidly, and the landfill will reach a stable condi- tion in a much shorter time. The U.S. EPA has been reluctant to permit such schemes, however, because of the significantly greater potential for groundwater contamination which also results. In contrast to landfills, compost operations, which will be addressed further in Sec. 12.5.3, are designed to ensure rapid biodegradation of susceptible materials. In composting, a water and oxygen-rich environment is maintained, along with a suitable inoculation of microorganisms to start the decay process. The time required for production of usable compost varies, but is most often less than a year. The composting operation can use open piles or windrows or closed containers. It can run on a very large scale as either a municipal or privately owned operation, or it can be a small compost pile in someone’s back- yard. It can be an open-air facility, contained inside a building, or operate in closed containers. It can contain yard waste only, source- separated organics, or mixed municipal solid waste. Composting of yard waste has grown rapidly in the United States over the last decade, significantly influenced by legislation in many states which prohibits the landfilling of yard waste. In Europe, the scarcity of landfill space led to adoption in many areas of systems for collecting source-separated organics which are then composted. In the United States, composting facilities which accept more than just yard waste are still relatively rare. In addition to moisture levels and the amount of oxygen, temperature plays an important role in determining the rate of biodegradation. Increases or decreases in temperature affect the growth rate and activity levels of microorganisms, and hence the rate of biodegradation. Different types of organisms are at their best at different temperatures. Usually, the activity increases with increasing temperature, as long as the temperatures do not get too hot. Thus rates of degradation in landfills are usually higher in warm climates than in colder ones. In a compost operation, degradation results in the evolution of a substantial amount of heat, which raises the temperature significantly above ambient conditions. A well-designed system will maintain a sufficiently high temperature for long enough to kill pathogens which may be present, so the compost does not spread either disease or weeds. Some biodegradable plastics may enter a different waste stream— liquid waste rather than solid waste. Sewage treatment facilities, like composting operations, are designed to hasten biodegradation of the collected wastes. For plastic products or packages which may end up in sewage systems, biodegradation is a significant asset. Rates of 12.76 Chapter Twelve 0267146_CH_12_HARPER 2/24/00 4:40 PM Page 12.76 degradation in sewage are generally different than rates of degradation in compost. Holding times are also different; a product which degrades reasonably well in composting may not degrade fast enough in sewage treatment facilities to avoid causing problems. We can conclude that in situations where landfill is the predominant disposal option, biodegradable plastics generally offer no significant advantage. Rates of degradation are slow, and the products of degradation, while they may include generation of methane to be used as fuel, are largely undesirable. Similarly, where incineration, with or without energy recovery, is practiced, biodegradable plastics are not advantageous. On the other hand, biodegradable plastics can play two types of roles in compost operations. First, if composting of a mixed organic stream is taking place, these materials will degrade along with the paper, food waste, and other biodegradable components. Second, even if yard waste is the only material composted, biodegradable plastics can be used as the bag in which compostable materials are collected. Biodegradable plastics can also be advantageous for products or packages which are likely to be disposed of in sewage. All the previous discussion is based on products or packages entering a regulated waste stream. Products and packages can also be littered or illegally dumped. In such cases, if the item is not degradable, it may stay in the environment for a very long time. In some cases, this presents no problem. The steel may slowly rust away at the bottom of the lake, the plastic bag may first be buried in leaf litter, and then eventually be covered up with soil. Too often, however, the object is less innocuous. The beverage ring connector may entrap a duck. The float- ing plastic bag may be swallowed by a sea turtle who thinks it is a jel- lyfish. A skunk may get its head caught in the yogurt container. These encounters with wildlife can result in injury or death of the animal, either through entrapment in or ingestion of plastic items. The problem appears to be particularly acute when the plastics reach bodies of water, either by being thrown into the water, or being carried to the water by runoff or storm sewer overflow. Thus there is also a potentially valuable role for degradable plastics in items which are frequently littered. An additional application for biodegradable plastics is in ships. Annex V of the International Convention for the Prevention of Pollution from Ships (MARPOL) prohibits ships from disposing of plastics into the ocean. While navies are exempt from the treaty, many nations, including the United States, have committed themselves to require their military forces to abide by the treaty. Ships of all sizes and types often have difficulty in appropriately storing or disposing of wastes. The problem is particularly acute for ships carrying large numbers of people, ships which spend long periods at sea, or ships Plastics Recycling and Biodegradable Plastics 12.77 0267146_CH_12_HARPER 2/24/00 4:41 PM Page 12.77 operating in areas where ports are not equipped to off-load and dispose of the refuse. An aircraft carrier, for example, has about 6000 crewmembers and serves 18,000 meals a day, generating substantial amounts of trash. Nuclear submarines spend months continuously at sea. Development of biodegradable plastics, which in some areas could be disposed of in the ocean along with food wastes, could be a considerable asset. 157 12.5.3 Composting Composting of municipal solid waste in the United States is still in its infancy. According to BioCyle, 18 such facilities are currently in operation, and two are under construction. 158 Some facilities process a mixed waste stream and others process source-separated organics (that is, the generators of the waste separate the compostable organics from the noncompostable wastes). Generally, the source-separated organics stream contains paper and food waste, and does not include any plastics. Some institutional composting of source-separated organics, such as of waste from fast-food restaurants, has included biodegradable plastics used for food containers and cutlery. The mixed-waste composting facilities do include plastics among the materials collected. The EPA counted 14 such mixed waste composting facilities in 1996, handling a total of about 900 tons/day. 2 In such systems, the waste is generally processed to remove large items, ferrous metals, and sometimes other components before processing. The compost produced in these facilities is generally higher in levels of contaminants, including unde- sirables such as heavy metals, than compost originating from source- separated streams. At their current level of use combined with the current level of nonyard-waste composting, biodegradable plastics play only an insignificant role. For biodegradable plastics to have a significant impact on waste management, a higher level of use and a large growth in composting programs would be required. If source-separation is part of the system, significant consumer education efforts would also be needed to get people to divert only the right kinds of plastics to the compost stream. Composting of yard waste is more prevalent in the United States than composting of other waste streams. In 1996, the U.S. EPA reported 3260 yard waste composting programs, handling approximately 25,500 tons/day. 2 Some facilities collect yard waste only in paper bags, which can be composted along with the yard waste, but which can cause problems if they become wet and consequently weaken. Some facilities collect leaves in loose form using a vacuum system. Some facilities permit plastic bags, but remove the yard waste from the bags before composting. This can add significantly to the cost of composting. A number of 12.78 Chapter Twelve 0267146_CH_12_HARPER 2/24/00 4:41 PM Page 12.78 [...]... 0267146_CH_12_HARPER 2/24/00 4:41 PM Page 12.101 Plastics Recycling and Biodegradable Plastics 12.101 27 Smith, S., “Fry-Sorting Process Promising in Post-Consumer Plastics Use,” Plastics News, November 11, 1996, p 27 28 Schut, J H., “Process for Reclaiming Durables Takes Off in U.S.,” Modern Plastics, March 1998, pp 56–57 29 Maten, A., “Recovering Plastics from Durable Goods: Improving the Technology,”... Afterlife,” Plastics News, January 13, 1997, p 9 37 Grande, J A., “Computer Manufacturers Make In-Roads in Use of Recyclate,” Modern Plastics, November 1995, pp 35–39 38 “Japan Firms Reusing Plastics in Electronics,” Plastics News, October 5, 1998, p 49 39 Denison, R A., Something to Hide: The Sorry State of Plastics Recycling, Environmental Defense Fund, Washington, D.C., 1997 40 Association of Plastics. .. Reclaimed Resin Markets,” Modern Plastics, February 1996, pp 51–53 116 Ford, T., “Hewlett-Packard Printers Use Recycled ABS,” Plastics News, August 7, 1995, p 40 117 Bisio, A L., and M Xanthos, eds., How to Manage Plastics Waste: Technology and Market Opportunities, Hanser Publications, Munich, 1994 118 Van Ness, K E., and T J Nosker, “Commingled plastics, ” in R Ehrig, ed., Plastics Recycling: Products... Vacuums,” Modern Plastics, January 1997, p 22 120 Mapleston, P., “Housing May Be Built from Scrap in Low-Pressure Process,” Modern Plastics, September 1995, p 21 121 “Five Standard Test Methods on Plastic Lumber Approved,” ASTM Standardization News, November 1997, p 11 122 “Plastic Pallets Rival Wood, Steel Models,” Plastics News, November 17, 1997, p 30 123 Bregar, B., “Plastic Rail Ties Gaining Favor,” Plastics. .. Commercial,” Modern Plastics, May 1997, p 16 129 Lavendel, Brian, “Recycled Wood and Plastic Composites Find Markets,” BioCycle, December 1996, pp 39–43 130 Urey, C., “Wood Composites Make Show at Meeting,” Plastics News, September 29, 1997, p 9 131 Urey, Craig, “Mikron Invests in Wood-Plastic Composite,” Plastics News, August 17, 1998, p 8 132 Ford, Tom, “Nortel May Add to Its Recycling Process,” Plastics. .. Recycling, May 1994, pp 59–64 52 Newcorn, David, Plastics Broken Loop,” Packaging World, June 1997, pp 22–24 53 “Process Yields Recycled PET in Food Packaging,” Modern Plastics, November 1994, p 13 54 Smith, Sarah S., “Precision Using PET as Recycling Alternative,” Plastics News, January 12, 1998, p 10 55 Toloken, Steve, “Campaign Asks Coke to Use Recycled PET,” Plastics News, September 14, 1998, p 6 56... Sarah S., “APR Urges Vinyl Institute to Find Markets,” Plastics News, July 14, 1997, p 6 67 Toloken, Steve, “PVC Bottle Recyclers Chastise Vinyl Institute,” Plastics News, August 18, 1997, p 36 68 Toloken, Steve, “Recycling Program in the Works for PVC,” Plastics News, August 31, 1998, p 5 69 ”Japanese Packagers to Phase Out PVC Bottles,” Modern Plastics, March, 1998, p 20 70 Wisner, D’Lane, “Recycling... Process,” Plastics News, December 18, 1995, p 10 74 Kiser, J., “Hospital Recycling Moves Ahead,” BioCycle, November 1995, pp 30–33 75 Moore, Stephen, Plastics Recycling Profit Soars in India,” Modern Plastics, June 1995, pp 19–21 76 Ehrlich, Raymond J., “The Economic Realities of Recycling,” Polystyrene News, Fall 1997, pp 1, 3–4 77 Toloken, Steve, “NPRC to Shut Failing PS Recycling Plant,” Plastics. .. p 1 91 “Eastman Kodak Recycles 50 Million Cameras,” Plastics News, August 14, 1995, p 10 92 “Snapshot of Recycling,” BioCycle, June 1996, p 88 93 Myers, S., “Recyclers of Appliances, Durables Looking to Germany’s Proposals,” Modern Plastics, March 1995, pp 14–15 0267146_CH_12_HARPER 2/24/00 4:41 PM Page 12.103 Plastics Recycling and Biodegradable Plastics 12.103 94 “A Noncatalytic Process Reverts Polystyrene... February 1995, pp 25–27 22 Plastics Recyclers Stay on the Cutting Edge,” BioCycle, May 1996, pp 42–46 23 Colvin, R., “Sorting Mixed Polymers Eased by Hand-Held Unit,” Modern Plastics, April 1995, p 34 24 Stambler, I., “Plastic Identifiers Groomed to Cut Recycling Roadblocks,” R&D Magazine, October 1996, pp 29–30 25 Smith, S., “PolyAna System Identifies Array of Plastics, ” Plastics News, December 15, . labeled. 143 Thus, as for automobile parts, equipment for identifying carpet materials will continue to be needed. 12.4 .16 Other plastics While the major types of plastics recycling have been addressed,. than 10 million tons of compost Plastics Recycling and Biodegradable Plastics 12.79 0267146_CH_12_HARPER 2/24/00 4:41 PM Page 12.79 are produced per year. 165 ,166 In 1998, the European Union. of wastes. The problem is particularly acute for ships carrying large numbers of people, ships which spend long periods at sea, or ships Plastics Recycling and Biodegradable Plastics 12.77 0267146_CH_12_HARPER

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