Plastics recycling and biodegradable plastics

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Plastics recycling and biodegradable plastics

The attention the public gives to environmental issues has long been recognized to wax and wane through time. For plastics, the first significant environmental pressure came during the mid - to late 1970s, when oil prices rose dramatically. At first, plastics were targeted as made from oil and, therefore, environmentally suspect. As time went on, however, the attributes brought by plastics in terms of energy efficiency became more widely recognized. In the recycling area, however, the rise in oil prices and, consequently, in the base price of plastic resins had significant impact. The scrap from plastics manufacturing processes became too valuable to simply discard. Use of regrind in manufacturing of plastic products increased. The literature of this time has a variety of publications addressing the concerns which arose from this practice, and they look at the effects of degradation and, to a lesser degree, of contaminants in the feedstock. Slowly but surely, the use of regrind in plastics manufacture became routine, just as the use of inhouse cullet in glass manufacture and edge trim in paper manufacture had become routine. Even when oil prices fell again, the economic benefits of using regrind were now recognized, and such use continued.

The next significant wave of environmental concern to impact the plastics industry began in the mid-1980s, and it had a considerably different focus-solid waste. There was a perception in the United States that, as a nation, we were running out of landfill space, and further that plastics were a particular problem because their nonbiodegradable nature meant they were occupying the limited landfill capacity available for seemingly an eternity. This also brought about an interest in plastics recycling, although this time the interest was primarily in recycling of products at the end of their useful lives, rather than of manufacturing scrap. Use of regrind, in fact, had become such a normal practice that it was no longer considered true recycling; rather it was just good business practice. At this same time, there was pressure for use of biodegradable plastics as a replacement for the synthetic nonbiodegradable polymers that were perceived as filling up valuable landfill space.

As time went on, landfill costs in the United States, which had risen dramatically, declined again. Fewer but bigger landfills relieved the capacity crunch. Studies about what really goes on in modern landfills demonstrated that even readily biodegradable materials, such as food, often degraded only very slowly. Further, some plastic products which had been marketed as biodegradable proved to have only very limited degradability. Interest in biodegradability decreased, while pressures and opportunities for recyclability increased. Nonetheless, technical progress toward the production of a greater variety of truly biodegradable plastics continued. Also, plastics recycling continued to grow.

More and more U.S. households had access to curbside recycling programs which accepted a few or many plastics, primarily bottles. By the mid-1990s, critics of plastic recycling began to get more attention. The high costs of adding plastic to curbside recycling programs were cited. Burgeoning production of virgin resin at different times caused falling prices for the two most widely recycled plastics, high-density polyethylene (HDPE) and polyethylene terephthalate (PET). The economic viability of plastics recycling was called into question. Nonetheless, the general public remained supportive of plastics recycling. Few communities dropped curbside recycling or dropped plastics from their recycling programs. In fact, interest in recycling plastic materials began a significant spread beyond packaging materials to the durable goods arena. The American public, by and large, has become convinced of the value of recycling. Many feel that it is one thing they, on a personal level, can do to help the environment, and they feel good about participating. Thus, though the solid waste «crisis» was over in the United States by the mid-1990s, recycling seems to be here to stay.

During the 1990s, attention to recycling of postindustrial plastics also grew. While it got little public attention compared to recycling of postconsumer plastics, many producers of resins with recycled content relied heavily on industrial waste as feedstock. These waste streams were not the clean single-resin regrind, but rather typically consisted of multiresin materials, materials which combined plastics and nonplastics, or materials which were contaminated in some other way, and which therefore had been going to disposal rather than being reused in house. While some of these streams were heavily contaminated and difficult to use, many were relatively clean, uniform in content, and more economical to collect than postconsumer materials. Producers of such scrap found that they were able to avoid paying for disposal of these materials by arranging to feed them to a recycler, and often could make a little money on the exchange as well.

Along with the changes in public concern about plastics use and recycling, there were changes during this time period in legislative pressures. During the «solid waste crisis,» the first wave of legislation often focused on bans of materials or products, particularly plastic packaging, which were seen as a particular problem. For example, nondegradable ring connectors for beverage cans were banned, first by a variety of states, and then throughout the United States. Mandatory recycling programs were instituted, sometimes at a statewide level and other times in individual communities. Taxes on plastic packaging were proposed and sometimes instituted. Grant and loan programs were instituted to help facilitate new recycling businesses as well as community education about recycling. Some states banned disposal of recyclable materials. Many of the legislative initiatives which were proposed never passed, but their sheer number was overwhelming. Most major plastics and packaging companies found it necessary to designate one or more people to devote all, or at least a substantial amount, of their time to environmental and recycling issues.

As time passed, the tenor of legislative initiatives became focused more on recycling. An interest in bans and taxes gave way to efforts to push for markets for recycled materials, including plastics. The pace of legislative activity decreased, but the issues did not go away. In Europe, where in many countries the issue of landfill scarcity was much more real, a very different approach emerged than in the United States. First in Germany, and then throughout the European Union, the producer responsibility principle was adopted.

On the biodegradability side, along with the technical work to develop truly biodegradable plastics, the growth of composting as an accepted companion to recycling has opened at least limited opportunities to make use of biodegradability of materials as an asset in their ultimate disposal. Along with all of these changes, the last 10 years have brought an increasing recognition of the complexity of environmental decision making. Most experts now agree, at least in principle, that decisions on what is best to do from an environmental perspective cannot be based on a single attribute, but must instead be based on an analysis of all the environmental impacts from the decision through the whole life cycle of the products or processes involved. This type of cradle-to-grave analysis is termed lifecycle assessment.

In this chapter, we will attempt to portray the current status of environmental issues as they relate to plastics recycling and biodegradable plastics, the current status of legislative requirements which have an impact in these areas, how we are doing and where we are headed in recycling of plastics, and the current status and prospects for biodegradable plastics. Issues related to the technique and practice of life-cycle assessment, except in the general context of our look at environmental issues, are beyond the scope. Similarly, in our look at plastics recycling we will focus primarily on postconsumer plastic (plastic which has served its intended use and been discarded), with some attention to postindustrial plastics. Routine use of scrap in the form of regrind will not be addressed.

Thus, around the world there is increasing reliance on recycling, not as the only method for handling solid waste, but as an important part of what has become known as integrated solid waste management-the mix of strategies used to handle disposal of the wastes we generate. An important consideration is how significant plastics are in contributing to problems with solid waste generation and disposal. There is no doubt that the amount of plastics entering the municipal solid waste stream has increased markedly in the last two decades, and continues to increase, as illustrated in Fig. 1 for the United States.

References

recycling solid waste

1. Glenn, J., «The State of Garbage in America, Part I,» BioCycle, April 1998, pp.32-43.

2. U.S. Environmental Protection Agency, «Characterization of Municipal Solid Waste in the United States: 1997 Update,» EPA 530-R-98-007, May 1998.

3. U.S. Environmental Protection Agency, «Updated Air Quality Standards: Fact Sheet,» Washington, D.C., 1997.

4. Modern plastics handbook / Modern Plastics, Charles A. Harper, New York, 1999.

5. Toloken, Steve, «Nike Nixing its Vinyl Use,» Plastics News, August 31, 1998, p. 5.

6. Intergovernmental Panel on Climate Change, IPCC Second Assessment Synthesis of ScientificTechnical Information Relevant to Interpreting Article 2 of the UN Framework Convention on Climate Change, 1995, United Nations, New York, 1995.

7. Thompson Publishing Group, Environmental Packaging: U.S. Guide to Green Labeling, Packaging and Recycling, Washington, D.C., 1998.

8. Raymond Communications, State Recycling Laws Update, College Park, Md., 1998.

9. «Oregon,» Resource Recycling, February 1996, p. 10.

10. «Plastic Recycling Rate in California,» Reuse/Recycle, April 1998, p. 30. 9002 / 10000

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