The SEARCH for a practical, affordable and completely compostable plastic bag has taken several steps forward in the past year. While there have been no giant leaps in either research or marketing, slow and steady progress in both areas is beginning to show tangible results. Some industry observers see 1996 as a period of recovery from earlier disappointments

During the 1980s, when so-called "compostable" bags were introduced to the market, environmental groups and others rejoiced. Many saw the development of these bags as a magic bullet that would end problems caused by non-degradable plastics lingering in the environment. The initial euphoria faded when it was found that the polyethylene-plus-starch films from which some bags were made did not completely biodegrade.

Those early bags disintegrated, to be sure, but left polyethylene residues that were invisible to the naked eye and hard to find by normal chemical analysis. More sophisticated testing methods, however, revealed that minute fragments of polyethylene were still present in the supposedly finished compost. Soil scientists expressed concern that these fragments would accumulate in soils and hinder both microbial and plant growth. The bubble of enthusiasm for these materials burst, discrediting their advocates and, some claim, setting back the biodegradable plastics industry by a decade. Nonetheless research and development work on biodegradable polymers continued, spurred by the promise of substantial] markets, particularly in Europe. (Scientists and engineers prefer to talk about "polymers." The term "plastic," they say, should be used only to describe the finished product, which may contain a variety of polymers, starches and additives.)

Scientists stress that the origin of a material ‹whether it is "natural" or "synthetic" ‹is unimportant if what one is looking for is a material that will biodegrade. Certainly, several polymers that are widely accepted as completely biodegradable, and that appear to leave no harmful residues behind after composting, are derived from petrochemicals. Some plastic films contain starches derived from renewable plant materials such as corn, but they also contain additives that are undeniably synthetic.

For example, one polymer used in biodegradable plastic bags is called Polycaprolactone, which, as Daniel Goldberg, development scientist for Union Carbide, points out, is synthetic based. Even so, he says, "I don't think you'll find anyone who questions its biodegradability. The raw materials source is irrelevant ‹what matters is the chemical structure." Union Carbide markets polycaprolactone under the registered trade name, TONE©

EnPac, a joint venture of DuPont and ConAgra, imports from Italy a biodegradable plastic film called MaterBi, which is made into bags in the U.S. Already successfully used for compostable bags in Europe and now making inroads into the US market, MaterBi contains corn starch. "That's not the only thing in it, however," says Randy Redd of EnPac. "It's true that MaterBi is based on corn starch, but it would be misleading to think that's the only‹or even the primary‹ component." EnPac recently announced that they will soon be marketing MaterBi bags made for them by Castle Bag Company. Another firm, Earthsoul® already is promoting and selling its Earthsoul®-bag, also made from MaterBi film. "Several large scale tests are under way in locations such as Malone, New York and San Bernardino, California," says Bilimoria, Earthsoul® CEO.

Cargill, one of the world's largest agricultural processing companies, uses corn to make polylactic acid (PLA) for its EcoPLA biopolymer. Like some other biodegradable materials, EcoPLA can be made into film fiber, and a paper coating, and can be thermoformed and injection molded. In 1997 Cargill will market a 30-gallon compostable bag under a recent arrangement with Duro Bag, based in Kentucky.

Dr. Ramani Narayan, Professor of Chemical and Biochemical Engineering at Michigan State University, and a longtime proponent of fully biodegradable polymers, is test marketing a material called Envar, made, he says, of "an aliphatic polyester called polycaprolactone that has been alloyed with a thermoplastic starch." In his opinion, regardless of whether it is made from synthetic or natural materials, what matters to users of biodegradable bags is whether they will disappear in compost without leaving a potentially harmful residue. "Unfortunately," says Narayan, "there are still bags in the market that, at best, disintegrate. But to be biodegradable, we must demonstrate under laboratory conditions that in a composting environment 100 percent of the carbon of that material will mineralize and be converted to CO2. Just claiming that something is disintegrating is of no use. We did that once, some time ago, and it didn't work."


The obvious need for technical standards to unambiguously define what is meant by such terms as "biodegradable" and "compostable," and to lay out strict testing methods, prompted a flurry of work by national and international standards organizations over the past few years. By the end of 1996 a handful of groups had published their results. The effects of these standards have tremendous commercial importance, especially to multinational corporations who make and/or distribute raw materials and blended film.

In the United States, the Institute for Standards Research (ISR) of the American Society for Testing and Materials (ASTM) published its Standard Guide to Assess the Compostability of Environmentally Degradable Plastics in 1996. Earlier, ASTM established rules for labeling packaging materials that "communicate environmental attributes" to consumers or users, known as D-5488, as well as a standard laboratory test method to measure biodegradability under composting conditions known as D-5338.

ASTM/ISR's "Standard Guide" is the result of an effort begun in 1991 when a group of companies formed and funded a Degradable Polymeric Materials Program that set out "to provide the basis for the scientific substantiation of disposability statements for degradable polymeric materials." The scope of the program was to determine the behavior of degradable polymeric materials in real disposal systems, and how those resuits correlate with laboratory results, "in order to assure that such materials are safe for disposal and effectively degraded."

One way to detect plastic film components that do not fully biodegrade during the composting process involves a sophisticated laboratory technology called respirometry. At the Biodegradable Polymer Research Center of the University of Massachusetts in Lowell, Drs. Stephen McCarthy and Richard Farrell are conducting a study that will include the use of this technology. "We have selected 10 bags, eight of which supposedly are biodegradable," says Farrell. "There is a negative control which is polyethylene and a positive control which is a lawn and leaf bag made of kraft paper. It's being done as a blind study, but I'm pretty sure that one of the bags is a polyethylene- starch blend. We're going to do a respirometry study a mineralization test that looks at conversion of polymer carbon into carbon dioxide. The polyethylene starch [blend] will disintegrate and disappear in the compost, but the polyethylene doesn't biodegrade, so we'll be able to track the CO2 that comes off of it. Even though the film will disintegrate and you won't be recovering any film pieces, all the CO2 that gets formed should be from the starch." This study, funded in part by the Massachusetts Department of Environmental Protection and the Chelsea Center for Recycling and Economic Development, is expected to be finished during 1997. Researchers will follow the ASTM guidelines, with laboratory and pilot studies followed by field tests at four outdoor composting facilities in Massachusetts.

The International Standards Organization (ISO), and, in Europe, the Committee for European Normalization (CEN), and the Deutsche Industrielle Normalische (DIN) also have produced their own standards and test procedures. This plethora of guidelines and procedures ‹similar but not identical to each other now poses a problem for companies that want to sell their products in more than one country. However, thanks to Bert Lemmes, managing director of the Brussels-based Organic Reclamation and Composting Association and executive director of the International Biodegradable Products Manufacturers Association, a move was afoot to achieve consensus between these varying standards. These standards were finally combined thereby giving the international manufacturing companies a breather and more open international market for these products.

"After a closed technical session, delegates from the biodegradables, converter, paper, consumer products and packaging industries will attend an open, plenary session to make presentations on their specific problems and opinions. "The paper industry in Sweden, for example, has a different point of view from the paper industry in Finland," notes Lemmes, "but together they provide about 90 percent of Europe's paper. Hopefully, the delegates will emerge from the meeting‹or a later working group session‹with a consensus on testing strategies, certification and, ultimately, perhaps, a logo for all biodegradable and compostable products."

Sifting needs and priorities from different areas of the globe is a balancing act. "In the United States the ASTM/ISR report goes a long way to explaining what is needed to substantiate a biodegradable/compostable claim," says Steven Mojo, an environmental consultant with Galatech of Clifton, New Jersey. "In many respects, this work parallels what is being done in Europe. In the United States it will be important to demonstrate the economics of landfilling versus composting."

A case for a single universal standard comes from Union Carbide's Daniel Goldberg: "Each market is trying to define its own standard, but realistically it would be better if there was one international standard so that any producer could meet conditions in all the different markets. We need resolution on this."

There is little doubt that Europe is currently the primary market for compostable bags. Lemmes reports that the European Council has draft legislation pending that will ban, throughout Europe, landfilling or incineration of materials containing more than 10 percent organic content. Germany he says, already bans from landfills anything with more than five percent organic content. This obviously creates a large market for compostable bags.

"Europeans in general don't have garbage disposal units [in kitchen sinks] so the collection of food waste becomes a very viable option for landfill reduction," notes Randy Redd of EnPac. "In Italy there is a substantial business in small, onegallon size bags into which you can put the day's food waste, then tie it up and put it in a special receptacle that's picked up once a week for composting." He also points out that with tipping fees at $400 or more per ton in northern Italy, the incentive to divert materials through this type of program is very high.

While legislative imperatives help to drive European sales, the U.S. market for compostable bags, on the other hand, currently depends upon a scattering of pilot programs as companies strive to get their products recognized and accepted. Compostable bags sell for higher prices than nondegradable bags, but it is questionable whether they in fact end up costing more when consideration is given to the high cost of removing nondegradable plastic at composting facilities.

The catch-22 of pricing is that, at least in the U.S., prices are unlikely to drop until a larger market opens up, but mass market sales are hindered by high prices. During a roundtable discussion at the Composting Council's Seventh Annual Conference in Arlington, Virginia in November 1996, Randy Redd addressed resin suppliers such as Union Carbide and Dow Chemical with these concerns: "If prices aren't cut substantially, nothing will ever happen in this marketplace. You've got to look further than next quarter's balance sheet to make this work."

Even with this kind of developmental difficulty, Mojo, who also works as a consultant to Cargill, is among those who feel things are on the right track‹with certain caveats: "In the United States, the future of biodegradables will depend on developing applications with competitive pricing and performance that demonstrate the economics of composting organic residuals versus landfilling, from a systems perspective." Another necessary component, he says, is identification systems to aid consumer and end user education. Finally, according to Mojo, legislation supporting composting and treating biodegradable plastics in the same manner as kraft bags, with regard to degradability, also would help.

Peter Garnham is former Recycling Officer for the Town of East Hampton, Long Island, New York, and the Composting Council's 1996 Outstanding Composter of the Year.
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