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DEGRADABLE PLASTICS
FOR COMPOSTING

There is little argument among composters that the top contaminant in feedstocks is plastic. At the same time, there is little disagreement among certain categories of generators — especially those in food service and to some extent grocers — that plastic bags are an integral part of their waste collection infrastructure. So as composters, generators and haulers work together to divert food residuals, soiled paper and other feedstocks, many have zeroed in on biodegradable/degradable plastic bags. “Participation in organics collection programs could expand with the use of degradable plastic bags — the problem is finding a bag that I’m comfortable recommending given cost, availability and quality concerns,” says Jack Macy, organics recycling coordinator for San Francisco’s Department of the Environment, which has an aggressive food residuals composting program.

The unease surrounding degradable plastics is not new. More than ten years ago, bags made from a blend of starch and polyethylene were introduced into the market. The problem was that while these bags broke apart in a composting environment, they did not mineralize (i.e. were not completely converted to carbon dioxide and water), leaving fragments of plastic in the compost. In the mid-1990s, a new generation of bags made from biodegradable polymers was introduced. The resins used to make the degradable bags fell into two broad categories — natural and synthetic. Natural, or biopolymers, were made from renewable resources. Synthetic polymers were made from biodegradable petroleum-based feedstocks and included polyester and polyethylene polymers (e.g. polycaprolactone). At that time, most biodegradable plastic bags were made from a blend of natural and synthetic polymers. The synthetic components were necessary, said product manufacturers, to give the bag the properties to perform like a bag.

Key to marketing of bags from those newer resins — and related products such as cutlery and tableware made from similar materials — was making the claim that they would completely biodegrade under composting conditions and within the timeframe of the composting process and not leave any plastic residues. It quickly became evident that industry standards on compostability were necessary to both back up the claims and to provide guidance to consumers. This credibility appeared to be essential to the growth of the biodegradable plastics industry. Initiatives were taken through the American Society for Testing and Materials (ASTM) and similar organizations in Europe and Japan. More recently, a compostable logo program was established in the United States by the International Biodegradable Products Institute (BPI) and the United States Composting Council (USCC), based on the ASTM standards that were established.

Despite the existence of standards and the logo, generators, haulers and composters still find it challenging to find biodegradable plastic products on the market for a reasonable price. Some program managers and composters are using bags marketed as “degradable” as opposed to “biodegradable” because of better availability and price. “We’re looking at going to different bags because they are more economical and easier to get a hold of,” says Sara Griswold, resource recovery coordinator for the city of Hutchinson, Minnesota, which operates a source separation program. When considering the bottom line, traditional plastic garbage bags weigh in at a dime each. Modified degradable polyethylene bags sell from less than 20 cents to about 30 cents each. Fully biodegradable bags can run from 20 cents to 80 cents a bag, depending on quantity ordered.

To help provide a roadmap of biodegradable and degradable plastic products available today, BioCycle surveyed resin producers, bag manufacturers and compost operators. This article includes a review of standards in the United States and overseas, describes available products, and identifies projects testing different degradable plastics.

CERTIFICATION AND STANDARDS

For the purposes of consistency, the definitions and terms used in this article are also those used by the ASTM. The definitions are:

Degradable plastic: A plastic designed to undergo a significant change in its chemical structure under specific environmental conditions, resulting in a loss of some properties that may be measured by standard methods appropriate to the plastic and the application in a period of time that determines its classification.

Biodegradable plastic: A degradable plastic in which the degradation must result from the action of naturally occurring microorganisms.

Compostable plastic: A plastic that undergoes biological degradation during composting to yield carbon dioxide, water, inorganic compounds and biomass at a rate consistent with other known compostable materials and leaves no visually distinguishable or toxic residues.

There is some question as to whether any inerts left by some plastics will cause problems in the soil over time. Long-term testing has not been performed to establish if there will be any consequences.

The specifics of the ASTM standards are discussed in the sidebar, “ASTM D6400-99 Standards Defined.” Standards and certification methods were initially devised to give credibility to products, according to Ramani Narayan, chair of the ASTM’s scientific advisory board. Throughout the 1990s, both abroad and in the United States, a variety of products were marketed as fully compostable and biodegradable. The claims were often unsubstantiated and led to dissatisfied composters and end users. As a result, individual countries started developing standards for products to meet in order to be “certified” or to gain recognition as biodegradable. The ASTM D6400-99 standards in the United States, Japan’s GreenPla program, and DIN certification and European Committee for Standardization (Comite Europeen de Normalisation or CEN) in the European Union nations, are all based on three basic concepts that bring the industry together: Biodegradability or mineralization, measured by carbon dioxide evolution after microbial assimilation; Ability to disintegrate, so as not to be visible or recognizable after composting; and No impact on the ability of the compost to support plant growth.

To help identify products in the United States, the Compostable Logo program was set up by BPI and the USCC. The ASTM D6400-99 standard differentiates between biodegradable and degradable plastics — meaning biodegradable plastics are biologically mineralized and consumed by soil microbes, compared to plastics that do not necessarily biologically mineralize completely but disintegrate due to thermal, photochemical or hydrolytic degradation, explains Narayan. The logo helps consumers identify which products meet the ASTM standard. To qualify for the logo, verification that the products meet the ASTM D6400-99 standards is done through an independent third-party reviewer chosen by the manufacturer. Many products on the market do not meet ASTM D6400-99 standards. “The bottom line is most people who buy ‘compostable’ products don’t know about the logo and certifying process,” says Sum-ner Martinson of the Massachusetts Department of Environmental Protection. “We need more public education. We have to get the makers of biodegradable materials out there promoting the certification process.”

Meanwhile, overseas, waste regulations and landfill directives are helping to fuel the compostable plastics industry by encouraging composting of organic solid waste and therefore the use of biodegradable plastics. For example, in Japan, large institutions must separate food residuals for composting, says Steve Mojo, executive director of BPI. Such rules, paired with increased tipping fees, create a higher demand for compostable products, which in turn creates a competitive market. Many facility managers expressed the need for a similar chain of events in the United States:

“If there is competition, the price will drop. The cost element is more prohibitive than anything else,” says Nelson Widell of Waste Options Inc., which operates municipal solid waste facilities that combine composting and recycling. He is looking into a pilot study with biodegradable bags for the Marlborough, Massachusetts facility it operates and says if the project is successful, the use of biodegradable bags would likely be required. “Right now, we’re looking into bags from Eastman Chemical Company,” he adds.

Manufacturers note the classic “chicken and egg” cycle in this pricing situation. If large orders for products were placed, the price of biodegradable bags would come down — but no one wants to commit to higher prices initially, therefore squelching the demand that brings increased production and lower prices.

Companies with home bases in the United States, including Cargill Dow and DuPont, already manufacture and market polymers that are certified as biodegradable for use in Asian and European products. Some that did not market these products previously in the United States because of insufficient market demand are starting to now. At the same time, products made and certified overseas are starting to be marketed in the United States, such as the Norway-based Polargruppen line, which uses Novamont’s Mater-Bi polymers. BPI estimates at least three manufacturers will be granted use of the Compostable Logo in the United States by the end of 2002, which is expected to accelerate the U.S. marketplace. Some of those products are commercially available and are going through the certification process. The only bag granted use so far of the Compostable Logo is from Biocorp Inc., which has now been reorganized into Biocorp North America (BNA) — and is still providing certified bags.

Table 1 lists the companies making degradable polymers and the products in which the polymers are being used. To help distinguish the products described in this article, the polymers are divided into two families — biodegradable and degradable. Degradable technologies start with a polyethylene base and degradation initially begins when the product is exposed to light (photodegradable), heat (thermodegradable), or water (hydrodegradable). Biodegradable polymers do not contain polyethylene and are engineered to completely biodegrade in a microbial environment. Such polymers include polylactic acid, aliphatic polyesters, polyester amides, and starch copolymers.

BIODEGRADABLE POLYMERS

Many major companies are now making polymers. For example, Cargill Dow LLC was formed in 1997 by Cargill and Dow Chemical Company to develop and market the polylactic acid (PLA) polymer family. Originally sold under the name EcoPLA, Cargill Dow now markets what’s known as NatureWorks PLA, which is actually a family of polymers that can be used alone or blended with other natural-based polymers. PLA is fully biodegradable when composted in a large-scale setting. It reduces the consumption of fossil fuels by 30 to 50 percent because the material comes from a natural fermentation process, according to Cargill Dow’s Michael O’Brien. However, he says because NatureWorks PLA is very rigid, it works best for thermoformed articles like cold drink cups rather than compostable plastic bags. The company has worked with Mater-Bi in developing biodegradable blends.
NatureWorks PLA meets Japan’s GreenPla standards, and Cargill Dow has made inroads in the Japanese market, including using the polymer in Dunlop golf ball packaging and Sony mini-disc packaging — making both compostable. “Japan is an island nation with serious concerns about waste management,” O’Brien says of the company’s involvement overseas. The PLA family can be used in many types of applications, from clothing fibers to carpeting to food and beverage packaging. The company finished construction of a manufacturing plant in Blair, Nebraska in November and expects to be operating at capacity in a few months. It will produce three million pounds of PLA annually for a variety of packaging and fiber applications. The plant will make the PLA family cost competitive with petroleum-based polymers, according to O’Brien.

Another big player is Procter & Gamble Co. (P&G), makers of the aliphatic copolyester Nodax line of polymers that are biodegradable in aerobic and anaerobic conditions, according to Norma McDonald, project manager for the Nodax line. The company has done extensive research into how to blend polymers to get the right stiffness or flexibility. It recently finalized a licensing agreement with Kaneka Corp., a Japanese manufacturer of plastics and resins, for the commercialization of PHBH, a polymer in the Nodax family.

Similar to Cargill Dow’s NatureWorks PLA, the Nodax polymers are produced by microorganisms through a fermentation process, and the plastics are extracted from the biomass. They can be blended with a host of different materials for use in a wide range of applications — from packaging to diapers to clothing. “Polymers in the aliphatic polyester family are strong like nylon but have great barrier properties,” McDonald says. The polymers typically are used in applications where polyethylene and polypropylene were used. “The trigger for degradation is bacterial,” she says. The company has worked extensively to determine when exactly that trigger is pulled — which has vastly improved end uses and stability, she adds. P&G is working with other resin producers to make blends that perform well within economic and environmental parameters. The company also gives samples of its licensed Nodax resins to other polymer developers for experimentation. “The industry is gaining momentum,” McDonald says. “It’s going to take more than one company to move biodegradable products into the mainstream marketplace.”

Eastman Chemical Company, whose Eastar Bio copolyester polymer is being used in lawn and garden bags, food packaging and horticultural applications worldwide, is getting lots of attention. It just began a high profile U.S. marketing campaign for its aliphatic copolyesters, the same family of polymers that Nodax falls into. In 1999, the company modified its Hartlepool, England plant, where it manufactures Eastar Bio, to meet market needs. It processes 330 million lbs/yr at the plant. The polymer has been marketed in Europe and Japan since 1997 and Eastman is just beginning to shift its focus to the United States as domestic market demand increases. The primary applications for Eastar Bio copolyester in Europe are for extruded films for biodegradable bags and single use fast food serviceware and other food packaging. The polymer meets ASTM and DIN standards and can be used alone or with additives.
DuPont has a 200 million lbs/year production facility in Tennessee for its Biomax polyethylene terephthalate copolymer which is available both overseas and in the United States. The family of polymers is made of hydro/biodegradable polyesters. Up to three aliphatic monomers can be added to the polyesters, which determines product applications. The added monomers create weak spots, making the Biomax polymer hydrodegradable. Once moisture breaks the polymer into smaller molecules, microbes can consume the material. Although the polymer has not yet met ASTM standards, a company spokesman says it is expected to pass the test. DuPont was one of the resin producers that made up the research team for the ASTM D6400-99 standard. The company has been collaborating with EarthShell Corporation to develop and market a variety of biodegradable food packaging. (See sidebar “EarthShell Greening the Food Packaging Industry.”)

A very noteworthy player from Italy, and one with a long history, is Novamont, which manufactures Mater-Bi starch copolyester pellets. BNA turns the pellets into reSource, the only bag on the U.S. market that currently meets ASTM D6400-99 standards and qualifies for the Compostable Logo. The company also makes cutlery, cups, straws, lids and plates. BNA is a reorganized version of Biocorp Inc., which declared bankruptcy and liquidated its assets at the end of 2001. “We believe that there is an increasing demand for biodegradable products, but our way of approaching the market has changed,” says Frederic Scheer, CEO of BNA. “It is clear that people need to be educated — now we are focusing on how we can introduce a product and have it make sense, both environmentally and economically. With a long term view, it is allowing us to organize supply of products at substantially lower prices.” Many experts in the industry note that Biocorp bags previously came with a high price.

Biocorp had been the exclusive North American user of the Mater-Bi starch copolymer since 1997. However, BNA now faces competition from other manufacturers. Polargruppen products, which utilize the Mater-Bi polymer, are available through Norsea BioSystems in Edmonds, Washington. The products are certified by DIN Certco in Germany and the “OK Compost” in many other parts of Europe. The Polargruppen product line includes bags, bin liners, agricultural mulch and food packaging.

It should be noted that Bayer Corp. stopped producing its aliphatic polyester polymer line, BAK, more than a year ago because it did not see a profitable future, according to Josef Hirschman of the Bayer Polymers Division.

DEGRADABLE PLASTICS

The remainder of products on the market typically start with some form of polyethylene and then add a degradability factor — either photodegradability, thermodegradability or hydrodegradablility. EPI Environmental Products Inc. makes the Degradable and Compostable (DCP) additive as well as other additives used in agricultural mulch and in alternative daily cover applications at landfills. Compostable bags and bin liners that use polyethylene modified by DCP additives are claimed to totally degrade within 90 days in commercial composting facilities. The DCP ingredients do not initially biodegrade, but rather chemically oxidize to lower and lower molecular weights, become brittle and fragment. The fragments are then ingested slowly by microorganisms, ultimately leaving carbon dioxide, water and biomass, according to Dick Freeman of Plastics Solutions Canada, Inc., a licensed agent of EPI’s DCP technology which markets the products in the United States under the brand name Ecosafe. (In the United Kingdom, the additives are made into products sold by Symphony Environmental Ltd.) Data provided by Plastics Solutions shows resulting compost quality is not compromised and passes ecotoxicity tests performed by third party reviewers.

Currently, DCP does not meet ASTM’s D6400-99 standards, because it degrades through chemical oxidation before the onset of biodegradation and mineralizes at a slower rate than is acceptable. The ASTM has accepted EPI’s proposal for alternative test method development, according to Graham Swift, a member of the ASTM subcommittee for polymers and a consultant for EPI who has been working on alternative test methods to submit to the ASTM. Plastics Solutions supplied Ecosafe bin liners to the 2002 Winter Olympic Games in Salt Lake City.

Indaco Manufacturing Ltd. in Toronto makes a recycled polyethylene-based bag known as Bio-Solo. The bags, which have been around since the early 1990s, use a nonstarch formula and have an adjustable degradation time activated by heat and oxygen. The bag is marketed as compostable and degradable. Brad Price of Earthbound Systems Inc. in Moses Lake, Washington, has been distributing the Bio-Solo bags in the Pacific Northwest. He says two of the reasons clients choose the bags are because they are less expensive than others on the market and are readily available. “Tests have shown that the bags have degraded in most systems from windrows to static piles and in most of the modern rapidly degrading composting systems of today,” Price says.

The impact of polyethylene dust that remains in compost for an unknown time period has been an ongoing question. Polyethylene products used at least ten years ago did not completely break down and remained visible. Today’s products leave a dust, not visible pieces and the virtues of that are debatable. The question is if any dust — prior to completely mineralizing — should be permitted and still pass ASTM tests. “Whatever we put into compost we must know will completely assimilate if it is to be considered biodegradable,” Narayan says. Price explains that, chemically, the dust should continue to mineralize until it is completely gone, and says that in the meantime the small amount of dust would present no more of a problem than other materials permitted in final compost.

WHAT USERS WANT

When a program hinges on getting bags on time, users need to order from companies that can undoubtedly deliver. “We had a real problem getting bags on time from our old supplier,” says Griswold of Hutchinson, Minnesota. “They came from overseas.” The city is buying Ecosafe bags from Plastics Solutions that are manufactured by Envision of Wichita, Kansas. “We’re trying them out because they are more economical and they will be here when we need them,” she says. The bags will be put through the facility’s Green Mountain in-vessel composting containers and Griswold anticipates complete degradation. The city operates a full-scale, source separated organics composting facility that processes residuals from commercial, residential and institutional sectors, all of which are collected in compostable plastic bags.

In Wichita, Kansas, many schools are diverting organic residuals from landfills. The schools, whose organics are processed in windrows, are also experimenting with Ecosafe bags, along with Eastar Bio and Norsea BioSystems bags. “Right now, we’re just testing different bags,” says Alan Chappell, owner of Environmental Concepts & Designs and a consultant to Wood Recycle and Compost Center, the facility that composts organics from the schools. “I’m looking for the bag that performs the best at the lowest cost.” He buys 30,000 to 40,000 bags at a time for the school program. Although the starch copolymer bags (Biocorp) he was using previously worked well, they were a hard sell because of cost, he adds. But, he notes, it’s all relative. “As tip fees go up, we have to look at the cost of bags from a full cost accounting approach. The more solid waste costs go up, the more people are willing to pay for degradable products.”

Several people surveyed indicated a need for cutlery and serviceware. Alex Cuyler, of the planning and development department for the city of Eugene, Oregon, says that there is a real lack of biodegradable cutlery choices. BNA is the only known company currently manufacturing and marketing compostable cutlery. It is also marketing biodegradable cups and servicewear but is focusing solely on large accounts. Polargruppen representative Steve Mojo says the Norwegian company is working to develop such products due to demand in Europe. For compostable dinnerwear, EarthShell Corp. provides plates, cups and clamshell sandwich containers.

QUESTIONS FOR THE FUTURE

Despite development of the ASTM standards and the BPI/USCC logo program, the majority of bags entering composting facilities in the U.S. today don’t meet the standard and don’t have the logo. As more companies start selling bags (and other products such as cutlery and serviceware) with the BPI/USCC logo, it is hoped that the marketplace will become more competitive, giving generators, waste haulers and composters more options.

In the meantime, the fact that the polyethylene based bags hold up during collection and disintegrate within the standard composting timeframe, appears to be meeting the criteria of many in the collection and composting market. But this doesn’t address the question about whether or not polyethylene dust, a remnant of some bags in the compost, will harm soil over the long term.

Bob Besso of Sunset Scavenger in San Francisco, has been working with the residential and commercial organics collection programs in that city for a number of years. In his opinion, organic waste generators and collectors are so desperate for “biodegradable” plastic products that they settle for compostable or degradable labels stuck on any product. “As for processors, my guess is that they are probably accepting these bags in otherwise good loads because they (bags) have not caused many problems,” he says.

Jack Hoeck of Rexius Forest By-Products in Oregon says that Bio-Solo bags delivered to his facility in Oregon after an event at a local amphitheater broke down completely from a processing standpoint. The bags, which held food residuals, were cocomposted with yard trimmings for about 12 weeks in both turned windrows and in aerated static piles that were physically moved from time to time. “There was complete visual degradation, but no chemical analysis of the compost was done,” he says.

Besso suggests one potential alternative, which he notes, has some manufacturing obstacles. “Maybe a new bag classification(s) could be established, keeping truly biodegradable products as the ‘Gold Standard,’ and having an acceptable ‘activated’ bag rating(s) for others marketed as compostable. My personal experience with degradable plastic bags tells me that some types would likely be more problematic than others in specific processing operations. This rating could allow each processor to identify, to their feedstock suppliers, which bag rating was acceptable for their specific operation. Some may not allow any and some may allow all types of bags, based on their ability to remove the pieces and market the finished product.”

In the grand scheme of things, what product is chosen for use really depends on what the user wants out of the product. “If you want your bags to completely mineralize, you’ll get a bag that meets ASTM standards. If you’re very conscious of cost, you’ll get a bag that doesn’t meet the standards,” asserts Mike Manna of Woodhue, a composting facility in Wrightstown, New Jersey that composts food residuals from commercial generators, primarily grocery stores.

Jack Macy of San Francisco’s organics recycling program senses the industry is moving in the right direction. “A lot of folks out there are making and testing new products. Ideally, through that process, the performance of products should improve,” he says. “I’d like to be able to recommend a reasonably priced bag that we know performs well and that doesn’t impact soil health once it degrades.”

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