Biodegradable Plastics: Too Good to Be True?

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Michel and his team looked for dirt on plastic additives by performing biodegradability experiments over the course of many months.  (Photo Courtesy of Fred Michel.)

The next time you drop a bottle marketed as biodegradable into your reusable grocery bag, pause. New research shows that not all of these plastics are made equal: some don’t actually biodegrade.

Plastic pollution is a global issue. Long-lasting plastics cramp landfills, pile up in city streets, and create toxic problems in rivers, oceans, and drinking water. Americans generate over 30 million tons of plastic waste each year, and only 8 percent of that is recycled.

In Ohio, plastics are the largest component going into the waste stream, according to recycling expert Terrie Termeer with the Ohio Environmental Protection Agency. Concerns about this influx throughout the U.S. have given rise to a new kind of “biodegradable” plastic, which Termeer says is gaining in popularity. Companies are actively designing products that degrade quickly and that are sometimes made from plant feedstocks, appealing to consumers who don’t want to leave behind piles of waste or use materials that are “bad” for the environment.

Researchers picked up on the trend, too, some of whom felt it was cause for concern.

“I was always curious about, you know, do they actually biodegrade?” said Fred Michel, a waste-management expert and professor at Ohio State University.


Biodegradability, a measure of how well something breaks down in compost, soil, or landfills, is an ambiguous term at best. Everything biodegrades completely over time, but your car might take a few thousand years longer to fall apart than, say, a tissue. The Federal Trade Commission (FTC) has attempted to clarify the term to prevent misleading advertising, but the definition is complex. According to the FTC, a product is biodegradable if it breaks down in certain environments, like compost bins, within a "reasonable" amount of time. But each environment dictates different interpretations of “reasonable.” Ultimately, the FTC notes that no matter where something breaks down, it needs to be completely returned to nature within a one-year timeframe in order to be marketed as “degradable.”

Michel and his team tested materials like coconut hull, asphalt-covered plastic, and additive-boosted polypropylene.
Michel and his team tested materials like coconut hull, asphalt-covered plastic, and additive-boosted polypropylene. Photo courtesy of Fred Michel.

To make a plastic biodegradable, manufacturers have started putting in additives that supposedly allow even the sturdiest plastics to degrade in a backyard compost pile. To Michel, this seemed like an example of greenwashing-- a term that refers to misleading marketing tactics that appeal to the Captain Planet in each of us.

“I was skeptical about it from the beginning because those materials don’t usually biodegrade,” Michel said. “It’s difficult to imagine a material you could add to them that would magically make them biodegradable.”

In theory, biodegradable additives work by attracting microbes that in turn attract more microbes, increasing the rate of degradation. Some manufacturers also claim the additives are organic and nontoxic.

Michel reviewed the research but was unable to find evidence to support manufacturers’ claims, so he ran his own experiment. Michel and his team rounded up all sorts of plastics to test their biodegradability: a motley collection of natural fibers, petroleum-based materials with the biodegradability additives, and plastics that shouldn’t biodegrade.

The results of the research, published in December 2013, were disconcerting. Traditional plastics with the “biodegradable” additives didn’t break down any more quickly than those without.

“I wasn’t surprised,” Michel said, “but it’s just interesting that there are materials in the market like that, that have claims that don’t seem to be justified in our testing.”

The FTC soon caught wind of the results and began investigating ECM BioFilms, an Ohio-based manufacturer that makes a plastic additive analyzed in Michel’s experiment.

The ECM investigation, which remains tied up in court, represents the first time the FTC has ever pursued plastic biodegradability claims. Meanwhile, the FTC has also begun a closed investigation into plastic bag manufacturer American Plastic Manufacturing, Inc. for misleading claims, which might set precedent for future interactions with plastic manufacturers. Manufacturers of other materials have been charged hundreds of thousands of dollars in civil penalties for misleading marketing, but as a first-time offender, APM was not fined but simply ordered to stop making false claims.

“Unfortunately, the marketplace is full of these misleading claims,” said Ramani Narayan, a biochemical engineering professor at Michigan State University and chairman of the ASTM Subcommittee at the Biodegradable Products Institute, a nonprofit that helped develop international biodegradability standards. He says it’s often difficult to come across strong research about plastics, but he is pleased with Michel’s paper.

“It has given very clear scientific data,” he said. “It’s shown that nothing happens [when these additives are used].”

But greenwashing isn’t always deliberate. The language surrounding “bio-friendliness” is so complex that many are just plain confused, said Michel.

“In addition to there being confusion among consumers about how these materials may be recycled or composted -- or where they end up -- there's also a certain amount of confusion among industries that are trying to become more sustainable and develop more sustainable products, about the end of life of these materials and products, and how they can best address their sustainability goals with these materials,” Michel said.

Some companies have their products tested and certified by the Biodegradability Products Institute. Those confused about particulars can look to the FTC’s Green Guides, documents that outline what the agency might perceive as deceptive practices. The FTC revised the guides in 2012 based on input from consumers who wanted to buy “green” products more intelligently, and enhanced its investigations accordingly.

The results of the soil experiment. See how poorly the additive-amended materials did?
The results of the soil experiment. See how poorly the additive-amended materials did? Photo courtesy of Fred Michel.

Being certified by the Institute isn’t mandated, and the Green Guides aren’t rules. You can market any product as biodegradable even if it’s not. There is, however, risk of civil lawsuits. If your product seems fishy, the FTC will investigate.

But Michel isn’t content to simply police eco-friendly claims. He hopes his team’s work gets consumers to consider whether they know how to use plastics correctly, or what these “green” terms even mean. Words like “bioplastic” and “biodegradable” are often used interchangeably, when in fact each implies a very specific method of creation or disposal.

If you know that something is a bioplastic, all you really know is that it is something made from plant feedstocks. On the other hand, if you know that something is biodegradable, you may not know what it’s made from, but you do have insight into what might happen to it in certain environments.

We don’t have much information about the lifecycles of new biodegradable plastics, and what we do know isn’t widely understood by the public. For instance, not all bioplastics are biodegradable, and leaving one in your compost pile would be a bad move. Worse, if people think biodegradable products can biodegrade anywhere, they might send them to landfills. Biodegradable products usually release carbon dioxide, but if they land in an anaerobic landfill environment, they release methane as they very slowly break down -- a greenhouse gas 21 times more potent than carbon dioxide. The bottom line is that you can’t count on something breaking down in your compost bin just because it’s made of coconut fiber, for example. Plastics don’t break down quickly because of what they’re made of but because of how engineers structure the molecules within them.

“If I were to draw the chemical structure of polyethylene (PET), derived from plants…or derived from petroleum fossils, [they’d be] identical,” said Narayan.

One way to handle this might be to change package labeling.

“A way to improve things would be to have some sort of lifecycle information on the container rather than just the word 'biodegradable,'” Michel said. “How much carbon went into making that material? What are the other impacts? And then, what should be done with it to have the least environmental impact?”

“I mean that's a lot for a label,” he added, “but those are the things you really need to think about.”

Deciphering Plastic Labels

  • Plant-based or Bio-based or Bioplastic: Plastics that are made from one or more plant starches, including feedstocks like corn, coconut, sugarcane, and wood cellulose. Not to be confused with biodegradable. This term describes the content of the material, not how it operates. Many bioplastics biodegrade in a timely way, but not all.
  • Biodegradable: This term does not indicate source material. Rather, it implies that the plastic can be broken down and eaten by microbes in environments like compost piles. All things biodegrade, but some things biodegrade more quickly than others. Biodegradable materials are those that break down in certain environments like compost bins within a reasonable amount of time, as determined by the FTC.
  • Compostable: Compostable products are biodegradable, but even more so. When compostable products biodegrade, they often do so at a quicker pace and leave behind only humus -- the essential component of soil.
  • Recyclable: As with biodegradable and compostable products, recyclable products can come from any number of feedstocks, but the term refers to their end-of-life situation. Recyclable products are those whose materials can be reused, either in a similar form or as part of another product. Plastics are recycled according to their recycling symbol -- a number 1 through 7 surrounded by three arrows in the shape of a triangle. These symbols correspond with types and structures of plastic, like vinyl (3) or polypropylene (PP).


For more information about green vocabulary, visit the FTC Green Guides.