The Truth About Biodegradable Plastics

In an effort to stymie plastic pollution, several companies have engineered so-called compostable “bioplastics.” But are biodegradable plastics really what they claim?

| June/July 2010

Most of us are aware of how long-lived petroleum-based plastic bags and packaging are — we’ve seen the trash along roadsides and in our lakes and oceans. Some new “bioplastics” claim to be “100 percent compostable,” but testing commissioned by MOTHER EARTH NEWS reveals that most of these claims are misleading at best.

Basically, there are two kinds of “composting.” Composting at home usually involves small-scale piles with low temperatures and less-than-optimum humidity. Then there’s large-scale commercial composting, in which materials are shredded, mixed, and maintained at 140 degrees Fahrenheit — a much higher temperature than that of typical home compost piles. Many cities compost yard waste, but only a few sites — about 100 in the entire nation — will also accept these “biodegradable” plastics.

We tested five types of bioplastic bags to see how well they would compost. None of them broke down completely after 25 weeks in home compost conditions (77 degrees). A product from Italian bioplastic manufacturer Novamont came closest to what we would call truly compostable, with a product called Mater-bi. Mater-bi is “made of corn starch, vegetable oil derivatives, and biodegradable synthetic polyesters” In our tests, only Mater-Bi was compostable at typical home compost pile conditions.

Three other brands did fairly well in commercial composting conditions, but they showed little or no degradation in home compost conditions. One type, Oxo-Biodegradable, did not begin to break down even after 25 weeks at 140 degrees.

Most bioplastic products currently being marketed carry incomplete and/or misleading labeling, according to composting expert William Brinton of Woods End Laboratories, who conducted the testing for MOTHER EARTH NEWS. One exception is the packaging developed by Frito-Lay for its Sun Chips. The new bag (which we did not test) proclaims “100 percent compostable” on the front, and on the back it states the bag is made from “90 percent renewable, plant-based materials and it breaks down completely into compost in a hot, active home or industrial compost pile.” We applaud Frito-Lay for its accurate labeling and its ongoing efforts to develop better packaging. The company’s bags may well be more compostable than their competitors’. But what most consumers won’t realize is that most of these bags, at this point, are unlikely to reach a “hot, active home compost pile.”

The bottom line: Most plastic packaging that claims to be “biodegradable” or “compostable” will only partially break down under the conditions typical of most residential compost piles.

5/9/2013 11:04:37 PM

The problem is that 25 weeks for composting a product is too long. Many composting faciities reject the use of compostable plastic, including the USDA. In Europe the time is 90 days as well as in the State of California, unless there are BioSolids(Human Waste) added to the compost. The Human waste aspect is allowed for longer periods of time to break down, but they still are shorter than 25 weeks. The other point to take in is that only a couple(1-5) compost facilities actually exist in the United State to take compostable plastic products.

This should be taken to heart as most of these compostable plastic products are not compostable at all.

Jack Roberts

BioSphere Plastic

10/5/2010 12:32:26 PM

Cheryl Long, Editor in Chief Regarding the post below by “Eco-Oxo” which was critical of the Woods End/Mother Earth News report about biodegradable plastic, the editors emailed Eco-Oxo and asked for information about his/her background and qualifications. EO’s reply was “At this point I cannot state who I am or which company I work for but I can tell you that I do work with 3 of the leading scientists in the biodegradable industry.” Why would a company have someone posting anonymous, highly critical comments when a magazine publishes a research report they disagree with? Why would “leadings scientists” be associated with such behavior? EO’s criticism of our report was harsh: “It is unfortunate that things like this get published by people that do not do the proper research before conducting studies or writing articles.” But notice that in the remainder of his/her post below, EO never really tells us what he/she believes was incorrect in our report. If companies want the public to trust their claims about their products, then they should not have their employees going around bashing reports about legitimate research by highly qualified scientists such as those at Woods End Laboratories. There are factions within the biodegradable plastics industry right now, and each side is trying to present their products in the best possible light. But as EO’s anonymous comment and Dr. Brinton’s post indicate, the Oxo faction is sometimes resorting to less than honorable tactics.

10/5/2010 12:32:24 PM

Cheryl Long, Editor in Chief P.S. Woods End researchers are running a Plastic Bags Degradation Comparison, which you can find here: They have placed a regular plastic shopping bag and an Oxo bag side by side on a fence and they are posting photos every 4 to 6 weeks so we can all watch just how these two kinds of bags do or do not degrade over time in the open air.

mother earth news fair 2018 schedule


Next: August 4-5, 2018
Albany, OR

Whether you want to learn how to grow and raise your own food, build your own root cellar, or create a green dream home, come out and learn everything you need to know — and then some!


Subscribe Today - Pay Now & Save 64% Off the Cover Price

Money-Saving Tips in Every Issue!

Mother Earth NewsAt MOTHER EARTH NEWS, we are dedicated to conserving our planet's natural resources while helping you conserve your financial resources. You'll find tips for slashing heating bills, growing fresh, natural produce at home, and more. That's why we want you to save money and trees by subscribing through our earth-friendly automatic renewal savings plan. By paying with a credit card, you save an additional $5 and get 6 issues of MOTHER EARTH NEWS for only $12.95 (USA only).

You may also use the Bill Me option and pay $17.95 for 6 issues.

Canadian Subscribers - Click Here
International Subscribers - Click Here
Canadian subscriptions: 1 year (includes postage & GST).

Facebook Pinterest Instagram YouTube Twitter flipboard