Recycling Mystery: Bioplastic

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"Compostable" typically implies that a product should be composted in an industrial facility, not at home. Photo: Flickr/Shira Golding

Bio-based, or plant-derivative plastics, in theory seem like the best idea since sliced bread. Bioplastics are used to create (and replace) products typically made from natural gas or petroleum.

They are biopolymers, derived from renewable biomass sources such as corn starch or vegetable oil. Polyactic acid (PLA) is one form of bioplastic, produced from glucose.

But while bioplastics seem like a great idea, in theory, the most important thing to understand is what to do with them once you’ve finished your to-go soda.

Are bioplastics recyclable?

Recycling plastics 1-6 is usually pretty straightforward, as each category correlates with a specific resin.

But plastic #7 is literally the “catch-all” category. Dubbed as “Other,” plastic #7 includes those resins that do not fit into categories 1-6, including most bioplastics.

The debate on recycling bioplastics, specifically PLA, with mainstream PET continues to rage on, and studies on the subject seem to contradict each other.

The National Association for PET Container Resources (NAPCOR) recently voiced its concern for potential contamination of the PET recycling stream associated with PLA bottles.

The trade association for the PET plastic industry in the U.S. and Canada cited its concerns involving cost of separation, increased contamination, yield loss and impact on recycled PET (RPET) quality and processing.

What “biodegradable” means

Bio-based plastics are often touted as “biodegradable.” But this term has several stipulations behind it. While these products may in fact have components that are capable of degrading, this process only occurs under specific conditions and biodegradable plastics cannot be composted in a backyard compost pile. Because the material requires very high heat, these plastics can only degrade in a commercial composting facility.

With all this discussion about biodegradable, the take-home message is that we should just be able to leave a bottle out in a park or bury it in the yard and it will decompose, right? Well, not exactly.

“When the consumer hears ‘biodegradable,’ often times they think it’s a material that you can throw out the window of your car and after one good rain, it will be back to nature, and it will fertilize the roadside,” said Richard C. Bopp, senior material scientist for Natureworks, LLC, one of the leading producers of PLA.

“Saying ‘biodegradable’ is not specific enough to be useful, and it leads to all kinds of misunderstandings,” he added.

Left to its own devices, PLA will not simply biodegrade on its own – which may be surprising, but is actually a benefit. “Thank goodness it’s that way [...] Otherwise you’d have a stability problem with your plastic – it’s like things going bad in your refrigerator,” said Bopp. Imagine mold growing on your cell phone, and you’ll understand why the basic concepts of “biodegradable” (a la the now-fuzzy fruit from last week’s lunch) don’t apply here.

Can you compost them?

“Compostable” implies that a product will break down in a composting environment (more to come on this), but typically implies that a product should be composted in an industrial facility, not at home.

One major hurdle right now is that finding a commercial composting facility is difficult, as they are are not as widely available and few cities across the U.S. have composting services.

According to the National Resource Defense Council (NRDC), only 8 percent of Americans compost their waste, including residents in cities like San Francisco and Seattle, where composting is part of the general waste pickup.

In the end, plastics that are “compostable” may make sense in an area that has disposal options. But if commercial composting is not available, it’s better to choose a material that is accepted for recycling.

So, what do you do?

If you use bio-based materials that can be recycled in today’s current stream, such as Coke’s new Plant Bottle or Dow’s sugar cane-based resins, then the answer is simple: Toss it in the recycling bin. But if you do buy compostable plastics, be sure to seek out an industrial composting facility near you.

The most important thing to understand is your own recycling program. Call your recycler and simply ask if these types of plastics are accepted in your program. If not, use Earth911 to find local recycling for plastic #7.

Related articles
The Next Wave in Composting
5 Fuel Alternatives to Petroleum
Recycling To-Go Plastics

Earth911 partners with many industries, manufacturers and organizations to support its Recycling Directory, the largest in the nation, which is provided to consumers at no cost. The American Chemistry Council is one of these partners.

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