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Biodegradable Plastics Won’t Put You on the Path to Circularity

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There is nothing circular about compostable packaging, according to one expert on sustainability. In fact, biodegradable plastics ultimately add to greenhouse gas emissions.

Making plastics disappear — it’s the wish of many, especially resonant as Earth Day approaches, and the aim of numerous bans on single-use plastics and plastic bags.

But outside of banning plastics, creating biodegradable plastic products that compost into nothing at the end of their life might seem like a reasonable alternative — an additional tool in the quiver of green tactics.

Not so fast, cautions one expert.

While biodegradable plastics certainly exist — in fact, eight versions are vying for this year’s Tom Ford Plastic Innovation Prize — the fact that material science affords the opportunity to create plastics that disappear doesn’t necessarily make this the best course of action.   

In fact, overall, biodegradable plastics ultimately add to greenhouse gas (GHG) emissions, said Bob Lilienfeld, Executive Director of the Sustainable Packaging Research, Information, and Networking Group (SPRING) in Broomfield, CO.

“The issue isn’t whether or not material is available,” Lilienfeld asserted. “The issue is whether or not it makes any kind of sense. If you’re a believer in the concept of the circular economy, there is nothing circular about compostable packaging. It’s designed to end up in an industrial or home compost facility — the result of which is greenhouse gases.”

In an October 2021 presentation titled, “Avoiding the Plastics Biodegradation Minefield,” Lilienfeld stressed several caveats and clarifications when discussing the concept of compostable plastics, to wit:

  • Biodegradation occurs when materials are broken down by bacteria, fungi, or other biological means.
  • Biodegradation is not the same as composting, and industrial and home composting are not the same. Some materials that are industrial compostable are not home compostable.
  • Fragmentation and disintegration are not forms of biodegradation, but can sometimes lead to biodegradation.

In fact, to be considered “industrial compostable,” Lilienfeld explained, a plastic product must meet ASTM-D6400 or EN 13432 standards by biodegrading 90% in 180 days in aerobic conditions (ASTM D5338) or disintegrating 90% in 12 weeks (ISO 16929).

With more states and municipalities entering the war against plastics — bans go into effect May 1 in Fort Collins, CO, and May 4 in New Jersey, for instance — Lilienfeld looks westward for a somewhat more nuanced approach.

“The state I think has the best handle on it is California. In California you will be sued if you use the term biodegradable. You’re not allowed to claim biodegradation; you can only claim compostability if the finished package has been certified as such by one of two organizations: TUV in Europe or BTI in the United States. Your package has to pass ASTM 6400 protocol in order to be certified.”

Ultimately, he stressed in his presentation, biodegradation is a strategy, not a goal — a process, not an end result — and, therefore, the last line of defense against environmental impact if packaging escapes a closed-loop system. Plastic reduction, reuse, and recycling should remain the primary goal in reducing plastic waste and its negative effects.

“We’re far better off recycling these materials because most of them are polyolefins,” he said. “From a recyclability standpoint, they are technically recyclable. Many of them are not economically recyclable, so that’s a problem.”

Still not convinced plastics that go “poof” into thin air aren’t the ideal solution? Lilienfeld put it thusly:

“What people don’t understand is: Let’s say you buy a film that’s made from PLA but you put inks, dyes, whatever on the film that are not compostable and they retard the compostability of the PLA underneath. That’s not going to pass. So it isn’t simply buying raw material; if you have a package that includes paints, dyes, inks, adhesives for closure … the odds are pretty good that all those things individually as well as collectively have to be certified compostable. So there’s nothing simple about it.”

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