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Which Biopolymers Degrade the Fastest in Real-World Environments?

How do the varied, fast-evolving biobased polymers infiltrating the market degrade in different real-world settings? And what do stakeholders watching the biopolymers space care most about?  These are among a mountain of questions answered in a recent 5 Gyres report.

January 30, 2024

5 Min Read
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How do the varied, fast-evolving biobased polymers infiltrating the market degrade in different real-world settings? And what do stakeholders watching the biopolymers space care most about?  These are among a mountain of questions answered in a recent 5 Gyres report. The authors looked at 22 materials in different U.S. regions and ecological conditions, from the East to West Coast, aiming to clear up some of the confusion around the degradation of natural polymers used in packaging.

Here’s a sound bite on the findings that packaging developers, end users, and policy makers would want to know: polymer type matters; product thickness matters; and environment matters. Read on for a deeper dive into the study’s unearthings, and for insight beyond the report from Marcus Eriksen, co-founder at 5 Gyres Institute and study-co-author.

Biomaterials range widely in their characteristics and environmental impact, and research is not keeping up with the torrent of emerging options. With this thought in mind, decisionmakers should consider that while some innovations could be environmentally sound plastic replacements, others might do harm, especially if they have certain chemical additives or nondegradable polymers in composite materials. So, there’s plenty to vet before signing on for widespread adoption, say the authors, whose position aligns with what other research shows.

Here are some variations around biodegradability broken down by product type, material type, and or environmental conditions:

  • Bioplastics tend to be more persistent on land than in marine settings. This is mainly due to lack of moisture and limited microbial activity to break down material.

  • Fragmentation rates vary by product too. Among study observations, paper straws fragment quickly (losing 75% of their weight in 8 weeks in a marine environment, while some bioplastic straws lost 25-50% of their weight in the same timeframe). Though a PHB straw fragmented fairly quickly, and PHA outperformed PLA.

  • Blending polymers can also impact degradation rates. Blends with PE especially had slow fragmentation rates, while PHA blended with other biodegradable polymers generally broke down more than pure PHA. Here’s a really fine detail: metal barrier to the polymer PBAT and a PLA blend inhibited fragmentation.

  • With film materials, PLA film fragmented slower than PHA, showing some degradation at a marine site after four weeks, although some replicates persisted for 64 weeks.

  • Utensils persisted in the environment far longer than straws. All of them were still visible at 64 weeks, with the PHA and PLA utensils the most fragmented in a marine environment (for context: commercial compost facilities typically expect materials to break down in 60 days, at least in southern states).

  • Biobased PBS film fragmented faster than PLA, but slower than PHA. PE film did not degrade at any of the tested sites.

Policymakers and product manufacturers want transparency around the chemicals in packaging so they can make informed decisions. And they want access to science-based evidence, including documented environmental impacts. What consumers want is clear labeling and honest advertising.

Transparency matters to waste management professionals too, and is essential to avoiding problems downstream, the authors say. They cite a report from The State of Oregon's Department of Environmental Quality to illuminate such problems. The Oregon agency referenced ads claiming PLA packaging and other biodegradable materials are compostable, allowing them to enter the compost stream that the agency said, “failed to live up to their marketing claims” and did not adequately degrade, “contaminating the compost and eroding public trust around alternative materials.”

“Better truth in advertising, informed by real data about material degradation in various environments, with different sizes, thickness, and shapes, could have potentially prevented the justified backlash from industrial composting facilities,” the authors say.

Harnessing bioplastics’ full potential will also require legislation to better ensure adherence to the expectations around advertising ethics and to promote responsible practices.

Eriksen has advice for bioplastics innovators: “Companies that are developing novel materials often keep details related to the chemistry close to their chests, saying that it's proprietary. If we are going to solve global-scale problems, like persistent plastic packaging polluting our planet, we need to recognize that we all benefit by sharing solutions. I would ask bioplastic developers to share more.”
For companies interested in bioplastics for their packaging he says take a look at the TOM FORD Plastic Innovation Prize, a $1.2- million prize purse for alternatives to conventional plastic thin film.

“See who won and invest in those companies. This prize had fairly elaborate testing mechanisms looking at environmental impact and product performance and also looked at their business models.”
Eriksen urges investors to look at the emerging companies that have done significant third-party testing of their material and have successfully launched products.

“Producers SWAY and Notpla are two companies that come to mind,” he says.
For composters he suggests they would benefit from agreeing on consistent nationwide labeling and coloring schemes to inform of “truly degradable packaging designs.”
Eriksen goes back to the topic of testing, focusing on evolving techniques that may or may not be tried and true. And he ties testing these novelties to the issue of developers’ claims: “If a company wants certain properties of packaging to protect their product— and let’s say they blend polymers together, or laminate metal, paper, and plastic together—they cannot claim the environmental properties of their novel design without adequate testing.”  

Keeping up with developments in the world of biopolymers is an ongoing job.

Says Eriksen, “If we could do our study over again, we would look at all new packaging available today, and ask questions like, ‘What happens if you sandwich a layer of PHB with PLA to make a strong piece of film, then put that film in the ocean for a year? What happens if you mix bioplastic and conventional plastics to make a product stronger; does it shed microplastics more easily into the environment as the biomaterials degrade?’

“We could come up with a dozen new questions to address the thousands of new types of novel packaging today.”

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