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Biodegradability & Compostability

Test Methods to Validate Claims: When in the course of new developments, industry manufactures bioplastics which are meant to be degradable or compostable, a need exists for independent, scientific validation. Ambiguous, unproven or false claims may harm consumers and the marketplace. There is an up-trend involving the Federal Trade Commission (FTC) investigating claims in this arena.

In Biodegradation Tests, CO2 that is evolved from the test sample is captured over 30-180 days. Traditional validation methods forced heating to 58C (136F) for 26 weeks which rarely occurs in real composting.

The Nature of Composting: Composting is a process which may contain brief episodes of elevated heat or “thermophilic” conditions (defined as higher than 45°C  or 115F) followed by long periods (2 – 6 months) of moderate-heating  or “mesophilic” conditions of ambient temperature up to 45°C. Mesophilic degradation of organic molecules is remarkably efficient since a diversity of organisms have evolved under such circumstances. High temperatures speed reactions and favor chemical hydrolysis.  Ideally, to match composting, test standards should include and  mimic both sets of environments.

Traditional Scientific Validation: To meet the demand for validation of bioplastics, a set of early, industry standards evolved (ASTM, EN and ISO), nor more than 2 decades old, and have been applied to qualify compostability. This approach helped bring structure and a semblance of regulation to the burgeoning biodegradable plastic movement and also bolstered consumer confidence. More recently, however, consensus has disappeared and new methods reflecting system ecology are being sought. Current evidence shows that these early standards were crafted enthusiastically to accommodate new bioplastic polymers, rather than to meet broader ecological conditions. The concept of the ecosystem property of compost defining biodegradability was largely overlooked. This has resulted in a crisis.

Challenge to Standards: Since 1995, the standardized protocols ASTM D6400 (USA) and EN 13432 and ISO 14855 (Europe) dominated validation and labeling of bioplastics. These methods were crafted largely to fit R-PLA molecules and for these and other reasons are no longer generally accepted by scientists as true compostability tests.  To partly deflect concerns, Belgium launched a “Home-Compostability” label (testing at 30C), and in America  the ASTM-D6400 certification process was renamed to “Industrial Composting Only”. These well-intended efforts have been met with increasing skepticism and several agencies and countries have defected from agreements, especially Germany.


Disintegration should progress to a point that no bioplastic is visible. European studies show that plastic levels as low as 0.1% weight are objectionable, in contrast to traditional industry rules of 1%.

Compostable vs. Biodegradable: Composting must be viewed as a subset of biodegradation and it is therefore not logical to construct compostability validation to be a stricter set of rules than operate in nature.  The problem that this mat cause is evidenced in bio-plastics having fixed melting points that require exposure to high temperatures to trigger hydrolysis before becoming degradable. ASTM 6400 incorporated pre-hydrolysis steps into the overall standard, obscuring the underlying factors. The result was that the public started rejecting PLA bags and utensils, since when exposed to normal composting, high heat hydrolysis was under-efficient. Credibility of the industry and the standard makers began a decline.

Industrial vs. Other Composting: In Nature, biodegradability is not essentially temperature limited in the rate of reactions over a broad range  of 5 – 70C. Extreme high heat composting (such as found with in-vessel systems) may even inactivate cellulase enzymes and therefore restrict degradation of even regular paper (resulting in a new artifact and a new standard for it called “extreme high heat” compostability). These are artifacts of industrialization of biological properties.

New advancements in bioplastics are taking place, including polyesters such as PVA and PVOH’s which may degrade well in a broader range of temperatures. New forms of PLA are recognized that do not possess the limiting thermal-transition (Tg) factor. Unfortunately, in the foreseeable future, any bioplastic may be seen as foreign matter contaminate in composting.

Woods End Laboratory possesses skilled awareness of this “work-in-progress” for achieving high-quality scientific validation of  biodegradable products at temperatures other than accepted industrial norms.

Strength of Satisfied Clients: Woods End’s clients in biodegradability testing include: DuPont, FritoLay, KraftFoods, Natureworks, DowAgroSciences, Novamont, Pepsico, Boise, Nordenia, Huhtamaki, Toray, US Army Environmental Center, Weetabix —  and many more.

The Woods End Bio Standard: As of 2014 Woods End has completed worked with several clients to craft a new compostability test process. This will require that a candidate-compound for compostability validation pass  test of at least 2 conditions.

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