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Biodegradability & Compostability

Test Methods to Validate Claims: If industrially manufactured bioplastics claim to be degradable or compostable, the need exists for scientific validation. Unproven or false claims can harm consumers and there is a trend to increasing prosecution by FTC.

In Biodegradation Tests, CO2 that is evolved from the test sample is captured over 30-180 days.

The Nature of Composting: Composting is a combination of short periods of high heat (“thermophilic”) conditions (>45°C  or > 115F) followed by long periods (2 – 6 months) of modest-heating (“mesophilic” <45°C or < 115F) behavior. Mesophilic degradation is remarkably efficient as organisms and natural compounds have evolved under such circumstances. Ideally, test standards must mimic both heating levels.

Traditional Validation: To date, a set of standard methods (ASTM, EN and ISO) have been applied to measure compostability. This approach has helped regulate and grow the biodegradable plastic movement and maintain consumer confidence. However, evidence has emerged that these standards were crafted too closely to accommodate bioplastic polymers, rather than to meet broad composting conditions. This has resulted in a crisis.

Challenge to Standards: Since 1995, the standardized protocols ASTM D6400 (USA) and EN 13432 and ISO 14855 (Europe) have dominated validation and labeling of bioplastics. The standards were accepted by composting agencies in Europe and USA.  These methods were largely crafted 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 back-lash, Belgium launched a “Home-Compostability” label (testing at 30C), and Americans renamed the ASTM-D6400 certifcation as “Industrial Composting Only”. These well-intended efforts have been met with increasing skepticism and several agencies and countries have defected from agreement.

Compostable vs. Biodegradable: Composting must be viewed as a subset of biodegradation, and not the opposite. It is therefore illogical to construct compostability validation to be a stricter set of biodegradation rules as is presently practiced.  The potential contradiction is evidenced by synthetic bio-plastics having fixed melt points that require being exposed to unusually high temperatures to trigger hydrolysis before becoming degradable.

Industrial vs. Other Composting: A consequence of attempts to protect the old ASTM D-6400 and EN standards is the arbitrary distinction of “industrial” (high heat) composting in contrast to “other”  composting (implying all other to be inferior). In Nature, biodegradability is only temperature limited in the rate of reactions over a broad range  of 5 – 70C. Extreme high heat compsoting starts inactivating cellulase enzymes and therefore restricts  even composting of cellulose (resulting in a new artifact and a standard for “extreme high heat” compostability).

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, DowAgroSciences,  FritoLay, KraftFoods, Natureworks, Novamont, Pepsico, Nordenia, Roy. F. Weston, 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.

for more information:
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