Biodegradation-promoting additives for plastics don't work, says study

A new study carried out at Michigan State University (East Lansing, MI) reveals that the additives touted to promote the biodegradation of polyolefins and PET do not live up to their claim. The study was posted by the American Chemical Society as a "Just accepted" manuscript on Feb. 27, 2015, under the title, "Evaluation of Biodegradation-Promoting Additives for Plastics."

As the study points out, a number of countries have adopted legislation promoting the use of biodegradation-promoting additives in polyolefins and PET. Yet, as the authors, who are from the MSU School of Packaging and the MSU Biosystems and Agricultural Engineering department noted: "Biodegradation-promoting additives for polymers are increasingly being used around the world with the claim that they effectively render commercial polymers biodegradable. However, there is a lot of uncertainty about their effectiveness in degrading polymers in different environments."

In an attempt to put some of this uncertainty to rest, they carried out a number of experiments over a period of three years to evaluate the effect of biodegradation-promoting additives on the biodegradation of polyethylene (PE) and polyethylene terephthalate (PET). While extensive work has already been conducted to understand the degradation of polyolefins and the effect of using biodegradation-promoting additives in these polymers, considerable controversy remains regarding the biodegradation of these polymers. "Making improper or unsubstantiated claims can produce consumer backlash, fill the environment with unwanted polymer debris and expose companies to legal penalties," wrote the researchers.

The study looked at the effects of three different types of biodegradation-promoting additives on the biodegradation of a blend of linear low and low-density polyethylene (commonly used for bread, supermarket and trash bags) and PET sheets under active anaerobic digestion, aerobic degradation (compost) and soil burial environments. The three additives selected consisted of an oxobiodegradable additive, a non-oxo additive and one that was a combination, manufactured by Symphony (d2w), Ecologic (Eco-one EL 10) and Wells Plastics Ltd. (Reverte for PE). Controls without additives were also produced. According to the authors, the base experiments evaluated all three types in all three environments for PE, and both available additives in all three environments for PET, to provide further understanding of the effect of the disposal of these polymers in the environment.

Remarkably, it was found that, despite the claims of the manufacturers, none of the five different additives tested significantly increased biodegradation in any of these environments. There was no evidence that these additives either promoted and/or enhanced biodegradation of PE or PET polymers.

As these researchers concluded: "Anaerobic and aerobic biodegradation are not recommended as feasible disposal routes for non-biodegradable plastics containing any of the five tested biodegradation promoting additives."

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