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Sorry: adding chemicals to regular plastic to make it biodegradable doesn’t work

by Green Plastics


A new study carried out at Michigan State University (East Lansing, USA) 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 27 February 2015 under the title “Evaluation of Biodegradation-Promoting Additives for Plastics” (reference below).

This is an important development in the long-standing battle between companies promoting “true bioplastics” (plastics where the polymer is a biodegradable polymer made from renewable resources, such as starch, chitin, or agar) and companies promoting additives that they claim will allow traditional petroleum-based plastics to actually biodegrade. The latter category include “oxo-degradable plastics” as well as other types of additives.

This study measured 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 3 additives selected consisted of an oxobiodegradable additive, a non-oxo additive and one that was a combination, and were 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, none of the five different additives tested significantly increased biodegradation in any of these environments. Thus, no evidence was found that these additives promote and/or enhance biodegradation of PE or PET polymers.

Part of the reason some companies push so hard for the use of additives in traditional plastics is that it will be easier, both practically and economically. Bioplastics cannot usually be processed by the same machines that process traditional plastics, so breaking into the bioplastics business requires a great deal of capital overhead in order to get new machines and processes in place. It would be much easier to find some magical additive that allowed all of the existing companies to use the machines they already own.

Unfortunately, it looks like that method doesn’t actually work. Is it time to bite the bullet and finally invest more in creating bioplastic from renewable resources?

Evaluation of Biodegradation-Promoting Additives for Plastics
Susan E. M. Selke, Rafael Auras, Tuan Antoine Nguyen, Edgar Castro Aguirre, Rijosh Cheruvathur, and Yan Liu
Environmental Science & Technology Just Accepted Manuscript
DOI: 10.1021/es504258u

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