Results of Michigan study into biodegradation-promoting additives evoke incensed response

It was not to be expected that the results of the study performed at Michigan State University (East Lansing, MI) into the effect of biodegradation-promoting additives on the biodegradation of PE and PET would be greeted with any enthusiasm by the manufacturers of these additives. The Michigan researchers, who evaluated biodegradation in compost, anaerobic digestion, and soil burial environments, were singularly unimpressed by the performance of the tested additives. As they wrote: "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."

After I reported on these results (March 3), two of the manufacturers of the additives—Symphony and Wells Plastics Ltd.—immediately contacted me to present their side of the story.

According to Wells, the study contains factual inaccuracies, invalid test results and is overall completely flawed. The company wrote that "the study methodology is completely inappropriate for evaluating the effectiveness of our Reverte oxo-biodegradable technology. These facts were explained in detail to the study authors both in meetings at MSU and in writing at the review stage prior to the start, as well as on numerous other occasions. Whilst MSU acknowledged the shortcomings of this study they chose to ignore our comments and continued to produce a worthless document. Wells agreed to offer the Reverte additive for use in the study but when it became clear that the methodology to be used completely ignored how oxo-biodegradable additives are designed to work, Wells informed the authors that their study could not possibly draw any valid conclusions. It is like conducting a study into the effects on a headache of paracetamol by testing it as a cancer cure and concluding that it doesn't work!"

Symphony weighed in with the following: "We are amazed by this report published 3rd March suggesting that biodegradation-promoting additives for polymers do not significantly increase biodegradation in compost, anaerobic digestion and soil burial environments. The OPA has asked its technical experts to analyze the report, and a detailed statement will be made, but it is clear that the tests performed at MSU are largely irrelevant. There is no point in testing an oxo-biodegradable plastic bag in anaerobic conditions because, as the name implies, it needs oxygen to degrade. It is not designed to degrade in landfill because degradation in anaerobic conditions creates methane, a dangerous greenhouse gas. For the same reason there is no point in testing by burying it in the soil. . . . Another fundamental point is that oxo-biodegradable plastic bags are designed to have a service life within which they will not degrade, and there is therefore no point in testing a bag which has not yet reached the end of its service life."

When asked whether she had indeed acknowledged the "shortcomings of the study," lead author of the study, Dr. Susan Selke, Professor & Associate Director, School of Packaging, Michigan State University, said she was not aware of having done so. And in response to Symphony's allegation that it appears that the irrelevant testing protocols were selected to harm the profile of the oxo-biodegradable plastics industry, she explained that they were by no means "picking and choosing."

"We set out to evaluate three different additives with three different modes of action in three different environments. That's it," she said. Moreover, she added: "We were not looking for complete biodegradation, just for evidence of biodegradation. "

"We got oxidative degradation. That happened. What we did not find after oxidative degradation--equal to several weeks of sunshine exposure--was biodegradation," she said. "That didn't happen."