‘Anaerobic testing has no relevance to oxo-biodegradable plastic’

Oxo-biodegradable Plastics Association claims MSU study on biodegradable plastics is misleading

By Jenny Eagle contact

- Last updated on GMT

Picture credit: Oliveoiltimes.com
Picture credit: Oliveoiltimes.com
The Oxo-biodegradable Plastics Association (OPA) has claimed that tests used in a study by Michigan State University, in the US, were largely irrelevant for oxo-biodegradable plastic.

FoodProductionDaily posted an article entitled: ‘Study suggests biodegradation-promoting additives​ for degrading PE and PET are not effective’ on May 11, 2015 amid claims from the American Chemical Society that most of the commercial polymers from the polyolefin and polyester families are not biodegradable.

Refuted by a team from a major European university

Speaking on behalf of OPA and Symphony Environmental Technologies, Max de Trense, FRSA​Carteret Communications said the films used by MSU in their tests for 'oxo' (in accordance with AFNOR Accord T51-808) have been evaluated by a team from a major European university, Blaise Pascal, in France, where the films were certified to be biodegradable.

In the MSU study, six researchers from the School of Packaging and the Biosystems and Agricultural Engineering department, MSU, carried out tests on LDPE/LLDPE (PE) films (commonly used for bread, supermarket, and trash bags) and poly(ethylene terephthalate)—PET sheets.

They investigated the effect of three different types of biodegradation-promoting additives in anaerobic digestion, aerobic degradation (compost), and soil burial environments.

According to the public information at the time of additive selection, one of these was of the oxo-biodegradable type, one was a nonoxo additive, and the third was a combination.

The base experiments evaluated all three types in all three environments for PE, and both available additives in all three environments for PET, to understand the effect of disposing these polymers in the environment.

'Seriously misleading information'

None of the five different additives tested significantly increased biodegradation in any of these environments​,” said Susan Selke, researcher, Michigan State University.

Thus, no evidence was found that these additives promote and/or enhance biodegradation of PE or PET polymers.

As a result, anaerobic and aerobic biodegradation are not recommended as feasible disposal routes for non-biodegradable plastics containing any of the five tested biodegradation-promoting additives​.

De Trense said the information provided by the team at MSU which produced this study is so inaccurate and specious that OPA and Symphony Environmental Technologies would like to correct their seriously misleading information.

‘We have read the report ‘Evaluation of Biodegradation-Promoting Additives for Plastics” by researchers at the Schools of Packaging and Biosystems and Agricultural Engineering, Michigan State University (MSU) led by Dr. Susan Selke. 

We discussed the protocol for this testing at length with MSU prior to the commencement of the programme, and it was clear to us they did not understand the basic principles of oxo-biodegradable technology - namely that oxidation is necessary to create the chemical changes in the material that will lead to biodegradation. This is clearly outlined in ASTM D6954. 

MSU therefore decided to subject oxo-biodegradable materials to a series of tests that were irrelevant to the purposes of oxo-biodegradable plastics. These were anaerobic biodegradation, industrial composting and soil burial. 

'No prospect of oxidation occurring'

Anaerobic testing, sometimes claimed to simulate landfill conditions and outlined in ASTM D5526-12, has no relevance to oxo-biodegradable plastic which is designed to combat the blight of plastic litter in the open environment

Subjecting these materials to anaerobic conditions, where there is no prospect of oxidation occurring, merely confirms the inertness of oxo-degradable plastics in this environment. This is fully intended.  It is intended to be inert because biodegradation in anaerobic conditions generates methane, which is a dangerous greenhouse gas. 

The results obtained by MSU were entirely predictable and serve only to reinforce the points we made to them before the commencement of the study. 

Similarly, oxo-biodegradable plastic is not intended to biodegrade in industrial composting processes such as those characterised by their aerobic composting study. 

Oxo-biodegradable plastics are intended to have a useful life during which they will NOT degrade, and if subsequently littered they will oxidise in the open environment and become biodegradable. They are simply not designed to oxidise and then rapidly mineralise in the 6 month timescale of an industrial composting test. Standards such as ASTM D6400, EN13432 are therefore irrelevant. 

The third element of the study - the soil burial tests - are of little value. Oxo-biodegradable plastics without access to oxygen to promote abiotic changes will not biodegrade in this type of environment, certainly not in the short timescale of this test. Again we made this clear to MSU at the beginning of the programme. 

'MSU did not have the necessary experience'

Symphony did offer advice to MSU on how to construct an appropriate study for oxo-biodegradable polyethylene, but since MSU had their own funding for the project we were unable to persuade them of the unsuitability of their approach. 

Symphony also funded a parallel two-year test programme at MSU to be conducted according to the established ASTM D6954 protocol. However, it soon became apparent MSU did not have the necessary experience or equipment to conduct this project, and Symphony terminated the project after one year.

Being concerned about the ability of MSU to perform the test correctly, Symphony asked the Centre National d’Evaluation de Photoprotection (University Blaise Pascal, Clermont  Ferrand, France) to evaluate the films used by MSU in accordance with AFNOR Accord T51-808.  The films were certified to be biodegradable.

In addition, Symphony’s d2w masterbatch has passed all the tests necessary to qualify for the internationally-recognised ABNT certification for environmental quality, and has been awarded certificate no. 365.001/14.

On March 15, 2014 at the Global Plastics Environmental Conference in Florida, Symphony’s technical director expressed our misgivings and criticism to Dr. Selke in an open forum when she gave a presentation titled ‘Independent Study on the Claims of Oxobiodegradable Additives ‘.We voiced our concern regarding the methodology, credibility and accuracy of the entire project, but no corrections or acknowledgements were made.

We are very concerned  by the study performed at MSU, and it does appear the irrelevant testing protocols were selected to harm the profile of the oxo-biodegradable plastics industry.’  

Related topics: Food Safety & Quality

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