The debate: Biodegradable and compostable plastic bags (part 1 of 3)

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2019/08/20 The debate: Biodegradable and compostable plastic bags (part 1 of 3)

The debate: Biodegradable and compostable plastic bags
by Victoria Hattersley
20 MAY 2019

source from: https://packagingeurope.com/the-debate-biodegradable-and-compostable-plastic-bags/

As we reported recently, a study conducted by researchers at the University of Plymouth, designed to provide insights into the environmental deterioration of plastic bags made from different polymer types, has been the subject of some dispute.

In brief, the five bags chosen for the study comprised two oxo-degradable bags, one fossil non-biodegradable polyethylene bag, one bag marked as biodegradable, and one bag certified compostable according to the European Norm 13432.

Its main conclusions, according to the official press release, were that: “After nine months in the open air, all the materials had completely disintegrated into fragments. However, the biodegradable, oxo-biodegradable and conventional plastic formulations remained functional as carrier bags after being in the soil or the marine environment for over three years. The compostable bag completely disappeared from the experimental test rig in the marine environment within three months but, while showing some signs of deterioration, was still present in soil after 27 months.”

While the researchers point out that the study was peer-reviewed and achieved the purpose for which it was designed, some organizations, notably European Bioplastics, have argued that the conclusions it makes are misleading. They emphasize, for example, that only the compostable bag was actually certified biodegradable in the first place – and only under the scenario of industrial composting, for which it was not tested.

We were interested in how this study, and reactions to it, highlight the continued confusion surrounding the use of plastics and terms such as ‘compostability’ and ‘biodegradability’. It has also put a spotlight on the sometimes negative role certain sections of the media can play in sensationalizing a complex and important issue that should perhaps be treated with a little more nuance.

With this in mind, Victoria Hattersley invited François de Bie from European Bioplastics, and Professor Richard Thompson from the team at the University of Plymouth, to give their respective takes on the study and its conclusions. The resulting discussion makes for interesting reading.

VH: It seems to me that one of the main issues European Bioplastics had with the study is that the results obtained on what it refers to as ‘fake and non-biodegradable oxo-bags’ were presented as results obtained on ‘biodegradable and compostable bags’. Would this be a fair summation?

FdB: Yes, the authors ‘purchased’ four different types of plastic bags and it was very clear, at the start of the study, that the PE bag with a false biodegradation claim, the oxo-degradable bag and the traditional PE bag would not degrade/decompose in the natural environment due to biological activity [n.b., we should point out here that oxo-degradability has already been widely discredited from an environmental standpoint - VH]. We have no issues with a university investigating ‘biodegradation’ of falsely labelled bags, but when reporting on the results these fake bags should be called out as greenwashing! Mixing the results obtained on those bags, together with ‘correctly EN13432 certified and labeled’ compostable and biodegradable bags is misleading.

The research actually confirms (here we quote from the university’s publication): “In the marine environment, the compostable bag completely disappeared within three months … the same compostable bag type was still present in the soil environment after 27 months but could no longer hold weight without tearing...”.
Bags which are certified compostable according to EN13432 have been checked and verified to meet ALL of the below conditions:
• Fragment into pieces < 2 mm in less than 12 weeks in an industrial composting facility
• Biodegrade into CO2, water, and biomass within 6 months due to biological activity
• Leave behind NO harmful substances in the environment after degradation and biodegradation.

RT: Our research sought to establish whether bags that are ‘labelled’ as degradable, biodegradable, or compostable do in fact deteriorate readily across a range of natural environments – and to look at how they compare with conventional plastic.
No other institution that we are aware of has previously conducted a test of this nature, over three years using multiple bag types and in different environments. The results revealed that over a three-year period, none of the materials examined could be relied upon to deteriorate sufficiently to reduce the negative effects of littering on biota or aesthetics across all three environments.
The European Bioplastics Association have since asserted that some bags labelled as biodegradable are fake and that they have been aware of this for some time. If that is the case, then this is an issue that they should address with the manufacturers concerned. Consumers will be guided by the labelling on the bag, as we were in our study, and they are unlikely to be able to distinguish whether a bag is fake or not.

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