The debate: Biodegradable and compostable plastic bags (part 2 of 3)

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2019/08/23 The debate: Biodegradable and compostable plastic bags (part 2 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/

FdB: The University of Plymouth is now, for the first time, mentioning the objective of the study was to check how bags ‘labelled’ as biodegradable would perform in the real-world environment. In the official press release this objective was less visible and also the conclusions were not at all directed to expose or ‘name & shame’ the ‘fake’ labelled bags.
If the objective was to establish how different bags would ‘deteriorate’, why was actual fragmentation and biodegradation of certified biodegradable and compostable bags not investigated in a scientific way? The way the results and conclusions were drawn left this very open; it was even written in such a way that the casual reader could also just as well conclude that “even the certified biodegradable bags do not biodegrade in CO2, water and harmless substances”. We invite the University of Plymouth for a further round of research to scientifically detail what happens with EN13432 certified bags if they end up in the environment.

Actually, we consider that the study is already out of date at the time of its publication, since:

Oxo-degradable plastics have been extensively researched by the European Commission and were recently banned in the context of the EU directive on single-use plastic products.
Biodegradability of plastics has been clearly defined in said directive and linked to the standard EN 13432 for industrial composting.
Additionally, the EU Plastics Strategy 2018 also acknowledges that industrial compostable products have value for separate collection of bio-waste and facilitate organic recycling (composting). Consequently, they shall be treated in a corresponding facility and shall produce high quality compost / soil improvers according to circular economy principles.

RT: A press release is not a summary of the entire study. The paper itself is very clear on what the rationale was and what it was not, as the following extract makes clear:
“The present study describes the deterioration in different natural environments of bags, which were stated to have biodegradable, oxo-biodegradable or compostable properties. We do not specifically attempt to quantify biodegradation performance in relation to any specific standard such as degradability in a commercial composting facility. Rather we assess whether or not there has been any meaningful deterioration in the context of reducing marine litter; for example, had the bag remained intact or deteriorated into visible fragments? A conventional polyethylene plastic carrier bag was also examined for comparison. All bags were available at the point of sale in UK high-street retailers.”
A scientific evaluation is not approached from the perspective of ‘name and shame’ – it is conducted to obtain objective outcomes to hypotheses. If you have funding for further research we would be happy to consider your requirements.

FdB: Again, our problem is not the fact that you tested the deterioration of different bags in different natural environments over a period of three years - this may, indeed, be something new.
As stated, the main issue we have is with the fact that the bags in your study labelled to be allegedly biodegradable were in fact not biodegradable - a fact obviously known to you (see table 1 in your study, where you refer to the website of the Exo-Plastics masterbatch, specifically citing that it did not claim biodegradability). This was not (sufficiently) made clear.
Given that the average journalist - let alone reader - cannot distinguish between biodegradable and compostable (i.e. biodegradable in industrial composting facilities), the impression was given that biodegradable bags will not deteriorate in any environment.

On the other hand, the compostable bag showed strong signs of deterioration in the different natural environments, as your study’s findings correctly pointed out. However, if a bag, intended and certified to biodegrade / compost in only the most aggressive of all environments (i.e. industrial composting facilities), actually deteriorates in far less aggressive environments, it is only logical that truly biodegradable bags would be prone to deteriorate even faster than the compostable ones. I am well aware that this kind of deduction would have been beyond the scope of your study. However, it is one thing to omit this rationale (for scientific reasons) and yet another to more or less state the opposite.
For the average consumer, the takeaway of your study is that biodegradable bags are no different from conventional PE bags when it comes to deterioration in natural environments, and this is clearly not the case, as your study shows for compostable bags.
These findings are a blow to our industry, something that, with sound communication, could and should have been avoided.

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