Oxo-biodegradable Plastic – more fake news!
March 7th, 2017
Bioplastics Magazine is a publication of the industry which produces crop-based hydro-biodegradable plastics – (also loosely known as “bio-based plastics” or “bioplastics” or “compostable plastics”) which are tested according to EN 13432 or ASTM D6400 to biodegrade in the special conditions found in industrial composting.
The February 2017 issue carries a very misleading article by Constance Ißbrücker of “European Bioplastics” which is a lobby group for that industry. She says that “publications in support of oxo-degradable plastics have claimed about 60% biodegradation in two years, leaving the fate of the remaining 40% up to speculation.”
We are not aware of any plastic called oxo-degradable plastic, but if she means oxo-biodegradable plastic, she fails to mention that it has been tested at the Technical Research Institute of Sweden and the Swedish University of Agricultural Sciences, and that a peer-reviewed report of the work was published in Vol 96 of the journal of Polymer Degradation & Stability (2011) at pages 919-928. They found 91% biodegradation within 24 months.
Oxo-biodegradation is officially defined by CEN as “degradation resulting from oxidative and cell-mediated phenomena, either simultaneously or successively.” It has been studied by scientists for many years, most recently by the Eurofins laboratory in Spain in 2016, who found that the prodegradant additive reduced the molecular weight of the material to the point where it became a low molecular weight material accessible by bacteria as a food-source. At that point they tested for the presence of metals, and found that there were none exceeding the limits prescribed in Annex A.1.2 of EN13432. They then subjected the degraded material to biodegradation testing, and found that the bacteria generated a quantity of CO2 which showed that they had consumed the residual material to the extent of 88.9%, at a rate which produced that consumption in 121 days.
Oxo-biodegradation has also been proved in France by an entirely different methodology set out in AFNOR AC T51-808, which uses bacteria which are found in soil and in marine environments. Adenosine triphosphate (ATP) is the energy- transfer molecule for all living organisms. It is thus a molecule that is indispensable for microbial life and its quantity is directly related to the quantity of active cells. This French test-method makes it possible to determine the total ATP quantity of the cells in suspension in the culture medium, as well as those attached to the polymer material fragment or flask surfaces on the one hand, and the ratio of the concentration of adenosine diphosphate (ADP) to the concentration of ATP on the other.
In addition, tests at Station d’essais de Vieillissement Naturel de Bandol have proved that oxo-biodegradable plastic will degrade to low molecular-weight materials under natural conditions in water.
The article then compares oxo-biodegradable plastic and crop-based plastic and points out that EN 13432 requires 90% disintegration in 12 weeks and biodegradation of 90% within six months. Again, she fails to mention that crop-based plastic is expected to achieve this under the special conditions found in industrial composting, which are completely different to the conditions found in the open environment where oxo-biodegradable plastics are designed to degrade and biodegrade. She does not mention ASTM D6954, which is the appropriate test for oxo-biodegradable plastic.
She then assumes that “oxo-degradable” materials only disintegrate and finally visibly disappear under the influence of light (UV radiation) and oxygen, and that if no real biodegradation takes place simultaneously and subsequently, the process of disintegration results in the formation of invisible plastic fragments, contributing to the ubiquitous environmental and health hazard of microplastics in the environment.”
She has of course ignored the scientific evidence mentioned above, and has ignored the fact that all plastics (whether oxo, bio-based, or conventional) create fragments when they degrade. The difference is that oxo-biodegradable plastic does NOT just fragment into small pieces. When it has become biodegradable it is no longer a plastic, and has become soluble in water. It has to pass the tests in BS8472 or ASTM D6954 or AFNOR AC T51-808 to prove that it is biodegradable and non-toxic. It does not therefore leave microplastics behind – and the particles of plastic which have been found in the oceans by NGOs and scientists are mostly particles of ordinary plastic.
If oxo-biodegradable plastic merely fragmented without biodegrading, CEN would not have defined oxo-biodegradability, and the American and British and French Standards authorities would not have included tests for biodegradability in ASTM D6954, BS8472 and AC T51-808.
This article in Bioplastics Magazine is the most recent in a series of attacks on oxo-biodegradable plastics over many years by the crop-based plastics industry, who are attempting to secure market share by unfair publicity, and not on the merits of their own product, which has serious limitations – see http://www.biodeg.org/biobased.html
Their type of plastic is designed to be taken to an industrial composting or anaerobic digestion unit. It does not address the problem of plastic litter in the open environment because the original vegetable materials have been polymerised and have become plastics.
A consortium consisting of Friends of the Earth, Surfrider Foundation, Zero Waste Europe, Ecos, and the European Environmental Bureau published a paper in 2017 in which they say “The bioplastics industry use their green-sounding credentials to position themselves as helping to speed the reduction in fossil fuel use and solving the ever-growing plastic pollution and marine litter issues. However, there is clear evidence that bioplastics do not solve many of these problems and in fact may create new ones.”
Oxo-biodegradable Plastics Association