President's Blog

11 Jun 2019 13:52 Age: 1 year

Guest Blog | Myths and Facts on Oxo-degradable, Biodegradable and Compostable Bags

Category: ISWA BLOG


This guest article was written by Mario Malinconico, Researcher at CNR, President of ATIA ISWA Italy, President of Assobioplastiche S&T Committee; and Antonis Mavropoulos, ISWA President.

There is an on-going discussion regarding the properties and the real environmental performance of the alternative bags usually called oxo-degradable, biodegradable and compostable. The debate is briefly like this: are we talking about materials that are more environmentally friendly and degrade faster and easier or is this just another form of green-washing?


The recent study “Environmental Deterioration of Biodegradable, Oxo-biodegradable, Compostable and Conventional Plastic Carrier Bags in the Sea, Soil, and Open-Air Over a 3-Year Period” conducted by Imogen E. Napper and Richard C. Thompson of the University of Plymouth, fueled further this debate. Several media reported on the study putting headlines such as “biodegradable bags survive three years in soil and sea” or “biodegradable bags can hold a full load of shopping three years after being discarded”. So, for several media outlets, it seems that the study supports that oxo-degradable, biodegradable and compostable bags are rather another green-washing effort that does not provide better environmental performance. A closer look at the study and its outcomes proves some very interesting details that makes those headlines somehow misleading. Even more, it proves that those headlines are based on a lack of understanding of the science behind those materials.


To start with the core outcome, the study examined the behavior of a high density polyethylene bag, two oxo-degradable bags, a bag with the word "biodegradable" on it and, finally, a biodegradable and compostable bag in different environmental conditions. The study found that 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.


So, the study tells us that only the bag that was both biodegradable and compostable (designed to be managed in the circuit for the collection of wet waste in special industrial plants) undergoes total decomposition in the marine environment in just three months and has a reduced environmental impact.


The study tells us nothing new, but it confirms that it is a mistake to use the term "biodegradable" compared to products based on traditional polymers or with the addition of chemicals intended to accelerate the fragmentation (so called oxo-degradable). The only products available to properly boast of this definition are those in compostable bioplastic, such as moreover already clarified in 2015 in Italy by the AGCM (Governmental Consumer Protection Department) in the case of oxo-degradable bags, used at the time by some large retailers. The results published by Imogen E. Napper and Richard C. Thompson are therefore not surprising for polymer chemistry and biodegradation experts, but rather confirm that the EU decision (Single Use Plastics directive) to prohibit all traditional materials with accelerators of fragmentation is correct.


Looking at the results from a scientific point of view, the study says that compostable bags are degraded within three months in the marine environment, thus providing a much better environmental behavior than biodegradable and oxo-degradable ones. It is also important to underline that, in a further press communication the Plymouth University has admitted that the headline on its press release stating that both compostable and bioplastic bags were still intact after three years in soil was wrong. A spokesperson for the external press office at the university said this was "essentially a typo, and it has been corrected". The spokesperson added: "Neither the body of the press release nor the academic paper made any mention of the compostable bag being able to hold items after the experiment. And it is not correct to say that there were changes made to the media release to make that clearer." They added that it was the press office's error and the authors of the report were not to blame.


So, here are some conclusions.


First, although the study demonstrates a further clear distinction between materials in terms of biodegradation properties (even if materials were found to the wrong environment), the study was used to communicate a wrong message that portrays all materials similar. A press office’s error might be the cause, but in scientific aspects like this, media are usually abuse the outcomes based on partial or wrong understanding.


Second, biodegradability, as the study suggests, must never be considered as a more convenient solution or an excuse for uncontrolled disposal in the environment (which would lead to the paradox of legitimizing for example the littering of the waste and organic residues in the sea, as they are biodegradable). Using biodegradability to advance the use of any kind of “alternative” bags is completely misleading and can be considered as green-washing.


Third, the media failed to address the most fundamental problem: the solution is not to advance biodegradation of bags as such (although compostable bioplastic performs much better), but the research and the application of models of proper integrated sustainable management of organic waste, of which Italy is a virtuous example.


The paper questions whether biodegradable formulations can be relied upon to offer a sufficiently advanced rate of degradation to offer any realistic solution to the problem of plastic litter. But the major problem is how we will avoid plastic litter and not how we will continue it with better materials.  ISWA has clearly demonstrated that the only way to reduce plastic marine litter is by eliminating the leakages of plastics, advancing recovery systems and improving waste management. Ignoring this reality and focusing only on how we will develop materials that will harm less the environment, not only we mislead the public opinion about the roots of the problem but we stimulate further deterioration of the marine environment.


The Institute of Polymers, Composites and Biomaterials of CNR - like many other research organizations in Italy and in Europe - has always been committed to the real challenge of this extraordinary moment: the research and development of innovative materials, of new models of production and conscious consumption, of awareness raising and efficient waste management systems, in the spirit of that circular economy that the European Union is pursuing. ISWA is going to work closer with CNR to address crucial issues regarding plastic alternatives and innovative materials.