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OXO-biodegradation is biodegradation defined by CEN (the European Standards Organisation) in CEN/TR 1535–2006 as "degradation resulting from oxidative and cell-mediated phenomena, either simultaneously or successively." It is sometimes described as "OXO-degradable", but this describes only the first or oxidative phase of degradation and this description should not be used for material which degrades by the process of OXO-biodegradation defined by CEN. The correct description is "OXO-biodegradable".
There are two different types of biodegradable plastic:
Vegetable based plastics (also loosely known as bio-plastics "bioplastics" or "compostable plastics"). These are tested in accordance with ASTM D6400 or EN13432 to biodegrade in the conditions found in industrial composting or biogas facilities.
Oxo-biodegradable plastic, made from polymers such as polyethylene (PE), polypropylene (PP), and polystyrene (PS), contain a pro-degradant catalyst (often salts of manganese or iron), and are tested according to ASTM D6954 or BS8472 or AFNOR Accord T51-808 to degrade and then biodegrade in the open environment. The prodegradant catalyze the abiotic degradation process so that Oxo-biodegradable plastic will degrade in the presence of oxygen much more quickly than ordinary plastic 
The material has then been converted into small-chain organic chemicals, such as ketones, alcohols, carboxylic acids, and low molecular mass hydrocarbon waxes. The remaining chemicals are no longer plastic and are biodegradable by bacteria, which are ubiquitous in the terrestrial and marine environments. The timescale for complete bio degradation at any time or place in the open environment is much shorter than for "conventional" plastics which, in normal environments, are very slow to biodegrade and cause large scale harm. Definitions:
It is important to distinguish between "oxo-degradable" plastics, which fragment but do not biodegrade, except over a very long time, and "oxo-biodegradable" plastics which degrade and then biodegrade.
CEN - The European Committee for Standardisation (Comite European de Normalisation) has established the following definitions, in TR 15351:
1 - Oxo-degradation is degradation resulting from "oxidative cleavage of macromolecules"
2 - Oxo-biodegradation is "degradation resultilng from oxidative and cell-mediated phenomena, either simultaneously or successively.
With regard to definition 2 above, an oxo-biodegredable polyolefin plastic file (e.g. polyethylene, polyproylene and all their combinations), incorporating a catalyst that ensures fast oxidative cleavage of its macromolecules, will become biodegradable by cell-mediated phenomena (bacteria and fungi) in the environment and much more quickly than conventional ordinary plastic.
Oxo-biodegradable plastics are not banned in California but they cannot be described as such in that state.
Degradation is a process that takes place in almost all materials. Conventional polyethylene (PE) and polypropylene (PP) plastics will typically fragment quite quickly, but will then take decades to become biodegradable. OXO-degradable products utilize a catalyst to speed up the fragmentation.
OXO-plastic, if discarded in the environment, will degrade to oxygenated low molecular weight chains (typically MW 5-10 000 amu) within 2–18 months, depending on the material (resin, thickness, anti-oxidants, etc.) and the temperature and other factors in the environment. By contrast, old-fashioned plastic will take decades to reach this stage, and in the meantime will have adsorbed toxins.
OXO-degradable products do not degrade immediately in an open environment because they are stabilized to give the product a useful service-life, during which they do not break down.
OXO-degradation of polymer material has been studied in depth at the Technical Research Institute of Sweden and the Swedish University of Agricultural Sciences. A peer-reviewed report of the work was published in Vol 96 of the journal of Polymer Degradation & Stability (2011) at pages 919-928; it shows 91% biodegradation in a soil environment within 24 months, when tested in accordance with ISO 17556. It has been studied at the Eurofins laboratory in Spain and in many other laboratories around the world. It has been degraded in real time in seawater at the Banyul laboratory in France.
OXO-biodegradable plastic degrades in the presence of oxygen, heat, and UV light will accelerate the process, but they—nor moisture—are not necessary. It is not designed to be compostable in open industrial composting facilities according to ASTM D6400 or EN13432, but it can be satisfactorily composted in an in-vessel process.
The standards for industrial composting (EN13432 and ASTM D6400) require the material to convert to CO2 gas within 180 days, because industrial composting has a short timescale and is not the same as degradation in the open environment. A leaf is generally considered to be biodegradable, but it will not pass the composting standards due to the 180-day limit. (Indeed, materials which do comply with ASTM D6400, EN13432, Australian 4736 and ISO 17088 cannot properly be described as "compostable." This is because those standards require them to convert substantially to CO2 gas within 180 days. You cannot therefore make them into compost—only into CO2 gas. This contributes to climate change, but does nothing for the soil.
OXO-biodegradable plastic conforms to the American Standard (ASTM D6954) and a British Standard (BS8472), which specify procedures to test degradability, biodegradability, and non-toxicity, and with which a properly designed and manufactured OXO product has to comply with these standards. These standards contain contains pass/fail criteria.
There is no need to refer to a Standard Specification unless a specific disposal route (e.g., composting), is envisaged. ASTM D6400 Australian 4736 and EN13432 are standard specifications appropriate only for the special conditions found in industrial composting.
Oxo-degradable plastic, including plastic carrier bags, may degrade quicker in the open environment than conventional plastic. However, according to a report from the European Commission, there is no evidence that oxo-degradable plastic will subsequently fully biodegrade in a reasonable time in the open environment, on landfills or in the marine environment . According to the report: "Sufficiently quick biodegradation is in particular not demonstrated for landfills and the marine environment. A wide range of scientists, international and governmental institutions, testing laboratories, trade associations of plastics manufacturers, recyclers and other experts have therefore come to the conclusion that oxo-degradable plastics are not a solution for the environment and that oxo-degradable plastic is not suited for long-term use, recycling or composting. There is a considerable risk that fragmented plastics will not fully biodegrade and a subsequent risk of an accelerated and accumulating amount of microplastics in the environment, especially the marine environment. The issue of microplastics is long acknowledged as a global problem in need of urgent action, not just in terms of clean-up of littering, but also of plastic pollution prevention."
One major problem with testing oxo-degradable plastics for safety is that current standards and test methods can't realistically predict the biodegradability of carrier bags within natural ecosystems. Moreover, existing biodegradability standards and test methods for aquatic environments do not involve toxicity testing or account for the potentially adverse ecological impacts of carrier bags, plastic additives, polymer degradation products, or small (microscopic) plastic particles that can arise via fragmentation.
On 6 November 2017, the Ellen MacArthur Foundation issued a paper supported by 150 organisations, including M&S, PepsiCo, and Unilever, backing a call to ban oxo-biodegradable plastics. The report had support from industry associations including the British Plastics Federation Recycling Group and Gulf Petrochemicals and Chemicals Association, NGOs such as the World Wildlife Fund (WWF), scientists including those based at Plymouth Marine Laboratory, and ten MEPs from nine EU countries.
The Oxo-Biodegradable Plastics Association (OPA) however, claimed the report was inaccurate. It argued many of the 150 organisations aggressively promoted a rival bio-plastic technology, while many of the others whose logos appeared in the document are themselves producers of the plastic items that get into the open environment as litter. The paper's conclusions were rejected by Professor Ignacy Jacubowicz, who said the degradation process was not merely a fragmentation, but a change from a high molecular weight polymer to a material that can be bio-assimilated.
The evidence for and against oxo-biodegradable plastic was also reviewed in November 2018 by Peter Susman QC a deputy judge of the High Court in England who have over 25 years experience of adjudicating cases in the Technology and construction Court branch of the high Court, involving the evaluation of expert evidence. He has declared the scientific case in favour of oxo-biodegradable plastic to be "clear nd compelling".
Peter Susman QC examined the processes of abiotic and biotic degradation of plastics, and then looked specifically at degradation in air and degradation in seawater.
He concluded, in a 15-page written opinion, that "It is no longer tenable to conclude that there is 'no firm evidence either way' whether oxo-biodegradable is effective. I consider that recent research provides clear and compelling evidence that oxo-biodegradable plastic is indeed effective in facilitating very significantly speedier degradation than is the case when that technology is not used."
He "cannot imagine that such significantly speedier final degradation occurs later than 'within a reasonable time', however that the expression might be defined." And he 'regards the idea that biodegradable plastics might encourage littering as "fanciful and unreasonable".
However the report from Peter Susman is criticized by others 
In addition, OXO-biodegradation of polymer material has been studied in depth at the Technical Research Institute of Sweden and the Swedish University of Agricultural Sciences. A peer-reviewed report of the work was published in Vol 96 of the journal of Polymer Degradation & Stability (2011) at pages 919-928; it shows 91% biodegradation in a soil environment within 24 months, when tested in accordance with ISO 17556. It has also been studied at the Eurofins laboratory in Spain (where on 25th July 2017 they found 88.9% biodegradation in 121 days) and in many other laboratories around the world. It has been degraded in real time in seawater at the Banyul laboratory in France.
European Strategy for Plastics in a Circular Economy
On 16 January 2018, the European Commission published its report on the use of oxo-degradable plastic. The document forms part of the European Strategy for Plastics in a Circular Economy, which was released the same day.
The Commission focussed on three key issues relating to oxo-degradables: the biodegradability of oxo-degradable plastics in various environments; the environmental impacts in relation to littering; and recycling.
The Commission found there was no conclusive evidence that, in the open environment, oxo-degradables fragmented to a sufficiently low molecular weight to enable biodegradation. There was no conclusive evidence about the time needed for oxo-degradable plastics to fragment in marine environments, nor about the degree of fragmentation. It said there was a considerable risk that fragmented plastics would not fully biodegrade, leading to a subsequent risk of an accelerated and accumulating amount of microplastics, especially in the marine environment. Rapid fragmentation increased the risk of microplastic ingestion by marine animals.
In relation to littering, the report found that although it appeared the oxo-degradable plastics industry could create products with minimal toxic impact on flora and fauna, it had not been conclusively proven that there were no negative effects. Marketing oxo-degradables as a solution for plastic waste in the environment may make it more likely items are discarded inappropriately and in marine environments, the fragmentation process made oxo-degradable plastic less likely to be recovered during clean-up exercises.
The report was criticised by the Oxo-Biodegradable Plastics Association (OPA) and said the European Commission had failed to understand the difference between oxo-degradable and oxo-biodegradable plastics. It accused the Commission of not listening to evidence relating to the breakdown of oxo-plastics, which it maintained showed the plastic broke down to a molecular level that could be bioassimilated. In relation to timescales for biodegradation, the OPA said it was not useful to examine how long it took for particular specimens to breakdown in particular conditions, due to the variability of environmental conditions. It said the key point was that oxo-biodegradable plastics would breakdown faster than conventional plastics in the same conditions. Regarding recycling, it said its members had been successfully recycling oxo-biodegradable plastics for more than ten years, with no adverse reports. It rejected the Commission's view on littering and said that, as oxo-degradable plastics were indistinguishable from other plastic products, they were unlikely to cause any additional levels of littering. It criticised the Commission's use of external reports, including that of the Ellen MacArthur Foundation, the findings of which it previously disputed.
A more recent report, Oktober 2018, is in line with the previous one. It states that micro-plastics need to be restricted, including oxo-degradable plastics.
Response of the Oxo-biodegradable Plastics Association against the EU Union
In its Proposal (2018/0172(COD)) for a Directive on “Reduction of the impact of certain plastic products on the environment” the EU Commission proposed various measures for reducing the quantity of plastic goods being produced, and measures for encouraging collection for recycling. Most people would support those measures, but plastic will still escape into the open environment in unacceptable quantities until such time as plastic waste has been eliminated. This is not likely to happen any time soon. According to the Oxo-biodegradable Plastics Association oxo-biodegradable technology is the only way to prevent the accumulation of plastic waste in the environment, and if oxo-biodegradable technology were severely restricted in the EU there would be unintended consequences. There would be distortion of markets if European companies were effectively prevented from manufacturing for countries where oxo-biodegradable plastic is mandatory. Alternatively some countries could follow Europe's lead with disastrous consequences, and much of their accumulated plastic waste would eventually find its way to the shores of Europe.
Recital (3) to the draft Directive says “Marine litter is of a transboundary nature and is recognized as a global problem. ”The Reis report to the European Parliament (11 Oct 2018) says “Every year in Europe, 150,000 tonnes of plastic are dumped into the sea. The situation is even more alarming at global level, with 8 million tonnes ending up in the sea each year,” and Recital (5) to the draft Directive says “In the Union, 80 to 85 % of marine litter, measured as beach litter counts, is plastic, with single-use plastic items representing 50 %.” This is why the plastic needs to be urgently upgraded so that it will convert into biodegradable materials much sooner than ordinary plastic if it does escape into the open environment, and especially the oceans.
Microplastics being recovered from the oceans are from “oxo-degradable” plastics, which degrade and fragment but do not biodegrade except over a very long period of time. These are conventional plastics which undoubtedly create persistent microplastics, and this is why they have been banned for a wide range of products in Saudi Arabia and 11 other countries, where oxo-biodegradable technology for making these products is now mandatory. The products have to comply with strict standards, based on ASTM D6954.
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