Oxo-degradation

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Oxo-degradation refers to the breakdown mechanism caused by heat, light or oxygen on plastics that contain additives that accelerate the process of breaking them into smaller fragments called microplastics.^[1] These plastics contrast biodegradable or compostable plastics, which decompose at the molecular or polymer level.^[2] Oxo-degradable plastics are currently banned in the EU,^[3] but are still permitted in other jurisdictions such as the UK.^[4]

The specific definitions are found in CEN (European Committee for Standardisation) Technical report CEN/TR 15351. "'Oxo-degradation' is degradation identified as resulting from oxidative cleavage of macromolecules".^{[citation needed]} It describes ordinary plastics which abiotically degrade by oxidation in the open environment and create microplastics, but do not become biodegradable except over a very long period of time.

Oxo-degradable plastics are intended to fragment if they are introduced into the open environment as litter and should not be confused with plastics intended to biodegrade in the special conditions found in an industrial composting unit. These compostable plastics use an entirely different technology, but confusion is caused by the fact that they are so often referred to in discussions of oxo-degradable plastic.

Oxo-degradable plastic packaging has been promoted as a potential solution to plastic pollution, with claims that it can degrade over time.^[5] However, questions have been raised regarding its actual performance and environmental impact. Some studies suggest that instead of fully biodegrading, oxo-degradable plastics tend to fragment into smaller pieces, including microplastics, which can persist in the environment. These microplastics may take longer to degrade than initially anticipated depending on environmental conditions.^[6]

Concerns have also been raised about the potential effects of microplastics on ecosystems, as well as the risk of bioaccumulation in food chains, which could impact both human health and the environment.^[7]

From a reuse and recycling perspective, oxo-degradable plastics are generally not considered suitable for long-term applications. They are designed to break down over time, making them less suitable for reuse. In addition, recyclers have expressed concerns that oxo-degradable plastics may reduce the quality and value of recycled materials. They are also difficult to detect and sort out in recycling streams, presenting challenges for recycling at scale.^[8]

Regarding composting, oxo-degradable plastics typically do not meet the requirements of international composting standards, as their degradation process is slower than required, and plastic fragments can remain in the compos, which has led to concerns about their compatibility with composting systems and their potential to affect compost quality.^[9]

Since 2017 there has been a move towards regulating or banning the use of oxo-degradable plastics, when the Ellen MacArthur Foundation published a statement supported by more than 150 organizations calling for a ban.^[10]

Effective July 2021 oxo-degradable plastics have been banned in the EU with Directive 2019/904 (also known as the Single-Use Plastics Directive). Oxo-degradable plastics were particularly targeted; the rationale behind this focus was that oxo-degradable plastics often do not break down completely but instead fragment into microplastics, which persist in the environment and contribute to pollution.^[3]

In December 2020 Symphony Environmental Technologies filed a lawsuit against the European Commission, arguing that the prohibition was arbitrary and unlawful.^[11] In January 2024 the European Court of Justice dismissed the suit, ruling that none of the commission's actions had been improper.^[12]

Although oxo-degradable plastics are not illegal in the US, the Federal Trade Commission (FTC) has taken the stance that oxo-degradable plastics cannot be called "degradable" or "biodegradable" without strong scientific evidence. In 2014 the FTC advised 14 firms to either remove their oxo-degradable claims or provide reliable scientific evidence.^[13]

Scotland is contemplating a ban on oxo-degradable plastics.^[14]

• Oxo Biodegradable Plastics Federation