Vague terminology

Even a brief dive into the world of oxo-degradable plastics will churn up a plethora of terms: oxo-degradable, degradable, oxo-biodegradable, biodegradable, biotransformation. The use of technical terminology isn't a problem in itself, but within this sector it's used so inconsistently that understanding what's actually being promised can be a challenge. 

For instance, Symphony Environmental, which makes a “dw2 oxo-biodegradable plastic”, uses the page header “Biodegradable Plastic Technology” to talk about its products. That's already two different terms applied to one technology. The company also differentiates between oxo-degradable and oxo-biodegradable. Oxo-degradable is defined as ordinary plastic that "abiotically degrades" (i.e. without the help of microbes or fungi) in the open environment, while oxo-biodegradable is defined as plastics that degrade in an open environment until their “molecular weight is accessible to bacteria and fungi, who then recycle it back to nature”.

Many, however, don't make any such distinction, and oxo-degradable is often used to mean plastic that will fragment as well as biodegrade. Others, like Polymateria, don't use either term, calling it "biotransformation" instead. In using multiple terms and applying multiple meanings to them, the makers of oxo-degradables muddy the waters, suggesting they are producing radically different products to each other and leaning on words like "bio" and "biodegrade" to imply that their products will disappear into nothing but organic matter. But we know from the UCL conclusion above that that's simply not the case. There is a lack of evidence to support the claim that plastics which contain these additives do indeed get "recycled back to nature", and what's more, the paper also states that most PAC plastics studied in literature would not pass the criteria for biodegradability according to new biodegradability standard PAS 9017:2020. The terminology may be vague, but the evidence is clear.

Broken promises, broken plastic

Thanks to the use of confusing and misleading terminology, there is a perception that oxo-degradable plastics disappear harmlessly in the natural environment if discarded. To live up to these claims, oxo-degradable plastics would have to fragment until they’re the ideal molecular weight, then the monomers would have to be entirely converted into biomass (water and carbon if oxygen is present, methane if it is not). But this simply isn’t the case.

In ideal hot and dry conditions, such as regions like the South of France and Florida, oxo-degradable plastics may well break down into smaller fragments at an accelerated rate compared to conventional plastics. Unsurprisingly, it’s these conditions which are synthesised in laboratory conditions by manufacturers aiming to showcase the properties of their materials. Due to factors such as the intensity and duration of UV light, temperature, and humidity used in these tests, it’s unclear how rapid fragmentation would play out in colder, wetter climates like those of the UK. Though a paper by Loughborough University estimated that it could take up to five years.

And what then happens to those fragments? In 2017, the European Commission released the catchily-titled report “Study to provide information supplementing the study on the impact of the use of “oxo-degradable” plastic on the environment”. The evidence reviewed suggested that while PAC plastics “can biodegrade under certain circumstances, there is still doubt as to whether they do so fully or within reasonable time periods”. It also stated that “evidence is not available to definitively conclude that [biodegradation] will happen in real world situations.”

This all tells us that oxo-degradable plastics can fragment more rapidly in very specific conditions, over varying, non-guaranteed timelines. But while they could technically biodegrade to some degree in certain circumstances, there is no real evidence that they actually do. What that leaves us with is a lot of plastic in the environment, breaking down into fragments that are impossible to clean up - an issue more typically known as microplastic pollution. When framed in such simple terms, oxo-degradable plastics don't sound like quite the environmental saviour they are made out to be. 

By marketing them as biodegradable, the manufacturers of oxo-degradable plastics offer a false promise to consumers: that if their plastic packaging was to end up in the environment, it would cause no harm. This could easily lead to careless attitudes towards disposal, with consumers under the impression that their packaging would simply disappear, when in fact it would exacerbate one of the foremost environmental issues of our generation. 

“Oxo-degradable soil mulches have been on the market for 20 years, and every farmer will tell you that their fields are littered with bits of plastic,” says Newman. “You have to ask yourself as a manufacturer, as a policymaker, what is the point of adding these additives which are going to be sitting around for years and years and years? Manufacturers like it because they can claim biodegradability.”

Dr Imogen Napper, aka “The Plastic Detective”, further supports this reality. In 2019, she led an experiment on the environmental degradation of biodegradable, oxo-biodegradable, compostable, and conventional plastic carrier bags in the sea, soil, and open air over a three-year period. She concluded that “none of the bags could be relied upon to show any substantial deterioration ... in all of the environments. It is therefore not clear that the oxo-biodegradable or biodegradable formulations provide sufficiently advanced rates of deterioration to be advantageous in the context of reducing marine litter, compared to conventional bags.” For a material category sold as a solution to "fugitive plastics", that's a damning conclusion. 

The regulation tide is turning

It's clear from all the research that oxo-degradable plastics cannot be relied upon to quickly and sufficiently break down, then biodegrade. As a result, regulators have begun to target both the material itself and the products made from it. Oxo-degradable plastics have been banned in the EU. Article 5 of Directive 2019 /904, which covers the “reduction of the impact of certain plastics products on the environment”, states that “Member States shall prohibit the placing on the market … products made from oxo-degradable plastic.” Symphony Environmental has sued the EU for losses and reputational damage as a result. 

Plastics with “pro-degradant additives” were banned from sale and manufacture as of October 2022 in New Zealand, oxo-degradable plastics were banned in Switzerland from April 2022, and parts of Australia have also banned them - South Australia banned oxo-degradable plastics in March 2022, while Western Australia banned the sale of dog waste bags made from oxo-degradable plastic from January 2023. Canada has included oxo-degradable plastics in its 2023 phase out of single-use plastics, and the US FTC sent cease and desist letters to certain manufacturers marketing oxo-degradable products as biodegradable.

Pushing for a ban in the UK, a coalition of signatories including BBIA, Greenpeace, and A Plastic Planet issued a letter to the Environment Secretary. This followed a letter published by the Ellen MacArthur Foundation which also recommended a ban as a precautionary principle. The paper was endorsed by organisations and brands including Unilever, Veolia, M&S, PepsiCo, TerraCycle, MCS, Surfers Against Sewage, Wrap, and WWF. When policymakers and brands are lining up to use their status to remove a material from the market, that’s a sign that the grand promises do not stand up to scrutiny.

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