Will degradable plastics really prevent marine pollution?

In our world of instant gratification, plastic has proved incredibly useful, allowing food and drink to be conveniently packaged and transported for consumption on the go, immediately satisfying our most basic of human needs. Unfortunately, if it is not handled correctly after its brief use, plastic can cause serious environmental problems, as hauntingly documented by Blue Planet II. People are rightly concerned about the pollution accumulating in our seas, and they want an immediate solution.

Industry insiders widely recognise that solving the problem will be fiendishly complicated, but there are some – who had significant airtime in the wake of government’s 25 year environment plan earlier in the month – that claim to have an available and simple solution in the form of oxo-degradable plastics. Unfortunately, they don’t.

Just how degradable are oxo-degradables?
Oxo-degradable (or oxo-biodegradable) plastics are conventional plastics with additives that encourage them to become brittle and fragment into tiny pieces when exposed to oxygen, UV rays and, to some extent, heat. In theory, these tiny pieces then biodegrade, with manufacturers saying that degradation happens safely in a matter of months or years. However, independent researchers and scientists don’t think this happens in practice, or that it takes a lot longer than manufacturers claim.

In the cool, dark marine environment in particular, conditions mean that biodegradation is even slower than on land. Instead of dissolving into harmless residues, the pieces persist indefinitely, or at least long enough to cause considerable damage. The fact that they split into tiny pieces so quickly makes them all the more damaging in some ways, as they can be so quickly gobbled up by organisms throughout the marine food web, harming marine life and even finding their way to our dinner plates, with as yet unknown consequences.

It could lead to a bigger litter problem
The problems with oxo-degradables don’t stop at our oceans’ shores. Because the plastics are designed to fragment so easily, they are not suitable for reuse or long term use, and because current technology cannot differentiate between conventional plastics and those with these special additives, reprocessors warn that they contaminate recycling streams and weaken recycled material over time. Oxo-degradables are also unsuitable for composting as they do not degrade fast enough, despite those additives, and the plastic fragments remain in the compost, meaning it cannot meet strictly controlled quality standards. And there is a worry that the marketing of oxo-degradable plastic as a safe choice could actually lead to an increase in littering if people believe the material is truly biodegradable.

There are much better solutions
In launching the 25 year plan for the environment, Theresa May recognised both that action is needed “at every stage of the production and consumption of plastic” and that “a relatively simple policy” can make a big difference for the environment.

This latter statement referred to the plastic bag charge which, we estimate, tackles one per cent of plastic pollution and which Theresa May says she wants to build upon. She could start by taking a number of steps now that fall within her remit, including banning oxo-degradables for all of the reasons outlined here. While there isn’t an instant solution, there are ways to solve our plastic problem soon, and that has to be gratifying.

[Image: MichaelisScientists (Own work) [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)%5D, via Wikimedia Commons]

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