Prof. Renald Blundell's article of 26 July rightly draws attention to the growing public concern about plastic pollution and microplastics. Nobody should minimise that problem. Plastic which escapes collection and accumulates for decades in the open environment is a global environmental issue, and Malta has every reason to take it seriously.
However, the article risks leaving readers with a misleading impression by treating all materials described as "biodegradable" as if they raised the same issues. They do not. There is an important distinction between plastics designed for industrial composting; ordinary plastics which merely fragment; and oxo-biodegradable plastics which are designed for oxidation followed by biodegradation.
This distinction is not a matter of marketing language. It is the distinction between a material which breaks into persistent fragments and one which converts by a molecular change so that it can be consumed by naturally-occurring microorganisms. Oxo-biodegradable technology is not designed simply to make plastic fall apart into smaller pieces. Its purpose is to reduce the molecular weight of polyethylene or polypropylene until the material no longer behaves as ordinary plastic and becomes biodegradable.
That is why it is important not to confuse "oxo-degradable" with "oxo-biodegradable." Ordinary plastics will, over time, degrade by oxidation and fragment into smaller and smaller pieces, and they can properly be described as oxo-degradable, and that is the main route by which persistent microplastics are created. Oxo-biodegradable plastic is different because it contains a carefully formulated masterbatch intended to enhance oxidation so that biodegradation can follow. The relevant question is therefore not whether the material visibly fragments, but whether the polymer has been converted into low-molecular-weight material which can then biodegrade.
The article refers to a 2019 University of Plymouth study in which some biodegradable bags remained functional after three years in soil or sea. That study is frequently cited, but testing a bag bought on the market, without first establishing whether it contained the correct oxo-biodegradable formulation, at the correct concentration; and then testing it under conditions not likely to be encountered in practice, tells us nothing about whether a properly made oxo-biodegradable plastic product will perform as designed. A valid regulatory assessment must start by knowing exactly what material is being tested.
This was done by Intertek, who proved complete biodegradation leaving no persistent particles and no toxicity. Also, the results of the French four-year Oxomar study were "We have obtained congruent results from our multidisciplinary approach that clearly shows that Oxo-biodegradable plastics biodegrade in seawater and do so with a significantly higher efficiency than conventional plastics. The oxidation level obtained due to the d2w prodegradant catalyst was found to be of crucial importance in the degradation process."
Oxo-biodegradable plastics are tested under ASTM D6954 and comparable standards. These do not simply ask whether a bag disintegrates. They address three stages: oxidation, biodegradation, and eco-toxicity. In other words, the test is designed to answer the practical environmental questions: does the plastic degrade? does the residue biodegrade? and are harmful residues left behind?
Nor should oxo-biodegradable plastic be confused with plastic marketed as "compostable" which are designed for special industrial composting conditions. They are not designed to disappear in the open environment if littered, and they cannot be included in a normal recycling stream. The name is also misleading, because they do not convert into compost. EN13432 and ASTM D6400 require them to convert rapidly into CO2 gas.
Oxo-biodegradable plastic addresses a different problem: what happens if ordinary plastic escapes collection and ends up on land or water, where it would otherwise persist for many years. Also it has been designed to be re-used and recycled during its useful life.
This is not an argument against reduction, reuse, recycling or better waste management. Those policies remain essential. But even in countries with advanced waste-management systems, some plastic inevitably escapes collection. The policy question is therefore not whether oxo-biodegradable plastic is a perfect solution. No single technology is. The question is whether, for short-life polyethylene and polypropylene items most likely to become litter, it is better to use ordinary plastic which may persist for decades, or a material designed and tested to biodegrade much more rapidly if it gets into the open environment.
The microplastics debate should focus on persistence. A fragment which remains in the environment as plastic is a problem. A residue which has been oxidised to a biodegradable form and is assimilated by microorganisms, is significantly different. Treating both as the same obscures the very issue regulators and the public are trying to understand.
The right approach is not to rely on broad labels such as "biodegradable," "compostable," "oxo-degradable," or "green." It is to require clear, performance-based evidence: What polymer is being used? What masterbatch is present? Has the product been tested to the appropriate standard? Does it biodegrade? Does it leave persistent microplastics? Is it non-toxic? Can it be recycled during its useful life?
If a product cannot answer those questions, it should not make environmental claims. But if it can, it should not be dismissed by confusing it with plastics with quite different characteristics.