Biodegradable & Compostable Michael Stephen Column OXO

Plastiphobia, More bad news for compostable, Ellen MacArthur Foundation, and misleading article in Brazil (FREE)

Today Michael talks about Plastiphobia; More bad news for plastics marketed as compostable; the Ellen MacArthur Foundation; and a misleading article about biodegradable plastics in Brazil. This is a FREE article


The urban dictionary contains a definition of plastiphobia, which is probably right.  It is “The irrational, and scientifically unsubstantiated, fear of plastics, propagated by those with a financial interest in spreading this fear to damage competitors or to raise funds.”  Some of these are described as “not for profit” but they can be multi-million dollar organisations who pay their senior staff very large salaries.


I have read a report in the Journal of Hazardous Materials (5.10.23) from the Environmental Chemistry Department, IDAEA –CSIC, Barcelona.  Some newspaper headlines suggest it is about biodegradable plastics, but it is about the type of plastic marketed as “compostable.” One of the plastics they tested was “Mater-Bi®, a commercial compostable thermoplastic containing polybutylene adipate terephthalate (PBAT) and starch.”

The report says “In recent years, governmental bodies worldwide have initiated measures to diminish and ban the use of fossil-based SUPs, and compostable plastics have been presented as one of the key solutions to replace conventional plastics. From January 2021, light and ultralight bags were banned in Spain, with the exception of compostable bags. Currently, the utilization of bags labelled as ‘compostable’ for bulk products (fruits, vegetables, etc.) is prevalent within the supermarkets and grocery stores and is anticipated to experience sustained growth in the coming years due to the implementation of new regulations.” And I would add, due to aggressive advertising and lobbying by the suppliers of these bags.

However, “few studies have investigated the toxicity of chemical leachates from compostable plastics especially following composting or photodegradation, when their components are released into the environment.”

The report continues, “The degradation of compostable plastics is accelerated during composting (high temperature, moisture, microorganisms), but it will be much lower in the natural environment, leading to the additional release of chemicals, but also micro- and nano-plastics.”

“one of the most striking findings was that the chemicals extracted from compostable plastics were cytotoxic to PLHC-1 cells, while those extracted from conventional plastics were not.”

“the toxicity of leachates from a biodegradable garbage bag (50% corn starch, 50% aliphatic polyester) significantly increased after exposure to sunlight, whereas photo-oxidized polyethylene leachates did not show any toxicity.”

“The extracts obtained from plastic fragments that remained after 60 days of composting showed increased cytotoxicity.”

“semi-degraded plastics present in compost have been identified as problematic, as a substantial amount of plastic fragments, particularly in bio-waste compost, can end up in farmland and ultimately in the aquatic environment.”

“Extracts were found to lead to a significant decrease of cell viability on PLHC-1 cells after 24 h exposure, while extracts of conventional plastics did not alter cell viability.   …. The toxicity of compostable plastics significantly increased after simulated photodegradation.”


Symphony Environmental have made a formal complaint to the UK Charity Commission about the activities of EMF, and their so-called “Oxo Statement.”  See   EMF were requested by lawyers acting for Symphony to disclose how much money they received from the “compostable” plastics industry, but failed to do so.


An article in a journal called “Sustainable Production and Consumption” alleging greenwashing by suppliers of biodegradable plastic products in Brazil has attracted a lot of attention in Brazil and elsewhere.

The authors draw attention to “the widespread occurrence of plastic debris in terrestrial and aquatic ecosystems” and note that “replacing single-use plastic products with biodegradable ones has emerged as part of suitable actions to reduce global environmental impacts.”

This is correct, and it is necessary because the conventional government policies of “Reduce, re-use, and recycle” are not solving the problem, and the plastic is lying or floating around for decades.  However, the authors fail to distinguish between biodegradable plastics which are designed to biodegrade in the open environment, and those designed to biodegrade in the special conditions found in an industrial composting facility.

Even if there were enough industrial composting facilities in Brazil willing to accept plastic of any kind (which there are not) the type of plastic marketed as compostable will not assist in solving plastic pollution in the open environment, because it would obviously have to be picked up and taken to a composting facility.  Even if taken to a composting facility it converts into CO2 gas, not into compost. See

On 2nd December 2022 the UK Environment Minister said: “Compostable plastics must be treated in industrial composting facilities to be broken down and, when processed incorrectly, can be a source of microplastics and contaminate recycling streams.”  …  “This packaging does not contribute to a circular economy in the same way as packaging that can be reused or recycled into new packaging or products do, as compostable plastic packaging is generally intended to be used only once.”

On 14th November 2022 the Minister said “our call for evidence suggests these materials are often stripped out at the start of the composting process and landfilled or incinerated.”

By contrast, the type of plastic designed to biodegrade if it gets into the open environment is called “oxo-biodegradable” because it is made with a masterbatch containing a catalyst which promotes oxidation, which in turn converts polymers into oligomers, which can be consumed by bacteria and fungi in the natural environment in the same way as a leaf. This type of plastic can be programmed to biodegrade much more quickly than a leaf.

The authors did not test the samples, but they made the broad statement that the biodegradability of oxo-polymers has been widely refuted by scientific literature.  This is not correct.  In particular the most recent four-year study sponsored by the French National Agency for Research has found 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.”  See 

The authors also say that “technical standards used to certificate biodegradability of plastics demonstrated that experimental settings used by these norms do not amply cover actual environment conditions.”  However, it is impossible to measure biodegradation in a compost heap or a field or a lake, so it has to be done in a laboratory according to standards written by expert scientists to simulate the conditions likely to be found in the environment.

Standards such as EN13432 and ASTM D6400 do not cover the conditions found in the open environment, because they are intended for the conditions found in an industrial composting unit.

By contrast ASTM D6954 and BS8472 are designed to simulate biodegradation in the open environment.  See the expert evidence to the UK government at Swift evidence to BEIS

The authors complain that plastic products are being marketed as biodegradable when they are not. For this reason, retailers should not buy or sell such products unless the masterbatch supplier can produce a certificate from an accredited laboratory showing a successful test according to ASTM D6954, BS8472, or a comparable standard, together with a test report showing that the finished-product has been correctly made with the correct masterbatch. Reputable suppliers such as Symphony Environmental will always provide this information for products made with their d2w masterbatch.

The supplier of the masterbatch does not label or advertise the finished products, but would always be glad to hear about any product which might have been incorrectly described.  For the avoidance of doubt, plates and cutlery are normally made of polystyrene, but oxo-biodegradable masterbatches are not supplied for that type of plastic, nor for PET.

Retailers should not describe any kind of plastic as “compostable” because EN13432 and ASTM D6400 require it to convert into CO2, not into compost. Nor should they sell that type of plastic as “biodegradable,” because it would mislead the public.  It is tested according to these standards to biodegrade in an industrial composting facility, not in the open environment. Nor should they describe it as bio-based without disclosing that it contains a significant proportion of fossil-based material.

Whilst the authors of this article would no doubt wish to solve the problem of plastic in the open environment, articles such as theirs are causing confusion and delaying the adoption of oxo-biodegradable technology.  There is no other way to prevent plastic in the open environment from creating microplastics and accumulating there for many decades.

Michael Stephen

Michael Stephen is a lawyer and was a member of the United Kingdom Parliament, where he served on the Environment Select Committee. When he left Parliament Symphony Environmental Technologies Plc. attracted his attention because of his interest in the environment. He is now Deputy Chairman of Symphony, which is listed on the AIM market of the London Stock Exchange, and is the founder and Chairman of the Biodegradable Plastics Association.

Earlier Postings in this Column

All articles from Michael Stephen

Interview with Michael Stephen

Questions and Answers on OXO-Biodegradability


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