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Compostable Plastic

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Compostable Plastic

A “Grocer” magazine survey of more than 1,000 individuals in 2019 found that “consumers think that plant-based compostable plastics are the most environmentally friendly packaging materials,” but most consumers don’t realise that “compostable” plastic does not convert into compost, and that it is tested to biodegrade in an industrial composting facility – not in the open environment.  It is required by ASTM D6400 and EN13432 to convert rapidly into CO2 gas, and the last thing the planet needs is more CO2.

Not only have the German courts in Güthoff v Deutsche Umwelthilfe (2014)  held that it is deceptive to market plastic as “compostable” but these plastics are really an irrelevance, because the main problem facing governments today is plastic waste which has escaped into the open environment, from which it cannot realistically be collected and taken to a composting facility

Also, in November 2019 a Danish court ruled in Ellepot v Sungrow that “compostable” PLA plant pots must not be described as biodegradable – because they are not biodegradable except in the special conditions found in an industrial composting facility.

Plastics marketed as compostable (ie hydro-biodegradable plastics) are far too expensive for everyday use, and there are very few industrial composting facilities available.  Moreover, as it is difficult and expensive to separate these plastics from other plastics, many industrial composters do not want plastic of any kind in their feedstock. Home composting of plastic packaging is dangerous and should not be encouraged, as it is often contaminated with meat, fish, or poultry residues, and temperatures do not rise high enough to kill the pathogens.

European standard EN 13432 and ASTM D6400 apply to biodegradation of plastic packaging under industrial composting conditions, but they not appropriate for testing oxo-biodegradable plastics. This is because they are based on measuring the emission of carbon dioxide during degradation. Hydro-biodegradable plastic is compliant with EN 13432, precisely because it emits CO2 (a greenhouse gas) at a very high rate.  If a leaf were subjected to the CO2 emission tests included in these Standards it would not be considered biodegradable or compostable!

These plastics are often marketed as renewable, but this ignores the fossil fuels used in the agricultural production process by the machines which clear the land, plough the land, bring the seeds to the farm and sow them, harrow the land, bring the fertilisers and pesticides to the farm and spread them,  harvest the crop and transport it to the factory, and by the machines which polymerise the raw material.  It also ignores the land and water resources devoted to producing the raw materials, which could be used for growing food. EASAC (March 2020 report) says that “replacing PE by a bio-PE would require almost all (93.5%) of global wheat production.” This is completely unsustainable.

Although these plastics are marketed as “bio-based” they can contain up to 60% oil-based material.

Conversion of organic materials to CO2 at a rapid rate during the composting process is not

“recovery” as required by the European Directive on Packaging and Packaging Waste

(94/62/EC). Nature’s lignocellulosic wastes do not behave in this way, and if they did the products would have little value as soil improvers and fertilisers, having lost most of their substance and their carbon.

On 11th September 2003 a Report to the Australian Government by the Nolan-ITU Consultancy concluded that: “oxo-biodegradable plastics based on polyolefins contribute to the amount and nutritive value of the compost because much of the carbon from the plastic is in the form of intermediate oxidation products, humic material and cell biomass. This is in contrast to plastics such as hydro-biodegradable polyesters (eg starch-based) that biodegrade at rates comparable to purified cellulose. At the end of the commercial composting process, all of the carbon from the latter has been converted to CO2 so there is a contribution to greenhouse gas levels but not to the value of the compost.”

The same Report concluded that “degradable polymers manufactured from renewable resources (e.g., crops) have greater impacts upon eutrophication due to the application of fertilizers to land.”

Even the industrial composters do not want them.

In January 2020, the industrial composters of Oregon gave 9 reasons why they did not want it

Then the City of Exeter UK rejected it

Then the City of Toronto, Canada

Then the SUEZ  waste-management company

Then a devastating exposé on Netherlands television /

And another TV exposé in Canada about how compostable plastics are typically not being composted but instead sent to landfill or incineration.

Many areas do not have industrial composting plants, and the Welsh Government has refused to invest in them. Plant-based compostable plastics are going to landfill rather than recycling because almost all Welsh councils are unable to deal with them.

“Compostable” resins are worse than conventional or oxo-biodegradable plastics when it comes to oxygen transmission-rate or moisture vapour transmission-rate. These resins are also water sensitive, and their physical, optical, mechanical, and chemical properties are inferior.

There are at least 21 reasons why “Compostable” plastic is not useful