Late last year Sam Bliss, wrote an article in Grist, an on-line environmental magazine (31-10-14) lambasting biodegradable bags. Despite the fact that this story is ‘old news’ we felt when it recently came to our attention that we had to address the lack of accurate information, so here goes.
Oxo-biodegradable plastic bags from reputable sources are clearly labelled. They have been tested by independent laboratories according to ASTM D6954 for abiotic degradation, biodegradation and finally eco-toxicity. Only when they have proved that they are indeed degradable, biodegradable and not eco-toxic can they claim to be oxo-biodegradable.
By the way, oxo-biodegradable plastic also complies with other standards including the British Standard BS 8472 and the French Accord ACT51-808. Reputable suppliers are members of the Oxo-biodegradable Plastics Association and entitled to use its logo. They will be able to produce independent test reports to prove what they say.
Most people agree that plastic bags suck? Do they? Not so, Mr Bliss. In fact recently in the US many of the bag bans and taxes have been cancelled, because shopkeepers and consumers know that there is nothing quite as strong, flexible or versatile for protecting food and other goods and transporting them from one place to another. Oxo-biodegradable plastic can be made by plastics factories with their existing machinery and raw materials at little or no extra cost. You are right in that a very small amount (approximately 1%) of metal salts (NOT heavy metals) are added to the polymer at the manufacturing stage. The wonderful thing about oxo-biodegradable plastic is that the service-life of the product can be pre-determined at manufacture (typically between 6 – 18 months) after which, it will degrade and biodegrade in the open environment, on land or sea, in the same way as a leaf, only quicker and leaving nothing behind.
If all it did was to fragment into small pieces, why would CEN have defined oxobiodegradation as ““degradation resulting from oxidative and cell-mediated phenomena, either simultaneously or successively” and why would respected standards organisations have written tests for Biodegration?
This is not a “story,” it is backed up by solid, scientific data. In fact it works so well that ten countries with a combined population of over half a billion people have realised that because they cannot realistically collect all the plastic waste, they insure against its escape into the open environment by legislating for oxo-biodegradable plastic. They very carefully considered the effectiveness and safety of the technology, and their governments checked out the “stories” and found them to be untrue.
With regard to the FTC well they also got it wrong, and were taken to task in the courts in the US. The outcome was that the Administrative Law Judge ruled against the FTC on several important points in case no. 9358 decided on 28th January 2015. The court described the “one year return to nature” test which the FTC had invented as arbitrary, and refused to apply it. The judge also stated, that acceleration of tests to save time and money in the laboratory does not invalidate the tests and that CO2 evolution tests may understate the amount of biodegradation. Which brings us to landfill. Oxo-biodegradable plastic bags are not intended for landfill, but they can be safely sent to landfill. In landfill they will not degrade in anaerobic conditions and will not therefore generate methane, which is a powerful greenhouse gas, nor will they cause harmful leachate, as they are not eco-toxic.
Plastic is a valuable resource which should not be sent to landfill and should either be recycled or incinerated for waste to energy recovery. It is likely that sending plastics to landfill will eventually be outlawed altogether. In the article where Joseph Greene from California State University is quoted it is not entirely clear whether he is talking about oxo-biodegradable plastic or vegetable based/hydro plastic. He is an expert in the latter but not the former, and is a well-known advocate of vegetable-based plastic – as to which see http://www.biodeg.org/biobased.html
The Guardian article referred to, stated that Greene favours corn-based PLA plastic, this is surprising because it has been shown in LCA’s by Intertek that bio-based plastics emit methane in landfill and are a lot worse for the environment than oxo-biodegradable bags when land use, water, fertilizers, transport and emissions are taken into account. They are not tested by ASTM D6400 to biodegrade in the open environment, but in the special conditions found in industrial composting units, where they do not convert into compost but into CO2, – another greenhouse gas.
The bits of plastic floating around in the ocean are either conventional or bio-based plastics, where they can indeed be mistaken for plankton or jellyfish. Oxo-biodegradable plastic will degrade and biodegrade on land or sea and will not cause an environmental nuisance or be a danger to wildlife.
Re-usable bags can also harbour dangerous germs including E-coli as they are very rarely, if ever, washed inside, added to the fact that cotton reusable bags would have to be used 173 times according to an Environment Agency Report in February 2011 in which the LCA of supermarket carrier bags was investigated, to ensure that they had a lower global warming potential than plastic carrier bags, and would more than likely end up in landfill at the end of their useful life. Plastic bag bans and taxes are not the best way to tackle plastic waste in the environment. If we really want to make a difference, let’s keep the plastic, but get rid of the environmental baggage that goes with old-fashioned plastic by using oxo-biodegradable technology. It is a cheap and easy solution to a global problem. Were it not for the nonsense in articles such as the one by Mr. Bliss the plastics industry would have realised long ago that oxo-biodegradable technology gives them a defence against attacks by environmentalists that their product will lie or float around in the environment for decades.
They already have a defence to the allegation that plastic consumes fossil-resources, because it is made from a by-product of refining fuels. The same amount of oil would be extracted even if plastic did not exist.