Oxo-Biodegradable Plastics

OXO-BIODEGRADABLE PLASTICS ASSOCIATION
20 Hanover Square, London W1S 1JY, England
+44203-1786070 http://www.biodeg.org/

© Oxo-biodegradable Plastics Association 2009
ISO 17088, ASTM D6400, ASTM D6868, and Australian 4736-2006). This is not correct.
EBP knows that while these standards are appropriate for composting they are not suitable for products designed to biodegrade in the environment. Indeed EN13432 itself says that is not appropriate for plastic waste which may end up in the environment through uncontrolled means.

Composting is not the same as biodegradation in the environment, as it is an artificial process operated according to a much shorter timescale than the processes of nature. I am a member of the relevant European standards committees, and have found that the “compostable” plastics industry has consistently lobbied to prevent the amendment of EN13432 to include tests suitable for plastics which are designed to biodegrade in the environment - because they have a commercial interest against a European Standard with tests appropriate to oxo-bio.

Consistent with this approach, EBP have disputed the validity of statements that oxobio products will biodegrade - on the ground that this could not be verified according to a recognised international standard. This is also incorrect. Oxo-biodegradable plastic products are normally tested according to ASTM D6954-04 “Standard Guide for Exposing and Testing Plastics that Degrade in the Environment by a Combination of Oxidation and Biodegradation.” There are two types of Standards – Standard Guides and Standard Specifications ASTM 6954 is an acknowledged and respected Standard Guide for performing laboratory tests on oxobiodegradable plastic. It has been developed and published by ASTM International –the American standards organisation – and it is impossible to say that it is not a recognised standard. The second Tier of ASTM D6954-04 is directed specifically to proving biodegradation.
Para 4.1 provides that “The guide may be used to compare and relatively rank, the rate and degree of thermal oxidative degradation of a plastic material to a molecular weight range that can be established as biodegradable in a chosen environment. Subsequently, the biodegradation of these degraded polymers in diverse environments such as soil, compost, landfill, and water may be compared and ranked using standard biometric test methods and measuring carbon dioxide evolution.”

The tests performed according to ASTM D6954-04 tell industry and consumers what they need to know – namely whether the plastic is (a) degradable (b) biodegradable and (c) non eco-toxic. It is not necessary to refer to a Standard Specification unless it is desired to use the material for a particular purpose such as composting. Note 3 to ASTM D6954-04 provides that if composting is the designated disposal route, ASTM D6400 should be used. ASTM D6954-04 not only provides detailed test methods but it also provides pass/fail criteria. For example, para. 6.6.1 requires that 60 % of the organic carbon must be converted to carbon dioxide. Therefore if the material does not achieve 60% mineralisation the test cannot be completed and the material cannot be certified. Having achieved 60% mineralisation, the Note to para. 6.6.1 provides that testing may be continued to better determine the length of time the materials will take to biodegrade. It is not however necessary to continue the test until 100% has been achieved, because it is possible, by applying the Arrhenius relationship to the test results, to predict the time at which complete biodegradation is likely to occur. It is in fact difficult to keep microorganisms working for years in closed respirometric cells. It is known that many soil microorganisms are unable to be cultured in a © Oxo-biodegradable Plastics Association 2009 laboratory and so it is already an artificial approximation to take microorganisms from the environment and observe them in the laboratory. They live in consortia with many other organisms, especially fungi and bacteria, under natural aeration and rainwater flow, changing mass and energy.

There is no requirement in ASTM D6954-04 for the plastic to be converted to C02 in 180 days because, while timescale is critical in an industrial composting process, it is not critical for biodegradation in the environment. Timescale in the natural environment depends on the amount of heat, light, and stress to which the material is subjected. Nature’s wastes such as leaves twigs and straw may take ten years or more to biodegrade, but oxo-bio plastics will biodegrade more quickly than that, and much more quickly than ordinary plastic.

In oxo-biodegradable plastics there are anti-oxidants mixed with the resins, and they must be consumed before degradation starts. People sometimes do not understand this sequence and conclude that the additives do not work. An induction period must elapse before degradation starts, due to the presence of the anti-oxidants.

The requirement in EN13432 and similar standards for 90% conversion to CO2 gas within 180 days is not useful even for composting, because it contributes to climate change instead of contributing to the fertility of the soil. “Compostable” plastic, 90% of which has been converted to CO2 gas, is virtually useless in compost. Nature's lignocellulosic wastes do not behave in this way. Composting of organic waste makes sense, but “compostable” plastic does not. It is up to 400% more expensive than ordinary plastic; it is thicker and heavier and requires more trucks to transport it. If buried in landfill, compostable plastic can emit methane, which is a greenhouse gas 23 times more destructive than CO2.

In addition, starch-based plastic is unlikely to be strong enough for weight-bearing packaging unless mixed with oil-based plastic. It is not even “renewable” because large amounts of non-renewable hydrocarbons are likely to be burned by the machines used to produce and polymerise the crop. It makes little sense at a time when there is concern about food-security, to use scarce land and water to grow crops to make plastic bags.
Tests on oxo-biodegradable plastic products are usually conducted according to the test methods prescribed by ASTM D6954-04 by independent laboratories such as Smithers-RAPRA (US/UK), Pyxis (UK), Applus (Spain), etc. I have seen many laboratory test reports and am satisfied that if properly manufactured, oxo-bio products will totally biodegrade in the presence of oxygen.

Conditions in the laboratory are designed to simulate so far as possible conditions in the real world, but have to be accelerated in order that tests may be done in a reasonable time. Pre-treatment does not invalidate the results as extrapolated to real-world conditions. There is no evidence that degradable plastics (whether oxo or hydro) have encouraged littering. Oxo-bio plastic can be recycled in the same way as ordinary plastic (see www.biodeg.org/recycling.htm), and does not need special collection points. By contrast, “compostable” plastic cannot be recycled with ordinary plastic, and will ruin

http://www.biodeg.org/files/uploaded/Oxo%20vs%20Hydro-biodegradable.pdf See http://www.biodeg.org/files/uploaded/Hydrobiodegradable20Plastic%20Production%20Process.pdf
© Oxo-biodegradable Plastics Association 2009 the recycling process if it gets into the waste stream. Recyclers should therefore be very worried about bio-based plastics – but not about oxo-bio. EBP also says “An environmental claim that is vague or non-specific or which broadly implies that a product is environmentally beneficial or environmentally benign shall not be used.” Reputable companies in the oxo-bio sector do not make such claims. EBP quotes the definition of “degradable” according to the ISO 14021 standard as:

“A characteristic of a product or packaging that, with respect to specific conditions, allows it to break down to a specific extent within a given time". Oxo-bio products possess this characteristic. Oxo-degradation has been defined by CEN/TR15351-06 (published by the European Standards Organisation) as “degradation identified as resulting from oxidative cleavage of macromolecules.” And oxo-biodegradation as “degradation identified as resulting from oxidative and cell-mediated phenomena, either simultaneously or successively.” This is exactly what oxo-bio plastic does.”

Landfill

1. The main benefit of oxo-biodegradability is not for plastic waste which is sent to landfill, but for plastic waste which gets out into the environment, where it will accumulate for many decades on land and in the oceans.

2. Some plastic waste will of course be collected and sent to landfill, but oxo-biodegradable1 plastic waste should not be sent to landfill at all. After collection it should be recycled2, or incinerated for energy-recovery. However, the recycling option for a normal plastic waste stream is not practicable for hydro-biodegradable3 plastics, which have to be treated separately and at high cost. Also, hydro-biodegradable plastics have a lower calorific value when incinerated.

3. The aims of the EU Landfill Directive 1999/31/EC (as amended4) are stated in the following recitals at the beginning of the document:

4. (3) the prevention, recycling and recovery of waste should be encouraged as should the use of recovered materials and energy so as to safeguard natural resources and obviate wasteful use of land.

5. Oxo-biodegradable plastics, like their traditional counterparts, can be re-used during their useful life and/or recycled and incinerated with high energy-recovery.

6. The most valuable asset for a landfill-operator is space. Plastic bags are extremely compact, and plastic grocery bags and all plastic retail bags together take up less than 1% of space in landfills - a tiny amount. However, conventional plastic bags take up more space than necessary because they trap air, they do not disintegrate rapidly, and thus inhibit the decomposition of their contents in the landfill.

7. Most commercially available oxo-biodegradable plastics will disintegrate in the surface layers of a landfill so long as oxygen is present. Oxygen levels will vary according to factors such as how loose or compressed the waste was when it was buried, how much u/v light is available, and how much further waste material or earth is added to the landfill over what period of time. A fragmented oxo-biodegradable bag will settle more easily than an ordinary plastic bag with trapped contents, and will occupy less space. Test reports for individual products will measure the ability of the material to degrade within a reasonable period.

8. (4) further consideration should be given to the issues of incineration of municipal and non-hazardous waste, composting, biomethanisation, and the processing of dredging sludges;

9. Oxo-biodegradable plastics can be incinerated with high energy recovery.

(12) protective measures [should] be taken against any threat to the environment in the short as well as in the long-term perspective, and more especially against the pollution of groundwater by leachate infiltration into the soil.

10. Oxo-biodegradable plastics do not cause harmful leachate infiltration, and commercial oxo-biodegradable additives approved by the OPA have been certified non eco-toxic.

11. (16) measures should be taken to reduce the production of methane gas from landfills, inter alia, in order to reduce global warming, through the reduction of the landfill of biodegradable waste and the requirements to introduce landfill gas control;

12. Hydro-biodegradable ("compostable") plastics will biodegrade and emit CO2 at a high rate in the surface layers of a landfill if there is enough microbial activity, and in the depths of a landfill, in the absence of air, they generate methane, which is a powerful greenhouse gas. Methane is also highly combustible and is a cause of explosions.

13. Decomposition deep in a landfill is not therefore desirable. Whilst oxo-biodegradable plastics fragment and biodegrade in the upper layers of the landfill (see above) and emit CO2 at a low rate there in the presence of oxygen, they are completely inert deeper in the landfill in the absence of oxygen.

14. Article 2 (m) of the Landfill Directive defines "biodegradable waste" as "any waste that is capable of undergoing anaerobic or aerobic decomposition, such as food and garden waste and paper and cardboard." However, the reason stated in recital 16 above for reducing the landfill of biodegradable waste does not apply to oxo-biodegradable plastics because, as indicated in para. 13 above, they are completely inert in the landfill in anaerobic conditions - unlike food and garden waste, paper, cardboard, and hydro-biodegradable plastics, which all emit methane.

15. It is an important factor that an oxo-biodegradable plastic bag is much lighter than a paper, cotton, or jute bag, and is even lighter than a hydro-biodegradable bag5. As municipalities and waste-management companies have to pay to put trash in landfills, and as charges are based on weight, it costs much more to put paper, cotton, jute or hydro-biodegradable plastic bags in a landfill than ordinary or oxo-biodegradable plastic bags.

16. The Report on "The impacts of degradable plastic bags in Australia" prepared by ExcelPlas/ Nolan-ITU on 11 September 2003 for the Australian Government noted at 7.3 that: "[hydro] degradable polymers with starch content have higher impacts upon greenhouse due to methane emissions during landfill degradation and N2O emissions from fertilizing crops." Methane is 23 times more potent for global warming6 than CO2.
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1. made from a by-product of oil in the same way as ordinary plastic, but with a pro-degradant additive which breaks the molecular chains and causes the material to degrade then biodegrade.
2. See OPA Position Paper on Recycling
3. Usually made from corn starch or other agricultural derivatives
4. 1882 of 2003
5. depending on the type of plastic, hydro-biodegradables are between 40% and 150% thicker and heavier than oxo-biodegradables for the same strength.
6. IPCC (Inter-Governmental Panel on Climate Change) Report page 47 www.ipcc.ch/pub/wg1TARtechsum.pdf
© Oxo-biodegradable Plastics Association 2009
Scientific Advisory Board: Chairman - Professor Gerald Scott (UK), Professor Jaques Lemaire1 (France), Professor Ignacy Jakubowicz2 (Sweden), Professor Telmo Ojeda (Brazil)3, Dr. Prakash Hebbar (USA)4

OPA RESPONDS TO ATTACK FROM HYDRO-BIO INDUSTRY
18th August 2009
On 22 July 2009 ”European Bio-plastics” (a Trade Association for the hydrobiodegradable or “compostable” plastics industry) published an extraordinary attack on the oxo-biodegradable plastics industry. The Chairman of the OPA’s Scientific Advisory Board, Professor Gerald Scott6 DSc, FRSC, C.Chem, FIMMM, has responded as follows:

“Oxo-bio plastic is intended to harmlessly degrade then biodegrade if it gets into the open environment. All plastics will eventually become embrittled, and will fragment and be bioassimilated, and the only difference made by oxo-biodegradable technology is that the process is accelerated. For millions of years nature has had enzymes known as oxygenases, which will degrade hydrocarbons, whether oxidized or not. The problem with the modern (xenobiotic) plastic molecules is that they are too long (increased by lack of polarity, crystallinity and chain rigidity). The pro-degradant additives which cause accelerated degradation are usually compunds of cobalt, iron, nickel or manganese and are added to conventional plastics at the time of manufacture. These reduce the molecular weight of the material over a pre-determined period – allowing them to be ultimately consumed by bacteria and fungi. The additives have themselves been tested and proved not to be eco-toxic. They do not contain “heavy metals.”

About 20 billion oxo-biodegradable plastic products were made in the last year. Reputable companies in the oxo-bio sector do not make “self-declared” claims – their products are subjected to independent testing, based on well-established science. The issues raised by EBP are not about clarification – they seem to me to be an attempt to confuse the public by suggesting that a plastic product is not “biodegradable” unless it can comply with EN13432 (and similar standards such as:

1. Professor of Chemistry at Ecole Nationale Supérieure de Chimie de Clermont-Ferrand and Université Blaise Pascal Clermont-Ferrand).
2. Associate Professor of Physical Chemistry, University of Gothenburg
3. Instituto Federal de Educação Ciência e Tecnologia Sul-Rio-Grandense, Brasil
4. Ph. D. Australian National University, Molecular Microbial Ecology; M. Sc. Medical Microbiology, and B. Sc., Botany, Zoology and Chemistry, Mysore University, India.
5. They have another trade association in the US called the “Biodegradable Products Institute” (BPI) which regularly makes similar allegations.
6 Professor Emeritus in Chemistry and Polymer Science of Aston University, UK; Chairman of the British Standards Institute Committee on Biodegradability of Plastics.
7 See eg Degradable Polymers: Principles and Applications, Kluwer, 2002, Chapter 3