- OXO-BIO plastic can be tested according to:
- American Standard ASTM D6954-04 – “Standard Guide for Plastics that Degrade in the Environment by a Combination of Oxidation and Biodegradation”
- British Standard 8472
- Swedish Standard SPCR 141
- UAE Standard 5009:2009
These Standards measure:
- Tier 1 – Degradability
- Tier 2 - Biodegradability
- Tier 3 - Eco-toxicity
They are not Specifications.
- It is not possible to provide a specific timescale in a general standard for oxo-biodegradable plastic, (as distinct from a standard for industrial composting) because the conditions found in industrial composting are specific and the conditions found in the open environment are variable.
- Also, the time taken for oxo-biodegradable plastic to commence and complete the processes of degradation and biodegradation can be varied.
OECD 207 and 208(Eco-toxicity tests)
- EN 13432 (except for eco-toxicity test)
- ASTM D6400 (except for eco-toxicity test) D5338, 6002;
- AUSTRALIAN 4736
- ISO 14855 and 17088
These are all standards for biodegradation in the special conditions found in industrial composting. They require short timescales and rapid CO2 emissions.
The standards for degradation in anaerobic conditions are also irrelevant, because oxo-biodegradation requires oxygen.
Biodegradation in the environment is NOT the same thing as composting.
Composting is an artificial process operated to a much shorter timescale than the processes of nature. Standards (such as ASTM D6400, D6868; EN13432, and Australian Standard 4736 see below) designed for compostable plastic are not therefore appropriate for plastic which is designed to self-destruct if it gets into the environment.
Oxo-biodegradable plastic products are bioassimilated in the same way as nature’s wastes after their molecular weight has reduced to 40,000 Daltons or less. They 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” British Standard 8472, Swedish Standard SPCR 141 or UAE Standard 5009:2009.
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 oxo-biodegradable plastic. It has been developed and published by ASTM International – the American standards organisation. 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 for which a specification is available. 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.
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. It is in fact difficult to keep micro-organisms working for years in closed respirometric cells. It is known that some soil micro-organisms are unable to be cultured in a laboratory and so it is already an artificial approximation to take micro-organisms 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, which have been included to give the product a pre-determined service-life.
There is a French Standard XP_T_54-980__F for oxo-biodegradable plastics in agriculture.
Tests on oxo-biodegradable plastic products are usually conducted according to the prescribed test methods by independent laboratories such as Smithers-RAPRA (US/UK), Pyxis (UK), Applus (Spain), OWS (Belgium) SP Technical Research Institute (Sweden) etc.
Packaging made from oxo-biodegradable plastic complies with paras. 1, 2 3(a), (b) and (d) of Annex II of the European Parliament and Council Directive 94/62/EC (as amended) on Packaging and Packaging Waste. This Annex specifies the essential requirements for the composition and the reusable and recoverable, including recyclable, nature of packaging.
Oxo-biodegradable plastic satisfies para. 3(a) because it can be recycled. It satisfies para. 3(b) because it can be incinerated. It satisfies para. 3(d) because it is capable of undergoing physical, chemical, thermal or biological decomposition such that most of the finished compost ultimately decomposes into carbon dioxide, biomass and water. It can even satisfy para. 3(c) if composted in an “in-vessel” process.
STANDARDS FOR COMPOSTABLE PLASTICS
EN13432, ASTM D6400, D6868, ISO 14855, 17088 and Australian Standard 4736-06 are designed for compostable plastic and are NOT appropriate for plastic which is designed to degrade then biodegrade if it gets into the open environment. Composting is an artificial process operated according to a much shorter timescale than the processes of nature, and EN13432 itself says that is not appropriate for waste which may end up in the environment through uncontrolled means.
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 improvement of the soil. “Compostable” plastic, 90% of which has been converted to CO2 gas, is therefore virtually useless in compost. Nature's lignocellulosic wastes, such as leaves and straw do not behave in this way.
EN 13432, ASTM D6400 and the other standards for compostability are not appropriate for testing oxo-biodegradable plastics are based on measuring the emission of carbon dioxide during degradation over a short timescale. Hydro-biodegradable plastic is compliant precisely because it emits CO2 (a greenhouse gas) at a high rate. Oxo-biodegradable plastics do not mineralise rapidly in the artificial biometric test in EN 13432 and ASTM D6400 but they do biodegrade in soil after application of the compost to the soil.
It is worth noting that EN 13432, does not require that plastics biodegrade during and after composting within any particular time-scale. The Note to paragraph 5 of EN 13432 says: "It is important to recognise that it is not necessary that biodegradation of packaging material or packaging be fully completed by the end of biological treatment in technical plants but that it can subsequently be completed during the use of the compost produced." This is what oxo-biodegradable plastic does, and it is consistent with the behaviour of nature's waste products such as twigs, leaves and straw, which take years to biodegrade fully. Oxo-biodegradable plastics will biodegrade much more quickly than these natural materials.
If a leaf were subjected to the CO2 emission tests included in EN13432 it would not pass! Leaves are not of course required to pass any such test, but it shows how artificial the laboratory test is.
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 as amended), and should not really be part of a standard for composting. Nature’s lignocellulosic wastes do not behave in this way, and if they did they would have little value as soil improvers and fertilisers, having lost most of their carbon.
The EU Directive does NOT require that when a packaging product is marketed as “degradable” or “compostable” conformity with the Directive must be assessed by reference to EN13432. The Directive provides that conformity with its essential requirements may be presumed if EN 13432 is complied with, but it does not exclude proof of conformity by other evidence. Indeed Annex Z of EN13432 itself says that it provides only one means of conforming with the essential requirements.
Oxo-biodegradable plastic if correctly formulated and thermally tested can be composted in industrial processes and does not affect the quality of the compost according to the mandatory French norm on organic waste NFU 44051.