Standards For Biodegradation of Plastic
Oxo-biodegradation is defined by CEN/TR 15351:2006 as " degradation resulting from oxidative and cell-mediated phenomena, either simultaneously or successively"
Oxo-biodegradable plastic is tested to biodegrade in the outdoor environment leaving no harmful residues, according to the following standards:
ASTM D6954 (United States)
This standard provides methods to determine oxo-biodegradability by a three-tier testing regime set out as follows:
Tier 1: Primary Stage. Abiotic degradation
This section measures the loss in strength and reduction of molecular-weight by thermal and/or photo-oxidation processes.
Tier 2: Secondary Stage. (Biodegradability)
When, after exposure to the tests in Stage One, the material has reached an elongation-at-break of 5% of less the average molecular weight is measured. When molecular weight loss had reduced to 10,000 Daltons or less the material is tested for biodegradation by CO2 evolution (or by ATP/ADT testing according to AFNOR AC T51-808).
Tier 3: Eco-Toxicity
The residue is tested for exo-toxicity by means of OECD 203 (Fish) 207 (Earthworms) and 208 (Terrestrial Plants).
BS 8472 (UK)
This standard (similar to ASTM D6954 above) provides methods for determining:
A) Degradation by oxidation (abiotic tests)
B) Biodegradation (biotic test in soil) and
C) Eco-toxicity (OECD tests)
AFNOR AC T51-808 (France)
A new method for determining biodegradation. It was developed in France by CNEP (Centre National d'Evaluation de Photoprotection) at Blaise Pascal University and is included in this Accord.
The CNEP approach is to pre-oxidise the film by a combination of light and then heat so that its molecular weight is reduced below 10,000 g/mole. The degradation process is monitored by FT-IR spectroscopy and the molecular weight confirmed by Gel Permeation Chromotography. The material after the oxidation stage is expected to be biodegradable.
Then the biodegradation of the smaple is measured according to the ATP/ADT ratio.
ATP (Adenosine Triphosphate) and ADP (Adenosine Diphosphate) are substances produced in the cell biochemical pathway of bacteria. As the cell metabolises it cycles between ADP and ATP so, by measuring the ratio, the biochemical activity of the cells living on the plastic as their sole food-source (whether they are viable, multiplying, etc.) can be observed. Typically the ratio will be 0.2-6.
For copies of the standards, please see links below:
ASTM
http://www.astm.org/search/fullsite-search.html?query=Standards&
AFNOR:
http://www.iso.org/iso/about/iso members/iso member body.htm?member id=1738
British Standards
http://shop.bsigroup.com/SearchResults/?g=Plastics
The following standards are not relevant, as they relate to biodegradation in the special conditions found in industrial composting: EN13432; ASTM; ISO 14855 and 17088.
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