Carbon dioxide compost standards

Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions - Method by analysis of evolved carbon dioxide, ISO Standard 14855, International Organization for Standardization, Geneva, Switzerland, 2005. 

The original film as supplied required approximately 600 days to reach 60% biodegradation in compost as measured by carbon dioxide evolution. This is well beyond the 180 days specified by ASTM Standard D6400 as acceptable for disposal by composting. However, the time is comparable with the rate of biodegradation of an oak leaf (OWS information) in a compost facility which suggests that specifications need to be revisited by standard organizations. 

The set-up is the same in these two standard tests and is very similar to that of liquid tests (Fig. lb). The samples are intensively composted in a static reactor over a 45-day period. A continuous air flow free of C02 is provided to the test vessels. The carbon dioxide produced in the test and blank vessels is either continuously monitored (by gas chromatography or infrared) or measured at regular intervals (titration). The bio degradability of the sample is also reported as a percentage of the bio degradability of a reference positive substance (e.g., cellulose for the thin-layer chromatography). The tests are valid if more than 70 % of the positive reference is degraded. 

The ISO standards 14852 and 14855 (88,89) have been recently revised in the form of ISO 14855-1 2012 (90). This standards describes a method for the determination of the ultimate aerobic biodegradability of organic plastics materials imder controlled composting conditions by the measurement of carbon dioxide evolved and the degree of disintegration of the plastic at the end of the test. 

According to these standard norms, a compostable plastic demonstrates a satisfactory rate of biodegradation when achieving 90% of the organic carbon in the whole item or for each organic constituent, which is present in the material at a concentration of more than 1 wt% (by diy mass), and is converted to carbon dioxide by the end of the test period when compared to a positive control. 

ASTM D6400. In 1999 ASTM announced its Standard Specification for Compostable Plastics (D6400-99). The standard establishes criteria to be met before a product can be labeled compostable. Briefly a product must, at minimum, satisfy ASTM tests showing conversion to carbon dioxide at 60% for a homopolymer or a statistical random copolymer and 90% for other types of copolymers and blends in 180 days or less, and leave no more than 10% of the original weight on a 2-mm screen. If carbon-14 tests are used a test period of 365 days is allowable. Environmental toxicity issues are also addressed, including limits for heavy metals. The ASTM standard has coimterparts in German (DIN 54900), European (EN 13432), and international (ISO 14855) documents. 

S.3.2.3 Biodegradation Test Method Standard iSO 14855-2 (EN 14046) Packaging. Evaiuation of the Uitimate Aerobic Biodegradabiiity and Disintegration of Packaging Materiais under Controiied Composting Conditions. Method by Anaiysis of Reieased Carbon Dioxide... 

ISO 14855-1 2007(E), Determination of the Ultimate Aerobic Biodegradability of Plastic Materials under Controlled Composting Conditions - Method by Analysis of Evolved Carbon Dioxide - Part 1 General Method, International Organization for Standardization, Geneve, Switzerland, 2007. 

DIN EN 14046 describes a test method to determine the total aerobic biodegradability of packaging materials (based on organic components). The test method is based on controlled composting conditions and analyzes the amount of carbon dioxide evolved by the end of the test. Test procedures (e.g., sample preparation, calculations) are detailed in the standard. 

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