Cellulose biodegradability test standards

Biodegradation preferably determined by ISO 14855 [42], alternatively determined by another suitable international standard such as ISO 14851 [14] or 14852 [9]. Pass level is 90% biodegradation in absolute terms or in relative terms compared to the positive reference, cellulose. Biodegradation is considered to be the sum of mineralisation and biomass formation. The maximum acceptable test duration is six months. Constituents below 1 % must not be evaluated as long as the total of these irrelevant constituents is below 5%. Also natural materials which are chemically not modified, must not be evaluated for biodegradation. 

CO2, a blank compost inoculum without an additional carbon source (polymer sample) is simultaneously tested under the same conditions. The CO2 content of the exhaust air of both vessels is compared. After subtracting the CO2 evolution of the blank inoculum, the CO2 evolution related to the test polymer is monitored and plotted as a biodegradation curve (see Fig. 1). Finally, the activity of the compost inoculum in the controlled composting test is validated using a cellulose reference instead of the polymer. In Fig. 1, the biodegradation curve of Ecoflex is depicted. After 80 days, 90% of the theoretical CO2 evolution is reached. Thus, Ecoflex is ultimately biodegradable according to the ISO standard for compostable polymers (ISO 17088), which requires 90% of the theoretical CO2 evolution within 180 days. 

Based on current standard testing methods and specifications, several renewable resource polymers may be considered biodegradable, the foremost being starch blends, cellulosic derivatives, polyhydroxyalkanoates and poly(lactic acid). Several new and old condensation polymers based on monomers obtained from fossil resources, such as polycaprolactone and the Bionolle series from Japan (Showa High Polymers) based on suucinic acid, are also acceptable by current standards, as are there blends with natural polymers such as starch. 

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