ISO 23517:2021 Plastics – Soil biodegradable materials for mulch films for use in agriculture and horticulture – Requirements and test methods regarding biodegradation, ecotoxicity and control of constituents.
5.2 Ultimate aerobic biodegradation
5.2.1 Test method and evaluation criteria
The ultimate aerobic biodegradability shall be determined br the whole material or [or each organic constituent.
Test samples shall not be subjected to conditions or procedures, such as a pre-treatment by heat and or an exposure to radiation exposure, designed to accelerate biodegradation prior to testing according to Iso 17556.
The material is considered to have demonstrated a satisfactory rate and level of biodegradation in soil if, when tested in accordance with ISO 17556, it achieves a minimum biodegradation percentage as specified hereunder:
a) 90 % of the organic carbon shall have been converted to CO2 by the end of the test period (relative to a reference material). Roth the reference material and the test item shall be tested for the same length of time and the results compared at the same point in time;
b) as an alternative, 90 % (in absolute terms) of the organic carbon shall have been converted to carbon dioxide by the end of the test period.
If the level of biodegradation exceeds 90 % (relative to a reference material or in absolute terms), then the biodegradation test can be terminated. However, the test period shall be no longer than 2 years.
The biodegradation test shall be performed at a temperature constant to within ±2 °C in the range between 20 °C and 28 °C, preferably 25 °C.
use, as reference material, a well-defined biodegradable polymer (microcrystalline-cellulose powder or ashless cellulose filters. If possible, the physical form and size of the reference material should be comparable to that of the test material.
The validity criteria as stated in ISO 17556 shall be fulfilled.
NOTE Biodegradability Is assessed by measuring the mineralization level, i.e. the conversion of the organic carbon of a product or a material into CO2 with the consumption of 02 under aerobic conditions, or into CO2 and CH4 under anaerobic conditions. During biodegradation, part of the organic carbon is also assimilated as biomass. This biomass yield typically ranges from 10 % to 40 %, depending on the substrate. As a consequence, the mineralization level rarely reaches 100 % also when the biodegradation is 100 %, because of biomass formation. Standard test methods for the accurate determination of product’s or material’s carbon assimilated in biomass during biodegradation are not available yet.ISO 23517 pdf download.