There are currently several leading international organizations that have established standards and testing methods for compostability, namely:
- American Society for Testing and Materials ASTM-6400-04
- European Committee for Standardization (CEN) EN-13432
- International Standards Organization (ISO) ISO14855 (only for biodegradation)
The ASTM, CEN and DIN standards specify criteria for biodegradation, disintegration and eco-toxicity for a plastic to be called compostable.
1. Biodegradability is determined by measuring the amount of CO2 produced over a certain time period by the biodegrading plastic. The standards require 60% conversion of carbon into carbon dioxide within 180 days for resins made from single polymer, and 90% conversion of carbon into carbon dioxide for co-polymers or polymer mixes.
2. Disintegration is measured by sieving the material to determine the biodegraded particulate size. Less than 10% should remain on a 2mm screen within 120 days.
Eco-toxicity is measured by having concentrations of heavy metals below the limits set by the standards and by testing plant growth by mixing the compost with soil in different concentrations and comparing it with controlled compost.