There are currently several leading international organizations that have established standards and testing methods for compostability, namely:

The ASTM, CEN and DIN standards specify criteria for biodegradation, disintegration and eco-toxicity for a plastic to be called compostable.

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.