Standards Development

Scope

This proposed deliverable specifies a method to determine the specific biodegradation rate of solid, non-water soluble plastic materials.

The specific biodegradation rate (which, strictly speaking, is a specific mineralization rate, implying the assessment of the conversion of organic carbon into CO2 but neglecting biomass formation) is expressed as amount of carbon mineralized into CO2, per unit time, per unit area. It is generally measured as millimoles C × day^(-1) × cm^(-2).

The method described in this document can be considered as an additional extension ("add-on") of the existing ISO standard test methods for measuring biodegradation of plastic materials to make it possible the determination of the specific biodegradation rate and the 50% Disappearance Time (DT50).

The method described in this proposal does not provide information on the ultimate biodegradability of the tested samples. Biodegradability criteria for plastic materials are provided for example by ISO/CD 23517-1 and ISO/DIS 22403. This proposal only considers the evolution of CO2 as direct measurement of mineralization of the tested sample.

Purpose

There is an increasing interest in determining the biodegradation rate and related parameters (such as the Disappearance Time 50, i.e. the time within which the initial concentration of the test substance is reduced by 50%) in order to assess the risk in the case of accidental or deliberate leakage of biodegradable plastics into the environment. Degradation of organic substances in the environment influences exposure and, hence, it is a key parameter for estimating the risk of long-term adverse effects on biota. This proposal enables to determine the specific biodegradation rate i.e. the amount of carbon mineralized per unit time per unit surface area.