Overview
ISO 23977-1:2020 - Plastics - Determination of the aerobic biodegradation of plastic materials exposed to seawater - Part 1: Method by analysis of evolved carbon dioxide - defines a laboratory respirometric test method to assess the potential aerobic biodegradability of plastics (and other materials) when exposed to natural seawater. The standard follows CO2 evolution from material samples incubated with seawater (with or without a small amount of sediment) to determine the degree and rate of biodegradation under controlled mesophilic conditions (typically 15 °C–25 °C, not exceeding 28 °C). Results are expressed as a percentage of the theoretical amount of evolved CO2 (ThCO2).
Key topics and technical requirements
- Test principle: Monitoring evolved carbon dioxide (CO2) as a proxy for aerobic biodegradation by marine microorganisms (respirometry).
- Test variations:
- Pelagic seawater test - seawater only, simulating offshore, low-current pelagic conditions.
- Suspended sediment seawater test - seawater plus small sediment addition, simulating more dynamic coastal conditions.
- Sample handling and environment: Seawater sampled from coastal areas; incubation in the dark or diffused light; enclosure free of vapours inhibitory to marine microbes; temperature control to ±1 °C.
- Duration and phases: Static aqueous test system run for up to two years with defined lag, biodegradation and plateau phases; maximum level of biodegradation determined from plateau.
- Analytical and ancillary requirements: Use of recognized analytical-grade reagents; measurement and calculation of CO2 evolved vs ThCO2; TOC/DOC considerations and pre-conditioning of inoculum where appropriate.
- Documentation: Test setup, sampling, CO2 measurement data, calculation method, and validity criteria are required in the test report.
Applications and users
ISO 23977-1:2020 is relevant for:
- Manufacturers and product developers assessing marine biodegradability of plastic formulations, biodegradable polymers, coatings and additives.
- Environmental and materials testing laboratories performing standardized biodegradability testing by CO2 evolution (respirometric systems).
- Regulators, certification bodies and ecolabelling schemes that need laboratory data to support environmental claims related to marine degradation.
- Researchers studying plastic–microbe interactions, environmental fate modeling and comparative performance of polymer materials in marine-like conditions.
Practical benefits include consistent, reproducible laboratory data to compare materials’ potential biodegradability in seawater and to inform risk assessment, material selection and product stewardship.
Related standards
ISO 23977-1 forms part of a suite of biodegradation standards. Relevant referenced and related documents include ISO 5667-3 (water sampling), ISO 8245 (TOC/DOC), ISO 10210 (sample preparation), ISO 14852/14851/14855 series and other ISO methods for biodegradation in compost, soil, sediment and aqueous systems. ISO 23977-2 addresses complementary marine test conditions.