ISO 23977-2:2020

Overview

ISO 23977-2:2020 - Plastics: Determination of the aerobic biodegradation of plastic materials exposed to seawater (Part 2) specifies a laboratory test method that measures the aerobic biodegradability of plastics (and other materials) in seawater by monitoring oxygen demand in a closed respirometer. The method provides an indication of the potential biodegradability of a material when exposed to coastal seawater microbial communities under controlled laboratory (mesophilic) conditions.

Key topics and technical requirements

• Test principle: Biodegradation is followed by measuring biochemical oxygen demand (BOD) in a closed respirometric system; evolved CO2 is absorbed and oxygen consumption is recorded. Results are expressed as % biodegradation relative to theoretical oxygen demand (ThOD).
• Two test variants:
  • Pelagic seawater test - seawater only (simulates offshore/pelagic conditions).
  • Suspended sediment seawater test - seawater with small amounts of sediment (simulates coastal areas with currents/tides).
• Test environment: Incubation under dark or diffused light at mesophilic temperatures (preferably 15–25 °C, not exceeding 28 °C), controlled to ±1 °C.
• Duration: Tests can run for extended periods (up to two years) to capture lag, biodegradation and plateau phases and determine the maximum level of biodegradation.
• Analytical considerations: Calculation and interpretation compare measured BOD to ThOD; nitrification influences must be considered. Pre-conditioning, test setup, reference materials, and visual inspection are specified.
• Quality and reporting: Sections cover validity of results, required test report content, and apparatus examples (e.g., respirometric systems). Normative references include ISO standards for sampling, TOC/DOC, pH, and sample preparation.

Applications

• Assessing marine biodegradability of plastics, polymers and other materials intended for use in or likely to reach marine environments.
• Supporting eco-design, material selection, environmental risk assessments, and claims about marine-degradable products.
• Generating standardized laboratory data for regulators, product developers, certification bodies and environmental testing laboratories.

Who should use this standard

• Materials scientists and R&D teams developing biodegradable plastics.
• Environmental testing laboratories and contract testing services.
• Product compliance, regulatory affairs, and sustainability teams in plastics and packaging industries.
• Certification bodies and academic researchers studying marine biodegradation.

Related standards

• ISO 23977-1 (other marine biodegradation tests)
• ISO 14852, ISO 14853, ISO 14855-1/2, ISO 17556, ISO 19679, ISO 22404, ISO 18830, ISO 5667-3, ISO 8245, ISO 10210 (sampling, TOC/DOC, sample prep and complementary biodegradation methods)

Keywords: ISO 23977-2:2020, biodegradation, seawater, closed respirometer, BOD, ThOD, marine biodegradability, plastics testing.