ISO 16929:2021

Overview

ISO 16929:2021 specifies a pilot-scale, aerobic composting test method to determine the degree of disintegration of plastic materials under defined composting conditions. It is part of the broader evaluation scheme for industrial compostability (see ISO 17088) and is used to assess how a material breaks down during a controlled composting process and whether it affects the composting process or final compost quality. This method is intentionally not a test for aerobic biodegradability.

Key topics and technical requirements

• Test scale and environment: Pilot-scale composting bins or sample nets buried in bins; bins must allow natural self-heating with adequate aeration. Minimum bin volume: 35 L.
• Test material preparation: Use the product in its intended form (films 10×10 cm; other products 5×5 cm). Optional fine powder/granulate (<500 µm) is used when producing compost for ecotoxicity tests.
• Carrier matrix and biowaste: Fresh or representative artificial biowaste shredded to <50 mm. Bulking agent (wood chips/bark) typically added 100–600 g/kg.
• Biowaste quality controls: target C:N ratio 20–30, moisture >50%, volatile solids >50%, pH >5. Minimum wet biowaste per series: 15 kg.
• Monitoring and control: Regular measurement of temperature, pH, moisture, oxygen and visual observation; turning/mixing according to the procedure; tests typically run until fully stabilized compost (commonly ~12 weeks).
• Assessment of disintegration: After composting, material and compost are sieved (screens of 2 mm and 10 mm). Disintegration is quantified by comparing retained test material mass to starting amount (based on total dry solids).
• Apparatus: temperature sensors, pH meter, oxygen measurement, sieves (ISO 3310-2 compatible), sample nets (1 mm mesh).
• Safety: compost can harbor pathogens-follow protective and hygiene measures.

Practical applications and users

ISO 16929 is used by:

• Laboratories and testing facilities performing compostability and disintegration testing.
• Manufacturers and product developers of biodegradable/compostable plastics validating product performance in industrial composting.
• Certification bodies assessing claims of industrial compostability in line with ISO 17088.
• Composting facility operators and waste managers evaluating how materials behave in pilot-scale systems.
• Regulators and procurement teams setting standards for compostable packaging and materials.

This standard helps stakeholders demonstrate that materials physically disintegrate under controlled composting conditions and supports downstream tests (e.g., ecotoxicity, chemical analysis) of the resulting compost.

Related standards

• ISO 17088 - Specifications for industrial compostability certification.
• ISO 14851, ISO 14852, ISO 14855-1/2 - Methods for determining aerobic biodegradability.
• ISO 3310-2 - Test sieves.