ISO 22404:2019

Overview

ISO 22404:2019 specifies a laboratory test method to determine the aerobic biodegradation (degree and rate) of non‑floating plastics exposed to marine sediment. The method simulates the sandy tidal (eulittoral) zone by burying test material in sandy marine sediment kept wet with seawater and quantifying biodegradation by measuring the CO2 evolved. Results are reported as a percentage of the theoretical CO2 (ThCO2) obtainable from total organic carbon (TOC).

Keywords: ISO 22404:2019, plastics biodegradation, marine sediment, aerobic biodegradation, CO2 evolved, eulittoral zone.

Key Topics and Requirements

• Principle: Biodegradation is followed by measuring evolved CO2 and comparing it with ThCO2 to obtain percentage biodegradation; maximum level is taken from the plateau of the biodegradation curve.
• Test medium: Sandy marine sediment sampled from the tidal zone and natural seawater; sediment TOC recommended between 0.1% and 2%.
• Test material: Preferably milled powder (ISO 10210 for sample preparation); recommended mass at least 25 mg per 100 g sediment, typically 40–75 mg/100 g to ensure measurable CO2 while avoiding oxygen limitation.
• Controls and references: Use microcrystalline or ashless cellulose as positive reference; a non‑biodegradable polymer (e.g., polyethylene) as a negative control.
• Apparatus and reagents: Biometer flasks (about 2–4 L), CO2 absorber (e.g., Ba(OH)2 0.025 N or KOH 0.5 N), analytical balance (0.1 mg sensitivity), pH meter, distilled/deionized water.
• Environment: Incubate in the dark at a constant temperature preferably 15–25 °C (not exceeding 28 °C, ±2 °C). A pre‑conditioning phase may be applied to acclimatize inoculum and reduce background organic matter.
• Calculations and reporting: Determine amount of CO2 evolved, express biodegradation as % of ThCO2; justify any deviations from prescribed conditions in the test report.

Applications and Who Uses It

• Plastics manufacturers and product designers assessing marine biodegradability of materials (e.g., fishing gear, marine applications).
• Accredited test laboratories performing biodegradability testing for claims, R&D or regulatory compliance.
• Environmental scientists studying fate of plastics in tidal/sandy sediment environments.
• Regulators, certification bodies and sustainability assessors validating biodegradability performance in marine scenarios.

Related Standards

• ISO 10210 - preparation of samples for biodegradation testing
• ISO 14852 - principle for measuring evolved CO2 (see Annex A references)
• ISO 19679 - related methods for evolved CO2 testing
• ISO 8245 - TOC determination methods

ISO 22404:2019 is a reproducible laboratory simulation to quantify aerobic biodegradation in a specific marine habitat; it supports material evaluation, regulatory assessment, and environmental risk characterization for non‑floating plastics.