ISO 23517:2021

Overview - ISO 23517:2021 (Plastics - Soil biodegradable materials for mulch films)

ISO 23517:2021 specifies requirements and test methods for soil‑biodegradable plastics used in mulch films for agriculture and horticulture. The standard covers both the material used to make mulch films and finished biodegradable mulch films, and it can be applied to other soil‑biodegradable products (for example drip tape, twine, clips, plant pots). Key focus areas are control of constituents, ultimate aerobic biodegradation, and negative effects on terrestrial organisms (ecotoxicity).

Keywords: ISO 23517:2021, biodegradable mulch films, soil biodegradable materials, biodegradation test methods, ecotoxicity, control of constituents, PFAS.

Key technical topics and requirements

• Control of constituents
  • Identification and characterization of materials before testing.
  • Determination of regulated metals and other elements (concentrations shall be less than 50% of national limits for sludges/fertilizers/composts where the product will be marketed).
  • Determination of organic and inorganic fluorine; PFAS should not be intentionally added (precautionary approach).
  • Assessment of other hazardous substances and volatile solids content.
• Ultimate aerobic biodegradation
  • Biodegradation must be demonstrated under controlled laboratory conditions using established methods (e.g., ISO 17556 is cited for measuring mineralization by CO2 evolution or oxygen demand).
  • Evaluation criteria and reporting requirements are specified.
• Negative effects on terrestrial organisms (ecotoxicity)
  • A testing scheme covers acute and chronic effects including:
    • Plant emergence and early growth tests.
    • Earthworm acute toxicity and reproduction tests.
    • Nitrification inhibition tests with soil microorganisms.
  • Soil preparation, test conditions and reporting requirements are included.
• Structure and supporting material
  • Normative and informative annexes provide examples, threshold lists, and detailed test procedures (Annexes A–H).

Practical applications - who uses ISO 23517:2021

• Mulch film manufacturers - product development, formulation control, and claims of soil biodegradability.
• Testing laboratories - standardized methods for biodegradation and ecotoxicity testing and test reporting.
• Certification and conformity bodies - assessing compliance for market authorization or ecolabels.
• Farmers, distributors, and procurement teams - specifying biodegradable mulch films that meet environmental and safety criteria.
• Regulators and policymakers - setting limits and guidance for safe use and disposal in soil environments.
• R&D teams - baseline for developing new biodegradable polymers and additives with minimized environmental impact.

Related standards (selected)

• ISO 17556 - ultimate aerobic biodegradability in soil
• EN 17033 - biodegradable mulch films (related guidance)
• ISO 11268 / ISO 11269 - soil ecotoxicity tests (earthworms, plants)
• OECD Test No. 208 - terrestrial plant test

ISO 23517:2021 is essential for ensuring that biodegradable mulch films are safe for soil ecosystems, compliant with constituent controls, and proven to biodegrade under defined conditions.