ISO 5148:2022

Overview

ISO 5148:2022 - Plastics - Determination of specific aerobic biodegradation rate of solid plastic materials and disappearance time (DT50) under mesophilic laboratory test conditions - defines a laboratory procedure to quantify how fast solid, non‑water‑soluble plastic materials mineralize to CO2 under mesophilic aerobic conditions. The standard provides a method to report the specific aerobic biodegradation rate (amount of organic carbon mineralized per unit time per unit surface area) and the disappearance time (DT50) - the time for 50% reduction of initial organic carbon - based on CO2 evolution measurements. It is an “add‑on” to existing ISO/ASTM biodegradation test methods and is intended for controlled laboratory assessment, not direct prediction of environmental fate.

Key topics and requirements

• Scope: Solid, non‑water‑soluble plastics under mesophilic laboratory conditions; CO2 evolution is the sole direct measurement of mineralization.
• Specific surface area (SSA): Determination of SSA of the test sample (film, sheet, powder) is required because biodegradation rate is surface‑area dependent.
• Mineralization rate and specific rate:
  • Calculate the mineralization rate coefficient (k) from CO2 vs time data.
  • Compute the specific aerobic biodegradation rate r as k divided by SSA (r = k / SSA). Units are expressed per time per area (e.g., mmol C · day⁻¹ · cm⁻²).
• DT50 determination: DT50 (disappearance time 50) is derived from the mineralization kinetics; note that DT50 is an underestimation of total dissipation because biomass incorporation is not measured.
• Precondition: Use this method to determine DT50 only when the material is already proven intrinsically biodegradable using suitable standards (e.g., ISO 23517, ISO 22403).
• Limitations:
  • Does not assess ultimate biodegradability or biomass formation.
  • Not applicable for making “marine, soil or freshwater biodegradable” claims; laboratory results are not directly transferable to in‑field environmental compartments.

Applications and users

Who uses ISO 5148:2022:

• Environmental testing laboratories and contract testing organizations measuring biodegradation kinetics.
• R&D and product development teams in plastics manufacturing formulating biodegradable polymers and blends.
• Regulatory bodies and risk assessors estimating persistence after accidental release or littering scenarios.
• Certification bodies and standardization specialists seeking quantitative rate metrics (specific biodegradation rate, DT50) to complement biodegradability classification.

Practical uses:

• Quantifying how changes in formulation or particle size affect biodegradation speed.
• Supporting risk assessments for environmental exposure modeling.
• Comparing materials and reference samples on a surface‑area‑normalized basis.

Related standards

• ISO 23517, ISO 22403 - criteria/test specifications for intrinsic biodegradability under mesophilic conditions.
• ISO 14852, ISO 17556, ISO 22404, ISO 19679, ISO 23977‑1, ASTM D5988, ASTM D6691, ASTM D7991 - biodegradation test methods to which ISO 5148 can be applied as an add‑on.

Keywords: ISO 5148:2022, specific aerobic biodegradation rate, DT50, plastics biodegradation, mesophilic laboratory test, CO2 mineralization, specific surface area (SSA), biodegradation kinetics.