ISO 14851:2019

Overview

ISO 14851:2019 specifies a laboratory method for determining the ultimate aerobic biodegradability of plastic materials in an aqueous medium by measuring oxygen demand in a closed respirometer. The test exposes the plastic (as the sole carbon source) to an activated sludge inoculum under controlled conditions to quantify biodegradation (biological mineralization to CO2, water and biomass). The method assesses potential biodegradability and gives an indication of behavior in natural aquatic environments; it is not intended to represent optimum degradation conditions.

Keywords: ISO 14851:2019, aerobic biodegradability, closed respirometer, oxygen demand, activated sludge, biodegradation test.

Key topics and requirements

• Test principle: Measurement of biochemical oxygen demand (BOD) in a closed manometric respirometer to follow oxygen uptake over time.
• Applicable materials: Natural and synthetic polymers, copolymers, mixtures, plastics with additives (plasticizers, colorants), and water‑soluble polymers - provided they do not inhibit the inoculum.
• Inoculum choices: Unadapted activated sludge to simulate natural aquatic biodegradation; mixed or pre‑exposed inocula to investigate potential biodegradability.
• Test conditions: Aqueous inorganic test medium, test-material concentrations typically in the range provided in the standard, controlled temperature and aeration history as specified; procedures for preparing inoculum and controls are defined.
• Data handling: Calculation of degree of biodegradation (often relative to theoretical oxygen demand, ThOD), optional carbon balance to improve assessment (Annex E), and corrections for interferences such as nitrification (Annex B).
• Validity and reporting: Criteria for valid runs, use of blanks and reference materials, and required information for test reports (test conditions, inoculum, results, interpretation).
• Safety note: Activated sludge may contain pathogens - appropriate lab precautions required.

Applications and users

ISO 14851:2019 is used to:

• Verify biodegradability claims for plastics and polymer formulations intended for aquatic exposure.
• Compare formulations, additives or water‑soluble polymers for environmental screening.
• Support product development, regulatory submissions, environmental risk assessments, and ecolabel or compliance testing. Primary users include:
• Polymer and plastics manufacturers
• Independent testing laboratories and contract research organizations (CROs)
• Environmental regulators and certification bodies
• R&D teams in packaging, coatings, and consumer products

Related standards

• ISO 8245 - Water quality: guidance for determination of TOC and DOC (referenced for carbon measurements)
• ISO 8192 - Methods to detect inhibitory effects on activated sludge (referenced for inhibitory testing)
• Other respirometric and biodegradation test standards for soil or compost environments (note: ISO 14851 excludes soil/compost inocula)

This standard is a practical respirometric protocol for assessing the aerobic biodegradability of plastics in water, enabling consistent, comparable biodegradation data for research, compliance and product stewardship.