ISO 15985:2014

Overview

ISO 15985:2014 specifies a laboratory method to determine the ultimate anaerobic biodegradability of plastics under high‑solids anaerobic digestion conditions by measuring the evolved biogas (methane and carbon dioxide). The procedure simulates typical anaerobic digestion of the organic fraction of municipal solid waste using a methanogenic inoculum from anaerobic digesters treating pretreated household waste. Results report the percentage of carbon in the test material converted to biogas and, optionally, loss in mass.

Key topics and technical requirements

• Test conditions: high‑solids (>20% total solids), static (non‑mixed), incubation in the dark at 52 °C ± 2 °C.
• Inoculum: derived from digesters fed only with pretreated household waste; post‑fermented ~7 days to reduce background activity; target biochemical properties include pH 7.5–8.5, VFA < 1 g/kg, and ionized ammonia nitrogen (NH4+-N) 0.5–2 g/kg.
• Sample sizing: typically a minimum of 20 g total dry solids containing ~8 g TOC per vessel; recommended vessel volume ≥ 750 ml.
• Analytical principle: cumulative biogas measured (continuous or at intervals); percentage biodegradation = biogas evolved from test material / theoretical maximum biogas calculated from total organic carbon (TOC). TOC determination can follow ISO 8245.
• Measurements and equipment: gas volume measurement (water displacement with pH <2 to prevent CO2 loss), optional gas analysis (gas chromatography) for methane/CO2 concentrations, and optional analyses for volatile fatty acids, dry solids, volatile solids.
• Outputs: percentage biodegradation, biodegradation rate (lag, biodegradation, plateau phases), and optional mass loss.

Applications and users

• Plastics manufacturers and R&D teams evaluating new biodegradable polymers or formulations intended for biological recycling or organic waste streams.
• Testing laboratories and certification bodies performing standardized biodegradability testing for product claims, labels, or regulatory compliance.
• Waste management and biogas plant operators assessing compatibility of materials with anaerobic digestion systems treating municipal solid waste.
• Policy makers and environmental consultants conducting life‑cycle assessments or setting standards for end‑of‑life treatment pathways.

Practical uses include product development, verification of anaerobic biodegradability for compostable/biodegradable claims, and assessing the potential biogas yield from novel plastic materials.

Related standards

• ISO 8245 - determination of TOC (referenced for carbon content).
• ISO 14855‑1 / ISO 14855‑2 - aerobic biodegradation under high‑solids conditions (comparable aerobic methods).
• ISO 11734 - anaerobic biodegradation under low‑concentration aqueous conditions (different scope).

Keywords: ISO 15985, anaerobic biodegradation, high‑solids anaerobic digestion, biogas analysis, plastics testing, TOC, methanogenic inoculum.