ISO 20136:2020

Overview

ISO 20136:2020 - Leather: Determination of degradability by micro-organisms describes a laboratory test method for measuring the aerobic biodegradation of animal hides, skins and leathers (tanned or untanned) by monitoring CO2 evolution from collagen breakdown. The standard quantifies the degree and rate of biodegradation under controlled conditions using an inoculum (activated sludge from tannery wastewater or municipal wastewater where tannery sludge is unavailable). Tests are valid when a collagen positive control reaches at least 70% biodegradation within 50 days.

Key topics and technical requirements

• Test principle: Biodegradation is assessed indirectly by measuring CO2 produced as collagen is metabolized; initial organic carbon is determined by elemental analysis.
• Inoculum: Activated sludge from tannery wastewater is preferred; municipal (urban) wastewater is an accepted alternative.
• Controlled conditions: Equipment must control air flow, temperature and agitation to provide optimum laboratory conditions for aerobic degradation.
• Two measurement methods:
  • Method A - Manual titration: CO2 trapped as barium carbonate via Ba(OH)2 and quantified by titration of remaining base with HCl.
  • Method B - Infrared (IR) detection: Continuous CO2 monitoring using an IR detector and multiplexer for multiple Erlenmeyer flasks (updated to an open O2 circuit to avoid oxygen limitation).
• Controls and validity: Tests run in duplicate with positive (collagen + inoculum) and negative (inoculum only) controls. Validity criteria are specified (collagen biodegradation ≥70% over the test period).
• Quantification and reporting: Procedures for converting CO2 data to percentage biodegradation, including area-under-curve calculations for IR data, are provided.

Applications and who should use it

ISO 20136:2020 is relevant to:

• Tanneries and leather manufacturers evaluating environmental performance of tanning processes and formulations.
• Laboratories and testing services performing biodegradability assessments for leather products.
• Footwear, apparel and accessory brands seeking data on end-of-life behavior and sustainability claims.
• R&D teams developing alternative tanning agents aimed at improving biodegradability.
• Regulatory and waste management authorities assessing landfill and waste-treatment impacts of leather wastes.

Practical uses include benchmarking leather formulations, comparing biodegradability with collagen, and informing product design for reduced environmental persistence.

Related standards and guidance

• Developed by ISO in collaboration with IULTCS (IUC Commission) and CEN/TC 289 (Leather).
• The document contains informative annexes on degradation rate calculation and comparative inoculum studies; consult national standards bodies or ISO for related leather testing and environmental assessment standards.

Keywords: ISO 20136:2020, leather biodegradability, CO2 measurement, collagen degradation, tannery wastewater, biodegradation test, IR detection, titration method.