ISO 21701:2025

Textiles -Test method for accelerated hydrolysis of textile materials and biodegradation under controlled composting conditions of the resulting hydrolysate

This document specifies a test method for the determination of the biodegradability of the hydrolysate of textile materials obtained after accelerated hydrolysis under controlled composting conditions, by measurement of the amount of evolved carbon dioxide with a gas chromatography or non-dispersive infrared. This test method can be applied to petroleum-based, man-made biodegradable textile materials which are manufactured from polyethylene terephthalate succinate, polycaprolactone, polypropylene carbonate, polybuthylene succinate or copolymer using them.

Textiles — Méthode d’essai pour hydrolyse accélérée des matières textiles et la biodégradation dans des conditions de compostage contrôlées de l'hydrolysat résultant

General Information

• Status: Published
• Publication Date: 21-Oct-2025
• ICS: 59.080.01 - Textiles in general
• Technical Committee: ISO/TC 38 - Textiles
• Drafting Committee: ISO/TC 38/WG 30 - Tests for Biodegradability
• Current Stage: 6060 - International Standard published
• Start Date: 22-Oct-2025
• Due Date: 09-Jan-2026
• Completion Date: 22-Oct-2025

Relations

• Revises: ISO 21701:2019 - Textiles -Test method for accelerated hydrolysis of textile materials and biodegradation under controlled composting conditions of the resulting hydrolysate
• Effective Date: 13-Jan-2024

Overview

ISO 21701:2025 - Textiles - Test method for accelerated hydrolysis of textile materials and biodegradation under controlled composting conditions of the resulting hydrolysate - specifies a laboratory method to evaluate the biodegradability of hydrolysates from textile materials. The method combines an accelerated hydrolysis (abiotic) step with a subsequent controlled composting (biotic) biodegradation test. Biodegradability is determined by measuring evolved carbon dioxide (CO2) using gas chromatography (GC) or non-dispersive infrared (NDIR) analysis and expressing results relative to the theoretical CO2 yield calculated from total organic carbon (TOC).

Key topics and technical requirements

• Scope: Applies to petroleum‑based, man‑made biodegradable textiles such as polyethylene terephthalate succinate, polycaprolactone, polypropylene carbonate, polybutylene succinate and related copolymers.
• Test principle: Perform accelerated hydrolysis under controlled temperature and humidity to generate a hydrolysate, then carry out small‑scale aerobic composting and monitor CO2 evolution to assess ultimate biodegradability.
• Measurement methods: CO2 quantification by gas chromatography (with suitable calibration and internal standards) or by NDIR; calculation of cumulative CO2 and percentage biodegradation against the theoretical CO2 (ThCO2) derived from TOC.
• Apparatus: environmental chamber (RH ±5 %, temperature tolerance ±1 °C), gel permeation chromatography (GPC) for molecular‑weight monitoring, composting vessels (1–5 L), air‑supply system, GC (FID) or NDIR measurement systems.
• Procedure elements: preparation of test material and inoculum, abiotic accelerated hydrolysis, biotic biodegradation test, periodic gas analysis, data calculation and validity criteria.
• Documentation: test report requirements include analytical method details, sampling intervals, flow rates (for NDIR), dates and any unusual observations.
• Caveat: ISO 21701:2025 is a laboratory method; claims on compostability or biodegradation must follow ISO 14855‑1 and appropriate certification-misleading claims are warned against in the standard.

Applications

• Product R&D and material screening for biodegradable textile fibers and polymer blends.
• Accredited testing laboratories performing biodegradability testing for technical dossiers.
• Sustainability teams and brand compliance groups assessing end‑of‑life behavior of man‑made fibers.
• Material scientists studying hydrolytic degradation, molecular‑weight loss and subsequent microbial mineralization.
• Regulatory or certification preparatory testing before full-scale compostability assessment.

Who uses this standard?

• Textile testing laboratories and contract testing services
• Fiber and polymer manufacturers (R&D and quality)
• Environmental test engineers and compostability assessors
• Certification bodies preparing for ISO 14855‑1 compostability protocols
• Academic researchers in polymer biodegradation and textile sustainability

Related standards

• ISO 14855‑1 - Ultimate aerobic biodegradability under controlled composting conditions (evolved CO2)
• ISO 13885‑1 - Gel permeation chromatography (GPC) using THF
• ISO 3071 - Determination of pH of aqueous extract (textiles)
• ISO 1628‑1 - Viscosity of polymers in dilute solution

Keywords: ISO 21701:2025, textiles, accelerated hydrolysis, biodegradation, composting, hydrolysate, gas chromatography, NDIR, biodegradability testing.

Standards Content (Sample)

International
Standard
ISO 21701
Second edition
Textiles — Test method for
2025-10
accelerated hydrolysis of textile
materials and biodegradation under
controlled composting conditions of
the resulting hydrolysate
Textiles — Méthode d’essai pour hydrolyse accélérée des matières
textiles et la biodégradation dans des conditions de compostage
contrôlées de l'hydrolysat résultant
Reference number
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
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or ISO’s member body in the country of the requester.
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reference material . 3
6 Apparatus . 3
7 Test procedure . 4
7.1 Preparation of test material .4
7.2 Preparation of the inoculum .4
7.3 Accelerated hydrolysis test (abiotic test) . .4
7.4 Biodegradation test (biotic test) of hydrolysate .4
7.5 Gas chromatographic analysis .5
7.6 Non–dispersive infrared (NDIR) analysis .5
8 Calculation and expression of results . 5
8.1 Amount of carbon dioxide in grams by gas chromatography .5
8.2 Amount of carbon dioxide in grams by non-dispersive infrared .7
8.3 Percentage of biodegradation .7
8.4 Validity of results .8
9 Test report . 8
Annex A (informative) Example of apparatus . 9
Annex B (informative) Example of accelerated hydrolysis test results .11
Bibliography .12

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
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with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
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Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 38, Textiles.
This second edition cancels and replaces the first edition (ISO 21701:2019), which has been technically
revised.
The main changes are as follows:
— in the Introduction, non-dispersive infrared has been added;
— in Clause 1, non-dispersive infrared has been added;
— in Clause 2, ISO 3071 has been added;
— in Clause 4, non-dispersive infrared has been added;
— in Clause 6, 6.7 Non-dispersive infrared(NDIR) has been added;
— in Clause 6, 6.9 pH-meter has been specified by ISO 3071;
— in Clause 7, 7.6 Non-dispersive infrared(NDIR) has been added;
— in Clause 8, 8.1 Amount of carbon dioxide in grams by gas chromatography has been modified;
— in Clause 8, 8.2 Amount of carbon dioxide in grams by non-dispersive infrared has been added;
— in Clause 9, d) the average flow rate and interval of sampling by non-dispersive infrared, f) date of test,
and g) any unusual features observed have been added;
— in Annex A, A.3, Non-dispersive infrared for thermal desorption has been added;
— in Annex A, A.4, Example of the analysis condition of gas cell has been added.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
Textile fibres can be classified into natural fibres and man-made fibres according to ISO/TR 11827. Some
man-made fibres manufactured from organic materials are biodegradable and can be divided into three
major categories in relation to their origin, i.e. natural material base, biology base and petroleum base.
The representative bio-based, man-made biodegradable fibre is polylactide and petroleum-based, man-
made biodegradable fibres are manufactured from polyethylene terephthalate succinate, polycaprolactone,
polypropylene carbonate, polybuthylene succinate or copolymer using them.
The biodegradation of petroleum-based fibres is relatively slow compared to biology-based or natural fibres
due to the chemical structure. In addition, the rate of biodegradation of textile materials such as fibres and
yarns can also be affected negatively by high molecular weight, degree of crystallinity and orientation
occurred during the spinning. Although some standards refer to the instrument analysis, such as gas
chromatograph or infrared analysis, the process and calculation method are not standardized. Therefore,
it is difficult to determine the biodegradation of petroleum-based textile materials using the existing
standards available for natural fibres, biology-based fibres or plastic materials used for packaging.
To overcome these difficulties, the new test method is proposed by a combination of accelerated hydrolysis
and biodegradation using instrument analysis for analysis of evolved carbon dioxide.
Under the composting of textile materials both mechanisms, abiotic and biotic processes, operate together
and the microorganisms eventually remove the hydrolysate in a synergistic process. It is difficult and
time consuming to reproduce this in the laboratory. For convenience, the accelerated hydrolysis, which is
an abiotic process, should be carried out followed by biodegradation subsequently. The rate and extent of
molecular weight loss is measured as indicative of losses in physical properties from accelerated hydrolysis
and then the biodegradability of hydrolysate is estimated by direct measurement of evolved carbon dioxide
with a gas chromatograph or a non-dispersive infrared.

v
International Standard ISO 21701:2025(en)
Textiles — Test method for accelerated hydrolysis of textile
materials and biodegradation under controlled composting
conditions of the resulting hydrolysate
1 Scope
This document specifies a test method for the determination of the biodegradability of the hydrolysate
of textile materials obtained after accelerated hydrolysis under controlled composting conditions, by
measurement of the amount of evolved carbon dioxide with a gas chromatography or non-dispersive
infrared.
This test method can be applied to petroleum-based, man-made biodegradable textile materials which
are manufactured from polyethylene terephthalate succinate, polycaprolactone, polypropylene carbonate,
polybuthylene succinate or copolymer using them.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 1628-1, Plastics — Determination of the viscosity of polymers in dilute solution using capillary viscometers
— Part 1: General principles
ISO 3071, Textiles — Determination of pH of aqueous extract
ISO 13885-1, Gel permeation chromatography (GPC) — Part 1: Tetrahydrofuran (THF) as eluent
ISO 14855-1, Determination of the ultimate aerobic biodegradability of plastic materials under controlled
composting conditions — Method by analysis of evolved carbon dioxide — Part 1: General method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
compost
organic soil conditioner obtained by biodegradation of a mixture principally consisting of various vegetable
residues, occasionally with other organic material and having a limited mineral content
3.2
composting
aerobic process designed to produce compost (3.1)

3.3
total dry solids
amount of solids obtained by taking a known volume of test material or compost and drying at about to
constant mass
[SOURCE: ISO 14855-1:2012, 3.4]
3.4
volatile solids
amount of solids obtained by subtracting the residue of a known volume of test material or compost after
incineration at about from the total dry solids (3.3) of the same sample
Note 1 to entry: The volatile-solids content is an indication of the amount of organic matter present.
3.5
abiotic process
process without the action of living organisms
3.6
biotic process
process through the actions of living organisms
3.7
hydrolysis
degradation identified as resulting from hydrolytic cleavage of macromolecules
3.8
accelerated hydrolysis
hydrolysis (3.7) under high temperature and humidity
3.9
hydrolysate
product of hydrolysis (3.7)
3.10
theoretical amount of evolved carbon dioxide
ThCO
maximum theoretical amount of carbon dioxide evolved after completely oxidizing a chemical compound,
calculated from the molecular formula and expressed as milligrams of carbon dioxide evolved per milligram
or gram of test compound
[SOURCE: ISO 14855-1:2012, 3.6]
4 Principle
WARNING — Any claim on biodegradation or (industrial) compostability of the textile material is
not allowed and considered misleading. For claims on biodegradation under controlled composting
conditions, testing shall be carried out in accordance with ISO 14855-1.
The test method determines the ultimate biodegradability of test material after accelerated hydrolysis
under conditions simulating an intensive aerobic composting process. It aims to determine the ultimate
biodegradability of the hydrolysate by using a small-scale reactor. The degradation rate is periodically
measured by determining the amount of the evolved carbon dioxide using gas chromatography or non-
dispersive infrared.
Firstly, the test material is hydrolysed under the constant temperature and humidity until the substantial
loss of molecular weight in order to initiate the biodegradation process shortly.
During the aerobic biodegradation of the hydrolysate, carbon dioxide, water, mineral salts and new microbial
cellular constituents (biomass) are the ultimate biodegradation products. The carbon dioxide produced
is continuously monitored, or measured at regular intervals, in test and blank vessels to determine the

cumulative carbon dioxide production. The percentage biodegradation is given by the ratio of the carbon
dioxide produced from the test material to the maximum theoretical amount of evolved carbon dioxide
that can be produced from the test material. The maximum theoretical amount of evolved carbon dioxide
produced is calculated from the measured total organic carbon (TOC) content.
5 Reference material
5.1 TLC (thin-layer chromatography) grade cellulose, used with a particle size of less than 20 μm as
the positive-control reference material.
5.2 For the calibration of gas chromatograph, preferably internal standards should be selected for the
CO /N mixtur
...