SIST EN ISO 14855-2:2026

• Abstract:

  This document specifies a method for determining the ultimate aerobic biodegradability of plastic materials under controlled composting conditions by gravimetric measurement of the amount of carbon dioxide evolved. The method is designed to yield an optimum rate of biodegradation by adjusting the humidity, aeration and temperature of the composting vessel.; The method applies to the following materials:; natural and/or synthetic polymers and copolymers, and mixtures of these;; plastic materials that contain additives such as plasticizers or colorants;; water-soluble polymers;; materials that, under the test conditions, do not inhibit the activity of microorganisms present in the inoculum.; NOTE If the test material inhibits microorganisms in the inoculum, another type of mature compost or pre-exposure compost can be used.

• Status: Published
• Public Enquiry End Date: 30-Dec-2025
• Publication Date: 29-Sep-2026
• ICS: 13.030.99 - Other standards related to wastes
• ICS: 83.080.01 - Plastics in general
• Technical Committee: IPMA - Polimer materials and products
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 29-Sep-2026
• Due Date: 04-Dec-2026
• Completion Date: 30-Sep-2026
• Ref Project: EN ISO 14855-2:2026 - Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions - Method by analysis of evolved carbon dioxide - Part 2: Gravimetric measurement of carbon dioxide evolved in a laboratory-scale test (ISO 14855-2:2026)

• Referred By: SIST EN 17427:2022 - Packaging - Requirements and test scheme for carrier bags suitable for treatment in well-managed home composting installations
• Effective Date: 17-Sep-2026
• Revises: SIST EN ISO 14855-2:2018 - Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions - Method by analysis of evolved carbon dioxide - Part 2: Gravimetric measurement of carbon dioxide evolved in a laboratory-scale test (ISO 14855-2:2018)
• Effective Date: 02-Oct-2024

Overview

SIST EN ISO 14855-2:2026 addresses the ultimate aerobic biodegradability of plastic materials under controlled composting conditions. This standard specifies a gravimetric method for measuring evolved carbon dioxide in a laboratory-scale test, providing a practical framework for evaluating how plastic materials behave in composting environments.

The method is designed to support an optimum rate of biodegradation by controlling humidity, aeration, and temperature inside the composting vessel. It is especially relevant for organizations working with biodegradable plastics, compostable materials, and plastic waste recovery strategies.

This standard applies to:

• Natural and synthetic polymers and copolymers
• Plastic materials with additives such as plasticizers or colorants
• Water-soluble polymers
• Materials that do not inhibit microbial activity in the inoculum

If the test material inhibits microorganisms, the scope notes that another mature compost or pre-exposure compost may be used.

Key Topics

This standard focuses on a controlled composting test method that measures biodegradation through the amount of carbon dioxide evolved. The result is used to assess the percentage biodegradation relative to the theoretical amount of carbon dioxide.

Key elements include:

• Laboratory-scale composting vessels
• Mature compost inoculum
• Carbon dioxide absorption and gravimetric measurement
• Controlled aeration and temperature
• Blank controls and reference material testing
• Validity criteria for test performance

The document also emphasizes practical test conditions, including:

• Use of carbon-dioxide-free, water-saturated air
• Measurement of dry solids, volatile solids, and total organic carbon
• Monitoring of inoculum activity using a reference material
• Reporting of results in a structured test report

For users seeking reliable compostability data, this standard supports consistent evaluation under controlled composting conditions and helps compare performance across materials and test series.

Applications

SIST EN ISO 14855-2:2026 is valuable in many technical and industrial contexts, especially where biodegradable plastics testing and environmental performance assessment are required.

Typical applications include:

• Product development for compostable and biodegradable plastics
• Quality control in polymer manufacturing
• Environmental compliance and sustainability assessment
• Research and development of bio-based materials
• Comparative testing of plastic formulations with additives

The method is particularly useful for stakeholders in:

• Plastics and packaging
• Waste management
• Composting technologies
• Materials research
• Regulatory and conformity assessment workflows

Related Standards

This standard is part of a broader ISO framework for biodegradability and composting evaluation. Related references include:

• 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
• ISO 11721-1 - Textiles - Determination of resistance of cellulose-containing textiles to micro-organisms - Soil burial test - Part 1: Assessment of rot-retardant finishing

Together, these standards support aerobic biodegradation testing, composting performance evaluation, and the documentation of biodegradable plastic material behavior under standardized laboratory conditions.

SLOVENSKI STANDARD
01-november-2026
Ugotavljanje končne aerobne biorazgradljivosti in razkroja polimernih materialov
pod nadzorovanimi pogoji kompostiranja - Metoda z analizo sproščenega
ogljikovega dioksida - 2. del: Gravimetrična metoda za določanje sproščenega
ogljikovega dioksida v laboratorijskem merilu (ISO 14855-2:2026)
Determination of the ultimate aerobic biodegradability of plastic materials under
controlled composting conditions - Method by analysis of evolved carbon dioxide - Part
2: Gravimetric measurement of carbon dioxide evolved in a laboratory-scale test (ISO
14855-2:2026)
Bestimmung der vollständigen aeroben Bioabbaubarkeit von Kunststoff-Materialien unter
den Bedingungen kontrollierter Kompostierung - Verfahren mittels Analyse des
freigesetzten Kohlenstoffdioxides - Teil 2: Gravimetrische Messung des freigesetzten
Kohlenstoffdioxides im Labormaßstab (ISO 14855-2:2026)
Détermination de la biodégradabilité aérobie ultime des matériaux plastiques dans des
conditions contrôlées de compostage - Méthode par analyse du dioxyde de carbone
libéré - Partie 2: Mesurage gravimétrique du dioxyde de carbone libéré lors d'un essai de
laboratoire (ISO 14855-2:2026)
Ta slovenski standard je istoveten z: EN ISO 14855-2:2026
ICS:
13.030.99 Drugi standardi v zvezi z Other standards related to
odpadki wastes
83.080.01 Polimerni materiali na Plastics in general
splošno
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 14855-2
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2026
EUROPÄISCHE NORM
ICS 83.080.01 Supersedes EN ISO 14855-2:2018
English Version
Determination of the ultimate aerobic biodegradability of
plastic materials under controlled composting conditions -
Method by analysis of evolved carbon dioxide - Part 2:
Gravimetric measurement of carbon dioxide evolved in a
laboratory-scale test (ISO 14855-2:2026)
Détermination de la biodégradabilité aérobie ultime Bestimmung der vollständigen aeroben
des matériaux plastiques dans des conditions Bioabbaubarkeit von Kunststoff-Materialien unter den
contrôlées de compostage - Méthode par analyse du Bedingungen kontrollierter Kompostierung -
dioxyde de carbone libéré - Partie 2: Mesurage Verfahren mittels Analyse des freigesetzten
gravimétrique du dioxyde de carbone libéré lors d'un Kohlenstoffdioxides - Teil 2: Gravimetrische Messung
essai de laboratoire (ISO 14855-2:2026) des freigesetzten Kohlenstoffdioxides im
Labormaßstab (ISO 14855-2:2026)
This European Standard was approved by CEN on 15 September 2026.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 14855-2:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 14855-2:2026) has been prepared by Technical Committee ISO/TC 61 "Plastics"
in collaboration with Technical Committee CEN/TC 249 “Plastics” the secretariat of which is held by SIS.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by March 2027, and conflicting national standards shall
be withdrawn at the latest by March 2027.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 14855-2:2018.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 14855-2:2026 has been approved by CEN as EN ISO 14855-2:2026 without any
modification.
International
Standard
ISO 14855-2
Third edition
Determination of the ultimate
2026-09
aerobic biodegradability of
plastic materials under controlled
composting conditions — Method
by analysis of evolved carbon
dioxide —
Part 2:
Gravimetric measurement of carbon
dioxide evolved in a laboratory-
scale test
Détermination de la biodégradabilité aérobie ultime des
matériaux plastiques dans des conditions contrôlées de
compostage — Méthode par analyse du dioxyde de carbone
libéré —
Partie 2: Mesurage gravimétrique du dioxyde de carbone libéré
lors d'un essai de laboratoire
Reference number
ISO 14855-2:2026(en) © ISO 2026

ISO 14855-2:2026(en)
© ISO 2026
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
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 14855-2:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
5 Reagents . 3
6 Apparatus . 4
7 Procedure . 5
7.1 Preparation of the inoculum .5
7.2 Preparation of the sea sand .6
7.3 Preparation of test material and reference material .6
7.4 Starting up the test .6
7.5 Measurement of the evolved carbon dioxide .7
7.5.1 Gravimetric analysis .7
7.5.2 Alternative quantitative analytical methods .7
7.6 Incubation period .8
7.7 Termination of the test .8
8 Calculation . 9
8.1 Theoretical amount of carbon dioxide evolved by test material .9
8.2 Percentage biodegradation .9
9 Expression and interpretation of results . 9
10 Validity of results . 10
11 Test report . 10
Annex A (informative) Basic principle of the test .11
Annex B (informative) Example of an apparatus using an electrically heated composting vessel .13
Annex C (informative) Derivation of the formula used to calculate the degree of biodegradation
from the amount of carbon dioxide evolved .15
Annex D (informative) Determination of the degree of biodegradation of plastics under
composting conditions — Synchronous gas sampling method .16
Bibliography .21

iii
ISO 14855-2:2026(en)
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
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
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)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 61, Plastics, Subcommittee SC 14, Environmental
aspects, in collaboration with the European Committee for Standardization (CEN) Technical Committee
CEN/TC 249, Plastics, in accordance with the Agreement on technical cooperation between ISO and CEN
(Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 14855-2:2018), which has been technically
revised.
The main changes are as follows:
— the NDIR method to the measurement of evolved carbon dioxide in addition to the conventional
gravimetric method has been added;
— a schematic diagram of the measurement device and an example of biodegradability measurement using
an NDIR sensor have been added to Annex D.
A list of all parts in the ISO 14855 series can be found on the ISO website.
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
ISO 14855-2:2026(en)
Introduction
Management of plastics waste is a serious problem in the world. Plastics recovery technologies include
material recovery (mechanical recycling, chemical or feedstock recycling, and biological or organic recycling)
and energy recovery (heat, steam or electricity as a substitute for fossil fuels or other fuel resources). The
use of biodegradable plastics is one valuable recovery option (biological or organic recycling).
Several ISO standards for determining the ultimate aerobic/anaerobic biodegradability of plastic materials
have been published. In particular, ISO 14855-1 is a common test method that measures the amount of carbon
dioxide evolved using methods such as continuous infrared analysis, gas chromatography or titration.
Compared with ISO 14855-1, the amounts of compost inoculum and test sample used in this document are
one-tenth the size. In order to ensure the activity of the compost inoculum, inert material that gives the
mixture the same texture as soil is mixed into the inoculum. The carbon dioxide evolved from the test vessel
is determined by absorbing it in a carbon dioxide trap and carrying out gravimetric analysis of the absorbent.
The method described in this document, which uses a closed system to capture the carbon dioxide evolved,
can also be used to obtain valuable information, by means of isotopic-labelling studies, on the way in which
the molecular structure of co-polymers degrades.
In addition to traditional gravimetric methods, this test method adds a new way to measure carbon dioxide
using spectroscopic non-dispersive infrared (NDIR) technology, significantly reducing the routine work and
chemical use required for quantitative measurement without compromising the quantitative accuracy of
chemical methods.
v
International Standard ISO 14855-2:2026(en)
Determination of the ultimate aerobic biodegradability of
plastic materials under controlled composting conditions —
Method by analysis of evolved carbon dioxide —
Part 2:
Gravimetric measurement of carbon dioxide evolved in a
laboratory-scale test
WARNING — Sewage, activated sludge, soil and compost can contain potentially pathogenic
organisms. Therefore, appropriate precautions should be taken when handling them. Toxic test
compounds and those whose properties are unknown should be handled with care.
1 Scope
This document specifies a method for determining the ultimate aerobic biodegradability of plastic materials
under controlled composting conditions by gravimetric measurement of the amount of carbon dioxide
evolved. The method is designed to yield an optimum rate of biodegradation by adjusting the humidity,
aeration and temperature of the composting vessel.
The method applies to the following materials:
— natural and/or synthetic polymers and copolymers, and mixtures of these;
— plastic materials that contain additives such as plasticizers or colorants;
— water-soluble polymers;
— materials that, under the test conditions, do not inhibit the activity of microorganisms present in the
inoculum.
NOTE If the test material inhibits microorganisms in the inoculum, another type of mature compost or pre-
exposure compost can be used.
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 11721-1, Textiles — Determination of resistance of cellulose-containing textiles to micro-organisms — Soil
burial test — Part 1: Assessment of rot-retardant finishing
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 14855-2:2026(en)
ISO and IEC maintain terminology 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
3.3
total dry solids
amount of solids obtained by taking a known volume of test material or compost and drying at about 105 °C
to constant mass
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 550 °C from the total dry solids of the same sample
Note 1 to entry: The volatile-solids content is an indication of the amount of organic matter present.
3.5
ultimate aerobic biodegradability
breakdown ratio by expressed as percentage of an organic compound by microorganisms in the presence of
oxygen into carbon dioxide, water and mineral salts of any other elements present (mineralization) plus new
biomass
[SOURCE: ISO 14852:2021, 3.1]
3.6
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
3.7
lag phase
time from the start of a test until adaptation and/or selection of the degradation microorganisms is achieved
and the degree of biodegradation of a chemical compound or organic matter has increased to about 10 % of
the maximum level of biodegradation
Note 1 to entry: It is measured in days.
3.8
maximum level of biodegradation
degree of biodegradation of a chemical compound or organic matter in a test, above which no further
biodegradation takes place during the test
Note 1 to entry: It is measured as a percentage.

ISO 14855-2:2026(en)
3.9
biodegradation phase
time from the end of the lag phase of a test until about 90 % of the maximum level of biodegradation has
been reached
Note 1 to entry: It is measured in days.
3.10
plateau phase
time from the end of the biodegradation phase until the end of the test
Note 1 to entry: It is measured in days.
3.11
pre-exposure
pre-incubation of an inoculum in the presence of the chemical compound or organic matter under test,
with the aim of enhancing the ability of the inoculum to biodegrade the test material by adaptation and/or
selection of the micro-organisms
3.12
pre-conditioning
pre-incubation of an inoculum under the conditions of the subsequent test in the absence of the chemical
compound or organic matter under test, with the aim of improving the test by acclimatization of the
microorganisms to the test conditions
3.13
water-holding capacity
WHC
mass of water that evaporates from soil saturated with water when the soil is dried to constant mass at
105 °C, divided by the dry mass of the soil
4 Principle
This method is designed to yield the optimum rate of biodegradation of a plastic material in mature compost
by controlling the humidity, aeration ratio and temperature in the composting vessel. It also aims to
determine the ultimate biodegradability of the test material by using a small-scale reactor. The degradation
rate is periodically measured by determining the mass of the evolved carbon dioxide using an absorption
column filled with soda lime and soda talc on an electronic balance.
The test material is mixed with an inoculum derived from mature compost and with an inert material such
as sea sand. The sea sand plays an active part by acting as a holding body for humidity and microorganisms.
Examples of suitable test arrangements are presented in Annexes A and B. The amount of carbon dioxide
evolved is measured at intervals on an electronic balance and the carbon dioxide content is determined
using the following method. The derivation of the formula used to calculate the degree of biodegradation
from the amount of carbon dioxide evolved is given in Annex C. In this method, the degree of biodegradation,
expressed as a percentage, is calculated by comparing the amount of carbon dioxide evolved with the
theoretical amount (ThCO ).
The test is terminated when the plateau phase of biodegradation has been attained. The standard time for
termination is 45 days, but the test can be continued for up to six months.
5 Reagents
Use only analytical-grade reagents. Use only deionized water.
5.1 Soda lime, particle size between 2 mm and 4 mm, for CO absorption.
5.2 Anhydrous calcium chloride, particle size between 2 mm and 3 mm, for water absorption.

ISO 14855-2:2026(en)
5.3 Sodium hydroxide on a talc support (commonly known as soda talc), particle size between 2 mm
and 3 mm, for CO absorption.
5.4 Silica gel (with moisture indicator), particle size between 2 mm and 4 mm, for water absorption.
5.5 Sea sand, particle size between 425 μm and 850 μm (20 mesh and 35 mesh).
5.6 Reference material: thin-layer chromatography (TLC) grade microcrystalline cellulose with a
particle size of less than 20 µm, for use as the reference material in the positive control.
6 Apparatus
Ensure that all glassware is thoroughly cleaned and, in particular, free from organic or toxic matter.
6.1 Air-supply system, capable of supplying each composting vessel with carbon-dioxide-free, water-
saturated air.
The air can be prepared by supplying compressed air through a carbon dioxide trap and a humidifier (see
examples in Annexes A and B), i.e. columns filled with soda lime and water, respectively. The air flow rate
shall be controlled with a flow controller so that it is high enough for aerobic conditions.
6.2 Composting vessels
Use bottles or columns that ensure a supply of water-saturated, carbon-dioxide-free air to the contents. A
suitable volume is 500 ml. If the loss in mass of the test material is to be determined, weigh each composting
vessel empty before starting the test.
6.3 System for the determination of carbon dioxide, capable of determining carbon dioxide directly
from the change in mass of a carbon dioxide trap. The carbon dioxide trap shall consist of columns filled
with soda lime, soda talc and anhydrous calcium chloride. The calcium chloride should preferably be in a
separate column from the soda lime and soda talc (see examples in Annexes A and B). An ammonia trap
(dilute sulfuric acid) and a water trap (silica gel and calcium chloride) are required between the composting
vessel and the carbon-dioxide-absorbing column.
6.4 Gas-tight tubes, used to connect the composting vessels to the air supply and the carbon dioxide
measurement system.
6.5 pH-meter, used for measurement of the pH of the test mixture. It shall be accurate to 0,1 pH-units or
better.
6.6 Analytical equipment, used for the determination of the dry solids (at 105 °C), volatile solids (at
550 °C) and total organic carbon (TOC), for elemental analysis of the test material and, if required, for the
determination of dissolved inorganic carbon (DIC), volatile fatty acids, oxygen in the air, water content and
total nitrogen.
6.7 Balance, used to periodically measure the mass of the carbon-dioxide-absorbing column, in order to
determine the amount of carbon dioxide evolved, and also to measure the mass of the composting vessel
containing compost and test material. A top-loading electronic balance with a display reading down to
10 mg and a capacity greater than 500 g is preferred.
6.8 Thermostatic-control unit, required to maintain the temperature of the composting vessels at
a controlled temperature during the test (see examples given in Annexes A and B). It shall be capable of
maintaining the temperature of the composting vessels constant to within ±2 °C.

ISO 14855-2:2026(en)
6.9 Composting bioreactor. A box, made from polypropylene or another suitable material, having a size
that allows the contents to be stirred easily with a spatula. The box shall be provided with a tightly fitting
lid to avoid excessive water loss. Three holes with a diameter of about 1 cm shall be made at equal distances
along the centreline of the lid. These holes allow air to enter and gases to leave the box, as well as the gradual
evaporation of excess water.
7 Procedure
7.1 Preparation of the inoculum
Well-aerated compost from a properly operating aerobic composting plant shall be used as the inoculum.
The inoculum shall be homogeneous and free from large inert objects such as glass, stones or pieces of
metal. Remove such items manually and prepare compost with a particle size of 2 mm to 5 mm using sieves
with 2 mm and 5 mm openings.
Compost can be made as follows. Wood shavings, sawdust, used mushroom beds, chaff or rice straw can
be used as the carbon source. Livestock excrement is added as a source of composting microorganisms
and mineral salt nutrients. This is placed in a container with a volume of about 1 m and mixed well. It
is recommended that the compost be adjusted to a carbon/nitrogen (C/N) ratio of 15 and a carbon/
phosphorous (C/P) ratio of 30. Insufficient phosphorous and nitrogen levels can be supplemented using
calcium superphosphate and ammonium magnesium phosphate hexahydrate or urea, respectively. Water is
added to reach a water content equal to 65 %. The C/N, C/P and water-content values may also be adjusted
to other values, determined by experience, depending on seasonal variations and climatic differences. The
compost should be removed from the container once a week to turn it and add water, if necessary, before
returning it to the container to continue the composting process. The age of the compost should preferably
be between two and four months.
Normally, non-exposed inoculum is preferred, especially in the case of standard tests simulating
biodegradation behaviour in real composting facilities. Depending on the purpose of the test, however,
pre-exposed compost may be used, provided that this is clearly stated in the test report (e.g. percent
biodegradation = X %, using pre-exposed compost) and provided the method of pre-exposure is detailed in
the test report.
Determine the total dry solids and volatile-solids content of the compost inoculum. The total dry solids
should be between 35 % and 55 % of the wet solids and the volatile solids more than 30 % of the dry solids.
Adjust the water content, if necessary, before the compost is used by adding water or drying gently, e.g. by
aerating the compost with dry air.
Prepare a mixture of 1 part of inoculum to 5 parts of deionized water. Mix by shaking and measure the pH
immediately. It should be between 7,0 and 9,0.
For further characterization of the inoculum, suitable parameters such as the content of total organic carbon,
total nitrogen or fatty acids can optionally be determined at the beginning and the end of the test.
Check the activity of the inoculum during the test by means of a biodegradable reference material and
by measuring carbon dioxide evolution in the blank vessels. The reference material shall be degraded by
70 % or more at the end of the test. The inoculum in the blank should produce between 50 mg and 150 mg
of carbon dioxide per gram of volatile solids over the first 10 days of the test. If the production of carbon
dioxide is too high, stabilize the compost by aeration for several days before using it in a new test.
If biodegradation is inhibited by physicochemical conditions, such as a decrease in the pH of the test system
due to hydrolysis of the sample, solidification or aggregation of the compost due to melting, or a decrease in
water activity due to water absorption, it is recommended to conduct the test under milder conditions in a
water system, soil system, or home compost system.

ISO 14855-2:2026(en)
7.2 Preparation of the sea sand
Dip the sea sand in tap water. After removing floating impurities by decantation, rinse the sand sufficiently,
drain off the water and dry the sand at about 105 °C.
NOTE Sea sand, or another inert mineral material (e.g. quartz sand) with SiO content ≥90 % and particle size
of 0,5 mm to 1 mm can be used. Sea sand plays an important role in maintaining appropriate moisture content and
promoting microbial growth.
7.3 Preparation of test material and reference material
Determine the total organic carbon (TOC) of the test material and the reference material using, for example,
ISO 8245 and report it preferably as grams of TOC per gram of total dry solids. Alternatively, provided that
the materials do not contain inorganic carbon, it is possible to determine the carbon content by elemental
analysis. For this, the test material should contain sufficient organic carbon to yield carbon dioxide in an
amount suitable for determination. Normally, a minimum of 10 g of total dry solids containing 4 g of TOC is
required per 500 ml-vessel.
The test material should preferably be used in powder form, but it may also be introduced as small pieces of
films or as fragments of shaped articles. A maximum particle size of 250 µm in diameter is recommended.
For materials containing inorganic carbon (e.g. carbonate fillers), the inorganic carbon shall be determined
and subtracted, or a suitable pre-treatment shall be applied to remove inorganic carbon before TOC
determination. The applied procedure shall be reported.
7.4 Starting up the test
Provide at least the following numbers of composting vessels:
a) three test vessels for the test mixture (symbol V );
T
b) three vessels for blank controls (symbol V );
B
c) three vessels for checking inoculum activity using a reference material (symbol V ).
R
The amount of test mixture, containing inoculum and the test material, used in the test depends on the
quality of the test material and the size of the composting vessels. The relation between the total dry solids
of the inoculum and the total dry solids of the test material should preferably be about 6:1. If added, inert
material is not considered in this relationship. The test mixture should have the same water content as the
inoculum. The water content of the test mixture should be set at 80 % to 90 % of the water-holding capacity
(WHC) of the test mixture. The same amount of inoculum by total dry solids should be placed in each test
vessel.
In a typical case, prepare lidded vessels that have a volume of about 500 ml, weigh out, for each vessel, an
amount of inoculum containing 60 g of total dry solids and add sufficient water to reach a water content of
65 %. After mixing well, leave the compost to stand at room temperature for 24 h. Then mix the compost
well with sea sand with a water content of 15 % that has previously been prepared by the addition of water
to about 320 g of sea sand and is used as inert material. Add 10 g, on a dry-mass basis, of test material to
the mixture and mix well. It should feel like soil when handled gently. If required, measure the WHC of the
test mixture in accordance with ISO 11721-1, then adjust the water content of the mixture to about 90 % of
the WHC by adding water or by aerating with dry air. Introduce the mixture into the composting vessel. If
vermiculite is used as the inert material, prepare it as specified in ISO 14855-1.
The WHC of the compost–sea sand mixture can be determined according to ISO 11721-1, adapted for compost
mixtures, or by an equivalent validated method. The method used shall be reported.
When mature compost preserved in the refrigerator is used as the inoculum, pre-condition the compost
before using it. In a typical case, place, for each vessel, 60 g, on a total dry solids basis, of mature compost
in a composting bioreactor, and adjust the water content of the compost to about 110 % of the WHC by
adding water. After mixing, allow it to stand at room temperature for 24 h, and then incubate it at 58 °C
for 24 h. Add the same volume of sea sand (about 320 g on a dry-mass basis) as the mature compost and

ISO 14855-2:2026(en)
mix well. Before addition, the water content of the sea sand should be adjusted to about 15 % (equal to the
sea sand WHC value). The C/N ratio for the test mixture should preferably be between 10 and 40. It may be
adjusted with ammonium magnesium phosphate hexahydrate or urea. Put the mixture in the composting
bioreactor and incubate for a week at 58 °C. A few times per day, stir the mixture for about 10 min in order to
ensure aerobic conditions and allow excess water to evaporate. After a week, adjust the water content of the
mixture to about 90 % of its WHC. The final mixture should weigh about 550 g, but a different final mass can
be obtained depending on the compost used (different composts will have different WHC values). Add 10 g,
on a dry-mass basis, of test material to the mixture and mix well. Introduce the mixture into the composting
vessels.
When ISO 14855-1 biodegradability tests are performed, mature compost with a water content of about
50 % shall be used, as specified in ISO 14855-1. Use 120 g of mature compost, containing about 60 g of total
dry solids, per composting vessel. Add 10 g, on a dry-mass basis, of test material to the mature compost and
mix well. Introduce the mixture into the composting vessel. If the test mixture dries out too fast, put an inert
water-containing material in the vessel together with the mixture. However, the water-containing material
shall not be mixed with the test mixture.
The organic carbon content can be calculated from the TOC of the inoculum and the test material. The total
nitrogen content can be measured in a representative sample of the test mixture, e.g. by the Kjeldahl method
described in ISO 5663.
Place the composting vessels in the test environment at (58 ± 2) °C and initiate aeration using air that is
free from carbon dioxide and has a normal water content. Both these conditions can be met by, for example,
passing the air through a carbon dioxide trap filled with soda lime and a humidifier filled with water (see
Annexes A and B). Adjust the air flow rate through each composting vessel to the same rate in the range
10 ml/min to 30 ml/min.
Use a sufficiently high flow rate to ensure that aerobic conditions are maintained throughout each
composting vessel during the whole test. Check the air flow regularly at the outlets, e.g. by using wash-
bottles or a soap bubble flow meter.
Handle the reference material in the same way as the test material. In the vessels for the blank controls,
place only inoculum and sea sand, in the same amounts as in the vessels with the test material.
7.5 Measurement of the evolved carbon dioxide
7.5.1 Gravimetric analysis
Fill the ammonia-absorbing bottle with 1 mol/l sulfuric acid to remove any ammonia from the gases which
pass out of the composting vessel. Fill the two dehumidifying traps with silica gel and anhydrous calcium
chloride, respectively.
Carbon dioxide is measured using a carbon dioxide absorption column and a water absorption column,
as shown in reaction Formulae (C.1) and (C.2) of Annex C. Fill the carbon-dioxide-absorbing column and
water-absorbing column with carbon dioxide absorbent and water absorbent, respectively. The carbon
dioxide absorbent should preferably be a mixture of equal quantities of soda lime and soda talc. The water
absorbent should preferably be anhydrous calcium chloride. Determine the mass of this trap (i.e. both
columns together) to within 10 mg on the balance. The amount of carbon dioxide evolved is determined
from the increase in mass of the unit.
Change the reagents in the carbon-dioxide-absorbing and water-absorbing columns when they have reached
80 % of their absorption capacity. Note that 80 g of a mixture of equal quantities of soda lime and soda talc
has the ability to absorb about 15 g of carbon dioxide.
7.5.2 Alternative quantitative analytical methods
This includes neutralization titration, gravimetric analysis of other carbonates, and spectroscopic analysis
using NDIR (Non-Dispersive Infrared Absorption) carbon dioxide sensors.

ISO 14855-2:2026(en)
NDIR measurement methods can be used as an alternative to gravimetric analysis only if their equivalence
to the standard value of gravimetric analysis is proven (e.g. deviation of 10 % or less).
Annex D contains an example of a 24-unit biodegradation measurement system using the NDIR method.
These systems achieve compatibility by eliminating gas sampling errors between samples through
synchronous gas sampling, performing cumulative flow measurement using a gas burette, and using NDIR
sensors with an error of 3 % or less. Figure D.1, Figure D.2, and Figure D.3 show schematic diagrams of a
synchronous gas sampling apparatus, a carbon dioxide quantification apparatus using a gas burette and
carbon dioxide sensor, and measurement results for cellulose, a reference substance demonstrating the
validity of the test.
7.6 Incubation period
Measure the amount of carbon dioxide evolved in the exhaust air from each composting vessel at intermediate
time intervals by measuring the change in mass of the trap for the evolved carbon dioxide. Measure the
carbon dioxide evolved at least once a day during the biodegradation phase and once every two days later
on, during the plateau phase.
Stir the compost weekly to prevent extensive channelling and to ensure uniform attack by the
microorganisms on the test material. Remove the compost from the vessel to do this. Add water if necessary.
Ensure that the water content of the test mixture in the composting vessels is neither too high nor too low
by visual observation. No free-standing water or clumps of material shall be present. Very dry conditions
are typically revealed by the absence of condensate in the headspace of the composting vessel. Moisture may
also be measured using suitable instruments. In this case, the water content shall be kept at 80 % to 90 %
of the WHC of the test mixture. The water content can be controlled by supplying water-saturated or dry
air. The desired water content can be obtained by adding water or by drainage via the top of the composting
vessel.
During the weekly stirring of the composting vessels and at the end of the test period, record any visual
...