SIST EN ISO 17556:2019

Plastics - Determination of the ultimate aerobic biodegradability of plastic materials in soil by measuring the oxygen demand in a respirometer or the amount of carbon dioxide evolved (ISO 17556:2019)

This document specifies a method for determining the ultimate aerobic biodegradability of plastic
materials in soil by measuring the oxygen demand in a closed respirometer or the amount of carbon
dioxide evolved. The method is designed to yield an optimum degree of biodegradation by adjusting the
humidity of the test soil.
If a non-adapted soil is used as an inoculum, the test simulates the biodegradation processes which take
place in a natural environment; if a pre-exposed soil is used, the method can be used to investigate the
potential biodegradability of a test material.
This method applies to the following materials:
— natural and/or synthetic polymers, copolymers or mixtures of these;
— plastic materials which contain additives such as plasticizers or colorants;
— water-soluble polymers.
It does not necessarily apply to materials which, under the test conditions, inhibit the activity of the
microorganisms present in the soil. Inhibitory effects can be measured using an inhibition control or
by another suitable method. If the test material inhibits the microorganisms in the soil, a lower test
material concentration, another type of soil or a pre-exposed soil can be used.

Kunststoffe - Bestimmung der vollständigen aeroben Bioabbaubarkeit von Kunststoffmaterialien im Boden durch Messung des Sauerstoffbedarfs in einem Respirometer oder der Menge des entstandenen Kohlendioxids (ISO 17556:2019)

Dieses Dokument legt ein Verfahren zum Bestimmen der vollständigen aeroben biologischen Abbaubarkeit von Kunststoffmaterialien im Boden durch Messen des Sauerstoffbedarfs in einem geschlossenen Respiro-meter oder durch Messen der Menge des entwickelten Kohlendioxids fest. Das Verfahren ist entwickelt worden, um einen bestmöglichen Grad des biologischen Abbaus durch Einstellen der Feuchtigkeit des Prüfbodens zu erhalten.
Wenn ein nicht angepasster Boden als Inokulum verwendet wird, simuliert die Prüfung den biologischen Abbauprozess, der in einer natürlichen Umgebung abläuft; wird ein vorexponierter Boden verwendet, kann das Verfahren zum Untersuchen der potenziellen biologischen Abbaubarkeit eines Prüfmaterials ange¬wendet werden.
Dieses Verfahren gilt für folgende Materialien:
—   natürliche und/oder künstliche Polymere, Copolymere oder deren Gemische;
—   Kunststoffmaterialien, die Zusatzstoffe wie Weichmacher oder Farbmittel enthalten;
—   wasserlösliche Polymere.
Dieses Verfahren gilt nicht notwendigerweise für Materialien, die unter Prüfbedingungen die Aktivität der im Boden vorhandenen Mikroorganismen beeinträchtigen. Inhibierungseffekte können durch Anwendung eines Inhibierungskontrollversuchs oder durch ein anderes geeignetes Verfahren gemessen werden. Wenn das Prüfmaterial die Mikroorganismen im Boden hemmt, kann eine geringere Konzentration des Prüfmate-rials, ein anderer Bodentyp oder ein vorexponierter Boden eingesetzt werden.

Plastiques - Détermination de la biodégradabilité aérobie ultime des matériaux plastiques dans le sol par mesure de la demande en oxygène dans un respiromètre ou de la teneur en dioxyde de carbone libéré (ISO 17556:2019)

Le présent document spécifie une méthode de détermination de la biodégradabilité aérobie ultime des matériaux plastiques dans le sol en mesurant la demande en oxygène dans un respiromètre fermé ou la quantité de dioxyde de carbone libéré. La méthode est conçue pour produire un taux de biodégradation optimal en ajustant l'humidité du sol d'essai.
Si un sol non modifié est utilisé comme inoculum, l'essai simule les processus de biodégradation qui ont lieu dans un environnement naturel; si un sol pré-exposé est utilisé, la méthode peut être utilisée pour étudier la biodégradabilité potentielle d'un matériau d'essai.
Cette méthode est applicable aux matériaux suivants:
—          polymères, copolymères naturels et/ou synthétiques ou leurs mélanges;
—          matériaux plastiques contenant des additifs tels que plastifiants ou colorants;
—          polymères solubles dans l'eau.
Elle ne s'applique pas nécessairement aux matériaux qui, dans les conditions de l'essai, ont un effet inhibiteur vis-à-vis de l'activité des micro-organismes présents dans le sol. Les effets inhibiteurs peuvent être déterminés au moyen d'un contrôle de l'inhibition ou par une autre méthode appropriée. Si le matériau d'essai a un effet inhibiteur vis-à-vis des micro-organismes présents dans le sol, il est possible d'utiliser une concentration de matériau d'essai plus faible, un autre type de sol ou un sol pré-exposé.

Polimerni materiali - Ugotavljanje končne aerobne biorazgradljivosti polimernih materialov v zemlji z merjenjem porabe kisika v respirometru ali količine nastalega ogljikovega dioksida (ISO 17556:2019)

Ta dokument opisuje metodo za ugotavljanje končne aerobne biorazgradljivosti polimernih materialov v zemlji z merjenjem porabe kisika v zaprtem respirometru ali količine nastalega ogljikovega dioksida. Namen metode je doseči čim večjo stopnjo biorazgradljivosti s prilagoditvijo vlažnosti preskusne zemlje.
Če se kot inokulum uporabi neprilagojena zemlja, preskus simulira postopke biorazgraditve, ki potekajo v naravnem okolju; če se uporabi predhodno izpostavljena zemlja, se lahko metoda uporabi za preiskavo potencialne biorazgradljivosti preskusnega materiala.
Ta metoda zadeva naslednje materiale:
– naravne in/ali sintetične polimere, kopolimere ali njihove mešanice;
– polimerne materiale, ki vsebujejo dodatke, kot so mehčala ali barvila;
– polimere, topne v vodi.
Ne nanaša se nujno na materiale, ki pod preskusnimi pogoji zavirajo delovanje mikroorganizmov, prisotnih v zemlji. Zaviralne učinke je mogoče meriti na podlagi nadzora zaviranja ali z drugo ustrezno metodo. Če preskusni material zavira delovanje mikroorganizmov v zemlji, se lahko uporabi manjša koncentracija preskusnega materiala, druga vrsta zemlje ali predhodno izpostavljena zemlja.

General Information

• Status: Published
• Public Enquiry End Date: 15-Jul-2018
• Publication Date: 17-Jun-2019
• ICS: 83.080.01 - Plastics in general
• Technical Committee: IPMA - Polimer materials and products
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 07-Jun-2019
• Due Date: 12-Aug-2019
• Completion Date: 18-Jun-2019
• Ref Project: EN ISO 17556:2019 - Plastics - Determination of the ultimate aerobic biodegradability of plastic materials in soil by measuring the oxygen demand in a respirometer or the amount of carbon dioxide evolved (ISO 17556:2019)

Relations

• Revised: SIST EN ISO 17556:2012 - Plastics - Determination of the ultimate aerobic biodegradability of plastic materials in soil by measuring the oxygen demand in a respirometer or the amount of carbon dioxide evolved (ISO 17556:2012)
• Effective Date: 06-Dec-2017
• Replaces: SIST EN ISO 17556:2012 - Plastics - Determination of the ultimate aerobic biodegradability of plastic materials in soil by measuring the oxygen demand in a respirometer or the amount of carbon dioxide evolved (ISO 17556:2012)
• Effective Date: 05-Jun-2019

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 17556:2019
01-september-2019
Nadomešča:
SIST EN ISO 17556:2012
Polimerni materiali - Ugotavljanje končne aerobne biorazgradljivosti polimernih

materialov v zemlji z merjenjem porabe kisika v respirometru ali količine nastalega

ogljikovega dioksida (ISO 17556:2019)

Plastics - Determination of the ultimate aerobic biodegradability of plastic materials in soil

by measuring the oxygen demand in a respirometer or the amount of carbon dioxide
evolved (ISO 17556:2019)
Kunststoffe - Bestimmung der vollständigen aeroben Bioabbaubarkeit von
Kunststoffmaterialien im Boden durch Messung des Sauerstoffbedarfs in einem
Respirometer oder der Menge des entstandenen Kohlendioxids (ISO 17556:2019)
Plastiques - Détermination de la biodégradabilité aérobie ultime des matériaux

plastiques dans le sol par mesure de la demande en oxygène dans un respiromètre ou

de la teneur en dioxyde de carbone libéré (ISO 17556:2019)
Ta slovenski standard je istoveten z: EN ISO 17556:2019
ICS:
83.080.01 Polimerni materiali na Plastics in general
splošno
SIST EN ISO 17556:2019 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 17556:2019
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SIST EN ISO 17556:2019
EN ISO 17556
EUROPEAN STANDARD
NORME EUROPÉENNE
May 2019
EUROPÄISCHE NORM
ICS 83.080.01 Supersedes EN ISO 17556:2012
English Version
Plastics - Determination of the ultimate aerobic
biodegradability of plastic materials in soil by measuring
the oxygen demand in a respirometer or the amount of
carbon dioxide evolved (ISO 17556:2019)

Plastiques - Détermination de la biodégradabilité Kunststoffe - Bestimmung der vollständigen aeroben

aérobie ultime des matériaux plastiques dans le sol par Bioabbaubarkeit von Kunststoffmaterialien im Boden

mesure de la demande en oxygène dans un durch Messung des Sauerstoffbedarfs in einem

respiromètre ou de la teneur en dioxyde de carbone Respirometer oder der Menge des entstandenen

libéré (ISO 17556:2019) Kohlendioxids (ISO 17556:2019)
This European Standard was approved by CEN on 17 August 2018.

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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey 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

© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 17556:2019 E

worldwide for CEN national Members.
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SIST EN ISO 17556:2019
EN ISO 17556:2019 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 17556:2019
EN ISO 17556:2019 (E)
European foreword

This document (EN ISO 17556:2019) 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

NBN.

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 November 2019, and conflicting national standards

shall be withdrawn at the latest by November 2019.

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 17556:2012.

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, Former Yugoslav Republic of Macedonia,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,

Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 17556:2019 has been approved by CEN as EN ISO 17556:2019 without any modification.

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SIST EN ISO 17556:2019
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SIST EN ISO 17556:2019
INTERNATIONAL ISO
STANDARD 17556
Third edition
2019-05
Plastics — Determination of the
ultimate aerobic biodegradability
of plastic materials in soil by
measuring the oxygen demand in
a respirometer or the amount of
carbon dioxide evolved
Plastiques — Détermination de la biodégradabilité aérobie ultime des
matériaux plastiques dans le sol par mesure de la demande en oxygène
dans un respiromètre ou de la teneur en dioxyde de carbone libéré
Reference number
ISO 17556:2019(E)
ISO 2019
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SIST EN ISO 17556:2019
ISO 17556:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019

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]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
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SIST EN ISO 17556:2019
ISO 17556:2019(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 3

5 Test environment ................................................................................................................................................................................................. 4

6 Materials ....................................................................................................................................................................................................................... 4

7 Apparatus ..................................................................................................................................................................................................................... 4

8 Procedure..................................................................................................................................................................................................................... 4

8.1 Preparation of the test material ............................................................................................................................................... 4

8.2 Preparation of the reference material ................................................................................................................................ 5

8.3 Preparation of the test soil ........................................................................................................................................................... 5

8.3.1 Collection and sieving of soil ................................................................................................................................. 5

8.3.2 Preparation of standard soil .................................................................................................................................. 6

8.3.3 Measurement of soil characteristics ............................................................................................................... 7

8.3.4 Adjustment of the water content and the pH of the soil ................................................................ 7

8.3.5 Handling and storage of the soil ......................................................................................................................... 7

8.4 Start-up and execution of the test .......................................................................................................................................... 7

9 Calculation and expression of results ............................................................................................................................................. 9

9.1 Calculation .................................................................................................................................................................................................. 9

9.1.1 Percentage biodegradation from oxygen consumption values ................................................ 9

9.1.2 Percentage biodegradation from carbon dioxide evolved ........................................................... 9

9.2 Expression and interpretation of results ......................................................................................................................10

10 Validity of results ..............................................................................................................................................................................................10

11 Test report ................................................................................................................................................................................................................10

Annex A (informative) Principle of a manometric respirometer (example) ...........................................................12

Annex B (informative) Example of a system for measuring the amount of carbon dioxide

evolved .........................................................................................................................................................................................................................13

Annex C (informative) Examples of methods for the determination of evolved carbon dioxide ........14

Annex D (informative) Theoretical oxygen demand (ThOD) ...................................................................................................16

Annex E (informative) Example of a determination of the amount and the molecular mass

of water-insoluble polymer remaining at the end of a biodegradation test .......................................17

Annex F (informative) Examples of long-term tests ..........................................................................................................................18

Annex G (informative) Interlaboratory test ...............................................................................................................................................22

Bibliography .............................................................................................................................................................................................................................26

© ISO 2019 – All rights reserved iii
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SIST EN ISO 17556:2019
ISO 17556:2019(E)
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 documents 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).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on 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 the following

URL: www .iso .org/iso/foreword .html.

This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 14,

Environmental aspects.

This third edition cancels and replaces the second edition (ISO 17556:2012), which has been technically

revised. The main changes compared to the previous edition are as follows:
a) the unit for BOD, COD and DIC has been corrected (see Clause 3);

b) the formula for calculating the percent biodegradation has been modified (see 9.1.1);

c) the test period has been revised to two years at the longest (see Clause 4);
d) the number of replicates has been corrected to three (see 9.2).

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 2019 – All rights reserved
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SIST EN ISO 17556:2019
ISO 17556:2019(E)
Introduction

A number of plastic materials and products have been designed for applications ending up in or on

soil. They have been developed for applications where biodegradation is beneficial from a technical,

environmental, social or economic standpoint. Examples can be found in agriculture (e.g. mulching

film), horticulture (e.g. twines and clips, flower pots, pins), funeral items (e.g. body bags), recreation (e.g.

plastic “clay” pigeons for shooting, hunting cartridges), etc. In many cases, recovery and/or recycling of

these plastic items is either difficult or not economically viable. Various types of biodegradable plastics

have been developed which have been designed to biodegrade and disappear in situ at the end of their

useful life. Several International Standards specify test methods for determining the ultimate aerobic

or anaerobic biodegradation of plastic materials in aqueous or compost conditions. Considering the

use and disposal of biodegradable plastics, it is important to establish a test method to determine the

ultimate aerobic biodegradation of such plastic materials in soil.
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SIST EN ISO 17556:2019
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SIST EN ISO 17556:2019
INTERNATIONAL STANDARD ISO 17556:2019(E)
Plastics — Determination of the ultimate aerobic
biodegradability of plastic materials in soil by measuring
the oxygen demand in a respirometer or the amount of
carbon dioxide evolved

WARNING — Appropriate precautions should be taken when handling soil because it might

contain potentially pathogenic organisms. 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 in soil by measuring the oxygen demand in a closed respirometer or the amount of carbon

dioxide evolved. The method is designed to yield an optimum degree of biodegradation by adjusting the

humidity of the test soil.

If a non-adapted soil is used as an inoculum, the test simulates the biodegradation processes which take

place in a natural environment; if a pre-exposed soil is used, the method can be used to investigate the

potential biodegradability of a test material.
This method applies to the following materials:
— natural and/or synthetic polymers, copolymers or mixtures of these;
— plastic materials which contain additives such as plasticizers or colorants;
— water-soluble polymers.

It does not necessarily apply to materials which, under the test conditions, inhibit the activity of the

microorganisms present in the soil. Inhibitory effects can be measured using an inhibition control or

by another suitable method. If the test material inhibits the microorganisms in the soil, a lower test

material concentration, another type of soil or a pre-exposed soil 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 10390, Soil quality — Determination of pH

ISO 10694, Soil quality — Determination of organic and total carbon after dry combustion (elementary

analysis)

ISO 11274, Soil quality — Determination of the water-retention characteristic — Laboratory methods

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
© ISO 2019 – All rights reserved 1
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SIST EN ISO 17556:2019
ISO 17556:2019(E)
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
ultimate aerobic biodegradation

breakdown 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

3.2
biochemical oxygen demand
BOD

mass concentration of dissolved oxygen consumed under specified conditions by the aerobic biological

oxidation of a chemical compound or organic matter

Note 1 to entry: It is expressed as milligrams of oxygen uptake per kilogram of test soil.

3.3
dissolved organic carbon
DOC

part of the organic carbon in water which cannot be removed by specified phase separation

Note 1 to entry: It is expressed as milligrams of carbon per litre.

Note 2 to entry: Typical means of separation are centrifugation at 40 000 m⋅s for 15 min or membrane filtration

using membranes with pores of diameter 0,2 µm to 0,45 µm.
3.4
theoretical oxygen demand
ThOD

maximum theoretical amount of oxygen required to oxidize a chemical compound completely, calculated

from the molecular formula

Note 1 to entry: It is expressed as milligrams of oxygen uptake per milligram or gram of test compound.

3.5
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

Note 1 to entry: It is expressed as milligrams of carbon dioxide evolved per milligram or gram of test compound.

3.6
lag phase

time, measured in days, from the start of a test until adaptation and/or selection of the degrading

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 (3.8)
3.7
biodegradation phase

time, measured in days, from the end of the lag phase (3.6) of a test until about 90 % of the maximum

level of biodegradation (3.8) has been reached
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
3.9
plateau phase
time from the end of the biodegradation phase (3.7) until the end of the test
Note 1 to entry: It is measured in days.
2 © ISO 2019 – All rights reserved
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SIST EN ISO 17556:2019
ISO 17556:2019(E)
3.10
pre-conditioning

pre-incubation of soil 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 performance of the test by

acclimatization of the microorganisms to the test conditions
3.11
pre-exposure

pre-incubation of soil in the presence of the chemical compound or organic matter under test, with the

aim of enhancing the ability of the soil to biodegrade the test material by adaptation and/or selection of

the microorganisms
3.12
water content

mass of water which evaporates from the soil when the soil is dried to constant mass at 105 °C, divided

by the dry mass of the soil

Note 1 to entry: This is simply the ratio between the mass of the water and that of the soil particles in a soil sample.

3.13
total water-holding capacity

mass of water which 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
3.14
total organic carbon
TOC
amount of carbon bound in an organic compound

Note 1 to entry: It is expressed as milligrams of carbon per 100 mg of the compound.

4 Principle

This method is designed to yield the optimum rate of biodegradation of a plastic material in a test soil

by controlling the humidity of the soil, and to determine the ultimate biodegradability of the material.

The plastic material, which is the sole source of carbon and energy, is mixed with the soil. The mixture

is allowed to stand in a flask over a period of time during which the amount of oxygen consumed

(BOD) or the amount of carbon dioxide evolved is determined. Provided the CO evolved is absorbed,

the BOD can be determined, for example, by measuring the amount of oxygen required to maintain

a constant gas volume in a respirometer flask, or by measuring either automatically or manually the

change in volume or pressure (or a combination of the two). An example of a suitable respirometer is

shown in Annex A. The amount of carbon dioxide evolved is measured at intervals dependent on the

biodegradation kinetics of the test substance by passing carbon-dioxide-free air over the soil and then

determining the carbon dioxide content of the air by a suitable method. Examples of suitable methods

are given in Annexes B and C.

The level of biodegradation, expressed as a percentage, is determined by comparing the BOD with

the theoretical oxygen demand (ThOD) or by comparing the amount of carbon dioxide evolved with

the theoretical amount (ThCO ). The influence of possible nitrification processes on the BOD has to

be considered. The normal test period is six months. The test may be shortened or extended until the

plateau phase (see 3.9) is reached, but the total test period shall not exceed two years.

Unlike ISO 11266, which is used for a variety of organic compounds, this document is specially designed

to determine the biodegradability of plastic materials.
© ISO 2019 – All rights reserved 3
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SIST EN ISO 17556:2019
ISO 17556:2019(E)
5 Test environment

Incubation shall take place in the dark or in diffused light in an enclosure which is free from vapours

toxic to microorganisms and is maintained at a temperature constant to within ±2 °C in the range

between 20 °C and 28 °C, preferably 25 °C.
6 Materials
6.1 Distilled water, containing less than 2 mg of DOC per litre.
6.2 Carbon dioxide absorber, preferably soda lime pellets.
7 Apparatus

Ensure that all glassware is thoroughly cleaned and, in particular, free from organic or toxic matter.

7.1 Closed respirometer, including test flasks and all other necessary equipment, located in a

constant-temperature enclosure or in a thermostatically controlled apparatus (e.g. a water-bath). An

example is described in Annex A.

Any respirometer capable of determining with sufficient accuracy the biochemical oxygen demand is

suitable, preferably an apparatus which measures and automatically replaces the oxygen consumed

so that no oxygen deficiency and no inhibition of the microbial activity occurs during the degradation

process.
7.2 Apparatus for measuring the amount of carbon dioxide evolved

7.2.1 Test flasks: glass vessels (e.g. conical flasks or bottles), fitted with tubing impermeable to

carbon dioxide to allow purging with gas, and located in a constant-temperature enclosure or in a

thermostatically controlled apparatus (e.g. a water-bath).

7.2.2 CO -free-air production system, capable of supplying CO -free air at a flow rate of several ml/

2 2

min to each test flask, held constant to within ±10 % (see example of system, including test vessels, in

Annex B). Alternatively, the incubation apparatus shown in ASTM D5988 may be used.

7.2.3 Analytical equipment for accurately determining carbon dioxide. Typical examples are

a carbon dioxide IR analyser, a dissolved inorganic carbon (DIC) analyser, apparatus for titrimetric

determination after complete absorption in a basic solution (see Annex C), and apparatus for the

gravimetric determination of carbon dioxide in accordance with ISO 14855-2.
7.3 Analytical balance.
7.4 pH-meter.
8 Procedure
8.1 Preparation of the test material

The test material shall be of known mass and contain sufficient carbon to yield a BOD or a quantity of

carbon dioxide that can be adequately measured by the analytical equipment used. Calculate the TOC

4 © ISO 2019 – All rights reserved
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SIST EN ISO 17556:2019
ISO 17556:2019(E)

from the chemical formula or determine it by a suitable analytical technique (e.g. elemental analysis or

measurement in accordance with ISO 8245) and calculate the ThOD or ThCO (see Annexes C and D).

NOTE Although elemental analysis is generally less accurate for macromolecules than for low-molecular-

mass compounds, the accuracy is usually acceptable for the purposes of calculating the ThOD or ThCO .

The amount of test material shall be sufficient to outweigh any variations in the background oxygen

consumption or any carbon dioxide evolved from the test soil: 100 mg to 300 mg of test material to

100 g to 300 g of soil is usually adequate. The maximum amount of test material is limited by the oxygen

supply to the test system. The use of 200 mg of test material with 200 g of soil is recommended unless

the soil contains an excessively large amount of organic matter.

When using test systems based on the determination of the carbon dioxide evolved, higher test material

amounts can be used (e.g. 2 500 mg for 200 g of soil) in order to increase the difference between the test

material CO production and the blank control CO production. Furthermore, a greater amount of test

2 2

material will be required if a final mass balance determination is to be carried out (see Annex E).

Pre-aeration of the test material or the addition of inert material is recommended, if necessary, to

reduce the respiration of the soil in the blank flasks.
The test material should
...