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)

This International Standard 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 biologischen Abbaubarkeit von Kunststoffmaterialien im Boden durch Messung des Sauerstoffbedarfs in einem Respirometer oder der Menge des entstandenen Kohlendioxids (ISO 17556:2012)

Diese Internationale Norm legt ein Verfahren zum Bestimmen der vollständigen aeroben biologischen Abbaubarkeit von Kunststoffmaterialien im Boden durch Messen des Sauerstoffbedarfs in einem geschlossenen Respirometer oder durch Messen der Menge des entwickelten Kohlendioxids fest. Das Verfahren ist entwickelt worden, um einen bestmöglichen Grad der biologischen Abbaubarkeit 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 angewendet werden.
Dieses Verfahren gilt für folgende Materialien:
-   natürliche und/oder künstliche Polymere, Copolymere und deren Gemische;
-   Kunststoffmaterialien, die Zusatzstoffe wie Weichmacher oder Farbmittel enthalten;
-   wasserlösliche Polymere;
-   Materialien, die unter Prüfbedingungen nicht 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 Prüfmaterials, 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 17556:2012)

L'ISO 17556:2012 spécifie une méthode pour l'évaluation 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 employée 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 17556:2012)

Ta mednarodni standard 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 mešanice obojih; – polimerne materiale, ki vsebujejo aditive, kot so mehčalci ali barvila; - v vodi topne polimere. 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
Withdrawn
Public Enquiry End Date
24-Sep-2011
Publication Date
20-Sep-2012
Withdrawal Date
09-Jun-2019
Current Stage
9900 - Withdrawal (Adopted Project)
Start Date
07-Jun-2019
Due Date
30-Jun-2019
Completion Date
10-Jun-2019

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SLOVENSKI STANDARD
SIST EN ISO 17556:2012
01-oktober-2012
1DGRPHãþD
SIST EN ISO 17556:2005
3ROLPHUQLPDWHULDOL8JRWDYOMDQMHNRQþQHDHUREQHELRUD]JUDGOMLYRVWLSROLPHUQLK
PDWHULDORYY]HPOML]PHUMHQMHPSRUDEHNLVLNDYUHVSLURPHWUXDOLNROLþLQHQDVWDOHJD
RJOMLNRYHJDGLRNVLGD ,62
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)
Kunststoffe - Bestimmung der vollständigen aeroben biologischen Abbaubarkeit von
Kunststoffmaterialien im Boden durch Messung des Sauerstoffbedarfs in einem
Respirometer oder der Menge des entstandenen Kohlendioxids (ISO 17556:2012)
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 17556:2012)
Ta slovenski standard je istoveten z: EN ISO 17556:2012
ICS:
83.080.01 Polimerni materiali na Plastics in general
splošno
SIST EN ISO 17556:2012 en,fr
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 17556:2012

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SIST EN ISO 17556:2012


EUROPEAN STANDARD
EN ISO 17556

NORME EUROPÉENNE

EUROPÄISCHE NORM
August 2012
ICS 83.080.01 Supersedes EN ISO 17556:2004
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
17556:2012)
Plastiques - Détermination de la biodégradabilité aérobie Kunststoffe - Bestimmung der vollständigen aeroben
ultime des matériaux plastiques dans le sol par mesure de biologischen Abbaubarkeit von Kunststoffmaterialien im
la demande en oxygène dans un respiromètre ou de la Boden durch Messung des Sauerstoffbedarfs in einem
teneur en dioxyde de carbone libéré (ISO 17556:2012) Respirometer oder der Menge des entstandenen
Kohlendioxids (ISO 17556:2012)
This European Standard was approved by CEN on 20 July 2012.

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, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.





EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 17556:2012: E
worldwide for CEN national Members.

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SIST EN ISO 17556:2012
EN ISO 17556:2012 (E)
Contents Page
Foreword .3

2

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SIST EN ISO 17556:2012
EN ISO 17556:2012 (E)
Foreword
This document (EN ISO 17556:2012) 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 February 2013, and conflicting national standards shall be withdrawn
at the latest by February 2013.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 17556:2004.
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, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
Endorsement notice
The text of ISO 17556:2012 has been approved by CEN as a EN ISO 17556:2012 without any modification.

3

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SIST EN ISO 17556:2012

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SIST EN ISO 17556:2012
INTERNATIONAL ISO
STANDARD 17556
Second edition
2012-08-15
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 17556:2012(E)
©
ISO 2012

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SIST EN ISO 17556:2012
ISO 17556:2012(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2012
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO’s
member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2012 – All rights reserved

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SIST EN ISO 17556:2012
ISO 17556:2012(E)
Contents Page
Foreword .iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
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
8.4 Start-up and execution of the test . 7
9 Calculation and expression of results . 9
9.1 Calculation . 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) Round-robin testing .22
Bibliography .26
© ISO 2012 – All rights reserved iii

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SIST EN ISO 17556:2012
ISO 17556:2012(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 17556 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 5, Physical-
chemical properties.
This second edition cancels and replaces the first edition (ISO 17556:2003), which has been technically revised.
The main changes are as follows:
a) the introduction has been revised;
b) a definition of the term “total organic carbon” has been added (see 3.14);
c) the temperature of the test environment has been changed (see Clause 5);
d) the specifications for the analytical instrument for determining the amount of carbon dioxide evolved have
been revised (see 7.2.3);
e) Subclause 8.1 describing the preparation of the test material has been revised;
f) Subclause 8.3.1 describing the collection and sieving of soil has been revised;
g) the use of a standard soil is now permitted as an alternative to natural soil (see 8.3.2);
h) Subclause 8.4 describing the start-up and execution of the test has been revised;
i) the test report has been extended (see Clause 11);
j) a new annex (Annex F) giving examples of long-term tests has been added;
k) a new annex (Annex G) giving the results of round-robin testing has been added.
iv © ISO 2012 – All rights reserved

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SIST EN ISO 17556:2012
ISO 17556:2012(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.
© ISO 2012 – All rights reserved v

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SIST EN ISO 17556:2012

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SIST EN ISO 17556:2012
INTERNATIONAL STANDARD ISO 17556:2012(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 International Standard 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 referenced documents are indispensable for the application 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 10381-6, Soil quality — Sampling — Part 6: Guidance on the collection, handling and storage of soil under
aerobic conditions for the assessment of microbiological processes, biomass and diversity in the laboratory
ISO 10390, Soil quality — Determination of pH
ISO 10634, Water quality — Guidance for the preparation and treatment of poorly water-soluble organic
compounds for the subsequent evaluation of their biodegradability in an aqueous medium
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
© ISO 2012 – All rights reserved 1

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SIST EN ISO 17556:2012
ISO 17556:2012(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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 It is expressed as milligrams of oxygen uptake per milligram or gram of test compound.
3.3
dissolved organic carbon
DOC
that part of the organic carbon in water which cannot be removed by specified phase separation
NOTE 1 It is expressed as milligrams of carbon per 100 milligrams of test compound.
–2
NOTE 2 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 It is expressed as milligrams of oxygen uptake per milligram or gram of test compound.
3.5
theoretical amount of evolved carbon dioxide
ThCO
2
maximum theoretical amount of carbon dioxide evolved after completely oxidizing a chemical compound,
calculated from the molecular formula
NOTE 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
3.7
biodegradation phase
time, measured in days, from the end of the lag phase of a test until about 90 % of the maximum level of
biodegradation 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
2 © ISO 2012 – All rights reserved

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SIST EN ISO 17556:2012
ISO 17556:2012(E)
3.9
plateau phase
time from the end of the biodegradation phase until the end of the test
NOTE It is measured in days.
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 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 It is expressed as milligrams of carbon per 100 milligrams 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
2
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 test
2
is terminated when a constant level of biodegradation has been attained or, at the latest, after six months.
Unlike ISO 11266, which is used for a variety of organic compounds, this International Standard is specially
designed to determine the biodegradability of plastic materials.
© ISO 2012 – All rights reserved 3

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SIST EN ISO 17556:2012
ISO 17556:2012(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/min
2 2
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 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).
2
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 .
2
4 © ISO 2012 – All rights reserved

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SIST EN ISO 17556:2012
ISO 17556:2012(E)
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 material
2 2
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 preferably be used in powder form, but it may also be introduced in the form of films,
fragments or shaped articles.
Test samples may be reduced in size by means of cryogenic milling.
Experiments have shown that the ultimate degree of biodegradation is almost independent of the form and
shape of the test material. The speed of biodegradation, however, does depend on the form and shape of the
material. Test materials of similar form and shape should therefore be used if different kinds of plastic material
are to be compared in tests of the same duration. If the test material is in the form of a powder, small particles
of known size distribution should be used. A particle-size distribution with its maximum at 250 µm diameter is
recommended. If the test material is not in powder form, the size of the pieces of material should not be greater
than 5 mm × 5 mm. Also, the size of the test equipment used might depend on the form of the test material.
It should be ascertained that no undesired changes are caused in the test material due to the design of the
equipment, such as grinders, used. Normally, processing of the test material will not significantly influence the
degradation behaviour of the material (e.g. the use of powder in the case of composites).
Optionally, determine the hydrogen, oxygen, nitrogen, phosphorus and sulfur contents, as well as the molecular
mass of the test material, using, for example, size exclusion chromatography. Preferably, plastic materials without
additives such as plasticizers should be tested. When the material does contain such additives, information on
their biodegradability will be needed to assess the biodegradability of the polymeric material itself.
For details on how to handle compounds with limited solubility in water, see ISO 10634.
8.2 Preparation of the reference material
Use as reference material a well-defined biodegradable polymer [microcrystalline-cellulose powder, ashless
cellulose filters or poly(β-hydroxybutyrate)]. If possible, the physical form and size of the reference material
should be comparable to that of the test material.
As a negative control, a non-biodegradable polymer (e.g. polyethylene) in the same physical form as the test
material may be used.
8.3 Preparation of the test soil
8.3.1 Collection and sieving of soil
Use natural soil collected from the surface layer of fields and/or forests. If the potential biodegradability of the test
material is to be assessed, this soil may be pre-exposed to the test material. Sieve the soil to give particles of less
than
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