ISO 17088:2021

INTERNATIONAL ISO
STANDARD 17088
Third edition
2021-04
Plastics — Organic recycling —
Specifications for compostable
plastics
Plastiques — Recyclage organique — Spécifications pour les
plastiques compostables
Reference number
©
ISO 2021
© ISO 2021
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ii © ISO 2021 – All rights reserved

Contents Page
Foreword .iv
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 General . 4
5 Basic requirements . 4
5.1 General . 4
5.2 Disintegration during composting . 4
5.3 Ultimate aerobic biodegradability . 4
5.4 No adverse effect of compost on terrestrial organisms . 4
5.5 Control of constituents . 5
6 Detailed requirements . 5
6.1 General . 5
6.2 Disintegration during composting . 5
6.2.1 General. 5
6.2.2 Variation in permitted thickness . 6
6.3 Ultimate biodegradation . 6
6.3.1 Aerobic biodegradation . 6
6.3.2 Potential for biogas production . 7
6.4 No adverse effects of compost on terrestrial organisms . 8
6.4.1 General. 8
6.4.2 Ecotoxicity test scheme . 8
6.4.3 Plant growth test (mandatory) . 8
6.4.4 Acute earthworm toxicity test (mandatory) . 9
6.4.5 Chronic earthworm toxicity test (mandatory) . 9
6.4.6 Nitrification inhibition test with soil microorganisms (optional) . 9
6.5 Control of constituents . 9
6.5.1 General. 9
6.5.2 Regulated metals and other elements . 9
6.5.3 Per- and poly-fluorinated compounds (PFCs) .10
6.5.4 Other hazardous substances .10
6.5.5 Volatile solids .10
7 Declaration of results .10
8 Test report .10
Annex A (informative) Examples of maximum concentrations of regulated metals and other
elements .12
Annex B (normative) Detection of per- and poly-fluorinated compounds and maximum
concentrations of other hazardous substances .13
Annex C (normative) Determination of ecotoxic effects on higher plants .14
Annex D (normative) Determination of acute ecotoxic effects to earthworm .16
Annex E (normative) Determination of chronic ecotoxic effects to earthworm .18
Annex F (informative) Determination of nitrification activity of soil microorganisms .20
Bibliography .22
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 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.
This third edition cancels and replaces the second edition (ISO 17088:2012), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— in Clause 3:
— the following terms have been added: organic recycling, anaerobic digestion, per- and poly-
fluorinated compound, well-managed industrial composting process, industrial composting,
organic constituents, home composting;
— the term catalyst has been deleted;
— 6.1.4 has been deleted;
— a new subclause, 6.2.2, on variation in permitted thickness has been added;
— in 6.3, requirements regarding biodegradability of constituents have been revised;
— in 6.3.1.1, the following references have been added as additional laboratory test methods for
biodegradation testing: ISO 14851, ISO 14852, ISO 17556;
— a new subclause, 6.3.2, on potential for biogas production has been added;
— 6.4 has been extended covering ecotoxicity tests with representative species from three trophic
levels;
— in 6.5, new requirements regarding control of constituents with respect to per- and poly-fluorinated
compounds (PFCs) and hazardous substances (as specified in Annex B) have been included;
— the list of regulated metals in EU + EFTA countries has been revised;
iv © ISO 2021 – All rights reserved

— new annexes, Annex B, Annex C, Annex E and Annex F, have been added.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
Introduction
Management of solid wastes is a problem of growing interest around the world. Cities, towns and
countries are attempting to divert more materials from disposal (landfills and incineration without
energy recovery) by performing different recovery options in order to transform waste into usable
products. Plastics recovery technologies include material recovery (mechanical recycling, chemical
or feedstock recycling, and biological or organic recycling) and the recovery of energy in the form of
usable heat under controlled combustion conditions.
This document intends to correctly identify compostable plastics, and compostable products made
from plastics, which can be recovered by organic recycling, i.e. will disintegrate and biodegrade
satisfactorily together with biowaste producing compost as an outcome, in composting or in anaerobic
digestion followed by composting, and will not leave any persistent or hazardous residues.
vi © ISO 2021 – All rights reserved

INTERNATIONAL STANDARD ISO 17088:2021(E)
Plastics — Organic recycling — Specifications for
compostable plastics
WARNING — Sewage, activated sludge, soil and compost might 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 procedures and requirements for plastics, and products made from plastics,
that are suitable for recovery through organic recycling. The four following aspects are addressed:
a) disintegration during composting;
b) ultimate aerobic biodegradation;
c) no adverse effects of compost on terrestrial organisms;
d) control of constituents.
These four aspects are suitable to assess the effects on the industrial composting process.
This document is intended to be used as the basis for systems of labelling and claims for compostable
plastics materials and products.
This document does not provide information on requirements for the biodegradability of plastics which
end up in the environment as litter. It is also not applicable to biological treatment undertaken in small
installations by householders.
NOTE 1 The recovery of compostable plastics through composting can be carried out under the conditions
found in well-managed industrial composting processes, where the temperature, water content, aerobic
conditions, carbon/nitrogen ratio and processing conditions are optimized. Such conditions are generally
obtained in industrial and municipal composting plants. Under these conditions, compostable plastics
disintegrate and biodegrade at rates comparable to yard trimmings, kraft paper bags and food scraps.
NOTE 2 “Compostable” or “compostable in municipal and industrial composting facilities” are expressions
considered to be equivalent to organically recyclable for the purposes of this document.
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 472, Plastics — Vocabulary
ISO 11268-1, Soil quality — Effects of pollutants on earthworms — Part 1: Determination of acute toxicity
to Eisenia fetida/Eisenia andrei
ISO 11268-2, Soil quality — Effects of pollutants on earthworms — Part 2: Determination of effects on
reproduction of Eisenia fetida/Eisenia andrei
ISO 11269-2, Soil quality — Determination of the effects of pollutants on soil flora — Part 2: Effects of
contaminated soil on the emergence and early growth of higher plants
ISO 14851, Determination of the ultimate aerobic biodegradability of plastic materials in an aqueous
medium — Method by measuring the oxygen demand in a closed respirometer
ISO 14852, Determination of the ultimate aerobic biodegradability of plastic materials in an aqueous
medium — Method by analysis of evolved carbon dioxide
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 14855-2, 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 15685, Soil quality — Determination of  potential nitrification and inhibition of nitrification — Rapid
test by ammonium oxidation
ISO 16929, Plastics — Determination of the degree of disintegration of plastic materials under defined
composting conditions in a pilot-scale test
ISO 17556, 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
EN 14582, Characterization of waste — Halogen and sulfur content — Oxygen combustion in closed
systems and determination methods
OECD (2006), Test No. 208: Terrestrial Plant Test: Seedling Emergence and Seedling Growth Test, OECD
Guidelines for the Testing of Chemicals, Section 2, OECD Publishing, Paris,
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
compost
organic soil conditioner obtained by biodegradation of a mixture consisting principally of vegetable
residues, occasionally with other organic material and having a limited mineral content
[SOURCE: ISO 472:2013, 2.1735]
3.2
compostable plastic
plastic that undergoes degradation by biological processes during composting to yield CO , water,
inorganic compounds and biomass at a rate consistent with other known compostable materials and
leave no visible, distinguishable or toxic residue
Note 1 to entry: "Hazardous" is used synonymously to "toxic".
3.3
composting
aerobic process designed to produce compost starting from biodegradable waste
Note 1 to entry: Composting is classified into industrial composting, home composting and worm composting.
3.4
disintegration
physical breakdown of a material into very small fragments
2 © ISO 2021 – All rights reserved

3.5
filler
relatively inert solid material added to a plastic to modify its strength, permanence, working properties
or other qualities, or to lower costs
3.6
organic recycling
aerobic (composting) or anaerobic (digestion) treatment of plastics waste under controlled conditions
using micro-organisms to produce, in the presence of oxygen, stabilized organic residues (compost),
carbon dioxide and water or, in the absence of oxygen, stabilized organic residues (compost), methane
and carbon dioxide
Note 1 to entry: The term “biological recycling” is used synonymously.
[SOURCE: ISO 15270:2008, 3.5, modified — "biodegradable" has been omitted and "(compost)" has been
added.]
3.7
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
3.8
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
3.9
volatile solid
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 (3.7) of the same sample
Note 1 to entry: The volatile-solids content is an indication of the amount of organic matter present.
3.10
anaerobic digestion
process of controlled decomposition of biodegradable materials under managed conditions where free
oxygen is absent, at temperatures suitable for naturally occurring mesophilic or thermophilic anaerobic
and facultative bacteria species, that convert the inputs to a methane rich biogas and digestate
Note 1 to entry: In a second phase, the digestate is typically stabilised by means of a composting (aerobic) process.
3.11
per- and poly-fluorinated compound
PFC
organofluorine compound containing only carbon-fluorine bonds and carbon-carbon bonds but also
other heteroatoms
3.12
well-managed industrial composting process
composting process performed under controlled conditions where the temperature, water content,
aerobic conditions, carbon/ nitrogen ratio and other conditions are optimized
3.13
industrial composting
composting process performed under controlled conditions on industrial scale with the aim of
producing compost for the market
Note 1 to entry: In some regions industrial composting is referred to as professional composting.
3.14
organic constituent
chemical constituent that contains carbon covalently linked to other carbon atoms and to other
elements, most commonly hydrogen, oxygen or nitrogen
Note 1 to entry: Inorganic carbonates, carbides, cyanides and simple oxides such as carbon monoxide and carbon
dioxide are not considered as organic constituent.
Note 2 to entry: Allotropes of carbon, such as diamond, graphite, carbon black, fullerenes, and carbon nanotubes
are also not considered as organic constituent.
3.15
home composting
practice performed by a private individual with the aim of producing compost for his own use
4 General
4.1 The purpose of this document is to establish requirements for plastics materials and plastics
products that can be recovered by means of organic recycling in well-managed industrial composting
facilities where the typical conditions of composting can be consistently obtained (i.e. a long thermophilic
phase, aerobic conditions, sufficient water content, a suitable carbon/nitrogen ratio, etc.).
4.2 The following characteristics are determined:
a) the ultimate level of aerobic biodegradation of the test material;
b) the degree of disintegration obtained;
c) any negative effects on the finished compost;
d) the maximum concentration of regulated metals and other elements and per- and poly-fluorinated
compounds (PFCs) (determined as fluorine) in the test material.
In addition, the use of other hazardous substances as specified in Annex B in the test material is
assessed.
5 Basic requirements
5.1 General
In order to comply with this document, plastics products and materials shall demonstrate each of the
characteristics found in 5.2 to 5.5, as quantified in Clause 6.
5.2 Disintegration during composting
The plastics product or material shall disintegrate during composting as quantified in 6.2.
5.3 Ultimate aerobic biodegradability
The ultimate level of aerobic biodegradation shall be established by testing under controlled conditions
as quantified in 6.3.
5.4 No adverse effect of compost on terrestrial organisms
The composting of plastics products or materials shall have no adverse effects on terrestrial organisms
as quantified in 6.4.
4 © ISO 2021 – All rights reserved

Ecotoxic effects on terrestrial organisms shall be determined by comparing compost produced with
and without the addition of a plastics product or a material.
5.5 Control of constituents
The plastics product or material under investigation shall be identified and characterized prior to
testing including:
— determination of the presence of regulated metals and other elements;
— determination of the presence per- and poly-fluorinated compounds (PFCs) (determined as fluorine);
— evaluation of the presence of other hazardous substances as specified in Annex B;
— determination of volatile solids;
as quantified in 6.5, taking legal compliance into consideration.
6 Detailed requirements
6.1 General
6.1.1 In order to be identified as compostable, products and materials shall meet the requirements
of 6.2, 6.3, 6.4 and 6.5, using appropriate laboratory tests representative of the conditions found in
industrial composting facilities.
6.1.2 Test samples shall not be subjected to conditions or procedures designed to accelerate
disintegration or biodegradation prior to testing as described in 6.2 or 6.3.
6.1.3 If the products or materials under test include inorganic fillers, the fillers shall be present when
the products or materials are tested as described in 6.2, 6.3, 6.4, 6.5.2 and 6.5.3. However, their inorganic
carbon content shall be excluded from the mineralization calculations in 6.3. Products or materials
to which fillers are subsequently added, or in which the filler content is changed, shall be retested to
demonstrate that the new material meets the requirements of 6.2, 6.3, 6.4, 6.5.2 and 6.5.3. Manufacturers
may establish an acceptable range by testing the highest and the lowest concentrations. In addition,
fillers shall be identified and assessed according to 6.5.4 with respect to potential hazardous properties
as defined in Annex B. Examples of inorganic fillers include (but are not limited to) calcium carbonate
and titanium dioxide.
An exception shall be made for materials containing calcium carbonate or other carbonates as a filler.
For biodegradation, these materials should be tested without the carbonate filler as this might disturb
an exact measurement. For chemical analyses, disintegration and toxicity the material should however
be tested with the carbonate filler included.
6.2 Disintegration during composting
6.2.1 General
When testing finished articles and products, testing shall be conducted starting with the articles and
products in the same form as they are intended to be used. For products and materials that are made in
several different thicknesses or densities, such as films, containers and foams, only the thickest or most
dense products and materials need to be tested as long as the chemical composition and structure of
the respective articles and products remain the same.
NOTE 1 In general, for practical reasons, samples of the plastic material are tested in order to define the
maximum thickness allowing disintegration. Finished articles and products are then manufactured with
thicknesses below the maximum thickness.
A plastics product is considered to have demonstrated satisfactory disintegration if, after 84 days in a
controlled composting test, it is completely disintegrated into less than 2 mm fragments. This is proven
if no more than 10 % of its original dry mass remains after sieving through a 2,0 mm sieve.
NOTE 2 The 90 % threshold is the result of complete disintegration (100 %) minus 10 % tolerance. A 10 %
tolerance is applied in order to take into consideration the variability occurring in biological processes.
The test shall be carried out in accordance with ISO 16929.
Alternatively, the lab-scale test in accordance with ISO 20200 can be used. The initial test item
concentration shall be 1 % (wet mass) in each of these tests following the procedure given in ISO 16929.
In case of differing results, ISO 16929 results shall prevail.
Special attention should be given to the visual aspects of compost. Visual contamination of compost
as evidenced by reduction of aesthetic acceptability should not be significantly increased by any post
composting residues of the introduced plastics product or material. Therefore, any residue shall be
indistinguishable to the naked eye from the other matter in the compost at a distance of 500 mm. The
visible assessment of the compost shall be documented by means of photography.
6.2.2 Variation in permitted thickness
In some cases, specific composting technologies require early sieving and fast disintegration. In this
case, the following rule shall apply in order to identify the maximum thickness.
If disintegration is achieved for the maximum thickness (X) in 12 weeks, it shall be deemed given that
a thickness of X x 0,45 will achieve sufficient disintegration within 42 days. Alternative declarative
statements are not permitted.
6.3 Ultimate biodegradation
6.3.1 Aerobic biodegradation
6.3.1.1 Laboratory test methods
Only biodegradation tests that provide unequivocal information on the intrinsic and ultimate
biodegradability of the material or its significant organic constituents shall be used. The test under
conditions of controlled aerobic composting in accordance with ISO 14855-1 and ISO 14855-2 shall be
applied preferentially unless inappropriate to the type and properties of the material under test (e.g.
in the case of printing inks, additives or colorants). Alternatively, the biodegradation tests according
to ISO 14851, ISO 14852 or ISO 17556 (after six months duration) shall be used. Inorganic carbon is
excluded from the calculation of biodegradation.
The ultimate aerobic biodegradation shall be determined for the whole material or for each organic
constituent.
6.3.1.2 Biodegradability of constituents
Biodegradability of organic constituents, which are present in the material at a concentration between
1 % and 15 % (by dry mass) shall be proven separately according to 6.3.1.1.
As an alternative, the level of biodegradation of an organic constituent may be determined using an
artificial blend of the same plastics material. This artificial blend shall consist of at least 15 % of the
respective organic constituent (by dry mass). The chemical composition and the structure of the
plastics material shall remain the same, but the amount of the organic constituent under consideration
shall be increased to a minimum of 15 % (by dry mass). The artificial blend shall be produced following
the same processing conditions (e.g. extrusion) as used for the production of the original plastics
material containing less than 15 % (by dry mass) of the respective constituent.
6 © ISO 2021 – All rights reserved

In case the artificial blend meets the criteria specified in 6.3.1.3 and 6.3.1.4, the constituent is considered
biodegradable in the context of this document. The constituent can then be used at the same (15 %) or
lower concentration (<15 %; by dry mass) in a material that also contains the same co-substrate as the
tested material.
NOTE 1 The objective of testing an artificial blend is to verify a synergistic effect on biodegradation of a
constituent in the presence of a biodegradable co-substrate in the same material.
NOTE 2 The concentration of the constituent in the artificial blend is set at a minimum of 15 % in order to
avoid false positive results, as theoretically a material with e.g. 10 % of a non biodegradable constituent can still
reach the pass level for biodegradation specified in 6.3.1.3 and 6.3.1.4.
Constituents that turned out to be readily biodegradable in a ready biodegradation test according to an
[3] [19]
OECD test guideline (OECD 301, Methods A to F ; OECD 310 ) are considered biodegradable in the
context of this document.
Constituents which are present at concentrations of less than 1 % (by dry mass) do not need to
demonstrate biodegradability. However, the sum of such constituents shall not exceed 5 % (by dry
mass). Non-biodegradable plastic materials should generally not intentionally be added.
6.3.1.3 Criteria and pass level
For all polymers, ≥90 % of the organic carbon (relative to a reference material) shall have been
converted to carbon dioxide by the end of the test period after 180 d (see 6.3.1.4). Both the reference
material and the test sample shall be composted for the same period and the results compared at the
same point in time after, for example, the activity of both has reached a plateau. The reference material
used shall be microcrystalline cellulose.
As an alternative, 90 % (in absolute terms) of the organic carbon shall have been converted to carbon
dioxide by the end of the test period.
NOTE Biodegradability is assessed by measuring the mineralization level, i.e. the conversion of the organic
carbon of a plastics product or a material into CO with the consumption of O , or into CO and CH under anaerobic
2 2 2 4
conditions. During biodegradation, part of the organic carbon is also assimilated as biomass. This biomass yield
typically ranges from 10 % to 40 %, depending on the substrate. As a consequence, the mineralization level
will rarely reach 100 % also when the biodegradation is 100 %, because of biomass formation. Standard test
methods for the accurate determination of plastics product´s or material`s carbon assimilated in biomass during
biodegradation are not available at the time of publication.
6.3.1.4 Test duration
If the level of biodegradation exceeds 90 % (relative to a reference material or in absolute terms; see
6.3.1.3), then the biodegradation test (see 6.3.1.1) can be terminated. However, the test period shall be
no longer than 180 days.
6.3.2 Potential for biogas production
Compost is not only the final product of the aerobic composting process but also the aerobically
stabilized product of the anaerobic digestion process. The level of anaerobic biodegradation can be
established by testing under controlled conditions using ISO 14853 or ISO 15985, in order to estimate
the amount of biogas recovered during the first anaerobic phase.
No pass/fail requirement for the percentage of anaerobic biodegradation has been set because most
commercial biogasification plants provide for a follow-on second phase of aerobic organic recycling.
In order to meet the requirements of this document, a material or plastics product shall meet the
compostability criteria set forth in Clause 6.
6.4 No adverse effects of compost on terrestrial organisms
6.4.1 General
In order to ensure that the composting of plastic products or materials does not have any harmful
effects on the finished compost or on the environment, all requirements specified in 6.4.3, 6.4.4 (or
6.4.5) and 6.4.6 shall be met.
6.4.2 Ecotoxicity test scheme
Ecotoxicity tests are performed with compost samples produced with and without the addition of a
plastics product or a material to determine and assess possible harmful effects on terrestrial organisms.
The test scheme considers:
— all relevant terrestrial organism groups such as plants, earthworms (invertebrates) and
microorganisms;
— important ecological processes critical due to their role in maintaining soil functions such as
breakdown of organic matter, formation of soil structure and cycling of materials;
— relevant exposure pathways of degradation products such as pore water and soil material.
The ecotoxicity test scheme is shown in Table 1.
Table 1 — Ecotoxicity testing scheme for the assessment of adverse effects of compost on
terrestrial organisms
Organism group Ecological process Soil exposure pathway Test methods
plants: plant growth test according
mainly soil pore water (by to OECD 208 or ISO 11269-2
— higher plants
primary production
root uptake) with the modifications speci-
fied in Annex C
diverse and multiple up-
acute earthworm test ac-
invertebrates: take routes:
cording to ISO 11268-1 with
the modifications given in
— earthworms — soil pore water:
breakdown of organic
Annex D or alternatively
matter; formation of soil
chronic earthworm toxicity
— ingestion of soil
structure
test according to ISO 11268-
material;
2 with the modifications
— soil air. specified in Annex E
mircoorganisms: (option- nitrification inhibition test
al) with soil microorganisms
recycling of nutrients mainly soil pore water according to ISO 15685 with
— bacteria
the modifications specified
in Annex F
6.4.3 Plant growth test (mandatory)
The seedling germination rate and the plant biomass of the tested plant species in the sample compost
exposed to the test material shall be more than 90 % of those from the corresponding blank compost
not exposed to the test material, determined in accordance with OECD 208 or ISO 11269-2 with the
modifications specified in Annex C.
Plastics products or materials that have already been assessed for plant toxicity following EN 13432,
EN 14995, ISO 18606, ASTM D6400, ASTM D6868, AS 4736, AS 5810, EN 17033 or equivalent standard
specifications and fulfilled the pass level for plant toxicity laid down in this document do not need to be
retested.
8 © ISO 2021 – All rights reserved

6.4.4 Acute earthworm toxicity test (mandatory)
The survival and the biomass of the surviving adult earthworms in the sample compost exposed to the
test material shall be more than 90 % of those from the corresponding blank compost not exposed to the
test material, determined in an acute earthworm test according to ISO 11268-1 with the modifications
specified in Annex D.
Plastics products or materials that have been already assessed for acute toxicity to earthworms
following AS 4736, AS 5810, EN 17033 or equivalent standard specifications and fulfilled the pass level
for toxicity to earthworm laid down in this document do not need to be retested.
6.4.5 Chronic earthworm toxicity test (mandatory)
As an alternative to the acute toxicity test (see 6.4.4), adverse effects of materials on the reproduction
of earthworms may be determined in a test according to ISO 11268-2 with the modifications specified
in Annex E.
After an incubation period of 28 days, the survival and the biomass of the surviving adult earthworms
in the sample compost exposed to the test material shall be more than 90 % of those from the
corresponding blank compost not exposed to the test material.
After an incubation period of 56 d, the observed number of offspring in sample compost exposed to the
test material shall be more than 90 % of those from the corresponding blank compost not exposed to
the test material.
Test items that have been already assessed for chronic toxicity to earthworms following EN 17033 or
equivalent standard specifications and fulfilled the pass level for long-term toxicity to earthworm laid
down in this document do not need to be retested.
6.4.6 Nitrification inhibition test with soil microorganisms (optional)
The nitrite formation in the sample compost exposed to the test material shall be more than 80 % of
those from the corresponding blank compost to which no test material was added at the start of testing,
determined in a nitrification inhibition test with soil organisms in accordance with ISO 15685 with the
modifications specified in Annex F.
Plastics products or materials that have been already assessed for toxicity to soil microorganisms
following EN 17033 or equivalent standard specifications and fulfilled the pass level for toxicity to soil
microorganisms laid down in the standard specification do not need to be retested.
NOTE This test is optional but can be required due to national regulations or requirements.
6.5 Control of constituents
6.5.1 General
In order to ensure that the composting of plastics products or materials does not have any harmful
effects on the finished compost or on the environment all requirements specified in 6.5.2 to 6.5.4 shall
be met.
6.5.2 Regulated metals and other elements
The concentrations of regulated metals and other elements in the plastics product or material shall be
less than 50 % of those prescribed for sludges, fertilizers and composts in the country where the final
product will be placed on the market or disposed of (see Annex A for examples).
6.5.3 Per- and poly-fluorinated compounds (PFCs)
From a precautionary perspective, per- and poly-fluorinated substances compounds (PFCs) shall not be
intentionally added to a plastics product or a material.
NOTE Most of per- and poly-fluorinated substances compounds (PFCs) are extremely persistent in the
environment and in addition, certain PFCs are suspected to have bioaccumulative properties and adverse effects
for environment and human health.
The concentration of per- and poly-fluorinated compounds (PFCs) in the plastics product or material
shall be determined as fluorine.
6.5.4 Other hazardous substances
From a precautionary perspective, hazardous substances as specified in Annex B shall not be
intentionally added to a plastics product or a material.
The applicable international and/or local regulations where the material is put on the market shall
be taken into consideration for identification and assessment. Information on the use of hazardous
substances shall be recorded and can be based on a self-declaration.
6.5.5 Volatile solids
The plastics product or material shall contain a minimum of 50 % of volatile solids.
7 Declaration of results
7.1 Plastics products or materials meeting all the requirements specified in Clause 6 may be considered
as “recoverable by organic recycling”, “organically recyclable”, “compostable in industrial composting”, or
“suitable for organic recycling”.
7.2 The term "biodegradable" shall not be used to describe the performance of plastics that meet this
specification in supplier-to-consumer communications.
7.3 This document is not applicable to biological treatment undertaken in small installations by
householders. Hence, it shall not be used for unqualified claims as “compostable in small installations by
householders”, “suitable for home composting” and similar.
In addition, whenever the risk exists of misunderstanding by the consumer of a plastics product,
it is recommended that the following warning shall be given: “not suitable for composting in small
installations by householders” or “not suitable for home composting”.
8 Test report
The test report shall provide all pertinent information, including:
a) all information necessary to identify and describe the product or material tested;
b) references to all standards, guidelines and regulations that are relevant to 6.5.2 regarding the
content of regulated metals and other elements, to 6.5.3 regarding the content of per- and poly-
fluorinated compounds (PFCs) and to 6.5.4 regarding other hazardous substances as defined in
Annex B.
A table of regulated metals shall be presented, specifying each such reference and stating the
prescribed limit for each metal, the concentration determined in the test and the percentage of
the prescribed limit. In addition, the concentration of per- and poly-fluorinated compounds (PFCs)
shall be determined as fluorine and reported. Information on the use of other hazardous substances
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as specified in Annex B shall be assessed and recorded and can be based on a self-declaration
considering international and/or local regulations where the material is put on the market;
c) a description of other relevant requirements in the referenced documents and a statement, for each
such requirement, as to whether the test result was in conformity with the requirement or not.
Annex A
(informative)
Examples of maximum concentrations of regulated metals and
other elements
Table A.1 — Examples of maximum concentrations of regulated metals and other elements
Values given in mg/kg of dry material
EU + EFTA
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