SIST-TP CEN/TR 17910:2023
(Main)Biodegradable plastics - Status of standardization and new prospects
Biodegradable plastics - Status of standardization and new prospects
This document summarizes the state of standardization in the field of biodegradable plastics and plastics products at CEN and ISO level. It explains the underlying scientific principles of biodegradation that provide the foundations for relevant test methods and enters into the merits of the individual tests to explain and clarify the reasons for the adoption of specific solutions and criteria.
In a second part, this document highlights areas where standardisation in this field is currently lacking and where future developments may be anticipated and useful.
Bioabbaubare Kunststoffe - Stand der Normung und neue Perspektiven
Plastiques biodégradables - État de la normalisation et nouvelles perspectives
Biorazgradljivi polimerni materiali - Stanje standardizacije in nove možnosti
Ta dokument povzema stanje standardizacije na področju biorazgradljivih polimernih materialov na ravni CEN in ISO. Pojasnjuje osnovna znanstvena načela biorazgradnje, ki zagotavljajo temelje za ustrezne preskusne metode, in na podlagi prednosti posameznih preskusov pojasnjuje in določa razloge za sprejetje posebnih rešitev in meril.
V drugem delu ta dokument izpostavlja področja, kjer standardizacija na tem področju trenutno manjka ter kakšna so predvidevanja za prihodnji razvoj in uporabo.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TP CEN/TR 17910:2023
01-marec-2023
Biorazgradljivi polimerni materiali - Stanje standardizacije in nove možnosti
Biodegradable plastics - Status of standardization and new prospects
Bioabbaubare Kunststoffe - Stand der Normung und neue Perspektiven
Plastiques biodégradables - État de la normalisation et nouvelles perspectives
Ta slovenski standard je istoveten z: CEN/TR 17910:2022
ICS:
01.120 Standardizacija. Splošna Standardization. General
pravila rules
13.020.20 Okoljska ekonomija. Environmental economics.
Trajnostnost Sustainability
83.080.01 Polimerni materiali na Plastics in general
splošno
SIST-TP CEN/TR 17910:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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CEN/TR 17910
TECHNICAL REPORT
RAPPORT TECHNIQUE
December 2022
TECHNISCHER REPORT
ICS 83.080.01; 13.020.20
English Version
Biodegradable plastics - Status of standardization and new
prospects
Plastiques biodégradables - État de la normalisation et Bioabbaubare Kunststoffe - Stand der Normung und
nouvelles perspectives neue Perspektiven
This Technical Report was approved by CEN on 18 December 2022. It has been drawn up by the Technical Committee CEN/TC
249.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 17910:2022 E
worldwide for CEN national Members.
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Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Biodegradation . 6
5 Biodegradation of polymers. 7
6 The principles of the biodegradation tests for plastics . 8
6.1 Measuring biodegradation . 8
6.2 Reliability and replication . 10
6.3 Formation of biomass during biodegradation . 12
6.4 General discussion on the 90 % biodegradability requirement . 12
7 Current biodegradation tests . 13
7.1 General . 13
7.2 ISO 13975 . 14
7.3 EN ISO 14851 . 15
7.4 EN ISO 14852 . 16
7.5 EN ISO 14853 . 16
7.6 EN ISO 14855-1 . 17
7.7 EN ISO 14855-2 . 18
7.8 EN ISO 15985 . 18
7.9 EN ISO 17556 . 19
7.10 EN ISO 18830 . 19
7.11 EN ISO 19679 . 20
7.12 ISO 22404 . 20
7.13 ISO 23977-1 . 21
7.14 ISO 23977-2 . 21
7.15 ISO 5148. 21
8 Additional testing used in product specifications . 22
8.1 General . 22
8.2 Test methods used to determine degradation other than biodegradation . 22
8.3 Test methods relating to eco-toxicity . 22
9 Biodegradation in different environments – Specifications and requirements . 23
9.1 General . 23
9.2 Biodegradation in Organic Recycling – Industrial Composting and Anaerobic
Digestion . 23
9.2.1 Introduction . 23
9.3 The Organic Recycling Framework. 24
9.4 The technical content . 25
9.5 Compatibility of compostable packaging with specific composting plants . 26
9.6 Biodegradation in Home Composting . 27
9.6.1 The scope and general requirements of the relevant standard . 27
9.7 Discussion on home composting . 27
9.8 Biodegradation in Soil . 29
9.8.1 The scope and general requirements of the relevant standard . 29
9.9 General discussion on soil biodegradation . 29
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9.10 Biodegradation in sea water . 30
9.10.1 The scope and general requirements of the relevant standard . 30
9.11 General discussion on marine biodegradability . 31
10 Biodegradation in open (uncontrolled) environment . 31
11 Discussion on Future standardization needs . 35
11.1 Organic Recycling . 35
11.2 Applications in agriculture . 36
11.3 Biodegradation in the open environment . 36
11.4 Reference materials . 36
11.5 Horizontal standardization . 37
Annex A (informative) List of relevant Standards and OECD Tests . 38
A.1 Introduction . 38
A.2 European Standards . 38
A.3 European/ISO Standards . 38
A.4 ISO Standards . 39
A.5 OECD Tests . 40
Bibliography . 41
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European foreword
This document (CEN/TR 17910:2022) has been prepared by Technical Committee CEN/TC 249
“Plastics”, the secretariat of which is held by NBN.
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.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
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Introduction
Biodegradable plastics have been developed starting from late 80s of the last century in parallel with the
development of methodologies for the characterization of degradation (including biodegradation,
disintegration, detection of potential ecotoxic by-products produced during biodegradation) of solid
materials. The industry developed together with standardization and certification bodies a reliable
governing framework needed to develop the market. After 30 years, a wide range of biodegradable
products are commercially available. Standard test methods and specifications are available enabling the
characterization and certification of those products.
There is an increasing interest to find out more information on the nature of biodegradable plastics and
their fundamental characteristics that was fulfilled by going to the source, i.e. by directly examining the
technical standards. The analysis of standards by persons who are not experts in the science of
biodegradation or standardization and therefore unaware of the underlying reasons for some test
schemes, has led to the direct application of such schemes in the context of communications, creating
paradoxical situations. Several criticisms did surface based on the erroneous interpretation of the testing
schemes. For example, many were puzzled by the 90 % mineralization pass level (rather than 100 % i.e.
“complete”) required by the standard specifications to show biodegradability, ignoring that
biodegradation involves biomass formation, a very basic knowledge in biochemistry and microbiology.
This commingling between technical requirements and media communication created a great deal of
confusion among the public and put the Industry, Standardization, and Certification under increased
pressure.
CEN experts acknowledge the communication issues and therefore created the underlying document that
summarizes the state of standardization and enters into the merits of the individual tests to explain the
reasons for some technical solutions and the criteria adopted. This exercise also becomes a preliminary
step to highlight potential gaps, the need for updating some standards, or new frontiers to be explored to
complete the characterization of biodegradable plastic materials.
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1 Scope
This document summarizes the state of standardization in the field of biodegradable plastics and plastics
products at CEN and ISO level. It explains the underlying scientific principles of biodegradation that
provide the foundations for relevant test methods and enters into the merits of the individual tests to
explain and clarify the reasons for the adoption of specific solutions and criteria.
This document primarily focusses on standards adopted by CEN covering environmental biodegradation
testing and relevant specifications. It also includes information on disintegration and eco-toxicity tests. A
full list of the international standards considered in this document is provided in Annex A.
In a second part, this document highlights areas where standardization in this field is currently lacking
and where future developments may be anticipated and useful.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
• ISO Online browsing platform: available at https://www.iso.org/obp
• IEC Electropedia: available at https://www.electropedia.org/
4 Biodegradation
Biodegradation is a term used in ecology to refer to the natural processes carried out by the decomposing
microorganisms (fungi, bacteria, protozoa) that convert the organic substances produced during
photosynthesis back into CO , water, inorganic substances and new biomass. Biodegradation and
2
photosynthesis function in opposite directions in the ecological cycles, most notably in the carbon
(biogeochemical) cycle.
Starting from atmospheric CO and through the utilization of solar energy via photosynthesis, plants,
2
algae, and all the autotrophic organisms synthesize sugars – the organic molecules that form the building
blocks of the countless substances present in the biosphere. Through the food chain, the flow of
substances and energy passes from plants (producers) to herbivores (primary consumers) and from
those to carnivores (secondary consumers).
In the other direction, biodegradation breaks down these organic molecules into smaller intermediate
constituents such as CO , CH , inorganic substances and new biomass. Ultimately, the carbon will be
2 4
converted back into CO . Biodegradation is carried out by the decomposers which grow on dead organic
2
matter; the solid waste of nature. The natural process of biodegradation is essential for the environment
and its natural cycles that must get rid of waste and residues in order to make space for new life. Without
biodegradation reactions releasing CO back into the atmosphere, photosynthesis would be devoid of its
2
key building block. Therefore, in the natural balance of the planetary ecosystem, biodegradation
processes are in balance and harmony with photosynthesis process in the naturally occurring ‘circular
economy’.
At the atomic level, once the carbon atoms which form part of CO have reached the maximum state of
2
oxidation they are considered as minerals and hence this final process of biodegradation is called
mineralization. The complete burning of a wood log in a fireplace into CO , water and ashes with instant
2
release of energy is a fast form of “mineralisation”. Microorganisms degrading the same wood log
reproduce this process in a controlled way so that they can exploit the energy for living.
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Biodegradation ultimately happens by means of aerobic respiration. As noted above, respiration is the
opposite of photosynthesis, which is the reduction of carbon dioxide into organic carbon i.e. carbon atom
bond with other carbon atoms or hydrogen. This reaction happens thanks to the solar energy.
photons
6 CO + 6 H O → C H O + 6O
2 2 6 12 6 2
Respiration is the opposite reaction.
C H O + 6 O → 6 CO + 6 H O + energy
6 12 6 2 2 2
5 Biodegradation of polymers
9
Worldwide photosynthetic fixation of carbon dioxide is estimated to yield annually up to 150 X 10 tons
of dry plant material (biomass). Almost half of this material consists of cellulose (28 % – 50 %); other
major components are hemicelluloses (20 % – 30 %) and lignin (18 % – 30 %) [1].
A polymer is best described as a class of natural or synthetic substances composed of very large
molecules, called macromolecules, that are multiples of simpler chemical units called monomers.
Polymers make up many of the materials in living organisms, including, for example, proteins, cellulose,
and nucleic acids where the polymer is produced by the cells of living organisms they are known as
biopolymers. Biopolymers consist of monomeric units that are covalently bonded to form larger
molecules. Cellulose is the most abundant biopolymer on earth, with plants producing about 180 billion
tonnes per year globally.
The biodegradation of cellulosic biomass represents an important part of the carbon cycle within the
biosphere. Microorganisms are able to provoke the complete degradation of cellulose which is ultimately
converted into CO , water and microbial biomass under aerobic conditions. Most cellulose is degraded
2
aerobically, but 5 % – 10 % is degraded anaerobically, and thus converted into CO , methane and biomass
2
under anaerobic conditions.
Cellulose is a water-insoluble polymer and thus it cannot get into the cells and cellulolytic enzymes are
by necessity secreted into the medium or bound to the outside surface of cellulolytic microorganisms.
Cellulose does not accumulate in the environment and therefore it can be considered as totally
biodegradable in any environment, independently from the environmental conditions. For this reason, it
is used as a reference material in biodegradation testing. The actual biodegradation rate of cellulose will
be clearly affected by the environmental conditions found in that specific location.
Biopolymers are made up of macromolecules, which due to their large size, do not pass through the cell
membrane and therefore cannot be absorbed directly by microorganisms [2, 3]. The first stage of
biodegradation occurs outside the microorganisms and is caused by extracellular enzymes that erode the
surfaces of solid materials [4]. In this extracellular phase, the main reactions are hydrolysis and oxidation.
The macromolecules are split up to the constituent elements, i.e. the monomers and oligomers, which
pass through the cell membrane and are metabolized becoming part of the biochemistry of the
microorganisms and of the living mass (“biomass”). Low molecular weight additives do not need the
depolymerisation phase to become available. The final degradation of the metabolites under aerobic
conditions involves an oxidation process that requires oxygen and leads to the evolution of carbon
dioxide [5].
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The process of biodegradation of the (bio)-polymers in an environment can be divided into four stages
(adapted from Folino 2020 [6]):
1. Firstly, the stage of bio-deterioration, in which the polymers undergo chemical, mechanical, and
physical change, as a result of the microorganisms’ biological activity on the surface of the material.
The porosity highly influences this step.
2. The second stage is that of bio-depolymerisation, where the microbial activity causes the breaking
down of polymers into oligomers and monomers.
3. The third stage describes the assimilation of the oligomers and monomers, in which the compounds
are taken up by the microorganisms.
4. In the fourth stage the assimilated compounds are converted to end products, such as H O and
2
biomass and the carbon mineralised into CO .
2
The depolymerisation (Stage 2) releases monomers that are assimilated by the surrounding
microorganisms (the “central dogma” for biodegradation of polymers; [7]). The enzymes and microbes
in the liquid phase interact with the constituents of plastics at the surface of the solid phase. The available
solid/liquid interphase is thus a potential limiting factor of the depolymerisation and consequently of the
overall biodegradation, including mineralization. Stage 2 is considered the limiting factor, while the
subsequent assimilation of monomers by the microbes (Stage 3) is expected to be immediate [8]. After
the assimilation (Stage 3), the organic substance is mineralized into CO and H O (Stage 4). This
2 2
conversion is fast in the early stages of biodegradation. The ultimate stage of biodegradation is actually
the respiration process i.e. the conversion of simply organic molecules into CO , water and energy.
2
Afterwards, when there are no further polymers to biodegrade, the microbes are under starvation
conditions, and mineralization affects the biomass which is stored and the metabolites formed in Stage 2.
This latter phase can be very long.
The processes which result in the final mineralisation of biopolymers and polymers are identical.
6 The principles of the biodegradation tests for plastics
6.1 Measuring biodegradation
The biodegradation of a plastic material is measured under specific laboratory conditions. It is generally
not possible to accurately and consistently replicate stage 1. As described before, four Stages have been
identified in biodegradation: in Stage 2 the plastic (the original reactant) is depolymerised into
monomers and oligomers; in Stage 3 the monomers and oligomers are taken up as biomass; in Stage 4
respiration of biomass consumes O and produces CO (under aerobic conditions).
2 2
The measurement of reactant consumption (i.e. the plastic material) is inconclusive, because it does not
prove whether the process has actually been completed or has stopped, for example, at depolymerisation
(Stage 1). Quantitative measurement of biomass formation presents technical difficulties that have not
been sustainably overcome to date. Therefore, all the standardized methods for determining
biodegradation of plastics are based on the measurement of respiration, i.e. the conversion into CO of
2
the carbon initially present in the plastic through the use of the oxidant (O ).
2
The overall reaction, which includes the four stages, can be represented as follows:
C + O → C + C
Plastic (polymer) 2 CO2 biomass
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The respirometric methods differ from each other in the state (solid, liquid and sometimes biphasic), the
origin of the microorganisms (the sampling environment of the microbial inoculum, for example soil,
compost, etc.), the temperature and the type of measurement (consumption of the O reagent or evolution
2
of the CO product). It should be remarked that all these methods measure the degree of mineralisation,
2
rather than the degree of biodegradation, because the production of biomass is not accounted. Reliable
methods for the measurement of biomass formed during a biodegradation process and the production
and use of energy are still missing and thus only one product of biodegradation – CO – can be monitored.
2
For simplicity, this value is called the degree of biodegradation despite the fact that new microbial
biomass growth is not considered.
The test methods are also meant to determine the so-called “Ultimate biodegradation” i.e. the level of
biodegradation achieved when the test compound is totally utilized by microorganisms resulting in the
production of carbon dioxide, water, mineral salts (if elements present in original polymer) and new
microbial cellular constituents (biomass). The outcome of these test methods is the percentage of
biodegradation. Percentage of biodegradation is a percentage yield i.e. it is the actual CO produced
2
compared to the maximum possible or theoretical CO (ThCO ) that can be produced in case of total
2 2
oxidation of the carbon present in the test material.
It is important to understand the difference between the potential of a material to undergo
biodegradation (biodegradability) and the rate at which that biodegradation occurs under given
conditions. The rate of biodegradation of any material known to have a chemical structure which enables
it to undergo complete mineralisation is limited by the environment. For example if we consider peat
bogs or deep ocean sediments then the time to biodegrade cellulose is in the centuries whereas the rate
will differ again between fertile tropical soils compared to a desert. In all of these environments, the fact
remains that cellulose is intrinsically biodegradable, what changes depending on the environmental
conditions is the rate at which biodegradation occurs. Due to the fact that cellulose is intrinsically
biodegradable, cellulose is used as a reference material in all of the biodegradation tests which have been
established for plastics including packaging.
During the biodegradation of a product three stages occur (example: see Figure 1):
1. lag phase:
it is the 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 (source:
ISO 15985:2014)
2. biodegradation phase:
it is the 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 (source: ISO 15985:2014)
3. plateau phase:
it is the time, measured in days, from the end of the biodegradation phase until the end of a test
(ISO 14855-1:2012)
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Key
X Time
Y Biodegradation (%)
1 Lag phase
2 Biodegradation phase
3 Plateau phase
Figure 1 — Example of the different stages of biodegradation.
Tests to assess the biodegradation of chemicals are long established. The most widely applied test
methods come from the 1992 OECD 301 series where “ready biodegradability” is assessed. The principle
of these tests is not to replicate every environment but to provide consistency and replicability of the test.
6.2 Reliability and replication
For the purposes of standardization and regulation, it is an absolute necessity that performance tests are
both reliable and replicable, not just as a test within a single laboratory but also between laboratories
anywhere in the world. For this reason, several of the ISO biodegradation test methods (see Clause 7
below) have been subject
...
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