Plastics — Determination of the ultimate anaerobic biodegradation of plastic materials in controlled slurry digestion systems — Method by measurement of biogas production

ISO 13975:2012 specifies a method of evaluating the ultimate anaerobic biodegradability of plastic materials in a controlled anaerobic slurry digestion system with a solids concentration not exceeding 15 %, which is often found for the treatment of sewage sludge, livestock faeces or garbage. The test method is designed to yield a percentage and rate of conversion of the organic carbon in the test materials to carbon dioxide and methane produced as biogas. The method applies to the following materials, provided they have a known carbon content: natural and/or synthetic polymers, copolymers or mixtures; plastic materials that contain additives such as plasticizers, colorants, or other compounds; water-soluble polymers. It does not apply to materials which exhibit inhibitory effects on the test microorganisms at the concentration chosen for the test.

Plastiques — Évaluation de la biodégradabilité anaérobie ultime des matériaux plastiques dans des systèmes de digestion de boue contrôlés — Méthode par mesurage de la production de biogaz

General Information

Status
Withdrawn
Publication Date
03-May-2012
Withdrawal Date
03-May-2012
Current Stage
9599 - Withdrawal of International Standard
Start Date
16-Apr-2019
Completion Date
16-Apr-2019
Ref Project

RELATIONS

Buy Standard

Standard
ISO 13975:2012 - Plastics -- Determination of the ultimate anaerobic biodegradation of plastic materials in controlled slurry digestion systems -- Method by measurement of biogas production
English language
13 pages
sale 15% off
Preview
sale 15% off
Preview

Standards Content (sample)

INTERNATIONAL ISO
STANDARD 13975
First edition
2012-05-01
Plastics — Determination of the ultimate
anaerobic biodegradation of plastic
materials in controlled slurry digestion
systems — Method by measurement of
biogas production
Plastiques — Évaluation de la biodégradabilité anaérobie ultime
des matériaux plastiques dans des systèmes de digestion de boue
contrôlés — Méthode par mesurage de la production de biogaz
Reference number
ISO 13975:2012(E)
ISO 2012
---------------------- Page: 1 ----------------------
ISO 13975:2012(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
---------------------- Page: 2 ----------------------
ISO 13975:2012(E)
Contents Page

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

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

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

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

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

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

5 Test and reference materials ............................................................................................................................ 3

6 Apparatus .............................................................................................................................................................. 3

7 Procedure .............................................................................................................................................................. 4

7.1 General ................................................................................................................................................................... 4

7.2 Preparation of inoculum .................................................................................................................................... 4

7.3 Start-up of the test .............................................................................................................................................. 4

7.4 Measurement of biogas produced (see Annex A) ...................................................................................... 5

7.5 Test duration ......................................................................................................................................................... 5

7.6 Measurement of dissolved inorganic carbon (see Annex B)................................................................... 5

8 Calculation and expression of results ........................................................................................................... 5

8.1 Amount of biogas produced ............................................................................................................................. 5

8.2 Amount of dissolved inorganic carbon ......................................................................................................... 5

8.3 Calculation of percentage biodegradation ................................................................................................... 6

9 Expression and interpretation of results ...................................................................................................... 6

10 Validity of results ................................................................................................................................................. 6

11 Test report ............................................................................................................................................................. 7

Annex A (informative) Examples of test systems ...................................................................................................... 8

Annex B (informative) Example of apparatus for measurement of biogas dissolved in slurry ..................10

Annex C (informative) Example of a biodegradation curve .................................................................................. 11

Annex D (informative) Table of water vapour pressures at various temperatures .........................................12

Bibliography .....................................................................................................................................................................13

© ISO 2012 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 13975:2012(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 13975 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 5, Physical-

chemical properties.
iv © ISO 2012 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 13975:2012(E)
Introduction

Biological recycling (biorecycling) is a viable option, together with mechanical recycling and chemical recycling,

for the recovery of plastic waste. This International Standard specifies a method of evaluating the anaerobic

biodegradability of such waste in a controlled anaerobic slurry system. This is a representative anaerobic

digestion test method and system for biodegradable plastic waste.

The production of a biogas is observed under anaerobic conditions suitable for the growth of thermophilic

or mesophilic microorganisms. The biogas is collected in a bag under atmospheric pressure, and the biogas

volume is measured with a syringe or a gas burette. The biodegradability of the test material is evaluated

from the sum of the amount of carbon dioxide dissolved in the supernatant and the cumulative quantity of

evolved biogas. This International Standard is a biodegradation test method for plastic materials in a controlled

anaerobic slurry system, and differs from ISO 15985 which uses high-solids anaerobic digestion conditions

and ISO 14853 which uses an aqueous system in an anaerobic environment.
© ISO 2012 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 13975:2012(E)
Plastics — Determination of the ultimate anaerobic
biodegradation of plastic materials in controlled slurry digestion
systems — Method by measurement of biogas production

WARNING — Sewage sludge and other organic waste might contain potentially pathogenic organisms.

Therefore appropriate precautions should be taken when handling such materials. Digestion of

organic materials produces flammable gases that present fire and explosion risks. These gases also

contain toxic chemicals, including hydrogen sulfide and ammonia, in substantial concentrations.

Appropriate safety measures, such as the use of a draft chamber, gas masks and/or well-ventilated

laboratory facilities, should be taken. Toxic test chemicals and chemicals whose properties are not

known should be handled with care and in accordance with safety instructions. Care should be taken

when transporting and storing quantities of organic matter undergoing digestion.
1 Scope

This International Standard specifies a method of evaluating the ultimate anaerobic biodegradability of plastic

materials in a controlled anaerobic slurry digestion system with a solids concentration not exceeding 15 %,

which is often found for the treatment of sewage sludge, livestock faeces or garbage. The test method is

designed to yield a percentage and rate of conversion of the organic carbon in the test materials to carbon

dioxide and methane produced as biogas.

The method applies to the following materials, provided they have a known carbon content:

— natural and/or synthetic polymers, copolymers or mixtures;

— plastic materials that contain additives such as plasticizers, colorants, or other compounds;

— water-soluble polymers.

It does not apply to materials which exhibit inhibitory effects on the test microorganisms at the concentration

chosen for the test.

NOTE Inhibitory effects can be determined by an inhibition test (e.g. ISO 13641-1 or ISO 13641-2).

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 14853:2005, Plastics — Determination of the ultimate anaerobic biodegradation of plastic materials in an

aqueous system — Method by measurement of biogas production
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
ultimate anaerobic biodegradation

breakdown of an organic compound by microorganisms in the absence of oxygen into carbon dioxide, methane,

water and mineral salts of any other elements present (mineralization) plus new biomass

© ISO 2012 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO 13975:2012(E)
3.2
digested sludge

mixture of the settled sewage and activated sludge which has been incubated in a mesophilic or thermophilic

anaerobic digester to reduce the biomass and odour and to improve the dewaterability of the sludge

NOTE 1 to entry: Digested sludge contains an association of anaerobic fermentative and methanogenic microorganisms

producing carbon dioxide and methane.
3.3
slurry
watery mixture of insoluble matter

NOTE 1 to entry: The suspended-solids concentration of a slurry might be as high as around 15 %, but slurry is fluid

and pumpable.
3.4
dissolved inorganic carbon
DIC

carbon dioxide dissolved in water or transformed into carbonic acid, hydrogen carbonate ion and carbonate ion

3.5
total dry solids

amount of solids obtained by taking a known volume of test material or inoculum and drying at about 105 °C

to constant mass
3.6
volatile solids

amount of solids obtained by subtracting the residue of a known volume of test material or inoculum after

incineration at about 550 °C from the total dry solids of the same test portion

NOTE 1 to entry: The volatile-solids content is an indication of the amount of organic matter present.

3.7
theoretical amount of evolved biogas
ThBiogas

maximum theoretical amount of biogas (CH + CO ) which will evolve after complete biodegradation of an

4 2
organic compound under anaerobic conditions

NOTE 1 to entry: ThBiogas is calculated from the molecular formula and expressed as litres of biogas evolved per gram

of test material under the standard conditions.
3.8
lag phase

time from the start of an anaerobic digestion 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
NOTE 1 to entry: It is measured in days.
3.9
biodegradation phase

time from the end of the lag phase of a test until about 90 % of the maximum level of biodegradation has been

reached
NOTE 1 to entry: It is measured in days.
3.10
plateau phase
time from the end of the biodegradation phase until the end of the test
NOTE 1 to entry: It is measured in days.
2 © ISO 2012 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 13975:2012(E)
3.11
maximum level of biodegradation

degree of biodegradation of a chemical compound or organic matter in a test, above which no further

biodegradation takes place during the test
NOTE 1 to entry: It is measured in percent.
4 Principle

This test method is designed to determine the biodegradability of plastic materials under anaerobic conditions

in a slurry system. The methanogenic inoculum is obtained from an anaerobic digester operating on sewage

sludge or, alternatively, on organic waste such as livestock faeces or garbage. The test material mixed with

the inoculum is anaerobically incubated in a test vessel at a pre-selected temperature for a period normally of

60 days. The test period may be shortened or extended until a plateau phase is reached, but the total period

shall not exceed 90 days. The digestion temperature shall be (55 ± 5) °C in order to simulate thermophilic

anaerobic digestion. Alternatively, the digestion temperature may be set at (35 ± 3) °C in order to simulate

mesophilic anaerobic digestion.

The volume of the gases produced in the test vessel, carbon dioxide (CO ) and methane (CH ), is measured. A

2 4

considerable amount of CO will also be dissolved in the digested sludge or dissociated to hydrogen carbonate

ion and carbonate ion under the conditions of the test. This dissolved inorganic carbon (DIC) is measured at

the end of the test. The amount of biogas produced is calculated from the volume of biogas collected and the

amount of DIC formed in excess of blank values.

The percentage biodegradation is calculated as the ratio of the sum of the net increase of produced biogas

and DIC to the theoretical amount of evolved biogas (ThBiogas). The biodegradation curve can be followed by

making intermediate measurements of biogas production.
5 Test and reference materials

5.1 Test material: The test material is normally added directly as solids to give a concentration of volatile

solids in the range of 7 g/l to 10 g/l. The test material should preferably be used in powder form or as film.

5.2 Reference material: TLC (thin-layer chromatography) grade microcrystalline cellulose with a particle

size <
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.