ISO/FDIS 19743

FINAL DRAFT
International
Standard
ISO/TC 238
Solid biofuels — Determination
Secretariat: SIS
of content of heavy extraneous
Voting begins on:
materials larger than 3,15 mm
2025-08-11
Biocombustibles solides — Détermination de la teneur en
Voting terminates on:
matériaux lourds exogènes de dimension supérieure à 3,15 mm
2025-10-06
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
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MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 238
Solid biofuels — Determination
Secretariat: SIS
of content of heavy extraneous
Voting begins on:
materials larger than 3,15 mm
Biocombustibles solides — Détermination de la teneur en
Voting terminates on:
matériaux lourds exogènes de dimension supérieure à 3,15 mm
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
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BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/CEN PARALLEL PROCESSING
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
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Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
5.1 Water container .2
5.2 Balances .2
5.3 Sieve .2
5.4 Drying oven .2
5.5 Dishes or trays .2
6 Sample preparation . 2
7 Procedure . 3
8 Calculation . 3
9 Performance characteristics . 4
10 Test report . 4
Bibliography . 5

iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
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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 238, Solid biofuels and pyrogenic biocarbon, in
collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 335,
Solid Biofuels and Pyrogenic Biocarbon, in accordance with the Agreement on technical cooperation between
ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 19743:2017), which has been technically
revised.
The main changes are as follows:
— introduction has been extended with a specification of where heavy extraneous materials can enter the
fuel. It has also been elucidated that HEM most often are found in wood hogfuel;
— procedure has been updated and clarified;
— calculation has been updated.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
Determination of the content of heavy extraneous materials larger than 3,15 mm is important when
evaluating the suitability of using biomass as biofuel. The presences of heavy extraneous materials lowers
the energetic value of the fuel and increases the residue after burning, thus increasing the costs of disposal.
Stones and other impurities contained in biomass from stumps, roots, mill residue and harvest and landscape
management residues can cause problems during size reduction, as well as during combustion.
Impurities smaller than 3,15 mm are not considered as part of this testing method but can still contribute to
the ash content.
The contents of heavy extraneous materials larger than 3,15 mm are not part of the ash content.
NOTE There are three main sources of heavy extraneous materials:
— they can be contained in the base material from which the biofuel (e.g. hog fuel) is produced;
— they can unintentionally be added to the fuel while loading from the ground, by digging too low;
— they can be residues from former loads in the transport vehicle.
The last two categories of heavy extraneous materials in the NOTE cannot be determined by the method
described in this document, because it is unlikely that the incidental impurities can be found in the random
sample on which this method is based. If such incidental impurities are found during visual inspection of the
delivered fuel, then this can be documented by pictures and contact can be sought with the supplier to make
sure that these incidents are avoided in the future.

v
FINAL DRAFT International Standard ISO/FDIS 19743:2025(en)
Solid biofuels — Determination of content of heavy
extraneous materials larger than 3,15 mm
1 Scope
This document specifies a method for the determination of the content of heavy extraneous materials
larger than 3,15 mm by the use of sink-and-float separation combined with elutriation. This document is
applicable to woody biomass in accordance with ISO 17225-1, and especially for hogfuel in accordance with
ISO 17225-9.
NOTE 1 This method is designed to determine the level of impurities larger than 3,15 mm with a specific
density >1 g/cm , such as stones, glass, rubber, metal and certain types of plastics.
NOTE 2 During the processing of the sample, hand sorting of light impurities with a specific density ≤1 g/cm (e.g.
plastic foil) can also be done.
NOTE 3 Some heavy extraneous materials (e.g. lumps of clay) can fall apart when submerged in water.
NOTE 4 Heavy extraneous materials smaller than 3,15 mm can damage milling equipment, when reducing the
material in size to produce laboratory samples.
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 3310-2, Test sieves — Technical requirements and testing — Part 2: Test sieves of perforated metal plate
ISO 14780, Solid biofuels — Sample preparation
ISO 16559, Solid biofuels — Vocabulary
ISO 18134-1, Solid biofuels — Determination of moisture content — Part 1: Reference method
ISO 18134-2, Solid biofuels — Determination of moisture content — Part 2: Simplified method
ISO 18135, Solid Biofuels — Sampling
ISO 21945, Solid biofuels — Simplified sampling method for small scale applications
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 16559 and the following apply.
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/
3.1
sedimentation
tendency for particles in suspension to settle out of the fluid in which they are entrained due to gravity and
come to rest against a barrier

3.2
elutriation
process for separating particles based on their size, shape and density using a stream of liquid that is flowing
opposite to the usual direction of sedimentation (3.1)
4 Principle
Heavy extraneous materials larger than 3,15 mm can be separated from the sample by using the sink-and-
float separation, combined with elutriation in water if needed. The content of heavy extraneous materials is
calculated by dividing the dry weight of the obtained material by the dry weight of the original sample and is
thus expressed as a percentage on dry weight basis.
5 Apparatus
5.1 Water container
The water con
...