oSIST prEN ISO 16994:2025

SLOVENSKI STANDARD
01-september-2025
Trdna biogoriva in pirogenski ogljik iz biomase - Določanje vsebnosti žvepla in
klora (ISO/DIS 16994:2025)
Solid biofuels and pyrogenic biocarbon - Determination of sulfur and chlorine content
(ISO/DIS 16994:2025)
Biogene Festbrennstoffe - Bestimmung des Gesamtgehaltes an Schwefel und Chlor
(ISO/DIS 16994:2025)
Biocombustibles solides et biocarbone pyrogène - Détermination de la teneur en soufre
et en chlore (ISO/DIS 16994:2025)
Ta slovenski standard je istoveten z: prEN ISO 16994
ICS:
75.160.40 Biogoriva Biofuels
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 16994
ISO/TC 238
Solid biofuels and pyrogenic
Secretariat: SIS
biocarbon — Determination of
Voting begins on:
sulfur and chlorine content
2025-06-19
ICS: 75.160.40; 27.190
Voting terminates on:
2025-09-11
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
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AND MAY NOT BE REFERRED TO AS AN
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Reference number
ISO/DIS 16994:2025(en)
DRAFT
ISO/DIS 16994:2025(en)
International
Standard
ISO/DIS 16994
ISO/TC 238
Solid biofuels and pyrogenic
Secretariat: SIS
biocarbon — Determination of
Voting begins on:
sulfur and chlorine content
ICS: 75.160.40; 27.190
Voting terminates on:
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
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BE CONSIDERED IN THE LIGHT OF THEIR
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Published in Switzerland Reference number
ISO/DIS 16994:2025(en)
ii
ISO/DIS 16994:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
4.1 General .1
4.2 Decomposition of the biofuel .2
4.3 Determination of the analytes in the decomposition solution .2
4.4 Automatic equipment .2
5 Reagents . 2
6 Apparatus . 3
6.1 General .3
6.2 Method A .3
6.3 Method B .3
7 Preparation of the test sample. 3
8 Procedure . 4
8.1 Decomposition .4
8.1.1 Method A: Combustion in a closed combustion vessel .4
8.1.2 Method B: Digestion in a closed vessel .5
8.1.3 Blank test .5
8.2 Detection methods .6
8.2.1 Ion chromatography .6
8.2.2 Other detection methods .6
8.3 Calibration of the apparatus .6
8.4 Analyses of the decomposition solutions .6
9 Expression of results . 6
9.1 General .6
9.2 Chlorine, fluorine and bromine .6
9.3 Sulfur .7
10 Performance characteristics . 7
11 Test report . 7
Annex A (informative) Performance data . 8
Bibliography .10

iii
ISO/DIS 16994:2025(en)
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 on the meaning of ISO specific terms and expressions related to conformity assessment,
as well as information about ISO's adherence to the WTO principles in the Technical Barriers to Trade (TBT)
see the following URL: Foreword - Supplementary information.
The committee responsible for this document is ISO/TC 238, Solid biofuels and pyrogenic biocarbon.
This third edition cancels and replaces the second edition (ISO 16994:2016), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— Fluorine and bromine are added to the scope and calculation in 9.2
— Normative references are updated
— Update of the detection methods and more details about the techniques
— The decomposition method with acid digestion and ICP for chlorine is removed

iv
ISO/DIS 16994:2025(en)
Introduction
Sulfur and chlorine are present in solid biofuels and pyrogenic biocarbon in varying concentrations. During
the combustion process, they are usually converted to sulfur-oxides and chlorides. The presence of these
elements and their reaction products can contribute significantly to corrosion and to environmentally
harmful emissions.
Chlorine can be present in different organic and inorganic compounds and is to exceed or equal the water
soluble amount that can be determined by ISO 16995.
Fluorine and bromine can also be present in solid biofuels and pyrogenic biocarbon, but in detectable
concentration only in specific types of biomass like in aquatic biofuels (Br) or as contamination because
of chemical treatment (F). Both elements can be analysed using the same techniques and equipment as for
chlorine and sulfur described in this standard.
Combustion in an oxygen atmosphere in a closed combustion vessel is the preferred method to digest biomass
samples for a determination of sulfur, chlorine, fluorine and bromine content. An advantage of the method
is that the digestion can be carried out in connection with the determination of the calorific value according
to ISO 18125. Other analytical techniques (e.g. high-temperature combustion under controlled gas flow in a
tube furnace, high-temperature combustion in closed systems with adequate detectors and acid digestion
in closed vessels) may also be used for selected analytes. The determination of the resultant chlorine,
sulfur, bromine and fluorine compounds can be done by different techniques, e.g. ion chromatography, ICP,
titrimetry.
Automatic equipment and alternative methods may be used when these methods are validated with biomass
reference samples of an adequate type and also meet the requirements of Clause 10.
A list with typical sulfur, chlorine and fluorine contents of solid biofuels and pyrogenic biocarbon can be
found in ISO 17225-1:2014, Annex B.

v
DRAFT International Standard ISO/DIS 16994:2025(en)
Solid biofuels and pyrogenic biocarbon — Determination of
sulfur and chlorine content
1 Scope
This International Standard describes methods for the determination of sulfur and chlorine content
in solid biofuels and pyrogenic biocarbon and specifies two methods for decomposition of the fuel and
different analytical techniques for the quantification of the elements in the decomposition solutions. The
determination of other elements such as fluorine and bromine is also possible with the methods in this
document, however performance data for these elements are not provided. The use of automatic equipment
is also included in this International Standard, provided that a validation is carried out as specified and that
the performance characteristics are similar to those of the method described in this International Standard.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 10304-1, Water quality — Determination of dissolved anions by liquid chromatography of ions — Part 1:
Determination of bromide, chloride, fluoride, nitrate, nitrite, phosphate and sulfate
ISO 11885, Water quality — Determination of selected elements by inductively coupled plasma optical emission
spectrometry (ICP-OES)
ISO 14780, Solid biofuels — Sample preparation
ISO 16559, Solid biofuels — Vocabulary
ISO 16967:2015, Solid biofuels — Determination of major elements — Al, Ca, Fe, Mg, P, K, Si, Na and Ti
ISO 18125, Solid biofuels — Determination of calorific value
ISO 18134-3, Solid biofuels — Determination of moisture content — Part 3: Moisture in general analysis sample
CEN Guide 13:2008, Validation of environmental test methods
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 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 https:// www .electropedia .org/
4 Principle
4.1 General
The determination of the analytes (sulfur, chlorine, fluorine and bromine) is performed in two steps (4.2 and
4.3) or by using automatic equipment (see 4.4).

ISO/DIS 16994:2025(en)
4.2 Decomposition of the biofuel
— Combustion in an oxygen atmosphere in a combustion vessel and absorption of the acidic gas components
in an absorption solution (method A).
— Acid digestion in a closed vessel as described in ISO 16967:2015, Part A (method B).
4.3 Determination of the analytes in the decomposition solution
— Ion chromatography, for the determination of sulfate, chloride, fluoride and bromide, in accordance with
the principles of ISO 10304-1
— ICP, for the determination of sulfur, in accordance with the principles of ISO 11885
4.4 Automatic equipment
Automatic equipment may be used when the method is validated with biomass reference samples of an
adequate biomass type. If automatic equipment is used, sulfur, chlorine and fluorine compounds may be
detected as gaseous components (e.g. by infrared methods). Examples for automatic analysers include
elemental analysers, AOX-analysers, combustion ion chromatography and sulfur-analysers.
If automatic equipment or X-ray fluorescence (see ISO/TS 16996) are used, the method shall be validated
for the respective main origin based biomass group (see ISO 17225-1, Table 1: woody biomass, herbaceous
biomass, fruit biomass or aquatic biomass) according to CEN Guide 13:2008, Clause 3 validation of alternative
methods with one of the following two approaches:
— full validation as applies to reference methods;
— relative validation in which a comparison is made to the reference method, e.g. by participation in inter-
laboratory comparison tests.
NOTE Equipment validated only with, for example, straw reference materials, is not automatically suitable for
the determination of sulfur and chlorine in, for example, wood samples, because of the usually significant lower
concentrations of the elements in wood and/or
...