oSIST prEN ISO 16994:2025

Solid biofuels and pyrogenic biocarbon - Determination of sulfur and chlorine content (ISO/DIS 16994:2025)

ISO 16994:2016 describes methods for the determination of the total sulfur and total chlorine content in solid biofuels. It specifies two methods for decomposition of the fuel and different analytical techniques for the quantification of the elements in the decomposition solutions. The use of automatic equipment is also included in ISO 16994:2016, provided that a validation is carried out as specified and that the performance characteristics are similar to those of the method described in ISO 16994:2016.

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)

L'ISO 16994 :2016 décrit des méthodes de détermination de la teneur totale en soufre et en chlore des biocombustibles solides. Elle spécifie deux méthodes de décomposition du combustible et différentes techniques d'analyse pour la quantification des éléments présents dans les solutions de décomposition. Elle englobe également l'utilisation d'équipements automatiques sous réserve que la validation soit effectuée conformément aux spécifications et que les caractéristiques de performance soient similaires à celles de la méthode décrite dans l'ISO 16994 :2016.

Trdna biogoriva in pirogenski ogljik iz biomase - Določanje vsebnosti žvepla in klora (ISO/DIS 16994:2025)

General Information

• Status: Not Published
• Public Enquiry End Date: 21-Sep-2025
• ICS: 27.190 - Biological sources and alternative sources of energy
• ICS: 75.160.40 - Biofuels
• Technical Committee: AGO - Refuse derived fuel
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 26-Jun-2025
• Due Date: 13-Nov-2025
• Completion Date: 18-Sep-2025
• Ref Project: prEN ISO 16994 - Solid biofuels and pyrogenic biocarbon - Determination of sulfur and chlorine content (ISO/DIS 16994:2025)

Relations

• Revises: SIST EN ISO 16994:2016 - Solid biofuels - Determination of total content of sulfur and chlorine (ISO 16994:2016)
• Effective Date: 01-Sep-2025

Overview

prEN ISO 16994 (ISO/DIS 16994:2025) is a CEN-circulated draft international standard for the determination of sulfur and chlorine in solid biofuels and pyrogenic biocarbon. It updates the 2016 edition and extends scope to include fluorine and bromine where detectable. The document specifies sample decomposition routes and analytical techniques to quantify these halogens and sulfur in decomposition solutions, and it allows the use of validated automatic equipment with performance characteristics comparable to the standard methods.

Key topics and requirements

• Scope and analytes: Total sulfur and total chlorine are the primary targets; fluorine and bromine can also be determined using the same approaches (performance data for F and Br are not provided).
• Decomposition methods:
  • Method A (preferred): Combustion in an oxygen atmosphere in a closed combustion vessel with subsequent absorption of acidic combustion products.
  • Method B: Acid digestion in a closed vessel (as referenced from ISO 16967:2015).
• Detection techniques:
  • Ion chromatography (IC) for sulfate, chloride, fluoride and bromide (per ISO 10304-1 principles).
  • ICP-OES (inductively coupled plasma optical emission spectrometry) for sulfur (per ISO 11885).
  • Note: the standard clarifies updates to detection methods and removes certain previous combinations (see the document changelog).
• Automatic equipment: Elemental analysers, combustion–IC systems, AOX-analysers and sulfur analysers may be used if validated against representative biomass reference samples and shown to meet Clause 10 performance requirements (validation guidance per CEN Guide 13).
• Quality and reporting: Includes blank tests, calibration procedures, expression of results (including treatment of halogens), and performance characteristic requirements.

Practical applications and users

• Who uses it: Laboratories testing biofuel quality, power plant fuel analysts, bioenergy producers, environmental regulators, and equipment manufacturers.
• Why it matters:
  • Assessing fuel corrosion risk and emission control (SOx and halogen-driven corrosion/particulate issues).
  • Supporting compliance with fuel specifications and environmental regulations.
  • Providing validated methods for R&D, quality control, and trade of solid biofuels and pyrogenic biocarbons.
• Typical workflows: Sample preparation (per ISO 14780), decomposition by closed-vessel combustion or digestion, analysis by IC or ICP-OES, and reporting against standard performance criteria.

Related standards

• ISO 10304-1 (ion chromatography for anions)
• ISO 11885 (ICP-OES)
• ISO 14780 (sample preparation)
• ISO 16559 (vocabulary)
• ISO 16967:2015 (digestion reference)
• ISO 18125, ISO 18134-3 (related solid biofuel tests)
• CEN Guide 13 (validation of alternative methods)
• ISO/TS 16996 (XRF guidance)

This standard is essential for reliable measurement of sulfur and halogens in bio-based solid fuels and for ensuring comparable, validated methods across labs and industry.

Standards Content (Sample)

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
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,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
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 SUPPORTING DOCUMENTATION.
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
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
CP 401 • Ch. de Blandonnet 8
TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
Phone: [phone]
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: [e-mail]
Website: www.iso.org
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
...