SIST EN ISO 16994:2026

• Abstract:

  This document 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 are 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 document, provided that a validation is carried out as specified and that the performance characteristics are similar to those of the method described in this document.

• Status: Published
• Public Enquiry End Date: 21-Sep-2025
• Publication Date: 15-Jul-2026
• ICS: 27.190 - Biological sources and alternative sources of energy
• ICS: 75.160.40 - Biofuels
• Technical Committee: AGO - Refuse derived fuel
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Jul-2026
• Due Date: 05-Sep-2026
• Completion Date: 16-Jul-2026
• Ref Project: EN ISO 16994:2026 - Solid biofuels and pyrogenic biocarbon - Determination of sulfur and chlorine content (ISO 16994:2026)

• Replaces: SIST EN ISO 16994:2016 - Solid biofuels - Determination of total content of sulfur and chlorine (ISO 16994:2016)
• Effective Date: 01-Sep-2026
• Refers: SIST-V CEN Guide 13:2009 - Validation of environmental test methods
• Effective Date: 01-Jul-2026
• Referred By: SIST EN 1860-3:2023 - Appliances, solid fuels and firelighters for barbecuing - Part 3: Firelighters for igniting solid fuels for use in barbecues and grill applications - Requirements and test
• Effective Date: 24-Jun-2026
• Referred By: SIST EN 15821:2011 - Multi firing Sauna stoves fired by solid fuel - Requirements and test methods
• Effective Date: 24-Jun-2026
• Referred By: SIST EN 14961-1:2010 - Solid biofuels - Fuel specifications and classes - Part 1: General requirements
• Effective Date: 24-Jun-2026
• Referred By: SIST EN 14961-4:2011 - Solid biofuels - Fuel specifications and classes - Part 4: Wood chips for non-industrial use
• Effective Date: 24-Jun-2026
• Referred By: SIST EN 14961-2:2011 - Solid biofuels - Fuel specifications and classes - Part 2: Wood pellets for non-industrial use
• Effective Date: 24-Jun-2026
• Referred By: SIST EN 14961-6:2012 - Solid biofuels - Fuel specifications and classes - Part 6: Nonwoody pellets for non-industrial use
• Effective Date: 24-Jun-2026
• Referred By: SIST EN 14961-3:2011 - Solid biofuels - Fuel specifications and classes - Part 3: Wood briquettes for non-industrial use
• Effective Date: 24-Jun-2026
• Referred By: SIST EN 15296:2011 - Solid biofuels - Conversion of analytical results from one basis to another
• Effective Date: 24-Jun-2026

Overview

SIST EN ISO 16994:2026 specifies standardized methods for the determination of sulfur and chlorine content in solid biofuels and pyrogenic biocarbon. The standard details two decomposition methods for sample preparation and supports various analytical techniques for quantifying these elements. These methods play a critical role in controlling harmful emissions, corrosion, and ensuring compliance for solid biofuels and related bioenergy products. The scope also allows, with certain limitations, for the detection of other halogens such as fluorine and bromine.

Key Topics

• Sample Decomposition: Two main methods are described: combustion in a closed combustion vessel (preferred for most analyses) and acid digestion in a closed vessel.
• Analytical Techniques: Ion chromatography is recommended for detecting sulfate, chloride, fluoride, and bromide. Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) is utilized for sulfur measurement.
• Automatic Equipment: The use of validated automatic analysis equipment, such as elemental analysers and combustion ion chromatography, is permitted if results are comparable to reference methods.
• Quality Assurance: Emphasis is placed on the use of certified reference materials for calibration and performance monitoring. Blank tests are required to ensure accuracy and prevent contamination.
• Result Expression: Results must be reported on a dry basis, according to standardized calculation methods provided in the document.

Applications

The determination of sulfur and chlorine content in solid biofuels and pyrogenic biocarbon is essential for:

• Emission Control: Accurate quantification supports compliance with environmental regulations by limiting the release of sulfur oxides and chlorides, which can cause air pollution and acid rain.
• Corrosion Prevention: Elevated chlorine and sulfur levels in fuels can significantly increase equipment corrosion risk in combustion systems, especially in biomass-fired boilers.
• Quality Assessment: Producers, suppliers, and users can use the data to classify solid biofuels and biocarbon according to international specifications and supply agreements.
• Process Optimization: Monitoring sulfur and chlorine allows optimization of combustion processes and post-combustion treatments for better efficiency and reduced maintenance needs.
• Regulatory Compliance: Laboratories and testing organizations rely on standardized methods to provide consistent and credible test results that are accepted internationally.

Related Standards

• ISO 10304-1: Water quality - Determination of dissolved anions by liquid chromatography of ions; relevant for ion chromatography methods.
• ISO 11885: Water quality - Determination of selected elements by ICP-OES.
• ISO 14780: Solid biofuels - Sample preparation, crucial for consistent test sample creation.
• ISO 16559: Vocabuary for solid biofuels, ensuring clear communication.
• ISO 16967: Determination of major elements, referenced for alternate decomposition methods.
• ISO 18125: Determination of calorific value for solid biofuels; often used alongside sulfur and chlorine determination.
• ISO 18134-3: Determination of moisture content for accurate dry basis calculations.
• CEN Guide 13: Validation of environmental test methods, required for alternative or automatic equipment validation.
• ISO/TS 16996: X-ray fluorescence analysis, referenced for chlorine and sulfur determination in residues.
• ISO 16995: Complementary method for high chlorine content samples.
• EN 14582: Method for iodide content analysis with similar principles.

Practical Value

Implementing SIST EN ISO 16994:2026 enhances the reliability, safety, and sustainability of solid biofuel utilization. By following these standardized methods for sulfur and chlorine determination, stakeholders can ensure product quality management, regulatory compliance, and environmental responsibility in the growing bioenergy sector.

SLOVENSKI STANDARD
01-september-2026
Nadomešča:
SIST EN ISO 16994:2016
Trdna biogoriva in pirogenski bioogljik - Določanje vsebnosti žvepla in klora (ISO
16994:2026)
Solid biofuels and pyrogenic biocarbon - Determination of sulfur and chlorine content
(ISO 16994:2026)
Biogene Festbrennstoffe - Bestimmung des Gesamtgehaltes an Schwefel und Chlor
(ISO 16994:2026)
Biocombustibles solides et biocarbone pyrogène - Détermination de la teneur en soufre
et en chlore (ISO 16994:2026)
Ta slovenski standard je istoveten z: EN ISO 16994:2026
ICS:
75.160.40 Biogoriva Biofuels
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 16994
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2026
EUROPÄISCHE NORM
ICS 27.190; 75.160.40 Supersedes EN ISO 16994:2016
English Version
Solid biofuels and pyrogenic biocarbon - Determination of
sulfur and chlorine content (ISO 16994:2026)
Biocombustibles solides et biocarbone pyrogène - Biogene Festbrennstoffe - Bestimmung des
Détermination de la teneur en soufre et en chlore (ISO Gesamtgehaltes an Schwefel und Chlor (ISO
16994:2026) 16994:2026)
This European Standard was approved by CEN on 22 May 2026.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

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
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 16994:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 16994:2026) has been prepared by Technical Committee ISO/TC 238 "Solid
Biofuels and Pyrogenic Biocarbon" in collaboration with Technical Committee CEN/TC 335 “Solid
Biofuels and Pyrogenic Biocarbon” the secretariat of which is held by SIS.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by December 2026, and conflicting national standards
shall be withdrawn at the latest by December 2026.
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.
This document supersedes EN ISO 16994:2016.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: 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 the
United Kingdom.
Endorsement notice
The text of ISO 16994:2026 has been approved by CEN as EN ISO 16994:2026 without any modification.

International
Standard
ISO 16994
Third edition
Solid biofuels and pyrogenic
2026-06
biocarbon — Determination of
sulfur and chlorine content
Biocombustibles solides et biocarbone pyrogène —
Détermination de la teneur en soufre et en chlore
Reference number
ISO 16994:2026(en) © ISO 2026
ISO 16994:2026(en)
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 16994:2026(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 .7
9.3 Sulfur .7
10 Performance characteristics . 7
11 Test report . 7
Annex A (informative) Performance data . 8
Bibliography .10

iii
ISO 16994:2026(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 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
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 third edition cancels and replaces the second edition (ISO 16994:2016), which has been technically
revised.
The main changes are as follows:
— fluorine and bromine added to the scope and calculation in 9.2;
— normative references updated;
— detection methods updated and additional details about the techniques added;
— decomposition method with acid digestion and ICP analyses for chlorine removed.
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
ISO 16994:2026(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 can 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 document.
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 may also be used for selected analytes. The determination of the
resultant chlorine, sulfur, bromine and fluorine compounds can be done by different techniques.
Automatic equipment and alternative methods may also be used for selected analytes.
A list with typical sulfur, chlorine and fluorine contents of solid biofuels can be found in ISO 17225-1:2021,
Annex B.
v
International Standard ISO 16994:2026(en)
Solid biofuels and pyrogenic biocarbon — Determination of
sulfur and chlorine content
1 Scope
This document 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 are 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 document, provided that a validation is carried out as specified and that the performance characteristics
are similar to those of the method described in this document.
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 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 14780, Solid biofuels — Sample preparation
ISO 16559, Solid biofuels — Vocabulary
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 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/
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 16994:2026(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 (see EN 17813) and sulfur-analysers.
If automatic equipment or X-ray fluorescence (see ISO/TS 16996) is used, the method shall be validated for
the respective main origin-based biomass group (see ISO 17225-1:2021, Table 1: woody biomass, herbaceous
biomass, fruit biomas
...