EN ISO 16994:2026
(Main)Solid biofuels and pyrogenic biocarbon - Determination of sulfur and chlorine content (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
- Publication Date
- 16-Jun-2026
- Technical Committee
- CEN/TC 335 - Solid biofuels
- Current Stage
- 6060 - Definitive text made available (DAV) - Publishing
- Start Date
- 17-Jun-2026
- Completion Date
- 17-Jun-2026
EN ISO 16994:2026 is a CEN European Standard that adopts ISO 16994:2026 without modification. It specifies methods for determining sulfur and chlorine in solid biofuels and pyrogenic biocarbon, and it also allows fluorine and bromine to be measured with the same procedures when they are properly validated. The document is aimed at laboratories, manufacturers, and users who need comparable results for fuel characterization and quality control.
What does EN ISO 16994:2026 specify?
EN ISO 16994:2026 specifies how to determine sulfur and chlorine content in solid biofuels and pyrogenic biocarbon, including two decomposition routes and several ways to measure the analytes in the resulting solutions. It also permits fluorine and bromine to be analysed by the same methods, but the performance data in the standard are focused on sulfur and chlorine.
The document is organized into the usual testing sequence: scope, normative references, terms and definitions, principle, reagents, apparatus, sample preparation, procedure, expression of results, performance characteristics, and test report. Annex A provides informative performance data from a European comparison study.
| Annex | What it covers |
|---|---|
| Annex A | Informative performance data from a round robin study on wood chips and exhausted olive residues |
What are the key requirements of EN ISO 16994:2026?
EN ISO 16994:2026 requires the test to be carried out on a prepared general analysis sample, with moisture measured in parallel so results can be reported on a dry basis. In practice, this means the analyst must control sample size, sample conditioning, and moisture correction before reporting any result.
Sample preparation and basis of result
- Clause 7 requires the test sample to be the general analysis sample with a nominal top size of 1 mm, prepared according to ISO 14780.
- The moisture content is determined at the same time on another portion of the sample according to ISO 18134-3.
- If a smaller top size is needed to keep precision and repeatability within the stated limits, the result should be checked with CRM or RM.
These steps matter because particle size and moisture content can change measured sulfur and chlorine levels, especially for heterogeneous biomass.
Decomposition of the sample
- Clause 8 gives Method A and Method B.
- Method A uses combustion in oxygen in a closed combustion vessel, with acidic gases absorbed into a solution.
- Method B uses acid digestion in a closed vessel as described in ISO 16967:2015, Part A.
Method A is the preferred approach in the introduction because it can also support fluorine and bromine measurement, and it can be combined with calorific value determination according to ISO 18125. Method B is described in the document, but the standard notes that it is not suitable for chlorine and fluorine because of the analytical technique and possible losses during acid digestion.
Detection and validation
- Clause 8.2 recommends ion chromatography for sulfate, chloride, fluoride and bromide, following the principles of ISO 10304-1.
- Other standardized techniques may be used, including ICP, photometric, coulometric and potentiometric methods, if they are validated and give similar performance.
- Automatic equipment is allowed, but only after validation with biomass reference samples of the appropriate biomass group and in line with CEN Guide 13:2008.
This matters in practice because many laboratories use different instruments. The standard allows alternative equipment, but only when the laboratory can show that the method works for the intended biomass type and produces equivalent performance.
Calibration, blank tests and quality control
- Clause 5 requires reagents to be analytical grade and to contain negligible amounts of chlorine, sulfur, fluorine and bromine.
- Certified reference materials or reference materials are used to check calibration accuracy and recoveries.
- Clause 8.1.3 requires a blank test to check contamination from reagents, equipment or the laboratory environment.
In everyday laboratory work, this is how the standard keeps contamination and matrix effects from distorting low-level measurements. If the blank is significant, the value must be corrected or the system cleaned and retested.
Expression of results and reporting
- Clause 9 requires duplicate determinations and reporting on a dry basis.
- Chlorine, fluorine and bromine are calculated from the concentration in solution after blank correction.
- Sulfur is calculated from sulfate concentration using the stoichiometric relationship given in the standard.
- Clause 11 requires the test report to identify the laboratory, the product or sample, the standard used, the digestion and determination methods, the result basis, unusual features, and any deviations.
For buyers and quality managers, this means the result should be traceable and comparable between laboratories, not just a single instrument reading.
What terms does EN ISO 16994:2026 define?
The terms and definitions from ISO 16559 apply to this document. The following terms are especially important for using the method correctly:
- Solid biofuels - solid fuels made from biomass that are tested for sulfur and chlorine content in this standard.
- Pyrogenic biocarbon - carbon-rich material covered by the scope of the standard and analysed by the same test approach.
- Method A - combustion in oxygen in a closed vessel, followed by analysis of the absorbed gases.
- Method B - acid digestion in a closed vessel, used as an alternative decomposition route.
- CRM (certified reference material) - a material used to check calibration and accuracy against known properties.
- RM (reference material) - a comparison material used for calibration, verification or quality control.
- Blank test - a test run used to measure background contamination from reagents, equipment or the environment.
- Dry basis - a way of expressing the result after correcting for moisture content.
Who uses EN ISO 16994:2026?
EN ISO 16994:2026 is used by analytical laboratories, fuel producers, and quality control teams that need to measure sulfur and chlorine in solid biofuels or pyrogenic biocarbon. It is also relevant to laboratories working with fluorine and bromine when they have validated the method for those analytes.
The standard is useful in procurement and product qualification because sulfur and chlorine content affect corrosion risk and emissions behavior during combustion. It is also used in routine laboratory work where comparable results are needed across different instruments, sites or laboratories.
What changed in EN ISO 16994:2026 from the previous edition?
EN ISO 16994:2026 supersedes EN ISO 16994:2016 and is described as a technically revised third edition.
The main changes stated in the document are:
- fluorine and bromine were added to the scope and to the calculation in 9.2;
- normative references were updated;
- detection methods were updated and given additional detail;
- the decomposition method using acid digestion and ICP analyses for chlorine was removed.
Which standards are used with EN ISO 16994:2026?
EN ISO 16994:2026 relies directly on several referenced standards and also points to companion standards for sample preparation, measurement and validation.
- ISO 10304-1 - gives the ion chromatography principles used for sulfate, chloride, fluoride and bromide.
- ISO 14780 - provides the sample preparation method for the general analysis sample.
- ISO 16559 - supplies the vocabulary used in the document.
- ISO 18125 - supports calorific value determination and is linked to the combustion vessel approach.
- ISO 18134-3 - provides the moisture determination used for dry-basis calculation.
- CEN Guide 13:2008 - gives the validation approach for alternative methods and automatic equipment.
- ISO 16967:2015 - supplies the closed-vessel acid digestion method used as Method B.
- ISO 11885 - is cited for ICP determination of sulfur.
- ISO 16993 - is cited for converting analytical results from one basis to another.
- ISO/TS 16996 - is cited for X-ray fluorescence when residue analysis or alternative elemental analysis is used.
- ISO 17225-1:2021 - is used to identify the main origin-based biomass group for validation.
- EN 17813 - is cited as an example of combustion ion chromatography.
- ISO 5725-2 - is used in Annex A for the performance data presentation.
What does the EN ISO 16994:2026 document contain?
EN ISO 16994:2026 contains a full laboratory method, not just a result limit or a short specification. It includes two decomposition routes, several detection techniques, calibration and blank-test guidance, and a reporting section.
It also includes a table of alternative detection methods and an informative annex with round-robin performance data. Annex A shows results for sulfur and chlorine from wood chips and exhausted olive residues, which helps laboratories judge what the method can achieve in practice with different biomass types.
Relations
- Effective Date
- 06-Mar-2024
- Effective Date
- 01-Jul-2026
- Effective Date
- 01-Jul-2026
- Effective Date
- 01-Jul-2026
- Effective Date
- 01-Jul-2026
- Effective Date
- 01-Jul-2026
- Effective Date
- 01-Jul-2026
- Referred By
EN 14961-1:2010 - Solid biofuels - Fuel specifications and classes - Part 1: General requirements - Effective Date
- 24-Jun-2026
- Effective Date
- 24-Jun-2026
- Effective Date
- 24-Jun-2026
- Effective Date
- 24-Jun-2026
- Effective Date
- 24-Jun-2026
- Referred By
EN 15296:2011 - Solid biofuels - Conversion of analytical results from one basis to another - Effective Date
- 24-Jun-2026
- Effective Date
- 24-Jun-2026
- Referred By
EN 15821:2010 - Multi-firing sauna stoves fired by natural wood logs - Requirements and test methods - Effective Date
- 24-Jun-2026
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Frequently Asked Questions
EN ISO 16994:2026 is a standard published by the European Committee for Standardization (CEN). Its full title is "Solid biofuels and pyrogenic biocarbon - Determination of sulfur and chlorine content (ISO 16994:2026)". This standard covers: 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.
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.
EN ISO 16994:2026 is classified under the following ICS (International Classification for Standards) categories: 27.190 - Biological sources and alternative sources of energy; 75.160.40 - Biofuels. The ICS classification helps identify the subject area and facilitates finding related standards.
EN ISO 16994:2026 has the following relationships with other standards: It is inter standard links to EN ISO 16994:2016, ISO 14780:2017, ISO 10304-1:2007, CEN Guide 13:2008, ISO 18125:2017, ISO 16559:2022, ISO 18134-3:2023, EN 14961-1:2010, EN 14961-4:2011, EN 14961-6:2012, EN 14961-3:2011, EN 14961-2:2011, EN 15296:2011, EN 1860-3:2023, EN 15821:2010. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
EN ISO 16994:2026 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
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
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Phone: +41 22 749 01 11
Email: copyright@iso.org
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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
...