ISO/FDIS 17225-5

Solid biofuels - Fuel specifications and classes - Part 5: Graded firewood

This document determines the fuel quality classes and specifications of graded firewood. This document covers only firewood produced from the following raw materials (see ISO 17725‑1:2021, Table 1): - 1.1.1 Whole trees without roots; - 1.1.3 Stem wood; - 1.1.4 Logging residues (thick branches, tops etc.); - 1.2.1 Chemically untreated by-products and residues from wood processing industry.

Biocombustibles solides — Classes et spécifications des combustibles — Partie 5: Classes de bois de chauffage

Le présent document détermine les classes et spécifications de qualité du combustible pour le bois de chauffage. Le présent document couvre uniquement le bois de chauffage produit à partir des matières premières suivantes (voir ISO 17725-1:2021, Tableau 1): — 1.1.1 Arbres entiers sans racines; — 1.1.3 Grumes; — 1.1.4 Rémanents forestiers (grosses branches, cimes, etc.); — 1.2.1 Produits dérivés et sous-produits de l'industrie de transformation du bois sans traitement chimique.

General Information

• Status: Not Published
• ICS: 27.190 - Biological sources and alternative sources of energy
• ICS: 75.160.10 - Solid fuels
• ICS: 75.160.40 - Biofuels
• Technical Committee: ISO/TC 238 - Solid biofuels
• Drafting Committee: ISO/TC 238/WG 2 - Fuel specifications and classes
• Current Stage: 5000 - FDIS registered for formal approval
• Start Date: 18-Nov-2025
• Completion Date: 26-Nov-2025

Relations

• Consolidates: ISO/IEC 24775-7:2021 - Information technology - Storage management - Part 7: Host elements
• Effective Date: 15-Mar-2025
• Revises: ISO 17225-5:2021 - Solid biofuels - Fuel specifications and classes - Part 5: Graded firewood
• Effective Date: 07-Jan-2025

Overview

ISO/FDIS 17225-5:2025 is an international standard defining the fuel specifications and classification of graded firewood. Developed by ISO Technical Committee ISO/TC 238, this document focuses specifically on firewood produced from raw materials including whole trees without roots, stem wood, logging residues, and chemically untreated by-products from the wood processing industry. This new edition updates and replaces the 2021 version, providing clear, harmonized quality classes to support efficient trading and reliable communication between producers, buyers, and equipment manufacturers.

The standard supports the use of graded firewood primarily for residential, small commercial, and public buildings, emphasizing higher quality fuels suitable for appliances like stoves, fireplaces, cookers, and boilers. It fosters improved fuel quality transparency, helps ensure safety, and encourages environmentally responsible biomass energy use.

Key Topics

• Scope and Applicability
  Only firewood from defined biomass categories is covered (whole trees, stem wood, logging residues, untreated wood industry residues). It excludes chemically treated or contaminated materials.

• Quality Classes
  The firewood is classified into three main graded quality classes:

  • Class A1 and A2: Suitable for stoves and fireplaces requiring higher-quality fuel.
  • Class B: Applicable for use in log wood boilers where fuel control is less stringent.

• Specifications and Parameters
  Fuel quality is specified based on:

  • Moisture content (wet basis ranges from 8% to 35% depending on the class)
  • Diameter and length of logs (with defined minimum proportions for specific size fractions)
  • Origin and raw material type
  • Physical properties such as energy density and net calorific value (optional but recommended)

• Measurement and Testing Methods
  Methods conform to related ISO standards including:

  • ISO 21945 for sampling
  • ISO 14780 for sample preparation
  • ISO 18134-1 and ISO 18134-2 for moisture content determination (reference and simplified methods)
  • ISO 18125 for calorific values

• Additional Informative Annexes

  • Moisture content comparisons (as received vs dry basis)
  • Firewood measurement techniques
  • Energy density calculation

• Firewood Dimensions
  Defined by maximum diameter and length parameters following specific maximum and minimum dimensional criteria to ensure uniformity in grading.

Applications

ISO 17225-5:2025 addresses practical needs relevant to:

• Residential Heating
  Ensuring the provision of clean, energy-efficient fuel for household appliances such as wood-burning stoves and fireplaces that typically lack advanced emission controls.

• Small Commercial and Public Buildings
  Provides guidelines for fuel suitable for boilers and heating systems in various building types where fuel quality impacts operational efficiency and air quality.

• Fuel Trading and Certification
  Facilitates transparent communication between suppliers and buyers by defining unambiguous firewood quality classes, assisting official market regulation and consumer protection.

• Environmental and Safety Compliance
  Helps minimize emissions and contamination risks by excluding chemically treated or potentially contaminated wood and defining moisture limits for optimized combustion.

• Manufacturer Communication
  Supports appliance manufacturers in specifying fuel requirements to maximize device performance and durability.

Related Standards

ISO/FDIS 17225-5 builds upon and complements several international standards, including:

• ISO 17225-1:2021 - General requirements for solid biofuels, providing foundational principles for classification and fuel quality.
• ISO 18134 series - Determination methods for moisture content, critical for fuel quality assessment.
• ISO 21945 - Sampling procedures tailored for small-scale solid biofuel applications like firewood.
• ISO 14780 - Sample preparation for solid biofuels ensuring consistency during analysis.
• ISO 18125 - Methods for net calorific value analysis, important for energy content determination.

These related standards form a comprehensive framework for managing solid biofuel quality - essential for ensuring compliance, safety, and performance in biomass utilization.

---

Keywords: ISO 17225-5, graded firewood, solid biofuels, fuel specifications, firewood quality classes, moisture content, biomass fuel standards, residential heating fuel, firewood grading, wood fuel specifications, ISO solid biofuels, biomass energy, pellet and log stove fuel standards.

Standards Content (Sample)

FINAL DRAFT
International
Standard
ISO/TC 238
Solid biofuels — Fuel specifications
Secretariat: SIS
and classes —
Voting begins on:
2026-01-06
Part 5:
Graded firewood
Voting terminates on:
2026-03-03
Biocombustibles solides — Classes et spécifications des
combustibles —
Partie 5: Classes de bois de chauffage
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.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/CEN PARALLEL PROCESSING LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 238
Solid biofuels — Fuel specifications
Secretariat: SIS
and classes —
Voting begins on:
Part 5: 2026-01-09
Graded firewood
Voting terminates on:
Biocombustibles solides — Classes et spécifications des
combustibles —
Partie 5: Classes de bois de chauffage
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 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/CEN PARALLEL PROCESSING
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
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 Reference number
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms. 2
5 Specification of graded firewood . 2
Annex A (informative) Comparison of moisture content as received and dry basis. 6
Annex B (informative) Measurement of firewood . 8
Annex C (informative) Calculation of energy density . 9
Bibliography .11

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
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 17225-5:2021), which has been technically
revised.
The main changes are as follows:
— moisture in Table 1 has been changed.
A list of all parts in the ISO 17225 series can be found on the ISO website.
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
The objective of the ISO 17225 series is to provide unambiguous and clear classification principles for solid
biofuels, to serve as a tool to enable efficient trading of biofuels, to enable good understanding between
seller and buyer and as a tool for communication with equipment manufacturers. It also facilitates authority
permission, procedures and reporting.
This document supports the use of graded firewood for residential, small commercial and public building
applications which require classified firewood quality.
Residential, small commercial and public building appliances require higher quality fuel for the following
reasons:
— small-scale equipment does not usually have advanced controls and flue gas cleaning;
— appliances are not generally managed by professional heating engineers;
— appliances are often located in residential and populated districts.
NOTE 1 Firewood produced according to this document can be used in stoves, fireplaces, cookers, room heaters
[1] [2] [3]
and multifired sauna stoves, which are tested according to European standards EN 13229, EN 12815, EN 12809,
[4] [5] [6] [7] [8] [9] [10]
EN 13240, EN 15250, EN 15821, EN 16510–2–1, EN 16510–2–2, EN 16510–2–3, EN 16510–2–5, EN 16510–
[11] [12] [13] [14]
2–7, EN 16510–2–10, and boilers systems tested according to EN 303–5, EN 16510–2–4 .
NOTE 2 For individual contracts, ISO 17225-1 can be used.
Although this document can be used separately, it requires a general understanding of the standards based
on and supporting ISO 17225-1. It is recommended to obtain and use ISO 17225-1 in conjunction with this
document.
v
FINAL DRAFT International Standard ISO/FDIS 17225-5:2026(en)
Solid biofuels — Fuel specifications and classes —
Part 5:
Graded firewood
1 Scope
This document specifies the fuel quality classes and specifications of graded firewood. This document
applies only to firewood produced from the following raw materials (see ISO 17225-1:2021, Table 1):
— 1.1.1 Whole trees without roots;
— 1.1.3 Stem wood;
— 1.1.4 Logging residues (thick branches, tops, etc.);
— 1.2.1 Chemically untreated by-products and residues from wood processing industry.
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 14780, Solid biofuels — Sample preparation
ISO 16559, Solid biofuels — Vocabulary
ISO 17225-1:2021, Solid biofuels — Fuel specifications and classes — Part 1: General requirements
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 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
firewood
cut and split oven-ready fuelwood used in household wood burning appliances like stoves, fireplaces and
central heating systems
Note 1 to entry: Firewood usually has a uniform length, typically in the range of 15 cm to 100 cm.
Note 2 to entry: Cut-offs from virgin wood can also be used as a firewood.

3.2
commercial application
facility that utilizes solid biofuel burning appliances or equipment that have similar fuel requirements as
residential appliances
Note 1 to entry: Commercial applications are not to be confused with industrial applications, which can utilize a much
wider array of materials and have vastly different fuel requirements.
4 Symbols and abbreviated terms
The following symbols and abbreviated terms are used in this document and conform with the SI system of
units, except where noted.
ar as received
D Designation for diameter (D) as received [cm]
d dry (dry basis)
3 3
E Designation for energy density as received, E [MJ/m or kWh/m loose or stacked volume or MJ/kg,
ar
kWh/kg]
L Designation for length (L) as received [cm]
M Designation for moisture content as received on wet basis, M [% in mass]
ar
q Designation for net calorific value as received, q [MJ/kg or GJ/t or kWh/kg or MWh/t] at constant
p,net,ar
pressure
U Designation for moisture content on dry basis, U [% in mass]
d
NOTE 1 1 MJ/kg or GJ/t equals 0,277 8 kWh/kg (1 kWh/kg equals 1 MWh/t and 1 MWh/t is 3,6 MJ/kg). 1 g/cm
equals 1 kg/dm . 1 mg/kg equals 0,000 1 %.
NOTE 2 Designation symbols are used in combination with a number to specify property levels in Table 1.
5 Specification of graded firewood
Specification of the firewood shall be stated in accordance with Table 1 and Figure 1. Sampling shall be
carried out in accordance with ISO 21945, sample preparation in accordance with ISO 14780 and analysis
of the properties of solid biofuels, specifically moisture, shall be carried out in accordance with ISO 18134-1
(reference method) or ISO 18134-2 (simplified method).
Ash, N, S, Cl and minor elements are not required as firewood is produced from virgin material which has
been grown in uncontaminated soil and therefore the likelihood of contamination is very low.
Firewood specified according to classes A1 and A2 are suitable to be used in stoves and fireplaces and class
B in log wood boilers.
How to state the dimensions of firewood is expressed in Figure 1.
...

ISO/TC 238
Secretariat: SIS
Date: 2025-10-2912-22
Solid biofuels — Fuel specificationspecifications and classes —
Part 5:
Graded firewood
Biocombustibles solides — Classes et spécifications des combustibles —
Partie 5: Classes de bois de chauffage
FDIS stage
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ISO/DISFDIS 17225-5:202x2025(en)
© ISO 2025
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: + 41 22 749 01 11
Fax: [phone]
EmailE-mail: [e-mail]
Website: www.iso.orgwww.iso.org
Published in Switzerland
ii © ISO 2025 – All rights reserved
ii
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
5 Specification of graded firewood . 2
Annex A (informative) Comparison of moisture content as received and dry basis . 6
Annex B (informative) Measurement of firewood . 8
Annex C (informative) Calculation of energy density . 10
Bibliography . 12

Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
5 Specification of graded firewood . 2
Annex A (informative) Comparison of moisture content as received and dry basis . 6
Annex B (informative) Measurement of firewood . 8
Annex C (informative) Calculation of energy density. 9
Bibliography . 10
iii
ISO/DISFDIS 17225-5:202x2025(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.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.htmlwww.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 238,
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 17225-5:2021), which has been technically
revised.
The main changes are as follows:
— — moisture in Table 10 has been changed.
A list of all parts in the ISO 17225 series can be found on the ISO website.
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.
Field Code Changed
iv © ISO 2025 – All rights reserved
iv
Introduction
The objective of the ISO 17225 series is to provide unambiguous and clear classification principles for solid
biofuels, to serve as a tool to enable efficient trading of biofuels, to enable good understanding between seller
and buyer and as a tool for communication with equipment manufacturers. It also facilitates authority
permission, procedures and reporting.
This document supports the use of graded firewood for residential, small commercial and public building
applications which require classified firewood quality.
Residential, small commercial and public building appliances require higher quality fuel for the following
reasons:
— — small-scale equipment does not usually have advanced controls and flue gas cleaning;
— — appliances are not generally managed by professional heating engineers;
— — appliances are often located in residential and populated districts.
NOTE 1 Firewood produced according to this document can be used in stoves, fireplaces, cookers, room heaters and
[1] [ ] [2] [ ] [3]
multifired sauna stoves, which are tested according to European standards EN 13229 , , 0 EN 12815 , , 0 EN 12809 ,
[ ] [4] [ ] [5] [ ] [6] [ ] [7] [ ] [8] [ ] [9]
, 0 EN 13240 , , 0 EN 15250 , , 0 EN 15821 , , 0 EN 16510–2–1 , , 0 EN 16510–2–2 , , 0 EN 16510–2–3 ,
[ ] [10] [ ] [11] [ ] [12] [ ]
, 0 EN 16510–2–5 , , 0 EN 16510–2–7 , , 0 EN 16510–2–10 ,, 0 and boilers systems tested according to EN 303–
[13] [ ] [14] [ ]
5 , , 0 EN 16510–2–4 . 0 .
NOTE 2 For individual contracts, ISO 17225--1 can be used.
Although this document can be used separately, it requires a general understanding of the standards based on
and supporting ISO 17225-1. It is recommended to obtain and use ISO 17225-1 in conjunction with this
document.
v
DRAFT International Standard ISO/FDIS 17225-5:2025(en)

Solid biofuels — Fuel specificationspecifications and classes — —
Part 5:
Graded firewood
1 Scope
This document specifies the fuel quality classes and specifications of graded firewood. This document applies
only to firewood produced from the following raw materials (see ISO 17225--1:2021, Table 1):
— — 1.1.1 Whole trees without roots;
— — 1.1.3 Stem wood;
— — 1.1.4 Logging residues (thick branches, tops, etc.);
— — 1.2.1 Chemically untreated by-products and residues from wood processing industry.
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 14780, Solid biofuels — Sample preparation
ISO 16559, Solid biofuels — Vocabulary
ISO 17225--1:2021, Solid biofuels — Fuel specifications and classes — Part 1: General requirements
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 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/obphttps://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
3.1 3.1
firewood
cut and split oven-ready fuelwood used in household wood burning appliances like stoves, fireplaces and
central heating systems
Note 1 to entry: Firewood usually has a uniform length, typically in the range of 15 cm to 100 cm.
Note 2 to entry: Cut-offs from virgin wood can also be used as a firewood.
3.2 3.2
commercial application
facility that utilizes solid biofuel burning appliances or equipment that have similar fuel requirements as
residential appliances
Note 1 to entry: Commercial applications are not to be confused with industrial applications, which can utilize a much
wider array of materials and have vastly different fuel requirements.
4 Symbols and abbreviated terms
The following symbols and abbreviated terms are used in this document and conform with the SI system of
units, except where noted.
ar as received
D Designation for diameter (D) as received [cm]
d dry (dry basis)
3 3
E Designation for energy density as received, E [MJ/m or kWh/m loose or stacked volume or MJ/kg,
ar
kWh/kg]
L Designation for length (L) as received [cm]
M Designation for moisture content as received on wet basis, M [% in mass]
ar
Qq Designation for net calorific value as received, qp,net,ar [MJ/kg or GJ/t or kWh/kg or MWh/t] at constant
pressure
U Designation for moisture content on dry basis, U [% in mass]
d
NOTE 1 1 MJ/kg or GJ/t equals 0,277 8 kWh/kg (1 kWh/kg equals 1 MWh/t and 1 MWh/t is 3,6 MJ/kg). 1 g/cm
equals 1 kg/dm . 1 mg/kg equals 0,000 1 %.
NOTE 2 Designation symbols are used in combination with a number to specify property levels in Table 1.0.
5 Specification of graded firewood
Specification of the firewood shall be stated in accordance with Table 10 and Figure 1.0. Sampling shall be
carried out in accordance with ISO 21945, sample preparation in accordance with ISO 14780 and analysis of
the properties of solid biofuels, specifically moisture, shall be carried out in accordance with ISO 18134--1
(reference method) or ISO 18134--2 (simplified method).
Ash, N, S, Cl and minor elements are not required as firewood is produced from virgin material which has been
grown in uncontaminated soil and therefore the likelihood of contamination is very low.
Firewood specified according to
...