International Tropical
Timber Organization

Forestproduct
conversion
factors

United Nations

Forest
product
conversion
factors

Published by
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONSandINTERNATIONAL TROPICAL TIMBER ORGANIZATION
andUNITED NATIONS ECONOMIC COMMISSION FOR EUROPE
Rome, 2020

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FAO, ITTO and United Nations. 2020. Forest product conversion factors. Rome. https://doi.org/10.4060/ca7952en

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CONTENTS
Foreword...........................................................................................................................................................................................................................................................V
Acknowledgements.................................................................................................................................................................................................................................VI
Acronyms and abbreviations........................................................................................................................................................................................................... VIII
Explanatory notes......................................................................................................................................................................................................................................IX
1. INTRODUCTION.................................................................................................................................................................... 1
1.1 General uses of conversion factors..............................................................................................................................................................................1
1.2 The use of conversion factors by FAO, ITTO and UNECE................................................................................................................................2
1.3 Methods........................................................................................................................................................................................................................................3
2. ROUNDWOOD....................................................................................................................................................................... 5
2.1 Volumetric measurement..................................................................................................................................................................................................5
2.2 Weight and physical properties.................................................................................................................................................................................. 11
2.3 Summary of country data on roundwood........................................................................................................................................................... 13
3. WOOD PARTICLES.............................................................................................................................................................. 17
3.1 Volumetric measurement............................................................................................................................................................................................... 17
3.2 Weight......................................................................................................................................................................................................................................... 17
3.3 Summary of country data on wood particles.................................................................................................................................................... 19
4. SAWNWOOD....................................................................................................................................................................... 21
4.1 Volumetric measurement............................................................................................................................................................................................... 22
4.2 Weight......................................................................................................................................................................................................................................... 24
4.3 Material balance.................................................................................................................................................................................................................... 24
4.4 Summary of country data on sawnwood............................................................................................................................................................. 26
5. VENEER AND PLYWOOD................................................................................................................................................... 29
5.1 Volumetric and surface measurement................................................................................................................................................................... 29
5.2 Weight......................................................................................................................................................................................................................................... 29
5.3 Material balance .................................................................................................................................................................................................................. 30
5.4 Summary of country data on veneer and plywood....................................................................................................................................... 31
6. PANELS MADE OF WOOD PARTICLES............................................................................................................................ 35
6.1 Volumetric and surface measurement................................................................................................................................................................... 35
6.2 Weight......................................................................................................................................................................................................................................... 35
6.3 Summary of country data on panels made of wood particles................................................................................................................ 36
7. WOOD PULP AND PAPER................................................................................................................................................. 39
7.1 Weight......................................................................................................................................................................................................................................... 39
7.2 Summary of country data on wood pulp and paper.................................................................................................................................... 40
8. ROUND AND SPLIT WOOD PRODUCTS......................................................................................................................... 43
8.1 Volumetric and surface measurement................................................................................................................................................................... 43
8.2 Weight......................................................................................................................................................................................................................................... 44
8.3 Material balance.................................................................................................................................................................................................................... 44
8.4 Summary of country data on round and split wood products............................................................................................................... 45
9. ENERGY WOOD PRODUCTS AND PROPERTIES........................................................................................................... 47
9.1 Volumetric measurement............................................................................................................................................................................................... 47
9.2 Weight......................................................................................................................................................................................................................................... 47
9.3 Energy values.......................................................................................................................................................................................................................... 47
9.4 Summary of country data on energy wood products and properties............................................................................................... 48
REFERENCES.............................................................................................................................................................................. 51
ANNEX......................................................................................................................................................................................... 55

III

Forest product conversion factors

LIST OF TABLESTABLE 2.1 Historical developments of m3 to mbf conversion factors by log scale and region...................................................................9TABLE 2.2 Swedish national board of forestry stacked measure guidelines for pulp logs........................................................................10
TABLE 4.1 Board foot actual-to-nominal sizes and volumes, by lumber (sawnwood) product type.........................................................23
TABLE 7.1 Typical pulp yields for various types of wood pulp................................................................................................................................................39
TABLE 8.1 Shakes and shingles produced from a cubic metre of western red cedar logs................................................................................44
ANNEX TABLE 1 List of equivalents .......................................................................................................................................................................................... 55

LIST OF FIGURESFIGURE 2.1 True log volume calculation.......................................................................................................................................................................................................5
FIGURE 2.2 Log volume comparison between national log scales for the log depicted in Figure 2.1...........................................................6
FIGURE 2.3 Board foot log rules: geographic distribution................................................................................................................................................................7
FIGURE 2.4 Estimated log volume using various log rule methods and small-end diameter classes to convert
from 1 000 board feet to cubic metres...............................................................................................................................................................................8
FIGURE 4.1 Example of roundwood-to-sawnwood conversion factors, by state of manufacture..................................................................21
FIGURE 4.2 Material balance and sawnwood recovery, by small-end diameter..........................................................................................................22
FIGURE 4.3 Material balance in the sawmilling process for coniferous sawnwood, by reporting country..............................................24
FIGURE 4.4 Material balance in the sawmilling process for non-coniferous sawnwood.......................................................................................25
FIGURE 5.1 Product recovery, by small-end log diameter, in a typical North American coniferous rotary plywood mill..............30
ANNEX FIGURE 1 Example of wood balance using conversion factors..............................................................................................................................56

IV

FOREWORD
The forest sector has long used conversion factors as a tool for analyzing forests and forest product manufacturing facilities.
Almost every aspect of forecasting and analysis in the forest sector involves the use of conversion factors. This includes:converting from one unit of measure to another, benchmarking the efficiency of manufacturing facilities, silvicultural
growth models, biomass calculations, estimates of forest carbon and timber-sale appraisals; to name just a few.
The Food and Agriculture Organization of the United Nations (FAO) recognized the need for a good understanding of
conversion factors and measurement units in 1946 at the FAO Conference in Copenhagen, which was in the process ofestablishing a statistical database on forest products. Following this, FAO convened two conferences on forest statistics in
1947: in February in Washington, DC, United States of America, and in April 1947 in Rome, Italy. A key component of thesemeetings was the work of the Subcommittee on Units of Measurement, the assignment of which was explained as follows:“Because of the great diversity between units in common use for the measurement of forest products, and because thestatistical programs will be world-wide in scope, it was necessary to prepare lists of converting factors”. Conversion factors
have since been a regular part of the work of FAO, the International Tropical Timber Organization (ITTO) and the United
Nations Economic Commission for Europe (UNECE). FAO, ITTO and the UNECE regularly use conversion factors for theirreporting and analysis of trade and production data on forest products. Accurate conversion factors are also critical for
accurate data, in particular when conducting periodic assessments of the outlook for the forest sector.
The last study on conversion factors was published in 2010, although this covered only Europe, the Commonwealth of
Independent States and North America. It was timely, therefore, for FAO, ITTO and UNECE to update existing factors, obtaina wider range of factors and improve geographic representation.
This publication builds on the 2010 study mentioned above by broadening the geographical coverage to the global level,
updating factors and adding some factors that were not included in the past. Differences in measurement standards andfactors have also been identified. Further investigation and cooperation will still be needed to improve the harmonizationof data and factors. This has a bearing not only on conversion factors but also on the comparability of nationally reported
forest product statistics.
The publication provides analysts, practitioners and private enterprises with the most up-to-date set of available forest
product conversion factors and a better understanding of the units used in the manufacture, trade and reporting of woodbased forest products.
We express our appreciation to the national experts who provided their inputs and to the secretariats of FAO, ITTO andUNECE for this timely publication.

Hiroto MITSUGIAssistant Director-General,
Forestry Department of the Foodand Agriculture Organization of
the United Nations

Gerhard DIETERLE
Executive Director,
International Tropical
Timber Organization

Olga ALGAYEROVA
Under-Secretary-Generalof the United Nations,Executive Secretary of the United Nations
Economic Commission for Europe

VForest product conversion factors

ACKNOWLEDGEMENTS
FAO, ITTO and the UNECE thank the following people who assisted with this project:
Mandy Allpass, Crickmay & Associates (Pty) Ltd
Alcinda Amaro, AIMMP – Association of Industries of Wood Furniture, Portugal
Jamal Balfas, Forest Products Research and Development Center, Indonesia
Gary Baylous, Pacific Rim Log Scaling Bureau, United States of America
Lars Bjorklund, Swedish Timber Measurement Council
Leonardo Boragno, Ministerio de Ganadería Agricultura y Pesca, Uruguay
Jorge Pedro Flores Marker, Comisión Nacional Forestal, Mexico
Peder Gjerdrum, Norwegian Forest and Landscape InstituteRoger Godsmark, Forestry South Africa
Schalk Grobbelaar, York Timbers, South Africa
Janina Gysling, Instituto Forestal, Chile
Hu Yanjie, Research Institute of Forestry Policy and Information, Chinese Academy of ForestryPeter Ince, United States Department of Agriculture, Forest Service, United States of America
Romain Jacques, Natural Resources Canada
Iain Kerr, Paper Manufacturers Association of South Africa (PAMSA)
Ruslan Kozak, Ukrainian National Forestry University
Andrius Kuliesis, State Forest Service, Lithuania
Aleksey Kuritsin, Lesexpert LLC, Russian Federation
Yury Lakhtikov, Russian Association of Pulp and Paper Organizations and Enterprises, RAO “Bumprom”, Russian Federation
Graça Louro, Institute for Nature Conservation and Forests, Portugal
Ludmila Lungu, National Bureau of Statistics, Moldova
Volodymyr Maevskyy, Ukrainian National Forestry University
Eleine Juliana Malek, Timber, Tobacco and Kenaf Industries, Development Division, Ministry of Primary Industries, Malaysia
Udo Mantau, University of Hamburg, Germany
Humberto Mesquita, Brazilian Forest Service
Anna Mohase, Guyana Forestry Commission
New Zealand Ministry for Primary Industries
Eoin O’Driscoll, Council for Forest Research and Development, Ireland
Jan Oldenburger, Probos Foundation, Netherlands
Mitja Piskur, Slovenian Forestry InstituteSusan Phelps, Natural Resources Canada
Juan Picos Martin, Monte Industria, Spain
Ewa Ratajczak, PhD, Wood Technology Institute, Poland
Matai Rewiechand, Foundation for Forest Management and Production Control, Suriname
Hiroyuki Saito, Wood Products Trade Office, Forestry Agency, Japan
Cristina Santos, Institute for Nature Conservation and Forests, Portugal
Peter Schwarzbauer, University of Natural Resources and Life Sciences, Austria
Roman Shchupakivskyy, Ukrainian National Forestry University
James Singh, Guyana Forestry Commission
Roy Southey, Sawmilling South Africa
Henry Spelter, United States Department of Agriculture, Forest Service, United States of America
Kjell Suadicani, University of Copenhagen, Denmark
Roman Svitok, National Forest Centre, Slovakia

VI

ACKNOWLEDGEMENTS

Michal Synek, Forest Management Institute, Czechia
Pedro Teixera, Centro Pinus, Portugal
Erhabor Theophilus, Forestry Research Institute of Nigeria
Alain Thivolle-Cazat, Institut Technique Forêt Cellulose Bois-Construction Ameublement, France
Stein Tomter, Norwegian Institute of Bioeconomy Research
Joberto Veloso de Freitas, Brazilian Forest Service
Erkki Verkasalo, Natural Resources Institute. Finland
Darius Vizlenskas, State Forest Service, Lithuania
Dinko Vusić, University of Zagreb, Faculty of Forestry, Croatia
Sheila Ward, Forestry Commission, United Kingdom of Great Britain and Northern Ireland
Holger Weimar, Federal Research Institute for Rural Areas, Forestry and Fisheries (Thünen Institute), Germany.
The following staff at FAO, ITTO and the UNECE supported the production of this publication:
Iana Arkhipova
Stéphane Bothua
Jean-Christophe Claudon
Matt Fonseca
Arvydas Lebedys
Alex McCusker
Florian Steierer
Matt Fonseca managed the project. Alastair Sarre edited the text. Many thanks to all the people listed above for theircontributions of time and expertise. People with relevant information on forest product conversion factors that might beused to improve future revisions of this publication are invited to contact FAO, ITTO or the UNECE at the following addresses:
Forestry Policy and Resources Division, Forestry Department
Food and Agriculture Organization of the United Nations (FAO)
Viale delle Terme di Caracalla, 00153 Rome, Italy
Phone +39 (06) 570-53641
FPS@fao.org
International Tropical Timber Organization (ITTO)
International Organizations Center
5th Floor, Pacifico Yokohama, 1-1-1 Minato-Mirai
Nishi-ku, Yokohama, 220-0012 Japan
Phone +8145 223 1110
itto-stats@itto.int
UNECE/FAO Forestry and Timber Section
Forests, Land and Housing Division
Palais des Nations
CH – 1211 Geneva 10
Switzerland
Phone +41-22-917 1379
info.ece-faoforests@unece.org

VIIForest product conversion factors

ACRONYMS AND ABBREVIATIONSBC

British Columbiabfboard foot/feetC

Celsiuscm

centimetreCO2

carbon dioxide

FAO

Food and Agriculture Organization of the United Nationsftfoot/feet

GJ

gigajoule(s)ggram(s)GOST

Government Standard of the Russian Federation

ITTO

International Tropical Timber Organizationkg

kilogram(s)mmetre(s)m2square metrem3

cubic metre

m3p

cubic metre productm3p bulk

cubic metre product (including void space)m3p solid

cubic metre product (excluding void space normally included in volume)

m3rw

cubic metre roundwood

m3sw

cubic metre of solid wood

mbf

1 000 board feetmcd

moisture content dry basis

mcw

moisture content wet basis

MDF

medium-density fibreboard

mmmillimetre(s)mttonne(s)NWLRAG

Northwest Log Rules Advisory Groupob

overbarkodmt

oven-dry tonne

OSBoriented strandboard

swesolid wood equivalentub

underbark

UNECE

United Nations Economic Commission for Europe

USDA

United States Department of Agriculture

USFS

United States Forest Service

VIII

EXPLANATORY NOTESThe term “softwood” is used synonymously with “coniferous”. “Hardwood” is used synonymously with “non-coniferous” and“broadleaved”. “Lumber” is used synonymously with “sawnwood”. References to “tonnes” in this text represent the unit of
1 000 kilograms (kg). The use of “ton” in this publication represents the imperial unit of 2 000 pounds (907 kg) unlessotherwise specified. “Billion” refers to 1 000 million (109). The term “oven dry” in this text is used in relation to the weight of a
product in a completely dry state: e.g. 1 oven-dry tonne of wood fibre = 1 000 kg of wood fibre containing no moisture atall. Basic density is defined as the ratio between the oven-dry weight of wood and its green volume.

IX

1
CHAPTER©iStock

1. Introduction
This publication is the result of a collaborative effort between
the Food and Agriculture Organization of the United Nations(FAO), the International Tropical Timber Organization (ITTO)
and the United Nations Economic Commission for Europe(UNECE). It builds on and supersedes the factors containedin UNECE/FAO (2010a) and provides factors from all theworld’s major timber-producing regions.
The term “forest product conversion factors” is used tocover a broad spectrum of ratios used in the wood-based
forest, manufacturing and energy sectors. For the purposesof this publication, “conversion factor” is defined as using
a known figure to determine or estimate an unknown
figure via a ratio. Often, these ratios are exact, for example
in converting cubic feet to cubic metres (there are 35.315
cubic feet in a cubic metre). Annex table 1 provides alisting of certain exact conversion factors (equivalents)
relevant to forest products.
The ratios may also be inexact – offering, rather, a goodaverage. For example, 1 m3 (underbark volume) of freshly
felled Norway spruce sawlogs might have an average
weight of 860 kg, of which 80 kg is bark and 780 kg is wood(with both bark and wood containing a certain amount ofmoisture), but this might vary as a result of, for example,
wood density, moisture content and the presence or lackof bark.
In other instances, conversion factors may have little
meaning unless some of the parameters of the numeratorsand denominators of the ratios are known. For example,
1 m3 of logs with an average small-end diameter of 15 cm
might make 0.41 m3 of sawnwood, and 1 m3 of logs withan average small-end diameter of 60 cm might make
0.63 m3 (i.e. about 50 percent more), given the same levelof processing efficiency in a sawmill. That is not to say,however, that a single factor cannot be used to convert
roundwood to sawnwood – it can be, if using an accurate
factor, when looking at a large population in the aggregate
and when approximate figures are sufficient.
Related to forest product conversion factors is the use of
the “material balance” (see annex figure 1). The sawnwood
example above could lead to the incorrect assumptionthat only 41 percent of the wood fibre in a sawlog with asmall-end diameter of 15 cm and 63 percent of a sawlog

with a small-end diameter of 60 cm could be obtained
from the log. In fact, almost 100 percent of the wood ineach of these logs may be utilized because the remaining
non-sawnwood volume – in the form of various wood
residues – has many potential uses. For example, 1 m3 ofsawlogs with a small-end diameter of 15 cm could havea material balance of 41 percent sawnwood, 43 percent
chips (raw material for paper, panels and wood energy,etc.), 9 percent sawdust (for making energy pellets, particle
board and medium-density fibreboard (MDF), etc.) and 7
percent shavings (particle board, MDF, animal bedding
and wood energy, etc.), with the various components
summing to 100 percent of the wood volume. Although
not part of the material balance (because the log volume
comprises the underbark volume), one might also apply
a conversion factor to estimate that 80 kg of bark (withmoisture) is potentially available per 1 m3 of roundwood(measured underbark) for energy or other uses. Note thatmaterial balances are used in manufacturing plants and at
the sectoral level, and they can be constructed to accountfor the cascading uses of wood raw material in a country,
subregion or region (Mantau, 2008).
Logs and their subsequent products have a predisposition
towards inexact conversion factors because of the wide
range of shapes and forms, the variability of physicalproperties (e.g. density, moisture content and shrinkage),and other natural variables that affect conversion factors,
such as species, size, defects and provenance. Wood fibre
is hygroscopic: its volume and weight change when it isdried in a kiln or exposed to the atmosphere.
Measurement procedures are subject to many externalbiases. For example, rounding conventions vary – withsome countries determining roundwood volume based on
truncated diameters and lengths and others using unbiased
rounding logic. Finally, differences may occur because of
product-manufacturing efficiency and utilization practices.

1.1 General uses of conversion factors
The forest sector has long used conversion factors as a tool
for analysing forests and forest product manufacturing
facilities. Almost every aspect of forecasting and analysis in1

Forest product conversion factors©FAO/ADRIAN WHITEMAN

will need to be estimated using conversion factors (e.g.
2 m3 of roundwood may produce 1 m3 of sawnwood). A
material balance will be used to assess the quantity andthus value of the residual products. Finally, ratios may be
used to estimate the quantity of unmeasured products
from the timber sale, such as bark and logging residue(i.e. top wood, limbs and foliage), which may be used forenergy generation or other purposes.
Conversion factors have been used to indicate illegallylogged roundwood in a supply chain – if the volumeof roundwood removals is less than the apparent
consumption (as determined using conversion factors),
the disparity could comprise illegally harvested logs. Some
organizations, including the Convention on International
Trade in Endangered Species of Wild Fauna and Flora (CITES),
have applied conversion factors to manufactured productvolumes to estimate the harvest volume of endangered
species such as bigleaf mahogany (CITES, 2008).

©FAO

Conversion factors for converting the input of raw
materials to the output of finished or semi-finishedproducts are often used to benchmark the efficiency ofa manufacturing facility. Climate policy analysts may use
conversion factors to determine the volume of carbon
sequestered in forests. Outlook studies on long-term wood
availability use conversion factors to predict the volumeof raw materials that will be needed to match forecasted
future wood demand.

1.2 The use of conversion factors by
FAO, ITTO and UNECE
the forest sector involves the use of conversion factors insome way, including silvicultural growth models, biomass
calculations, estimates of forest carbon and timber-saleappraisals.
For example, a sawmill is conducting a timber-sale appraisal
to determine a bid price. The stand volume may be reported
in cubic metres overbark, but the purchaser may needto convert this volume to underbark volumes, weight orboard feet1 to match its traditionally used units of measure.
To determine the value of the timber, the purchaser willneed to know the cost of getting the timber from thestump to the mill site; therefore, weight-to-volume ratios
are likely to be important for determining weight-basedtransport costs. The volume of primary product recovered

1 A board foot is ostensibly the equivalent volume of a board that is
1 inch thick x 1 foot wide x 1 foot long (i.e. 0.00236 m3).

2

A major objective in collecting and publishing informationon conversion factors at the international level is toestimate national and international wood requirements
and balances. Such information is also useful in the
preparation of national and international studies involving
wood balances.
Conversion factors are used in data collection, as follows:
1.

Where a country has explicitly provided datain non-standard units. Typically, this involves a
conversion from square metres to cubic metres orfrom tonnes to cubic metres.

2.

Where it is suspected that data are incorrect.
Often, the unit value (dividing the value of trade ofa product by its volume of trade) indicates that anelement is incorrect. For example, data on plywood
and fibreboard are occasionally reported in square
metres rather than cubic metres, without this being

1. INTRODUCTION

3.

4.

5.

explicitly stated. Here, a standard unit value (e.g.
an average thickness) is applied to convert area tovolume.

in 2008 by the Task Force on Forest Product Conversion
Factors (UNECE/FAO, 2010a), which, with minor revisions,remained relevant in this publication.

When converting data from other sources to FAO/
ITTO/UNECE standards (e.g. UN Comtrade2 datareported in kilograms). Official trade statistics usuallyindicate trade volumes by weight (usually kilograms,
although other units are also used). Thus, when
extracting data from UN Comtrade, for example,
weight needs to be converted from tonnes to cubic
metres using conversion factors.

Conversion factors are listed by region and country, as
follows:

To calculate national and international woodbalances. For example, conversion factors are used
to check whether reported data from a country seemreasonable (e.g. does the net apparent consumptionof wood raw materials balance with the productionof wood products when wood raw materials areconverted to forest products using a reasonableassumption of mill conversion factors?).
To estimate future potential wood requirements
under different scenarios, including in UNECE/FAO
forest sector outlook studies.

RegionAFRICAASIAEUROPE

FAO, ITTO and the UNECE recognize the importance ofclearly defining the units used in harmonization efforts.
Such definitions are needed to obtain accurate conversion
factors and also for comparisons between countries.

1.3 Methods
A questionnaire was sent to national correspondents tocollect national conversion factors; where necessary andfeasible, literature searches were conducted for countries
to augment information. The following forest products
were included in the questionnaire:
1.
2.
3.
4.
5.
6.
7.
8.

Country
NigeriaSouth Africa

China

Japan

Indonesia

Malaysia

Austria

PolandCroatia

Portugal

Czechia
Denmark

RussianFederation

Finland

Slovakia

FranceSlovenia

Germany

Spain

IrelandSwedenLithuania

Switzerland

Moldova

UkraineNetherlands

UnitedKingdom

NorwayBrazilMexicoChile

Suriname

GuyanaUruguay

NORTH AMERICA

CanadaUnited Statesof America

OCEANIANew Zealand

LATIN AMERICA

Roundwood
Wood particles
Sawnwood
Veneer and plywood
Panels made of wood particles
Wood pulp and paper
Round and split wood products
Energy wood products and properties©Shutterstock

These eight forest product categories, and the relevant
ratios for each included in the questionnaire, were
determined primarily from recommendations made2 The UN Commodity Trade Statistics Database is available at http://
comtrade.un.org.

3

2
CHAPTER©UNECE2. Roundwood
The conversion factors for roundwood requested in thequestionnaire related to two areas:

2.1 Volumetric measurement1.

physical properties; and2.

the national method of measuring roundwood as it
relates to the “true volume”.

Assessing the volume of roundwood is typically referred toas log scaling. In general, log scales attempt to predict thedisplaced volume of the log (i.e. cubic log scale), or, as in
the United States of America and some regions of Canada,
the output of sawnwood (e.g. board foot log rule).

Note that the true volume of roundwood for the purposesof this publication and for UNECE/FAO statistics onroundwood volume always means underbark volume.
Conversion factors for roundwood are often used toconvert from one unit of measure to another (e.g. fromweight to volume). Conversion factors within the sameunits are also quite common: for example, a cubic metreof roundwood measured by the national standard in one
country may differ if measured according to the national
standard of another country.
Most countries were able to submit data on conversion
factors relating to the general physical properties ofroundwood. Note that species-specific data was not
asked for; data fields were limited to coniferous and nonconiferous, with separate fields for saw and veneer logs
and pulp and energy logs.
Data availability on conversion factors for harmonizing
national standards of roundwood measurement to true
volume was insufficient to include in this publication.
Nevertheless, it is clear that there can be substantial
differences in the standards used for determining log
volume between countries and even within countries.

FIGURE 2.1

A third category of log scales uses cubic (Brereton log
scale) or quasi-cubic volume (Hoppus log scale) and may
apply a standard ratio of board feet per cubic volumetricunit (see section 2.1.3).

2.1.1

Cubic volume

Cubic formulas include the Smalian, Huber, Newton,
centroid and two-end conic, each of which has its
strengths and weaknesses depending on log dimensions
and stem form. All these formulas will give similar results
most of the time when measurement conventions areapplied uniformly and on logs with typical parameters.
Figure 2.1 provides an example of volume calculation
using unbiased rounding logic and the Smalian and Huber
formulas.
Of much greater concern for harmonizing log volume
and conversion factors based on national volumes isthe common practice of truncating (rounding down)
diameters and lengths. For example, the length of a log
may be recorded as 10.0 m when its actual length is 10.3 m

TRUE LOG VOLUME CALCULATION

5.02 m23.2 cm

25.5 cm
22.7 cm

28.1 cm

25.3 cm

27.8 cm

Smalian formula: (((23.2+22.7)/2)2+((28.1+27.8)/2)2) × 5.02 × 0.00003927 = 2.58 m3
Huber formula: ((25.5+25.3)/2)2 × 5.02 × 0.00007854 = 2.54 m3
Source: UNECE/FAO, 2010a.

5Forest product conversion factors(thus, there is 30 cm of unmeasured “trim allowance”) andthe diameter of a log end may be recorded as 27.0 cm
when its actual diameter is 27.9 cm. The purpose oftruncation should not be construed as a purposeful
effort to understate volume; generally, it is done to makemathematical calculations easier and to enable the
manufacture of products at least as long as the recorded
log length.
Other practices also create discrepancies between log
scales: for example, some systems reduce log volumes
to account for defects and others use a value-reducing
mechanism (such as log grade). Additionally, nationaland subregional log-scaling standards may: treat logs as
cylinders using the small-end diameter of the log; assume
that the log form is a cylinder using the diameter that exists
in the middle of the log length; or use assumed taper rates
to establish diameters other than the small-end. Somenational standards include bark in the roundwood volume.
All these differences can lead to differences in estimates ofroundwood volume. Figure 2.2 shows the saw/veneer log
volume for the log in Figure 2.1, as calculated using 13 log
scaling standards; it shows the considerable variationthat can arise by the use of different methods. Moreover,logs with different dimensions and characteristics may
produce different relative results, depending on individual
characteristics: for example, truncating a diameter of
13.9 cm to 13.0 cm will have a more significant impact on
the estimated volume (i.e. 12.5 percent) than truncating a
diameter of 77.9 cm to 77.0 cm (2.3 percent).
Although not included in Figure 2.2, the log shown in
Figure 2.1 would have a volume of:■ 30 board feet (bf ) if measured in coastal Alaska,
Oregon and Washington, United States of America(the Scribner long log rule);■ 40 bf if measured in the western United States ofAmerica, except as noted above (Scribner short log
rule);■ 25 bf if measured in the southeast of the UnitedStates of America (Doyle log rule);■ 50 bf if measured in the northeast of the UnitedStates of America (International ¼ inch log rule);■ 45 bf if measured in Ontario, Canada (Ontario log
rule);■ 48 bf if measured in New Brunswick or Nova Scotia,
Canada (New Brunswick log rule); and■ 54 bf if measured in Newfoundland, Canada(Newfoundland log rule).

6

FIGURE 2.2

LOG VOLUME COMPARISON BETWEEN
NATIONAL LOG SCALES FOR THE LOG
DEPICTED IN FIGURE 2.1(m3 and difference in percent from .258 m3)

US Forest Service 0.250-3.4%

US Northwest Log Rules
Advisory Group 0.246-4.9%

Canada British Columbia 0.267

3.4%

Canada Alberta 0.256-0.6%

UK Hardwood 0.286

9.9%

UK Conifer 0.228-13.3%

Russia GOST 2708-75 0.270

4.4%

Norway 0.245-5.1%

Germany 0.244-5.8%

Ireland 0.287

10.2%

Finland 0.299

13.8%

Japanese AgriculturalStandard 0.242-6.6%

Brereton(Papua New Guniea) 0.250-3.2%

Hoppus (Myanmar) 0.195-32.3%

0.000 0.050 0.100 0.150 0.200 0.250 0.300
Log volume (m3)Notes: Calculated using the log dimensions in Figure 2.1 and applying
the procedures for national roundwood measurement standards inthe countries and organizations listed. GOST 2708-75 is the standard
for domestically consumed roundwood in the Russian Federation; UK
Conifer = top-diameter method; UK Hardwood = mid-diameter method.
Source: See references in subsection on roundwood measurement
standards in section 10.

In this publication, conversion factors using roundwood
input are assumed to be based on true volume. It is known
that some countries (e.g. Finland, Ireland, Sweden, theUnited Kingdom of Great Britain and Northern Ireland andthe United States of America) adjust their national standard
roundwood measurement volumes to reflect true volume
for reporting. This is an area in which further study could
improve the accuracy, comparability and harmonizationof what is often the starting point (the numerator) of manyof the forest product conversion factors used.

2. ROUNDWOOD

2.1.2

Board foot log rules

Some subnational regions in the United States of America
and Canada still use board foot log rules (Figure 2.3).
Most of these rules date from the nineteenth century
and attempt to predict the quantity of sawnwood (or“lumber”), as measured in board feet, that could be milledfrom a given log. In most cases, modern mills produce
far more lumber (in some cases more than double thevolume) to that predicted by the rules (known as overrun);occasionally, less lumber is produced than predicted by agiven log rule (underrun). Log rules are based on either
diagrams or formulas, with assumptions made on saw
kerf and slab loss. Except for the International ¼” rule, log
segments are considered to be cylindrical (i.e. have notaper).
A study in the United States of America used a populationof 175 logs to model the conversion factors of various
board foot rules in North America. It found, for the Scribner

FIGURE 2.3

rules (of which there are three subregional variants) alone,that bf per m3 ranged, on average, from as little as 108 (i.e.
9.26 m3 per 1,000 bf3) for logs with a small-end diameterof 4.5 to 7.49 inches to as much as 246 (4.06 m3 per mbf )for logs with a small-end diameter above 15.5 inches(Fonseca, 2005). Figure 2.4 shows the conversion (inm3 per mbf ) using the British Columbia standard (BCFirmwood method).4 Because these rules do not correlateconsistently with cubic volume across all diameter classes,
it is necessary to view the ratios as they relate to various
diameter groupings.
In the past, many sources of published conversion factors(including those of UNECE/FAO) used a universal 4.53 m3
per mbf ratio (0.221 mbf per m3) to convert board feet to
3 Note that “mbf” is an abbreviation for “1,000 board feet”, and thisabbreviation is used hereafter in this publicaton.
4 The BC Firmwood log scale was used as the index because it has
unbiased rounding logic and involves the uniform application of
formulas and measurements.

BOARD FOOT LOG RULES: GEOGRAPHIC DISTRIBUTION

Scribner short log BF

Newfoundland BF

Scribner long log BF
NWLRAG cubic footBritishColumbia
firmwood
cubic

Alberta
cubic
metre Saskatchewan
cubic
meter

Ontario
cubic metre

Quebeccubic metre
Nova Scotia m3 and BF

Scribner short log BF

New Brunswick m3 and BF

USFS cubic footDoyle BF

International 1/4 inch BF
USFS cubic foot

USFS national
cubic footNotes: The states of Alaska, California, Oregon and Washington use a revised volume table, which gives slightly different volumes for several diameterand length combinations.
Source: UNECE/FAO, 2010b. Map conforms to United Nations The World map, 3-Mar-2020.

7

Forest product conversion factors

FIGURE 2.4

ESTIMATED LOG VOLUME USINGVARIOUS LOG RULE METHODS AND
SMALL-END DIAMETER CLASSES TOCONVERT FROM 1 000 BOARD FEET TO
CUBIC METRES (m3 BC Firmwood per mbf )Scribner Short (revised)

6.81
6.53
5.15
4.06

Scribner Short (not revised)

7.24
6.55
5.15
4.06

Spelter (2002) found that the conversion factor for the
Scribner long log mbf (a variation of the Scribner log ruleused in the US Pacific Northwest) to cubic metres hadchanged from about 4.69 m3 per mbf in 1970 to 6.71 m3
per mbf in 1998. More recent studies conducted by the
Pacific Rim Log Scaling Bureau on 3.7 million dual-scaled
logs in 2010–2015 showed conversion factors in the range
of 6.68–6.92 m3 per mbf (6.83 average) (Pacific Rim Log
Scaling Bureau, personal communication, 2016), which
supports the findings of Spelter (2002). In the Washington
state interior (Scribner short log method), the ratio
increased from 4.42 m3 per mbf in 1970 to 5.93 m3 per mbf
in 1998 (Spelter, 2002).

9.24
8.06
6.62

Scribner Long Log

4.65
17.23
8.03

Doyle

5.57
4.06
6.27
5.17
4.44
3.87

International 1/4 inch

0

2

4

6

8

10 12

14

16

18

4.5 - 7.49 inches (11.4 - 19.0 cm)

11.5 - 15.49 inches (29.21 - 39.3 cm)

7.5 - 11.49 inches (19.1 - 29.2 cm)>15.5 inches (>39.4 cm)

Notes: Cubic metres (net), as scaled by the BC Firmwood log scale,indexed in units of 1 000 board feet (mbf; net), (e.g. 6.81 m3 BC Firmwood= 1 mbf net scale). This analysis is based on a control group of 175 logs.
Scribner Short (revised) = revised rule used in California and interior
Oregon and Washington, USA; Scribner Short (not revised) = nonrevised rule used outside the Pacific Coast states, USA; Scribner Long Log
used only in coastal Alaska, Oregon and Washington, USA; Doyle usedprimarily in the mid-west and southeast of the USA; International ¼ inch
used primarily in New England, USA, and eastern Canada.
Source: Fonseca, 2005.

cubic metres. This ratio dates from the 1940s (FAO, 1947),
when the timber harvest on the west coast of North
America involved very-large-diameter trees, and it is
responsible for countless erroneous assumptions madeby researchers and practitioners who have attempted touse it. In reality, conversion factors vary widely based on
the scaling standards used (both for m3 and bf standards),
log attributes (e.g. diameter, length, defects and taper), andhow the log is manufactured. There is substantial variation
between the various board foot log rules and in the logs
they are applied to; an approach stratified by geographic
area and log-scaling method, therefore, appears to be mostappropriate. Table 2.1 shows the historical development of
cubic-content-to-mbf conversion factors in North America.

In summary, there is no universal figure for converting logs
measured in board feet to cubic volume (and vice versa).
The ratio will vary significantly depending on the board
foot rule used, and there will also be substantial variation
due to characteristics such as log diameter, length, taperand defect. Exacerbating the difficulty of using a ratio toconvert between board foot and cubic log rules is theway in which logs are manufactured from tree stems tominimize or maximize the impacts of log characteristics
on board foot log scaling volumes (either increasing or
decreasing the volume). For rough estimates across a wide
area and variety of forest types, Table 2.1 contains what
is probably the most up-to-date, comprehensive set of
conversion factors for converting from board feet to cubic
metres in the geographic regions listed.

2.1.3

Brereton and Hoppus log scales

2.1.3.1

Brereton

The Brereton system of measurement is essentially a cubiclog volume formula and therefore not dissimilar to manyof the other systems of cubic measure. The Brereton log
scale, however, uses its own methodology for determining

82. ROUNDWOODTABLE 2.1

HISTORICAL DEVELOPMENTS OF M3 TO MBF CONVERSION FACTORS BY LOG SCALE AND REGION

SourceYear

Log scale

Regionm3/
mbf

Sample size

FAO

1947

Not specified

USA

4.53

Unknown

Spelter1970

Long log Scribner

Western Washington

4.69

Calculated*

Spelter

1998

Long log Scribner

Western Washington

6.76

Calculated*

Pacific Rim Log Scaling Bureau

2010

Long log Scribner

Western Oregon, Washington

6.92

363 378 m3

Pacific Rim Log Scaling Bureau

2011Long log Scribner

Western Oregon, Washington

6.84

568 566 m3

Pacific Rim Log Scaling Bureau

2012Long log Scribner

Western Oregon, Washington

6.86

793 435 m3

Pacific Rim Log Scaling Bureau

2013

Long log Scribner

Western Oregon, Washington

6.76

937 188 m3

Pacific Rim Log Scaling Bureau

2014Long log Scribner

Western Oregon, Washington

6.85

667 425 m3

Pacific Rim Log Scaling Bureau

2015

Long log Scribner

Western Oregon, Washington

6.68

151 386 m3

Spelter1970

Short log Scribner

Eastern Washington

4.42

Calculated*

Spelter

1998

Short log Scribner

Eastern Washington

5.93

Calculated*

Fonseca

2001-2003

Short log Scribner

Montana

6.74

4.1 million m3

Brandt et al.

2006

Short log Scribner

Idaho

5.99

Calculated*

Mclever et al.

2012

Short log Scribner

California

5.25

Calculated*

Pacific Rim Log Scaling

2013

Short log Scribner

Eastern Oregon

5.28

33 105 m3

Pacific Rim Log Scaling

2014

Short log Scribner

Eastern Oregon

5.47

19 075 m3

Nova Scotia Natural Resources

2001

New Brunswick log rule Nova Scotia

5.66

Unknown

Notes: British Columbia Firmwood m3 is the standard used in this table (except for Nova Scotia, which uses its own cubic log scale). Other methods ofmeasuring cubic volume would likely yield different results. *Calculated ratios are determined using sawnwood production and material balance to calculate
the input of cubic log volume. The figures for Montana include a substantial quantity (7.3 percent by gross volume) of “salvage logs” cut from standing deadtrees, primarily beetle-killed lodgepole pine. This list only includes conversion factors for converting logs manufactured for scale in board feet because board
foot rules are sensitive to log length, minimum top size, taper and log defects (and thus are manufactured with log volume in mind). Logs manufactured
using measurement in cubic metres will likely yield different values if converted to board feet. All examples are in the USA except for Nova Scotia (Canada).
Sources: FAO, 1947; Spelter, 2002; Pacific Rim Log Scaling Bureau, personal communication, 2016; Fonseca, personal communication, 2006; Brandt et al.,2012; Mclever et al., 2015; Nova Scotia Department of Natural Resources, 2001.

log cross-sections; moreover, in some regions, it is stillreflected in board feet, which is simply the volume incubic feet × 12. The Brereton log scale is one of the mostcommonly used methods for tropical hardwoods inAfrica, Oceania, South America and Asia (South East Asia
Lumber Producers Association, 1981; Freese, 1973). Several
national and international standards use Brereton as thebasis of log volume calculation, with the methodologies
differing slightly in their approaches to assessing lengths
and diameters and whether reflected in board feet, cubicfeet or cubic metres.
2.1.3.2

HoppusHoppus, also called the “quarter girth formula” (or the“Francon system” when measured with and reflected inmetric units), became popular as a method for assessing

roundwood volume in the early 1700s and is still usedin the tropical regions of Asia, Africa and South America
and occasionally in Australia, New Zealand and the United
Kingdom of Great Britain and Northern Ireland. The
Hoppus formula is:(middle circumference of log in inches ÷ 4)2 × length infeet ÷ 144 = Hoppus cubic feet
Hoppus cubic feet may be further converted to “Hoppus
superficial feet” (i.e. Hoppus cubic feet × 12 – ostensibly
converting cubic feet to board foot); or the “Hoppus ton”
(i.e. Hoppus volume in cubic feet ÷ 50). Both the Hoppus
superficial foot and the Hoppus ton are misnomers,
because the former in no way predicts output in board
feet and the latter is likely to weigh significantly more than9Forest product conversion factors

a ton (or tonne). Note that because the Hoppus formula
essentially uses one-fourth of the log circumference as ade facto cross-dimension of a square, it will always reflect
only 78.54 percent of the true cubic volume (assuming
consistent measurement methodology) (Freese, 1973).

2.1.4

Stacked measure©FAO

In estimating the volume of stacked roundwood, it isoften assumed that about two-thirds (66.7 percent) of
the displaced volume is wood, 11.5 percent is bark, and21.6 percent is void (Ontario Ministry of Natural Resources,
2000). In fact, wood volume may constitute less than
50 percent of the volume or more than 80 percent,depending on a range of factors. A guide for adjustingfor such factors can be found in Estimation of the Solid
Volume Percentage (VMF Nord, 1999) and also in Table 2.2,
which allows the estimation of the solid wood ratio basedon visually assessed attributes. Two units of measure areassociated with stacked measure volume:

TABLE 2.2

1.

stere, which is 1 m3 of stacked wood (including void
space and bark); and2.

cord, which is 128 cubic ft of stacked wood (including
void space and bark) and equivalent to 3.62 steres.

SWEDISH NATIONAL BOARD OF FORESTRY STACKED MEASURE GUIDELINES FOR PULP LOGS
Starting value 60%

Average log diameter under bark<8.99 cm-4%
9–9.99 cm-3%-2%
10–10.99 cm-1%
11–11.99 cm
12–12.99 cm
0%
13–13.99 cm+1%+2%
14–14.99 cm+3%
15–15.99 cm
16–16.99 cm+4%+5%
17–17.99 cm+6%
18–19.99 cm+7%
20–22.99 cm+8%
23–26.99 cm+9%>27 cmQuality of stacking
Very good
0%
Good
-1%
Fair
-2%
Bad
-3 to -4%
Very bad-5% to -7%

Trimming of knots and buttress
Very well trimmed, few buttresses
A few knot stumps and buttresses
Many knot stumps and buttresses
Many large knot stumps, clusters and buttresses
Very bad trimming

0%
-1%
-2%
-3% to +4%-5% to +7%

Crookedness
Straight softwood, straight aspen
Crooked softwood, straight deciduous wood
Very crooked softwood, crooked deciduous wood
Very crooked deciduous wood
Extremely crooked deciduous wood0 to -1%-2% to +3%-4% to +5%-6% to +7%-8% to +12%

Bark volume
Debarked wood
More than 2/3 thin barkMore than 1/3 thin barkNormal softwood (conifer)
Softwood with thick bark, normal deciduous barkMore than 50% non-coniferous (deciduous) wood with thick bark

+7%
+2%
+1%
0%
-1%
-2%

Notes: A more recent and detailed version is available. The 1999 version was used in this publication for conciseness, however, thereader is encouraged to refer to “SDC’s instruction for timber measurement: measurement of roundwood stacks” (SDC, 2014).

10

Source: VMF Nord, 1999.

2. ROUNDWOOD

2.2 Weight and physical properties
Roundwood is bought and sold by weight in many areasof the world. The presence of drive-on weight scales on
many transportation routes and at processing plants
and national ports of entry means that weight data areoften more readily available and less expensive to obtainthan individually measuring all logs for volume. Weight
generally correlates well with volume, and the relationshipis usually established in conjunction with sample volume
measurements. A few factors are key in determining theweight of a given roundwood volume, and vice versa:
wood density, moisture content, and bark.

2.2.1

Wood density

Wood largely comprises cell walls and void spaces. Woodcell walls all have about the same basic density, regardless of
species – approximately 1 560 kg per m3 (Van Vuuren et al.,1978). What varies is the ratio of cell walls to cell cavities.
Wood density is typically measured as either basic density(i.e. the weight of oven-dry fibre per cubic metre, where“oven dry” means devoid of moisture) or specific gravity,
which is an index of the relationship of oven-dry fibre to
the same volume of water (water weighs 1 000 kg perm3). For example, 1 m3 of wood (volume measured whengreen) without water may weigh 400 kg; it therefore has
a basic density of 400 kg per m3 and a specific gravity of
0.40. Globally, the basic density of wood (green volume
and oven-dry weight) varies from about 290 kg per m3 to
540 kg per m3 for coniferous wood and from about 160 kg
per m3 to more than 1 000 kg per m3 for non-coniferous
wood, with most species falling in the range of 320–720 kg
per m3 (United States Forest Service, 1999).

2.2.2

Moisture content

Freshly cut wood contains large amounts of water, bothin the cell cavities (free water) and within the cell walls
themselves (bound water). Normally, wood moisture
content is measured in terms of the weight of the moisture
relative to the weight of the dry wood fibre. For example, if
a sample of wood weighs 812 kg per m3 in its green stateand 400 kg per m3 in the oven-dry state, it is said to have
103 percent mcd. In this example, the wood has 400 kg
of wood and 412 kg of moisture, and dividing the weightof the moisture by the weight of the dry wood gives the
moisture content. Note that the mcd of freshly cut wood
can vary from 30 percent to more than 200 percent (UnitedStates Forest Service, 1999).
Moisture content can also be reflected in the ratio of
moisture weight to the total weight of the wood fibreplus moisture content, referred to as moisture content“wet basis” (mcw). This is typically used for measuring the
moisture content of wood particles (Chapter 2), pulp andpaper (Chapter 6) and wood for energy (Chapter 8). It is
not usually used for solid wood because the numerator ismade up partly by the denominator.
The moisture content of roundwood is dynamic and candecline quickly once a tree is felled, especially in hot,

©UNECE

Care should be taken when using published averages
to calculate the basic density or specific gravity of a
species to note whether the volume was established in
the green state (i.e. before shrinkage) or in the dry state(after shrinkage). Wood volume will shrink volumetricallyby about 10 percent for most coniferous species and by
about 15 percent for most hardwood species when takenfrom green to fully dry (although the difference could be
as low as 7 percent to more than 20 percent). The exact
amount of shrinkage varies between species and evenbetween wood samples from the same tree. In general,
basic density based on green volume (the standard for thispublication unless otherwise noted) has the advantage ofbeing applicable to standing tree volume and roundwood
without needing to know or estimate volumetricshrinkage. When using published volumetric shrinkage

rates, it is generally accepted that shrinkage in wood is
initiated at moisture contents below 30 percent moisture
content “dry basis” (mcd), and the amount of shrinkage isrelated linearly to the moisture content as it relates to the
30 percent figure. For example, a species that averages
10 percent volumetric shrinkage when taken from a green
to a dry state that is dried to 15 percent mcd will lose
about 5 percent of its volume when dried and thus will bedensified (because what was once 1 m3 of wood would
now be only 0.95 m3).

11

Forest product conversion factors©Shutterstock

section 2.3, bark constitutes 11–12 percent, on average,of the overbark volume. Roundwood weight is normallyreported with bark present; however, roundwood volume
for global reporting purposes, including in the majority ofnational roundwood measurement standards, is reported
for wood only, meaning that bark increases the weight-tovolume ratio of roundwood. Bark is an important sourceof forest-based energy, and it also has other uses, suchas decorative ground cover and soil treatment (mulch).
Knowing the ratio of bark to roundwood volume is usefulfor understanding weight ratios but also potentially forthe energy and other products that can be produced
from bark. It is important to note, however, that some bark
volume is almost always lost during handling from forest
to mill, so the potential volume (based on subtracting
underbark from overbark volume, as measured instanding inventories) is seldom available and highly
volatile depending on log-handling practices and season.
Another point to consider when assessing bark volume,
especially when using overbark-minus-underbark volume,is that the bark of many species has fissures and voids,
which can lead to incorrect estimates of bark volumeunless taken into account.
dry weather. Section 2.3 lists weight-to-volume ratios
for freshly felled logs (green weight with bark/green m3(wood only)), but these ratios may not be representative inregions where logs are stored for long periods at roadside
before transport and weighing. Note also that the moisture
content of the wood and bark of many species has distinct
seasonal variations, with significantly higher moisture
content in winter and early spring than in summer andearly fall (Thivolle-Cazat, 2008).
Finally, in many species, particularly conifers, heartwoodoften has less moisture than sapwood. Thus, older(generally larger) trees often have a lower weight-tovolume ratio than that of younger (generally smaller)
trees by virtue of the age-related increase in the ratio ofheartwood to sapwood. Related to this, many species
have a higher ratio of bark when young and small thanwhen old and large, thereby magnifying this difference.

2.2.3

Bark and other unmeasured volume

Bark, like wood, typically contains large amounts of water
when fresh. In general, the bark of most species has
weight-to-volume characteristics similar to the woodof the same species. The bark of both coniferous andnon-coniferous species ranges from less than 5 percentof the total overbark volume (and weight) to as high as
30 percent. Based on the questionnaire results shown in

12Defects in roundwood, such as unsound fibre (decay),
fractures, splits and crooked portions, have weight but
often no volume when the scaling method calls for adeduction, thus increasing the ratio of weight to volume
for roundwood.

2.2.4

Carbon content and sequesteredcarbon dioxide

It is generally accepted that, although there are variationsin the carbon content of wood, the average figure is close
to 50 percent of the dry weight of wood and bark andthat this figure is accurate enough for carbon accounting
purposes (Matthews, 1993). There is potential for confusion
between the carbon and carbon dioxide (CO2) content ofwood, which are not the same. The ratio of CO2 to carbon
weight is 3.67: thus, 1 tonne of dry wood sequesters
about 0.5 tonnes of carbon and 1.83 tonnes of CO2. Ifusing carbon or CO2 ratios that have been developed forvolumetric units rather than dry weight, care needs to betaken to account for the effect of shrinkage on the dryweight of a given volume, which would densify the woodand thus increase the quantity of contained carbon perunit volume (see section 2.2.1).

kg/m3

kg/m3

ub/ob

Green weight with bark/green m3
wood only

Wood basic density (dry weight ofwood/green m3 wood only)

Volume ratio wood/bark plus wood

kg/m3

kg/m3

ub/ob

share %

kg/m3

kg/m3

ub/ob

Green weight with bark/green m3
wood only

Wood basic density (dry weight ofwood/green m3 wood only)

Volume ratio wood/bark plus wood

Non-conifer

Green weight with bark/green m3
wood only

Wood basic density (dry weight ofwood/green m3 wood only)

Volume ratio wood/bark plus wood

Nigeria

0.91

675

1 184

100

South Africa
550

450

0.95

430

940

100

Median/average
550

450

0.85

0.91

0.90

460

890

80

0.88

410

820

20

620

1 060

675

1 184

0.88

0.95
38

420

940

430

940

China
62

Japan

Indonesia
1

0.85

525

1 090

97 47

0.87

410

720

3 53

0.87

540

1 130

98

0.85

420

740

2 99

Malaysia
0.88

680

1 156

100

Median
0.87

420

840

Average
493
0.88

493
0.88

990

0.88

0.88

990

410

770

1

613

410

770

1

620

1 130 1 115

0.87

420

840

Brazil
0.85

460

0.85

410

0.85

500

0.85

385

Chile
0.92

625

1 368

43

0.92

405

872

57

0.92

625

1 368

3

0.92

405

872

97

Guyana
0.79

843

1 180

100

100

86

0.88

405

882

14

Uruguay

0.90

600

960

30

0.90

400

850

70

0.85

700

0.90

449

900

100

0.92 0.90

783 489

1 120 1 152 910

30

0.90

450

900

70

Median
0.90

530

960

0.90

405

861

0.88

663

1 152

0.89

405

882

0.89

534

1 076

0.89

405

861

0.87

657

1 146

0.89

411

885

Average

North
Oceania
America

0.89

471

893

40

0.89

444

855

60

0.88

527

1 086

27

0.88

455

1 000

73

Source: FAO/ITTO/UNECE Forest product conversion factors questionnaire, 2018.

Notes: The share of conifer to non-conifer reflects reported industrial roundwood and is included so that a weighted average for both can be calculated; ob = overbark; ub = underbark.

share %

Conifer

PULP LOGS

ub/obshare %

kg/m3

Wood basic density (dry weight ofwood/green m3 wood only)

Volume ratio wood/bark plus wood

kg/m3

Green weight with bark/green m3(wood only)

Non-conifer

share %

unit in/unit out

Conifer

SAW/VENEER LOGSPRODUCTS

MéxicoLatin America

Suriname

Asia
United Statesof America

0.85

433

1 000

100

0.85

433

1 000

100

2.3.1

New ZealandAfrica

2. ROUNDWOOD

2.3 Summary of country data on roundwood
Africa, Asia, Latin America, North America and Oceania

13

14

ub/ob

Volume ratio wood/bark plus woodub/obVolume ratio wood/bark plus woodub/obVolume ratio wood/bark plus wood

kg/m3

ub/ob

Wood basic density (dry weight ofwood/green m3 wood only)

Volume ratio wood/bark plus wood

Croatia

Czechia
390

870

91

Denmark
5

90.90 0.90

434

940

95

4

0.89

410

930

96

Finland

560

390

870

100

7

0

0.90 0.90

434

940

93

0.87 0.90

680

0.91

564

560

0.87 0.90

680

997 1 150 1 020

70

0.89

382

983

30

0.91

553

0.86

490

950

24

0.87

400

850

76

0.88

510

1 003 1 150 1 020 1 050

80

0.89

371

979

20

France

7

0.85

550

360

420

919

68

360

100

420

931

59

0.90

474

51

0.91

563

0.89

474

929

41

Netherlands
440

780

77

400

820

100

Norway
480

800

83

99

420

500

900
614

400

820

98

500

900

2

614

911

25

0.85 0.85 0.87

420

940

43

8

0.8

0.82

516

976

92

0.74

500

800 105775

0.82 0.90 0.88

440

780

57

2

0.8

368

989

98

911 1 000170.87 0.85 0.85 0.88

610

940

23

0.88 0.82 0.90 0.88

460

720

1

Moldova

899 1 015

32

0.89 0.89 0.89

389

779

49

0.91

563

1 050 1 125

44

0.83

407

950

56

0.88

560

Ireland100

Lithuania

0.89 0.89 0.90

389

779

93

Germany

1 100 1 125

27

0.87

420

970

73

RussianFederation
Slovakia
22

0.90

940

78

15

0.89

405

875

85

Slovenia

50

0.90

940

50

0.89

50

0.87

405

900

50

0.94

570

0.89

570
0.89

0.91

570

Sweden
1

0.90

415

950

99

Switzerland
10

440

900

90

Source: FAO/ITTO/UNECE Forest product conversion factors questionnaire, 2018.

99

UK

17

0.87

430

1

0.89

870 1 018

83

Median
420
0.88

0.89

887
420

891

Average

62

0.84

436

882

38

0.88

554

0.85

620

40

444

900

60

625

0.88

500

625

970 1 100

9

0.90

400

920

91

0.88

550

0.85

550

416
0.87

0.89

892
406

900

0.88

0.88

0.88

551
0.88

562
0.88

1 143 1 009 1 022

0

0.89

1018

100

0.88

561

560

902 1 050 1 100 1 050 1 143 1 035 1 023

28

0.87

436

881

72

Spain

800 1 180 1 100 1 155

50

0.90

450

740

50

0.89

640

870 1 180 1 050

30

0.90

517

815

70

UkraineNotes: The share of conifer to non-conifer reflects reported industrial roundwood and is included so that a weighted average for both can be calculated; ob = overbark; ub = underbark.

kg/m3

Green weight with bark/green m3
wood only

share (%)

kg/m3

Wood basic density (dry weight ofwood/green m3 wood only)

Non-conifer

kg/m3Green weight with bark/green m3
wood only

Conifershare (%)

kg/m3

Wood basic density (dry weight ofwood/green m3 wood only)

PULP LOGS

kg/m3

Green weight with bark/green m3
wood only

share (%)

kg/m3

Wood basic density (dry weight ofwood/green m3 wood only)

Non-conifer

kg/m3

share (%)

Unit in/unit out

Green weight with bark/green m3(wood only)

Conifer

SAW/VENEER LOGSPRODUCTS

Poland2.3.2

Portugal

EuropeForest product conversion factors

Europe©Shutterstock

2. ROUNDWOOD

15

3
CHAPTER©Fotolia

3. Wood particles
Wood particles (chips, sawdust, flakes and shavings) canbe measured by volume and weight (both in the dry stateand “as delivered”). All wood-particle products start out
as solid wood from logs of varying density, are broken
down into somewhat irregularly shaped particles, andoften contain varied amounts of moisture and void space
between particles.
Conversion factors for wood particles are determinedby wood density, moisture content and compaction. In
general, large enterprises that produce and use woodparticles obtained from many sources use oven-dry
weight for measuring wood particles. Enterprises thatwork with wood particles obtained from fewer andmore homogeneous sources might favour the use ofvolume or weight as delivered. Ultimately, the yield of
most manufacturing processes using wood particles as araw material is driven by the quantity of fibre, excluding
moisture and void.
Another driver of the yield of wood particles is classification.
Often, users of wood particles require classification by size
aimed at ensuring the suitability of particles for the productthey are manufacturing (e.g. some pulping processes andoriented strandboard – OSB). A sawmill or wood-chipping
operation may need to remove small particles (fines) from“on specification” chips, which otherwise would result in alower yield of chips and a higher yield of small particles;
these small particles may be classified and marketed as
sawdust.

the greater the depth (thus increasing weight), the morecompaction will occur.
Based on data obtained from the questionnaire, themedian volume of wood particles per cubic metre ofsolid wood is 2.80 m3 for chips and 2.87 m3 for sawdust(meaning that 1 m3 of solid wood will produce chips that
displace 2.80 m3, including void space). The following arelisted in Conversion Factors for the Pacific Northwest Forest
Industry (Hartman et al., 1981) as ratios of m3 loose to m3
solid for wood particles:■ pulp chips (compacted)

2.50■ pulp chips (uncompacted)

2.86■ sawdust			2.50
■ planer shavings		

4.00

3.2 Weight
The weight of wood particles is generally given “asdelivered” or as oven-dry weight (all moisture removed,
often called “bone dry” in North America). The “asdelivered” weight may vary substantially due to differences
in moisture content. For example, chips produced in asawmill may have 50 percent mcw (i.e. 50 percent of theweight is water and 50 percent is dry fibre), but a veneer
plant using logs identical to those used in the sawmill
might produce chips in which only 6 percent (mcw) of the

3.1 Volumetric measurement
The procedure for establishing the volume of particles
is straightforward. Volumes contained in truckloads,
ship hulls and bins can easily be calculated. Even huge,irregularly shaped stockpiles at manufacturing facilities
can be measured with surveying equipment to establish
volume.
©UNECE

Solid wood equivalent is more complicated, however,
because of the variation in void space. Wood particles incontainers or piles will settle over time and the heavier
the particles (due to density or moisture content) and17

Forest product conversion factors

weight is moisture. In this example, the sawmill chips weregreen and the veneer chips were produced from dried
veneer. Based on the questionnaire results, the medianratio (all countries) of delivered tonnes of wood chips isabout 2.0 for chips (delivered tonne to oven-dry tonne)
and sawdust (indicating 50 percent dry fibre, 50 percentmcw); and 1.16 for shavings (indicating 86 percent dry
fibre and 14 percent mcw).
The normal procedure for establishing the oven-dry
weight of wood particles is via a sampling system, as per
the following example:©iStock■ The net weight of a truckload of chips is 32 200 kg.

18■ A sample of “as delivered” chips is taken, weighing
922 g.
■ The sample is placed in a vented oven at
approximately 103 °C for 24 hours, until the weightstabilizes at 497 g (devoid of moisture).
■ The oven-dry weight of the sample is divided by
the “as delivered” weight and this ratio is multipliedby the “as delivered” net weight of the truckload ofchips.

■ i.e. (497 ÷ 922) × 32 200 = 17 356 kg or 17.356
oven-dry tonnes.

3. WOOD PARTICLES

3.3 Summary of country data on wood particles
3.3.1

Africa, Asia, Latin America, North America and Oceania

UnitedStates ofAmericaNew
Zealandm3 loose to solid m3

3.76 3.76 3.05

2.80 2.80 2.80 2.88

2.33

2.60 2.60

3.04

2.22 2.23 2.23 2.23

2.31

Average

2.30

2.15

Median2.31

1.52 1.52

Uruguay

2.22 2.23 2.22 2.21

1.52

Average

2.19

2.15 2.00 2.15 2.10

Median2.60 2.40 2.40 2.43

Malaysia

2.3

2.19 2.19 2.15

South
Africa2.44 2.44

Average delivered tonne/odmt mt/odmt

Unit in/unit out

Nigeria

MexicoOceania

Chile

North
AmericaIndonesia

Latin America

China

Asia
Median/averageAfricaWOOD CHIPS
Green swe to oven-dry tonne

m3/odmt

m3/m3

2.86

SAWDUSTm3/odmt

2.02

2.44 2.23 2.38

2.60 2.40 2.40 2.46

Average delivered tonne/odmt mt/odmt

1.83

2.19 2.01 2.16

2.15 2.00 2.15 2.10

m3 loose to solid m3

2.36

3.76 3.06 3.05

2.80 2.80 2.80 2.88

m3/odmt

2.44 2.44 2.34

2.60 2.30 2.34 2.41

Average delivered tonne/odmt mt/odmt

1.15 1.15 1.16

1.15 1.16 1.16

m3 loose to solid m3

3.76 3.76

Green swe to oven dry tonne

m3/m3

2.30

2.15
3.23

2.87 2.87

3.04

2.22 2.23 2.23 2.23

2.31

1.15 1.15 1.15

1.15

2.50

SHAVINGS
Green swe to oven dry tonne

m3/m3

2.30

3.23 3.23

3.23

Notes: odmt = oven-dry tonne; swe = solid wood equivalent (assumes green volume of wood, prior to any shrinkage); loose m3 = indicates bulk volume(including the void space between wood particles).
Source: FAO/ITTO/UNECE Forest product conversion factors questionnaire, 2018.

3.3.2

EuropeAverage

MedianSwitzerland

SwedenSpain

Slovenia

Slovakia

RussianFederation

Portugal

PolandNorwayNetherlands

Lithuania

IrelandGermany

FranceFinlandDenmark

Unit in/unit out

Czechia

EuropeWOOD CHIPS
Green swe to oven dry tonne

m3/odmt 2.41

Average delivered tonne/odmt mt/odmt 2.00
m3 loose to solid m3

m3/m3

2.40 2.25 2.49 2.78 2.29
2.00 1.85

2.88 2.70 2.55 2.50

2.11

2.50

2.86 2.40 2.44 2.20 2.45 2.30 2.25

2.41 2.43

2.00

2.00 1.97

2.70 2.80

2.80 2.84

3.33 2.29 2.44 2.34 2.45 2.30 2.25

2.41 2.47

1.80 2.22

1.98 1.80

2.70 2.78 2.86 3.30 2.86

2.78 3.38 3.00

SAWDUST
Green swe to oven dry tonne

m3/odmt 2.41

2.40 2.25 2.49 2.78 2.29

2.50

Average delivered tonne/odmt mt/odmt 2.00

2.00 1.50

2.11

1.80 2.22

1.98 1.80

m3 loose to solid m3

2.55 3.00

2.70 3.03 2.86 3.30 2.86

3.03 3.38 3.00

m3/m3

2.88

2.00

2.00 1.93

2.70 2.80

2.88 2.93

2.45 2.30 2.25

2.41 2.37

SHAVINGS
Green swe to oven dry tonne

m3/odmt 2.41

2.40 2.25 2.49 2.78 2.29

2.50

2.44

Average delivered tonne/odmt mt/odmt
m3 loose to solid m3

m3/m3

Notes: odmt = oven-dry tonne (oven dry tonne); swe = solid wood equivalent (assumes green volume of wood, prior to any shrinkage); loose m3 =indicates bulk volume (including the void space between wood particles).
Source: FAO/ITTO/UNECE Forest product conversion factors questionnaire, 2018.

19

4
CHAPTER©UNECE4. Sawnwood
Sawnwood covers a large spectrum of sawn solid wood
products, ranging from semi-processed cants,5 boules andflitches,6 which are often still green, to fully edged, dried,
trimmed and planed sawnwood. The state of manufacture(e.g. boules/flitches versus dried and planed sawnwood)
has a large impact on the conversion factor: for example,
1 m3 of roundwood might produce 0.8 m3 of green boules
and flitches but only half that amount (0.4 m3) of fully dried,
edged, grade-trimmed and surfaced (planed) sawnwood.
Thus, countries were asked to provide conversion factors
for subcategories of sawnwood products in order tounderstand the considerable variation between national
conversion factors for sawnwood.

For example, Germany reported a conversion factor for
coniferous sawnwood of 1.59 m3 of roundwood per m3of sawnwood, and the United States of America reported
a factor of 2.04. On face value, this might indicate thatsawmills in the United States of America are much lessefficient than sawmills in Germany (because the values
suggest that mills in the former require 28 percent
more roundwood volume to make the same quantityof sawnwood as mills in the latter). A further analysisof the subcategories of sawnwood, however, showsthat roundwood-to-sawnwood conversion factors for
subproduct categories such as rough green and surfaced
dry are similar for both countries. What differs is thepoint in the manufacturing process at which sawnwood
production volume is measured. It may also be that
Germany produces more rough wood (i.e. not surfaced byplaning) than does the United States of America.

5 A cant is a semi-processed log with at least one (generally two orfour) flat faces (either sawn or chipped).
6 A flitch is sawnwood that has not yet had the edgings removed; thus,
the wide face is tapered lengthwise and includes the rounded profileof the log on its edges. A boule is a log manufactured into flitches andstacked together into a unit resembling the original log.

FIGURE 4.1

A significant number of correspondents reported thatsawnwood production in their countries is measured in

EXAMPLE OF ROUNDWOOD-TO-SAWNWOOD CONVERSION FACTORS, BY STATE OF MANUFACTURE

SAWMILL

Roundwood

Loss m3

DRY KILN OR YARD

PLANING MILL AND/ORGRADING CHAIN

Roughgreen inRoughdry inLoss m3

Loss m3

TO CUSTOMER

Sawnwood
shipped

m3

saw
kerf

slabs/trim/
edge/cullm3

RW
factorshrinkage

m3

RW
factorsaw
kerf

slabs/trim/
edge/cull

Softwood(construction)

1.00

0.07

0.29

0.64

1.57

0.03

0.62

1.63

0.08

0.06

0.48

2.08

Hardwoods(appearance)

1.00

0.14

0.22

0.64

1.57

0.07

0.57

1.75

0.10

0.03

0.44

2.27

sawdustchips

shavings

chips

H2O vapour

m3 RW factor

Source: UNECE/FAO, 2010a.

21

Forest product conversion factors

In addition to the state of manufacture, many other driversof efficiency can affect conversion factors for roundwood
to sawnwood. The issue of volumetric measurement is
discussed in section 4.1, but log quality and size havesubstantial impacts on conversion efficiency, as dodifferences in how roundwood volume is measured (seesection 2.1). In addition, recovery ratios are affected by theefficiency of the milling process and the types of productmade. Figure 4.2 shows the typical sawnwood productrecovery and material balance for dried and planed
dimension lumber7 (sawnwood) in North America. Notethe substantial improvement in sawnwood recovery as
diameter increases.

4.1 Volumetric measurement

FIGURE 4.2

MATERIAL BALANCE AND SAWNWOODRECOVERY, BY SMALL-END DIAMETER

100
90
80

Percent of log volume

the rough green state to avoid “double counting” volume,
which may be dried, grade-trimmed or planed at separate
off-site facilities. This contrasts with other countries, notably
in the Nordic region and North America, where sawnwood
volume is more often tallied and reported in a final state of
manufacture. This can lead to a situation in which the ratioof roundwood needed to make sawnwood is reported as
1.57 (64 percent recovery) in the rough green state; 1.75
(57 percent recovery) in the rough dry state; and 2.27
(44 percent) in a fully planed and finished state (Figure 4.1).

70
60
50
40
30
20
10
0
13 15 18 20 23 25 28 30 33 36 38 41 43 46 48 51 53 56 58 61 64

Small-end diameter of log processed in cm
Sawnwood

Green chips

Shavings

SawdustShrinkage

Dry chips

Notes: Based on studies at dimension lumber mills in the northwestern
USA. Green chips are produced in the sawmill, and dry chips come from
trimming or edging to remove defects (after the wood is dried).
Source: Fonseca, 2005.

4.1.1

Cubic volume

Sawnwood is measured in cubic metres in most of theworld outside North America. It is generally assumed thatvolumes are determined based on actual dimensions
allowing for small variations (e.g. ± 2 mm). The formula is:width in mm × thickness in mm × length in m ÷ 1 000 000= m3 sawnwood
In some areas of Europe, sawnwood is sold in the retailmarket based on volumes determined by nominal sizes.8
For example, the volume of dried and planed lumberthat is 45 mm × 95 mm, and which might have started
out at 50 mm × 100 mm before planing, will be reported

7 Dimension lumber (sawnwood) is a term used in North America
to classify sawnwood which is 2 inches or greater in nominal
thickness and is for use in applications where structural strengthand serviceability are the primary concerns. It is normally producedin lengths from 8–20 feet (in two-foot increments) and in widths of
4–12 inches (in two-inch increments).
8 Nominal size is the approximate or roughcut dimensions by which amaterial is generally called or sold in trade but which differs from theactual dimensions due to shrinkage in the drying process and theremoval of rough and uneven surfaces.

22

based on the latter dimensions. Where the ratio of actualto-nominal volume can be assessed accurately, forexample in North America for sawn softwood, production
statistics and conversion factors are adjusted to reflect
actual volume; where they are not known, however, no
adjustments are made.

4.1.2

Board foot volume

In North America, sawnwood is usually measured in board
feet, with a board foot defined as a board 1 inch (2.54 cm)
thick and 1 foot square (30.48 cm × 30.48 cm), equivalent
to 0.00236 m3. Therefore, 1 m3 of sawnwood ostensibly
equals 424 bf. This measure arose when sawnwood
was commonly sold in rough, green form. Today, sawn
softwood is typically dried and surfaced at the sawmill
before sale. To accommodate this, a set of standards allows
wood of smaller dimensions to be sold on a nominal basisthat ignores the shrinkage and material removed during
surfacing. For example, the volume of dried and planed
sawnwood may be calculated based on the nominal
dimensions of 2 inches thickness × 4 inches width × 96

4. SAWNWOOD

TABLE 4.1

BOARD FOOT ACTUAL-TO-NOMINAL SIZES AND VOLUMES, BY LUMBER (SAWNWOOD) PRODUCT TYPE
NominalPRODUCTThick(inches)Width(inches)

Green target size*
bf/m3

Thick
(inches)

Dried-planed size

Width(inches)

bf/m3

Thick
(inches)Width(inches)bf/m3

SOFTWOOD BOARDS
1×4

1

4

424

0.94

3.8

475

0.75

3.5

646

1×6

1

6

424

0.94

5.88

461

0.75

5.5

616

1×8

1

8

424

0.94

7.88

458

0.75

7.25

624

1×10

1

10

424

0.94

9.88

457

0.75

9.25

611

1×12

1

12

424

0.94

11.88

456

0.75

11.25

603

2×4

2

4

424

1.75

3.8

510

1.5

3.5

646

2×6

2

6

424

1.75

5.88

495

1.5

5.5

616

2×8

2

8

424

1.75

7.88

492

1.5

7.25

624

2×10

2

10

424

1.75

9.88

491

1.5

9.25

611

2×12

2

12

424

1.75

11.88

489

1.5

11.25

603

1.25

actual424

1.417

actual374

1.156

actual458

1.5

actual424

1.68

actual378

1.406

actual452

1.75

actual424

1.878

actual395

1.594

actual465

2

actual424

2.108

actual402

1.813

actual468

2.25

actual424

2.404

actual397

2.094

actual456

2.5

actual424

2.7

actual392

2.375

actual446

DIMENSION AND STUDSSOFTWOOD SHOP

5/4
6/4
7/4
8/4
9/4
10/4
HARDWOOD LUMBER

2/4
3/4
4/4
5/4
6/4
7/4
8/4
9/4
10/4
11/4
12/4
13/4
14/4
15/4
16/4

0.5

actual424

0.605

actual701

0.313

actual

1,356

0.75

actual424

0.874

actual

485

0.563

actual753

1

actual424

1.142

actual371

0.813

actual522

1.25

actual424

1.411

actual375

1.063

actual499

1.5

actual424

1.68

actual378

1.313

actual484

1.75

actual424

1.882

actual394

1.5

actual494

2

actual424

2.151

actual394

1.75

actual484

2.25

actual424

2.487

actual384

2.063

actual462

2.5

actual424

2.688

actual394

2.25

actual471

2.75

actual424

2.957

actual394

2.5

actual466

3

actual424

3.226

actual394

2.75

actual462

3.25

actual424

3.495

actual394

3

actual459

3.5

actual424

3.763

actual394

3.25

actual456

3.75

actual424

4.032

actual394

3.5

actual454

4

actual424

4.301

actual394

3.75

actual452

Notes: * Green target sizes are set by the manufacturer based on shrinkage, size control, etc., and thus these are reasonable averages. Softwood “shopgrades” (used as stock to extract cuttings for further manufacture, such as door and window components) and hardwood lumber – widths are based on
actual, which is commonly referred to as “random width”, and thickness is often reflected in ¼ inch increments – e.g. 5/4 has a nominal thickness of 1.25”.
Sources: Western Wood Products Association, 1998; National Hardwood Lumber Association, 1994; Fonseca, 2005.

23

Forest product conversion factors

4.2 Weight

inches length (0.0126 m3), but its actual dimensions may
be 1.5 inches thickness × 3.5 inches width × 92.625 inches
length (0.008 m3). The formula for determining board feetis:

The relationship between the weight and volume ofsawnwood varies because of basic density, moisture
content and shrinkage (see sections 1.2.1–1.2.3). The
relationship is useful, however, for estimating shipping
weight from known volumes and volumes from known
shipping weights. It is also common to estimate this ratiousing the following formula (Briggs, 1994):

Nominal width in inches × nominal thickness in inches× nominal length in feet ÷ 12 = bf
Thus, a board that is nominally 2 inches × 4 inches
× 8 feet would comprise 5.333 bf.
For measuring sawn softwood volume, the width,
thickness and, to a smaller degree, length have nominal
measurement allowances. In other words, what nominallyis represented as having 1 m3 is often as little as 0.66 m3.
This fact is accounted for in the FAOSTAT and UNECE/
FAO timber databases using an actualization factor of
72 percent. Thus, it is assumed there are 589 bf per m3.

(basic density ÷ (1 – shrinkage)) × (1 + moisture content)
For example, the calculation of weight per volume for
Scots pine sawnwood originating in a region where it
has an average basic density of 400 kg per m3 (volume
measured before shrinkage), and a volumetric shrinkage
of about 7.5 percent for sawnwood dried to 15 percent
mcd, is as follows:

The standards for sawn hardwood in North America differ
from those for sawn softwood and are considered to betruer to the implied 0.00236 m3 per bf (424 bf per m3); thus,
no actualization factor is used. Often, sawn hardwood issawn oversize to the nominal thickness, and widths andlengths are based on actual dimensions. Additionally, asignificant component of sawn hardwood is produced inrough form.

(400 ÷ (1 – 0.075)) × (1 + 0.15) = 497.3 kg/m3

4.3 Material balance
In completing the questionnaire, many countries submitted
the material balance for the manufacture of sawnwood.
The sawnwood component accounts for roughly half
the roundwood volume that is input to the sawmilling
process, and it is important, therefore, to understand theresidual products that later become the raw materials forother wood products – such as chips and slabs, sawdust
and shavings. Figure 4.3 and Figure 4.4 show the materialbalances for those countries that reported it.

The board feet contained in a cubic metre varies according
to the state of manufacture of the sawnwood (e.g. green,
dry and rough, or surfaced and dry) and the type ofsawnwood manufactured (Table 4.1).

7

11

13

2
1

25

36

34

28

25

35

60

52

50

55

59

53

5

6

11

10

36

34

48

50

2
3

12

5

7

12

12

5
2

6

3
3

28

30

56

54

10

38

27

51

45

49

Sawnwood

Chips/slabs

SawdustSource : FAO/ITTO/UNECE Forest product conversion factors questionnaire, 2018.

24

1
11

UK

esi
a

4
2

da
dS
tat
es
Cze
chi
a
De
nm
ark
Fin
lan
d
Fra
nce
Ge
rm
an
y
Ire
lan
d
Lit
hu
an
ia
No
rw
ay
Po
lan
d
Slo
va
kia
Slo
ve
nia
Sp
ain
Sw
ed
en
Uk
rai
ne

ina

11

13

11

22

19

27

22

60

58

56

59

na

a

Ch

5

10

ite

50

3
1

Un

50

2

11

10

8

30

ile

48

on

26

4
10

10

12

10

30

20

4
5

7

10

10

24

Ind

So
u

2
8

Ca

3
5

th
Afr
ic

100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%

MATERIAL BALANCE IN THE SAWMILLING PROCESS FOR CONIFEROUS SAWNWOOD, BY REPORTING
COUNTRY (percentage)Ch

FIGURE 4.3

Shavings

Shrinkage loss

12

32

49

4. SAWNWOOD

FIGURE 4.4

MATERIAL BALANCE IN THE SAWMILLING PROCESS FOR NON-CONIFEROUS SAWNWOOD

Sawdust %huaShavings %

10

18

17

63

66

24

27

61

53

ne

50

14

rai

48

53

9

Uk

34

5

Sp
a in

36

6

kia

8

8

Slo
va

11

2
5
12

Po
lan
d

8

No
rw
ay

60

5

Lit

Fra

Chips/slabs %

35

lan
d

47

De
nm
a

ta t
dS

Un
ite

Sawnwood %

47

16

Ire

54

36

1
11

an
y

51

35

4
7
13

Ge
rm

45

15

3
4
10

nce

30

3

rk

33

es

44

Ca

52

12

2
1
13

e

60

Ind
on
esi

55

a

23

Ch
ina

25

4

na
da

1
10

3
10

a

21

9

rin
am

7
10

2
5
8

Su

7

Nig
eri

100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%

nia

(percentage)

Shrinkage loss %Source: FAO/ITTO/UNECE Forest product conversion factors questionnaire, 2018.

©Shutterstock25

m3rw/m3p

Sawnwood dry roughSawnwood dry planed
Flitches and boules(green rough)Flitches and boules (dryrough)
Material balance

%

%

%

%

Chips/slabs

SawdustShavings

Shrinkage loss

100

2.11

3

3

1.40
1.51

m3rw/m3p

m3rw/m3p

m3rw/m3p

m3rw/m3p

m3rw/m3p

Sawnwood dry roughSawnwood dry planed

Flitches and boules(rough green)
Flitches and boules(rough dry)Material balance

kg/m3

7

2

7
720

8
5

7

21
10

60
25

55

Indonesia
2

90

Japan
10

100

Malaysia

670

9

3

10

23

52

1.50

1.30

2.10

1.70

2.00

2.10

800

8

63

1.59

1.90 1.82 1.59

98

520

7

10

10

26

50

1.50

1.25

2.10

1.70

2.00

1.65

2.00 1.57

Median
1.51

1.51

720

8

4

9

24

Brazil
3

508

7

12

30

51

2.28

1.97

97

Chile

10

44

45

2.29

52

97

464

7

12

30

48

3

4

5

8

38

45

730

754

10

44

45

754

10

44

47

2.23 2.23

2.21 2.16

12

33

51

2.20 2.10 1.96

464

7

12

30

49

2.28 2.28

1.97 1.97

2.12 2.12 2.22

4

40

43

49

2.29 1.91

100

57
2.02

North America

6
858

52

2.20

100

Guyana

0

650

45

2.23

2.22 1.93

420

45

2.22

Median

4

9

24

58

1.51

1.51
60

1.35

2.26

2.26
1.35

2.00
1.84

2.00
1.84

1.83

1.81

556

5

9

10

27

1.81

1.86

556

5

9

10

27

50

1.33

1.33

50

2.11

2.11

1.71

2.03

2.03
1.71

1.68

1.86

Average

1.68

2.00

Average

Notes: m3rw = cubic metre roundwood; m3p = cubic metre product. / Source: FAO/ITTO/UNECE Forest products conversion factors questionnaire, 2018.

Average sawnwood
shipping weight%

Shrinkage loss

7

10

%

%

SawdustShavings

Chips/slabs

55

21

%

%

Sawnwood

2.42

1.98

1.81

Sawnwood green planed

2.15

2.15

m3rw/m3p

32
1.92

1.82

Sawnwood green rough

1.82

Share (%)

m3rw/m3p592

2

Sawnwood all

430

8

5

5

430

10

24

24

30

20

20

50

48

48

NON-CONIFER

kg/m3

%

Sawnwood

Average sawnwood
shipping weight

2.08

2.08

1.72

2.05

1.71

1.66
1.75

2.00

68
2.08

1.75

1.66

2.08

1.51

m3rw/m3p

Sawnwood green planed

Nigeriam3rw/m3p

m3rw/m3p

Sawnwood green roughSouth
Africa100

Median/Average
1.40

m3rw/m3p

Sawnwood all

China

m3rw/m3p

Share (%)

m3rw/m3p

CONIFER

Unit in/unit out

Suriname

Latin America
Uruguay

Asia
Canada

26
2

1

13

30

54

2.38

1.92

1.79

1.85

32

581

4

10

10

27

49

2.08

1.69

2.00

1.62

2.04

68

3

1

13

32

53

2.38

1.92

1.79

1.91

581

4

8

9

33

47

2.08

1.69

2.00

1.62

2.13

UnitedStates ofAmericaMedian/Average

Oceania

1.81

100

4.4.1

New
ZealandAfricaForest product conversion factors

4.4 Summary of country data on sawnwood
Africa, Asia, Latin America, North America and Oceania

98

Austria
2

83

27

kg/m3

3

15

54

3

4

10

36

94

Germany
7
4

1

11

35
13

53

13

1.89

1.89

0

415

1

11

35

53

2.13

1.99

1.89

1.89

100

Ireland

60

1.66

1.66

6

2

1

13

25

59

1.99

1.66

1.67

68

Lithuania
538

5

11

36

48

2.08

32

477

5

11

36

48

2.08

70

Netherlands
51

1.96

1.96

30

53

1.88

1.88

99

550

8

8

34

50

1.70

1.40

2.20

2.00

2.00

1

440

6

10

34

50

2.50

2.00

1.75

2.00

89

700

2

5

12

18

63

1.58

1.59

11

550

2

3

13

22

60

1.63

1.64

98

Portugal
57

1.76

2

50

2.00

Slovakia

Slovenia
87

73

Sweden99

Ukraine74

UK
98

Average

MedianRussianFederation

13

600

5

12

27

56

1.85

37

7

12

22

59

1.90

1.69

1

5

2

12

32

49

2.04

1.69 1.71

26

6

10

21

56

2

549

3

3

10

30

54

519

2
5

2
5
549

28
11

28
11

55

55

1.50 1.50

1.26 1.26

2.27 2.26

2.05 2.00 2.00 1.94

2.05 2.05

790

8

9

17

66

1.49

1.33

1.72

1.54 1.55

6

14

27

53

2.10

1.90

53

1.90

5

10

24

61

699

40

5

5

655

5

5

699

28
11

11

52
31

53

1.70 1.65

1.40 1.44

3.25 3.25

1.91 2.50 2.01 2.09

2.85 2.85

1.89 1.81

1.52 1.55 1.89 1.90 1.62 2.50 1.90 1.95

27

600

12

11

19

58

1.49

1.33

1.72

1.85 1.54 1.75

1.72 1.75 1.69 2.04 1.78 1.85 1.81 1.82

73

Spain

Notes: m3rw = cubic metre roundwood, m3p = cubic metre product. / Source: FAO/ITTO/UNECE Forest product conversion factors questionnaire, 2018.

Average sawnwood
shipping weight%%

Shavings

Shrinkage loss%

Sawdust

35

47

%

%

Sawnwood

1.75

m3rw/m3p

Chips/slabs

1.60

m3rw/m3p

Flitches and boules(rough green)
Flitches and boules(rough dry)Material balance

2.50
3.25

m3rw/m3p

m3rw/m3p

2.20

Sawnwood dry rough

1.85

17
2.13

Sawnwood dry planed

47

1
1.85
2.85

46

17
2.10

2
4

m3rw/m3p

35

5
2.17

5

28
11

m3rw/m3p

2.00

2

34
11

Sawnwood green rough

2.81

3

36
10

55

Sawnwood green planed

Share (%)

m3rw/m3p

Sawnwood all

kg/m3

NON-CONIFER

Average sawnwood
shipping weight

1

%

%

Shavings

Shrinkage loss

25
11

%

%

Chips/slabs

Sawdust50

1.50

m3rw/m3p%

1.18

m3rw/m3p

Sawnwood

1.80
2.40

m3rw/m3p

1.65

m3rw/m3p

2.00

83
1.81

Sawnwood dry rough

52

99
2.00

Sawnwood dry planed
Flitches and boules(green rough)Flitches and boules (dryrough)
Material balance
60

83
1.92
2.05

1.67

95

Czechiam3rw/m3p

60

17

Croatia
1.54

Denmarkm3rw/m3p

1.66

Finland

Sawnwood green roughSawnwood all

FranceSawnwood green planed

Share (%)

m3rw/m3p

CONIFER

Unit in/unit out

Norway4.4.2

PolandEurope4. SAWNWOOD

Europe5
CHAPTER©iStock

5. Veneer and plywood

Plywood is a composite product manufactured bylaminating sheets of veneer together into panels,
generally with the layers of veneer oriented at 90 degrees
to the previous layer (to improve multidirectional strengthcharacteristics).
The determinants of veneer and plywood recovery
ratios are similar to those for sawnwood: log size andcharacteristics, product specifications, and milling
efficiency.

5.1 Volumetric and surface measurement
Two systems are generally used to measure veneer andplywood: surface measure, which strictly measures thesurface area and does not account for volume (because
thickness is not accounted for); and volumetric. Volumetricmeasures have two distinct variations: straight cubic
volume (i.e. thickness × width × length); and surface
measure on a thickness basis.
In most places, veneer and plywood is measured in m2, m2
1 mm basis, and m3. For example, a sheet of plywood thatmeasures 1.22 m × 2.44 m × 12 mm has 35.72 m2, 1 mm
basis, which is easily converted to m3 by dividing by 1 000(= 0.03572 m3).

Typically, shrinkage has a significant effect on veneer
and plywood because of the low moisture content(<6 percent) required.

5.2 Weight
As for sawnwood (see section 3.2), a theoretical approach
can be used to calculate the weight of veneer. This will
also work for plywood, but an allowance may need to bemade for the weight of the glue line between the veneer
plies. An approximate glue weight is 122 g per m2 of glueline surface area (United States Forest Service, 1956).
For example, an estimate is needed for the weight pervolume (kg per m3) for plywood made from Norway
spruce measuring 1.22 m × 244 m × 0.013 m with five plies(i.e. four glue lines). The assumptions are that the wood
will have a basic density of 380 kg per m3, the moisture
content of the wood will be 8 percent, and shrinkage willbe 9 percent. Weight per m3 of the wood component,
therefore, is calculated as: 380 ÷ (1 – 0.09) × (1 + 0.08) =panel wood weight of 451 kg per m3.
The volume of the panel is calculated as 1.22 × 2.44 ×
0.013 = 0.0387 m3. Thus, the wood weight for the panel is0.387 × 451 = 17.45 kg.

©Shutterstock

Veneer is produced in one of two ways: by means of alathe, in which the log is chucked and rotated against astationary knife (rotary peeled veneer); or sliced, whereby
the log is halved or quartered into flitches (sometimes
called cants) with a saw and the flitch is then pressedagainst and moved across a knife (sliced veneer). Rotary
peeling is generally used to produce thicker veneers
for structural applications, and sliced veneer is used to
produce thin veneers with decorative uses (but there are
exceptions to these generalizations).

In North America, veneer and plywood are often
measured in square feet 3/8-inch basis. For example, a sheetof plywood measuring 4 feet × 8 feet × 0.472 inches has
40.37 ft2 3/8-inch basis (4 × 8 × [0.472 ÷ 0.375] = 40.37). Notethat 0.375 is the decimal equivalent of the 3/8-inch basis
thickness. To convert ft2 3/8 inch to cubic volume, divide by
1,130 to get m3, or by 32 to get ft3.

29

Forest product conversion factors

There are four glue lines, each with a surface area of
2.98 m2 for a total of 4 × 2.98 = 11.9 m2 of glue line. The
glue weight per panel is 122 × 11.9 = 1 453 g (1.45 kg);
each panel weighs 1.45 kg glue + 17.45 kg wood = 18.9 kg;
weight per m3 is 18.9 ÷ 0.0387 = 488 kg/m3.

FIGURE 5.1

100

5.3 Material balance

Peeler cores, which are a coproduct of the manufactureof rotary peeled veneer, are often sold as roundwood(e.g. fence posts), and they can be chipped. Some peeler
cores, however, are large enough for the manufacture ofsawnwood. Figure 5.1 shows the typical product recovery
and material balance in a North American coniferous
rotary plywood mill.

90
80

Percent of log volume

The material balance for the production of plywood
and veneer is relatively complex because, to varying
degrees, other solid wood products are also madeduring the production of veneer – that is, sawnwood in
the production of sliced veneer, and peeler cores9 in the
production of rotary peeled veneer. Sawnwood is often a
coproduct in the production of flitches for slicing; it is madefrom sections of the log that are unsuitable for veneer but
adequate for sawnwood. Sawnwood is also manufactured
in the slicing process from that portion of the flitch that is
grasped and held by the arm that moves the flitch acrossthe stationary slicing knife. This sawnwood is commonlyreferred to as backing board.

PRODUCT RECOVERY, BY SMALL-END
LOG DIAMETER, IN A TYPICAL NORTHAMERICAN CONIFEROUS ROTARYPLYWOOD MILL

70
60
50
40
30
20
10
0
13 15 18 20 23 25 28 30 33 36 38 41 43 46 48 51 53 56 58 61 64 66 69 71 74 76

Small-end diameter of log processed in cm
VeneerGreen chips

Peeler core

Shrinkage

Dry chips

Source: Fonseca, 2005.

9 When a log is rotary peeled, it is often held and pivoted by lathechucks. In this situation, the minimum diameter limit of the log at
which veneer can no longer be peeled is usually determined by thediameter of the chucks. Thus, a lathe chuck with a diameter of 8 cm
will produce peeler cores that are slightly larger in diameter (e.g.
8.5 cm) to prevent the veneer knife from coming into contact withthe lathe chucks.

©UNECE30

m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p(plywood and veneer)

Rotary peeled veneer, green roughRotary peeled veneer, dry roughRotary peeled plywood, dry roughRotary peeled plywood, dry sanded

Sliced veneer, green roughSliced veneer, dry roughSliced plywood, dry roughSliced plywood, dry sanded

m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p(plywood and veneer)

Rotary peeled veneer, green roughRotary peeled veneer, dry roughRotary peeled plywood, dry roughRotary peeled plywood, dry sanded

Sliced veneer, green roughSliced veneer, dry roughSliced plywood, dry roughSliced plywood, dry sanded%%

Sanding dust

Shrinkage/losses

31
mm

South
Africa
4

1

42

53

1.85

100

China
25

Indonesia
1

93

Japan

99

15.0

620

2

3

30

65

21.0

650

1.80 1.95

1.75 1.85

1.72 1.80

1.65 1.70

1.95 2.00

1.90 1.95

1.90 1.80

1.85 1.70

Malaysia

Average

Median

98

Chile
2.20

1.90 1.90

2 100

9

5

5

15.0 18.0 18.0

650 650 650 470

8

4

38

4

4.30

1.88 1.88

4

4.20

1.80 1.80

5.0

764 700

10

5

45

40

3.20

1.76 1.76

34

3.00

1.68 1.68

58

2.30

2.25 2.00 2.07

34

2.20

2.20 1.95 2.02

58

2.10

50

1.90

1.85 1.85

2.00 1.91

57

Uruguay

North America

87

9

6

35

50

9

6

35

47

43

11.0 11.0

519 519 496

424.30 4.30

4.20 4.20

3.05 3.05

3.00 3.00

2.10 2.10

2.10 2.10

1.90 1.90

1.60 1.60

13

5

6

37

52

2.38 2.29 2.29 1.92

Median
10

5

45

41

10

5

45

41

5.0

5.0

545 623 620

424.30 4.30

4.20 4.20

3.20 3.20

3.00 3.00

2.30 2.30

2.20 2.20

2.10 2.10

1.90 1.90

5

7

35

53

2.00 2.38 2.19 2.19 1.89

30 100

11.0

5

5

6

35

50

15.0 15.0

5

5

50.0

550

30

30

620 620 420

60

60

1.00

4.30

1.93 1.93

3.20

1.70 1.70
4.20

3.00

1.58 1.58
1.85 1.85

2.10

1.96 1.96
2.90

1.80
2.00

1.60

70

2.00

Brazil2.08 2.08

2.20

Guyana1.78 1.78

2.00 1.91

Mexico2.00 1.85 1.85

7 100

2.00 2.10 1.62

75

5

5

30

60

1.95 1.90

1.90 1.80

1.65 1.75

1.55 1.60

1.96 1.95

1.90 1.90

2.25 1.90

1.95 1.60

2.12 2.00 1.62

Average

Notes: m3rw = cubic metre roundwood, m3p = cubic metre product. / Source: FAO/ITTO/UNECE Forest product conversion factors questionnaire, 2018.

Average panel thickness

kg/m3

%

Other products (chips, peeler cores, etc.)

Average panel shipping weight%

VeneerMaterial balance

Share (%)

NON-CONIFER

mm%

Shrinkage/losses

Average panel thickness%

Sanding dust
kg/m3

%

Other products (chips, peeler cores, etc.)

Average panel shipping weight%

VeneerMaterial balance

Share (%)
m3rw/m3p

CONIFER

Unit in/unit out

Suriname

Latin America
Canada

Asia

4

4

40

53

3

2

47

48

4

5

41

51

1.92 1.92

1.87 1.87

1.60 1.60

1.51 1.51

2.14 2.14

2.05 2.05

2.00 2.00

2.00 2.00

2.09 2.09

13

3

2

42

53

1.92 1.92

1.87 1.87

1.60 1.60

1.51 1.51

1.92 1.92

1.87 1.87

1.60 1.60

1.51 1.51

1.84 1.88

87

UnitedStates ofAmericaMedian/average

Oceania

100
1.79

5.4.1

New
ZealandAfrica5. VENEER AND PLYWOOD

5.4 Summary of country data on veneer and plywood
Africa, Asia, Latin America, North America and Oceania

32
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p(plywood and veneer)

Rotary peeled veneer, green roughRotary peeled veneer, dry roughRotary peeled plywood, dry roughRotary peeled plywood, dry sanded

Sliced veneer, green roughSliced veneer, dry roughSliced plywood, dry roughSliced plywood, dry sanded

m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p
m3rw/m3p

Rotary peeled veneer, green roughRotary peeled veneer, dry roughRotary peeled plywood, dry roughRotary peeled plywood, dry sanded

Sliced veneer, green roughSliced veneer, dry roughSliced plywood, dry roughSliced plywood, dry sanded

Croatia

Finland
33

1.90

43

5

4

30

67

535 550

7

3

41

50

2.31 2.00

2.27 2.00

47

680

9

2

54

37

2.68

2.63

100

Germany

45

2.40

55

2.00 1.82

2.31 2.00

70

France2.46 2.68 2.40

100

0Ireland
18.0

650

18.0

650

Lithuania
6

3

45

46

2.17

Poland63

Portugal

650

2

2

45

51

2.30

1.95

69

650

3

5

41

51

2.40

37

1.95 2.47

31

64

15.0

500

1.70

1.60

2.25

2.00

36

Slovakia
1.70

1.60

12.0 25.0

650 600

14

4

38

44

2.54

2.44 2.25

1.79 2.15

1.62 1.95

2.27

95

5

Slovenia
8

2

50

40

2.50

95

5

Spain
1.90

100

Sweden

3.00

2.40

3.20

60

5.20

1.85 2.50

2.35

40

Ukraine
1.77

2.28

649

UK

Notes: m3rw = cubic metre roundwood, m3p = cubic metre product. / Source : FAO/ITTO/UNECE Forest product conversion factors questionnaire, 2018.

mm%

Shrinkage/losses

Average panel thickness%

Sanding dust

kg/m3

%

Other products (chips, peeler cores, etc.)

Average panel shipping weight%

VeneerMaterial balance

m3rw/m3p
m3rw/m3p(plywood and veneer)

Share (%)

NON-CONIFER

mm%

Shrinkage/losses

Average panel thickness%

Sanding dust
kg/m3

%

Other products (chips, peeler cores, etc.)

Average panel shipping weight%

VeneerMaterial balance

Share (%)

CONIFER

Unit in/unit out

1.70

1.70

8
646
18.3

8
650
18.0

3

2.30
1.70

46

2.54
2.30

2

2.44
2.54

44

2.08
2.44

45

2.27
2.15

45

2.29

16.5

2.17

16.5

600

2.40

5
589

5

4

3.40
1.70

43

2.16
3.40

4

2.16
2.16

50

2.11
2.14

41

2.04

2.08

51

2.20

Median2.00

Average

2.28

5.4.2

RussianFederation

EuropeForest product conversion factors

Europe5. VENEER AND PLYWOOD©UNECE33

CHAPTER© Shutterstock66. Panels made of woodparticles

Many panel producers use the oven-dry weight of raw
material, rather than the volume of solid wood input, totrack the efficiency of raw-material-to-product conversion.
The higher the wood density of the raw materials, thelower the volume of wood particles needed to make agiven quantity of panels. For example, Norway spruce
has a basic density of 380 kg/m3: 2 m3 of solid-woodequivalent raw material would therefore be required per
m3 of MDF panel pressed to a basic density of 760 kg/m3.
If, on the other hand, Siberian larch (with a basic density of
460 kg/m3) is used as the raw material, only 1.65 m3 would
be needed (discounting the small effects of binders andfillers).

■ OSB				3/8 inch (0.375 inch)■ Particle board and MDF

3/4 inch (0.75 inch)■ Hardboard			

1/8 inch (0.125 inch)■ Insulation board		

1/2 inch (0.5 inch).

6.2 Weight
The weight of panels made from wood particles varies
according to the density of the parent wood, the density
at which the wood fibre is pressed into the panel, moisture
content (typically 6–8 percent – Briggs, 1994), and theweight of binders and fillers.

©Shutterstock

Unlike panels made of veneer, panels made of woodparticles (e.g. particle board, OSB and fibreboard) canhave significantly different ratios of solid wood volume
per product volume, depending on the wood fromwhich they are produced and the target density of thepanel. Wood particles can be pressed into panels thatare more or less dense than the parent wood; thus, a
cubic metre of product will seldom equal a cubic metreof solid wood equivalent. In addition, introduced nonwood components such as binders and fillers add to thebulk and weight of the product. In some countries, nonstructural panels may include a significant percentage ofbark volume (Thivolle-Cazat, 2008).

6.1 Volumetric and surface measurement
As for plywood and veneer, panels made of wood particles
are typically measured by cubic volume, surface measure,and surface measure on a thickness basis. The surface
measure is square area (e.g. m2), irrespective of thickness;
surface measure on a thickness basis (commonly 1 mm
outside North America) refers to measures that establish
thickness. In North America, various basis standards apply
to panels made from wood particles and measured on a
thickness basis, depending on the product, as follows:35

Forest product conversion factors

6.3 Summary of country data on panels made of wood particles
Asia, Latin America and North America

Particle board (without OSB)

m3sw/m3p

1.60 1.60 1.40 1.60 1.53

1.58 1.50 1.54 1.54 1.48

Average thicknessmm

18.0 18.0 18.0 18.0 18.0

15.0 18.0 16.5 16.5 15.9

Product basic density

kg/m3

660

700

700

700

687

Binders and fillers

%

10

9

8

9

9

Bark

%

3

1

2

2

Moisture

%

8

8

7

8

8

Wood

%

79

82

84

82

Median/Average

UnitedStates ofAmerica

CanadaNorth America
Average

MedianMexicoBrazilAverage

Latin America
Median

Malaysia

Indonesia

Unit in/unit out

China

Asia

Chile

6.3.1

1.60 1.54
15.9

640

720

640

667

720

720

8

9

9

9

9

9

7

7

7

1

1

8

7

8

8

7

7

82

84

77

81

81

84

84

640

Material balance

Share of recycled fibre in panels%

OSB and waferboard

m3sw/m3p

1.66

1.70

1.68 1.68

1.41

1.41 1.41 1.61

Average thickness

mm

16.0

18.0

17.0 17.0

15.1

15.1 15.1 11.1

Product basic density

kg/m3

660

650

655

655

705

673

Binders and fillers

%

3

3

3

Bark

%

1

0

1

Moisture

%

6

7

7

90

90

90

11.1
407

407

3

3

3

1

1

1

7

7

7

7

90

90

90

90

640

673

1.65 1.63

Material balance

Wood
Fibreboard, hard (wet process)%4

m3sw/m3p

1.80 1.80

1.80 1.80

Average thicknessmm3.00 3.00

3.00 3.00

Product basic density

kg/m3

900

900

900

900

Binders and fillers

%

7

9

8

8

Bark

%

8

0

4

4

Moisture

%

5

7

6

6

Wood

%

80

85

83

83

2.37 1.90 2.14 2.14 1.79

1.75 1.77

3.00 3.00 3.00 3.00 3.20
940

960

850

940

917

7

7

3.20
880

880

Material balance

Fibreboard, medium/high (MDF/HDF)

m3sw/m3p

71.80 1.80

1.80

1.53 1.53 1.45

1.53

Average thicknessmm

16.0 12.0 14.0 14.0

Product basic density

kg/m3

700

750

725

725

Binders and fillers

%

9

9

9

9

9

Bark

%

0

0

0

0

0

0

Moisture

%

7

6

7

7

8

6

7

7

Wood

%

85

85

85

85

83

83

83

1.60 1.53

15.0 18.0 16.5 16.5 15.9
660

620

700

660

660

9

9

0

0

15.9
704

704

Material balance

Insulation board

m3sw/m3p

Average thicknessmmProduct basic density

kg/m3

0.71 0.71
300 300

Material balance
Binders and fillers

%

Bark

%

Moisture%

Wood
Fibreboard, all%m3sw/m3p

Notes: m3sw = cubic metre solid wood; m3p = cubic metre product; HDF = high-density fibreboard.
Source: FAO/ITTO/UNECE Forest product conversion factors questionnaire, 2018.

36

1.59

1.59 1.59

6. PANELS MADE OF WOOD PARTICLES

6.3.2

Europe

1.59

Average

MedianUnitedKingdomUkraineSwedenSpain

Slovakia

Portugal

PolandNorway1.30 1.93 1.51 1.50 1.60 1.40 1.20

Slovenia

Lithuania

1.70

IrelandGermany

m3sw/m3p

FranceParticle board (without OSB)

Finlandunit in/unit out

Czech
Republic

Europe1.40 1.50 1.80 1.62 1.51 1.54
18.0 18.6

Average thickness

mm

23.0

19.0

18.0

18.0

17.8 19.0

16.0

18.0

Product basic density

kg/m3

668 675650

625

665 650 680 650

650

620 680 650 656

Material balance
Binders and fillers

%

9

6

8

Bark

%

5

5

5

Moisture

%

7

7

8

7

Wood

%

79

83

Share of recycled fibre in panels%

OSB and waferboard

m3sw/m3p

1.53

Average thickness

mm

19.0

Product basic density

kg/m3

565

9

7

10

1

0

7

7

82

79

85

83

25

45

50

30

1.90

1.30 1.93

1.85

9

9

5

5

4

8

8

7

7

83

88

9

630

83

83

38

38

1.58 1.72 1.68
12.0 18.0 16.3

18.0
610

8

620 620 615

650

Material balance
Binders and fillers

%

5

4

3

4

4

Bark

%

0

0

10

0

3

Moisture

%

7

6

7

7

7

Wood

%

88

90

80

88

86

Fibreboard, hard (wet process)2.23

2.40 1.93 2.03

Average thickness

m3sw/m3p
mm

3.00

3.00

3.00

2.20 1.90

Product basic density

kg/m3

950

950

900 940

950
8

1.75

2.30 2.37 2.20 2.12

3.00

3.20

830

820 950 945 911

3.00 3.04

Material balance
Binders and fillers

%

0

9

Bark

%

3

0

Moisture

%

6

6

5

Wood
Fibreboard, medium/high(MDF/HDF)
Average thickness

%

91

85

87

m3sw/m3p

1.51

1.70 1.93

2.00

Product basic density

8
1.80 1.75

8

6

2

2

6

6

87

88

1.85 1.80 1.79

mm

24.0

16.0

15.0

16.0

16.5

16.0 17.5

kg/m3

765

750

650 740700 740

850 730

720 740 738

Material balance
Binders and fillers

%

9

9

8

8

9

9

Bark

%

3

0

10

0

2

3

Moisture

%

6

6

3

7

6

6

Wood

%

82

85

79

85

84

83

Insulation board

m3sw/m3p

0.60

Average thickness

mm

100.0

Product basic density

kg/m3

220 290

150

1.10
400

0.68

0.63 0.68 0.82

1.10
25.0

62.5 62.5

300

260

250 260 267

5

2

5
0

0

6

6

6

90

90

Material balance
Binders and fillers

%

5

Bark

%

0

Moisture

%

6

5

89

90

Wood
Fibreboard, all%m3sw/m3p

1.98

1.80

4

1.89 1.89

Notes: m3sw = cubic metre solid wood, m3p = cubic metre product; HDF = high-density fibreboard.
Source: FAO/ITTO/UNECE Forest product conversion factors questionnaire, 2018.

37

7
CHAPTER©iStock

7. Wood pulp and paper
Pulp is the raw material for paper and paperboard(cardboard), as well as specialty pulps for the manufactureof textiles. The manufacturing process involves separatingwood fibres by means of mechanical or chemical
processes, or a combination of these.

900 kg of oven-dry fibre and 100 kg of contained water.
Pulp and paper can also be measured on an oven-dry basis.
For the purposes of the conversion factor questionnaire,
conversions to tonnes were requested and respondents
were informed that 10 percent mcw was assumed.

Chemical pulping involves the use of chemicals andheat to dissolve the lignin, leaving behind long wood
fibres (which means relatively high strength) but at thecost of low yield compared with mechanical processes
because much of the original wood fibre is dissolved andsuspended in the chemical treatment. There are several
chemical processes, the choice of which depends on
the species comprising the source of the wood fibre andthe desired characteristics of the paper. Bleached pulp
produces white paper but the yield is lower comparedwith non-bleached pulp. Chemical pulping generally
results in yields in the range of 40–50 percent (measured
as oven-dry input to oven-dry output) (Briggs, 1994).
Pulp is also produced using mechanical grinding in
conjunction with chemical processes. There are several
variations of this process, and yield is generally slightly
less than that of strictly mechanical processes. Table 7.1
shows typical yields for various pulp types, measuring
pulp output in dry weight divided by the dry weight of
the wood-fibre input.

7.1 Weight
Pulp and paper are usually measured by weight. Note that
pulp and paper moisture content is assessed on a “wetbasis” (mcw); generally, an unspecified tonne or an “airdried” tonne is assumed to be 10 percent mcw, and 1 airdried tonne of pulp is assumed, therefore, to comprise©Shutterstock

Mechanical pulp is produced through a grinding action
applied to wood fibre, typically wood particles. Becauseof the grinding, the wood fibres tend to be short and thuslack strength compared with chemically produced pulp.
The yield is high, however, because little of the original
wood fibre is lost. One oven-dry tonne of wood fibre
input will yield approximately 0.95 tonnes of oven-dry
mechanical pulp (i.e. 95 percent yield).

TABLE 7.1

TYPICAL PULP YIELDS FOR VARIOUS
TYPES OF WOOD PULP

Pulp type

Pulp yield (% oven-dried
output/input)

MECHANICAL
Mechanical (groundwood)
Thermomechanical
Chemithermomechanical
Chemimechanical

93–95
80–90
80–90
80–90

SEMIMECHANICAL

70–85

CHEMICAL
Sulfate (kraft)
SulfiteMagnefite
Soda
Soda-oxygen
Soda-anthraquinone

45–55
40–50
45–55
40–50
45–55
45–55

DISSOLVING

35

Notes: The presentation of yield in this manner (oven-dry output/
input) minimizes the variability that can occur when measuring input
in volume, or input weight, with moisture. For example, generally lessvolume of wood from high-wood-density species is required to produce
a given quantity of pulp than from low-wood-density species, and more
wet chips than dry chips are needed to produce a given quantity of pulp.
Source: Briggs, 1994.

39

m3sw/mt
m3sw/mt
m3sw/mt
m3sw/mt
m3sw/mt
m3sw/mt
m3sw/mt
m3sw/mt
m3sw/mt

Uncoated mechanical

Coated paper

Sanitary and household paper

Packaging materials

Case materials

Folding boxboards

Wrapping paper

Other paper mainly for packaging

Other paper and paperboard

39

Japan

Indonesia

China
425
450
450
450
420
450
440
5.75

3.50

35

425

425

2.78 2.78

438

520

500
449

500

483

415
450
415

5.75 5.75

415

4.50 4.50

450

4.80 4.80

67405

4.70 4.70

4.20 4.20

3.50 3.50

3.00 3.00 2.80

3.50 3.50

78

3.35 3.35

3.53 3.53

3.53 3.53

3.90 3.90

89

500

512

512

2.80 2.80 2.50

1.20 1.20 1.20

405

405

524

415

477

3.80 4.00

Source: FAO/ITTO/UNECE Forest product conversion factors questionnaire, 2018.

500

5.31 5.31

450

3.38 3.38

3.00 3.70

500

4.63 4.63 5.31

1.30 1.25 1.26

530

3.85 3.85

3.30 3.75

405

4.19 4.45 4.58 4.32 4.50 3.43 4.32 4.08

530

3.50 4.20
3.30 3.75

405

4.19 4.19 4.36 4.26 4.00 3.43 4.00 3.90 5.22

Malaysia

North America

405

Chile

2.72 2.72 2.39

Mexico438

3.43 3.43 3.43

Average

2.50 2.50 2.72

3.80 3.70

Average3.50 3.25

4.90 4.50

4.50 3.90

3.50 3.50

3.20 2.80

78

1.22 1.25

390

4.40 4.60

450

5.00 4.60

410

4.80 4.45

450

5.10 4.45

520

4.90 4.00

400

2.80 2.75

450

2.50 2.50

3.80 4.00 3.30

MedianNotes: m3sw = cubic metre solid wood; mt = tonne (in this case assumed air-dry – 10% moisture, wet basis).

m3sw/mt

m3sw/mt

Paper and paperboard

Newsprint

odmt/mtDry-solid organic black liquor / tonne chemical
woodpulp%

Share of recycled fibre in total pulp

600

kg/m3
mt/mt

Basic density of wood input

6.54

450

4.27

550

450

2.55

South
Africam3sw/mtkg/m3

m3sw/mtkg/m3

m3sw/mtkg/m3

m3sw/mtkg/m3

m3sw/mtkg/m3

m3sw/mtkg/m3

m3sw/mt

Recovered paper (input to output)

Dissolving grades

Basic density of wood input

Sulfite unbleached

Basic density of wood input

Sulfite bleached

Basic density of wood input

Sulfate unbleached

Basic density of wood input

Sulfate bleached

Basic density of wood input

ChemicalBasic density of wood input

Semi-chemical

kg/m3

m3sw/mt

Mechanical

Basic density of wood input

m3sw/mt

Wood pulp

Unit in/unit out

UruguayLatin America
MedianAsia
Canada

40
38

2.50

38

503 5033.35 4.29

466 466

2.51 2.45

UnitedStates ofAmericaMedian/Average

Oceania

3.93

2.54

3.66

3.66

2.00

7.2.1

New
ZealandAfricaForest product conversion factors

7.2 Summary of country data on wood pulp and paper
Africa, Asia, Latin America, North America and Oceania

kg/m3Austria
445
445

5.01

m3sw/mt
m3sw/mt

Other paper mainly for packaging

Other paper and paperboard

4.15

2.49

421

440
450

4.85

420

57

410

4.88

410

5.08

3.70

4.00

4.10

4.00

4.20

4.90

4.30

4.40 3.40

3.50 3.18

3.20

5

1.30

Germany
2.70

3.25

3.25

3.25

3.50

3.50

2.80

3.70

4.00

4.10

3.25

3.25

3.25

4.00 3.25

4.20

4.90

4.40

3.50

3.20

84

1.20

5.10

4.90 4.70

420

2.98

Source: FAO/ITTO/UNECE Forest product conversion factors questionnaire, 2018.

PolandNorway
2.50

2.60

2.70

400

4.75

400

5.10

400

390

500

3.40

3.76

575

4.00

575

4.30

560

4.30

640

4.90

635

4.10

600

3.00

580

2.88

3.86

Slovakia
4.50

3.00

2.50
405

2.60

2.60

Slovenia

46

4.10

45

3.30

3.30

4.40

4.30

4.00

4.30

4.20

4.00

4.00

3.15

4.15

34

3.60

24

62

1.10 1.19 1.10 1.30 1.20

470

4.70

530

500

5.20

2.48 2.50 2.60 2.70

Netherlands

Notes: m3sw = cubic metre roundwood; mt = tonne (in this case assumed air-dry – 10% moisture, wet basis).

m3sw/mt
m3sw/mt

Folding boxboards

Wrapping paper

m3sw/mt
m3sw/mt

Packaging materials

m3sw/mt

Sanitary and household paper

Case materials

m3sw/mt
m3sw/mt

Uncoated mechanical

Coated paper

m3sw/mt

Newsprint%
m3sw/mt

Paper and paperboard

Share of recycled fibre in total pulp

445

kg/m3
mt/mt

Basic density of wood input

Finland
2.48 2.52

France4.10 3.80 4.76

445

4.75

6.27

4.06

Czechiam3sw/mtkg/m3

m3sw/mtkg/m3

m3sw/mtkg/m3

m3sw/mtkg/m3

m3sw/mtkg/m3

m3sw/mtkg/m3

m3sw/mt

Recovered paper (input to output)

Dissolving grades

Basic density of wood input

Sulfite unbleached

Basic density of wood input

Sulfite bleached

Basic density of wood input

Sulfate unbleached

Basic density of wood input

Sulfate bleached

Basic density of wood input

ChemicalBasic density of wood input

Semi-chemical

Basic density of wood input

m3sw/mt
m3sw/mt

Wood pulp

Mechanical

Unit in/unit out

Portugal

Spain
69

1.15

553

2.98

Sweden3.70

Median3.76 3.60

Average

UnitedKingdom

6.20

4.40

4.70

4.50

4.80

2.30

449
510
495
503
456
475
493
445

2.50 3.30 3.29

3.65 3.64

4.10 3.96

4.00 3.89

4.10 3.91

3.78 3.78

4.30 4.31

3.75 3.70

3.50 3.50 3.40

2.80 2.98 2.98

4.10 3.95

46% 47%1.20 1.19

445

6.20 5.86

493

4.40 4.43

458

5.00 4.85 4.80

433

4.40 4.37

490

4.50 4.75 4.50

500

4.70 4.46

510

2.75 2.75 2.75

413

2.40 2.50 2.50 2.56

7.2.2

RussianFederation

Europe

7. WOOD PULP AND PAPER

Europe41

8
CHAPTER©iStock

8. Round and split wood
products
For the purposes of this publication, this category of forest
products includes barrel staves, utility poles, posts, pilings,
house logs (manufactured roundwood for constructing
log buildings) and shakes and shingles. Shingles are sawn
rather than split, but they are included in this grouping
because they are generally manufactured along withshakes, which are split. Similar to this, barrel staves areboth split and sawn, depending on the characteristics of
the wood species used.

Shakes and shingles are generally used for roofing andsiding. Shakes are split on one or both faces and shingles
are always sawn, thus losing a substantial volume tosawdust. Weatherization is an important factor, andquality standards tend to be exacting in terms of knots
and other permeations that could allow water seepage. A
substantial percentage of the original log volume is often
unusable, therefore, and ends up as residue.

These are relatively minor products in terms of volume,and information on them is limited. When no country data
were reported (as was the case for shakes and shingles),information from previously published sources is provided.

8.1 Volumetric and surface measurement

This category of products is not as technology-driven as
many other forest products; thus, this aspect does notappear to be a strong contributor to product recovery.
Some of the significant determinants of product recovery
are listed below, by product.
The yield of barrel staves (tapered wooden slats used in thecooperage industry) is determined, to a great degree, by
the production process. Some species used for wine barrels(notably European oak species and Oregon white oak) need
to be split to prevent the staves from being overly porous(caused by vessels that run parallel to the grain of the wood);on the other hand, white oak sourced from central andeastern North America does not have the same problem
with porosity and can be sawn. The yield of sawn staves issignificantly higher than that of split staves. Staves generally
have exacting standards in terms of quality, reducing theyield according to the presence of knots and blemishes in
the raw material used to produce them.

It is usually straightforward to convert from piece tovolume for staves, poles, posts, pilings and house logs,
which tend to be manufactured to exacting specifications.
This is not the case for shakes and shingles, however, which
are typically measured on the basis of surface coverage. In
North America, the unit is the “square”, which is the quantityof shakes or shingles to cover 100 square feet (10.76 m2). In
Europe, the unit is square metres of coverage. Converting
shakes and shingles from a surface (coverage) measure toa solid wood equivalent volume is not as straightforward
because there are many combinations of thickness, taper,©Shutterstock

The yield for utility poles, posts, pilings and house logs
is affected by peeling performed to remove bumps
and protrusions and to round the profile. In addition,a portion of these products is peeled to remove taper,
thereby creating a loss of 10–40 percent, depending on
the diameter and length of the product, with smallerdiameter, longer products at the upper end of this range
and larger-diameter, shorter products at the bottom.

43

Forest product conversion factors

TABLE 8.1

SHAKES AND SHINGLES PRODUCEDFROM A CUBIC METRE OF WESTERN RED
CEDAR LOGS (squares/m3 log volume)

Log quality

ShinglesShakesLow-grade logs

1.55 squares(14.4 m2 coverage)

N/A

Medium-grade logs

1.65 squares(15.3 m2 coverage)

N/A

High-grade logs

1.70 squares(15.8 m2 coverage)

1.9 squares(17.7 m2 coverage)

Source: Herring and Massie, 1989.

portions or overly large knots, the removal of such defects
from the logs used as raw material reduces the yield of
these products and increase the yield of secondary
products such as chips and energy wood.
Shakes and shingles. Hartman et al. (1981) listed thematerial balance for shingles at roughly 40 percent
shingles, 27 percent solid residue and 33 percent sawdust.
Briggs (1994) cited an unpublished study showing a
recovery of only 24 percent for shingles and 53 percent
for shakes, with the remaining balance of both (76 percent
and 47 percent, respectively) classified as residue. It is likelythat the large differences in these material balances could
be due to the use of high-grade versus lower-grade logs
as a raw material, which may change over time due (forexample) to competition from sawmills.

width, length and overlap, by product classification.
Additionally, shake thickness is irregular because of the
splitting process. Recovery of shakes and shingles per m3
log appear to range from about 14.4 m2 to about 17.7 m2(1.55 squares to 1.9 squares) (table 8.1).

8.2 Weight
Like all other wood products, the weight-to-volume
ratio is driven by the basic density, moisture content
and shrinkage of the wood. The methodology outlined
in section 4.2 can be used to calculate the theoreticalweights of round and split wood products. It is important
to consider, however, that many of these products are
chemically treated to prevent fungal decay and attacks bywood-boring insects and molluscs, and wood treatment
will add roughly 160 kg per m3 to poles and pilings(Hartman et al., 1981). Thus, if the untreated weight of awood component is 600 kg per m3, the same component,
treated, would weigh about 760 kg per m3. Shakes andshingles are also often treated (to minimize decay andretard fire).

8.3 Material balance

Utility poles, posts, pilings and house logs. Because
these products generally cannot have any decay, crooked

44©Shutterstock

Barrel staves. The manufacture of staves can produce
residual products such as chips, sawdust, shavings andsawnwood. Some wood residue from stave production
finds its way into the wine industry in the form of chips or
sticks used to flavour wine in non-oak (e.g. stainless steel)barrels.

8. ROUND AND SPLIT WOOD PRODUCTS

8.4 Summary of country data on round and split wood products
Africa, Asia, Latin America, North America and Oceania

1.55

m3rw/m3p

1.65

1.50

1.58

m3rw/m3p

1.65

Pilings (round)House logs (round)

1.7

1.00

1.00

1.1

1.40

Median/average

1.25

1.50

1.2

UnitedStates ofAmerica

1.30

1.6

1.74

m3rw/m3p

North America
Canada1.2

1.2

m3rw/m3p

Posts (round)Median/Average

Median/Average

1.55

Utility poles (round)

Uruguay

Indonesia

1.35

Unit in/unit out

Nigeria

China

Latin America

Median/Average

Asia

South
AfricaAfricaGuyana

8.4.1

1.65

Barrel staves
Wood shingles

m3rw/m2p

0.0654 0.0654 0.0654

Wood shakes

m3rw/m2p

0.0565 0.0565 0.0565

Notes: m3rw = cubic metre roundwood; m3p = cubic metre product; m2p = square metre product.
Source: FAO/ITTO/UNECE Forest product conversion factors questionnaire, 2018.

8.4.2

EuropeSlovenia

MedianAverage

1.30

1.12

1.20

1.10

1.15

1.18

1.67

1.15

1.17

1.23

m3rw/m3p

1.50

1.11

1.20

1.15

1.50

1.18

1.67

1.20

1.33

Pilings (round)m3rw/m3p

1.50

1.11

1.20

1.75

1.35

1.39

House logs (round)m3rw/m3p

1.70

1.67

1.67

3.58

3.60

0.025

0.025

Barrel staves

1.67
4.25

Wood shingles

m3rw/m2p

Wood shakes

m3rw/m2p

Spain

Slovakia

m3rw/m3p

Posts (round)

NorwayPolandLithuania

FranceUtility poles (round)

Ireland

Unit in/unit out

FinlandGermany

Europe

1.65

5.0

2.25

2.90
0.025

Notes: m3rw = cubic metre roundwood; m3p = cubic metre product; m2p = square metre product.
Source: FAO/ITTO/UNECE Forest product conversion factors questionnaire, 2018.

45

CHAPTER

9©Shutterstock9. Energy wood products
and properties
This category includes fuelwood, bark and chipped
fuel, as well as manufactured products such as pellets,
briquettes, charcoal and wood-based ethanol. Chapters
1 and 2 include information applicable to the analysis ofconversion factors for fuelwood, wood residue and barkfor energy.
The questionnaire did not include a category forconversion factors related to black liquor, a coproductproduced in the chemical pulping process (e.g. for paper
and paperboard production). However, several sourcesindicate that 1.5 tonnes of black liquor solids (about
10 tonnes of weak black liquor) is produced for every 1 airdried tonne of kraft pulp, which accounts for about twothirds of the global virgin pulp production and 90 percentof the chemical pulp production (Tran and Vakkilainnen,
2008; Clay, 2008). The higher heating value of black liquor
solids is about 14 GJ/tonne.

9.3 Energy values
The energy content of wood can be reflected in various
measures, with assumptions made on the proportionof the energy content that realistically can be used (noprocess of using wood for energy is 100 percent efficient).
The measurement unit specified in the conversion factors
questionnaire was the joule, and energy values wererequested in “higher heating values”. Although such values
are unachievable, they provide a consistent basis on whichusers can apply their own assumptions on conversion
efficiency.

9.1 Volumetric measurement
Energy wood products can be measured in solid m3 orloose m3 (bulk m3). In the case of fuelwood, loose m3 is often
differentiated from stacked m3, with loose m3 applicable torandomly placed wood and stacked to structures that fit
neatly together. Section 1.1.3 outlines the measurementof stacked wood.

9.2 Weight
When moisture content is accounted for, the weight ofenergy products is likely to be the most reliable unit forunderstanding the energy-generating potential of a given
quantity of wood. Moisture not only displaces the potential
weight of combustible material but also consumes someof the energy because it is vaporized when the wood is
combusted.
©FAO

47

Share (%)

kg/m3
m3rw/odmt

Wood-based ethanol

1.45

2.30

0.08

660

7.30

6.00

0.09

360

0.09

0.08

710

1 100 1 050

1.50

Indonesia
2.50

Japan
7.40

5.00

200

2.25

600

2.25

Average
2.25
1.48

2.25
1.48

200
0.09
6.13
7.30

0.09
6.00
7.30

360
200

360

0.09

2.25

2.25

0.09

657
0.08

660
0.08

1 075 1 075

2.50

2.50

800
520

6.00

650

1.53

620

1.61
650

1.54

99

550

6.00

650

1.53

620

1.58

6.00

650

1.53

597

1.58

65

478

65

2.14

480

Average

2.14

6.80

0.08

689

1.44

2.09

North
America
UnitedStates ofAmerica

Source: FAO/ITTO/UNECE Forest product conversion factors questionnaire, 2018.

Notes: The ratios shown for wood pellets assumes only the wood fibre input into the manufacture of pellets and does not include any wood fibre that may have been burned by heat dryers
to remove moisture from the wood fibre. Note that, as for all ratios involving roundwood, volume is measured underbark.

m3rw/tonne
m3rw/kilolitre

Charcoal (average 3–4% mcd)

m3 rw/GJ

kg/m3

Bulk density (loose volume at 50% mcw)

Higher heating value

kg/m3

Product basic density (solid volume, oven dry)

Bark and chipped fuelm3bulk/GJ

kg/m3

Higher heating value

kg/m3

Bulk density (loose volume)

m3sw/mt p (5–10% mcw)

Product basic density (solid volume, oven dry)

Solid wood input to tonne productPressed logs and briquettes

m3bulk/Gj

Bulk density (loose volume, 5–10% mcw)

Higher heating value (bulk volume)

kg/m3

Product basic density (solid volume, oven dry)

China
2.20

Median
800

88

65

405

1
1.81

Asia, Latin America and North America

m3sw/m3p bulk

m3sw/mt p (5–10% mcw)

m3sw/m3p solid

Malaysia
800

Brazil
480

12
2.47

9.4.1

Solid wood input to bulk m3 pellets

Solid wood m3 per tonne pellets

Pellets%m3 rw/GJ

Higher heating value

Solid wood volume/stacked volume

kg/solid m3

m3rw/tonne

Share (%)%

m3 rw/GJkg/ solid m3

m3rw/tonne

Wood basic density (dry weight/green m3)(typical shipping weight)

Non-conifer

Solid wood volume / stacked volume

Higher heating value

Wood basic density (dry weight/green m3)(typical shipping weight)

Conifer

Fuelwood

Unit in/unit out

Chile

Latin America

Uruguay48
MedianAsia

Forest product conversion factors

9.4 Summary of country data on energy wood products and properties564

kg/ solid m3

236
0.12

kg/m3
5.70

393

kg/m3

m3 rw/GJ
m3rw/tonne
m3rw/kilolitre

0.06

761
0.07

kg/m3
m3bulk/GJ
465

1 000

2.38

m3rw/odmt
m3sw/mt p(5–10% mcw)

0.060

1 100

2.00

0.105

482

Czechia

kg/m3

0.083

m3bulk/GJ

kg/m3

652

1.44

m3sw/m3p bulk

kg/m3

2.21 1.82

m3sw/m3p solid
m3sw/mt p(5–10% mcw)

%

69%

96%
1.00

Share (%)
m3rw/tonne

m3 rw/GJ69%(%)

m3 rw/GJ

382

kg/ solid m3

Austria4%

Croatia

Share (%)
m3rw/tonne

Unit in/unit out

Denmark
560

33%

65%

390

67%

Germany

France389

Finland

563

650

650

300

400

0.13
6.10 7.00 5.00
8.62

400

900
0.09 0.13

1 080 1 000 1 200

2.00 1.96

2.38

Lithuania

920 1 067

2.16

2.20 2.30

Ireland0.13

950 1 075

2.20 2.32

0.090 0.070 0.090 0.130650

1 080 1 200 1 120

1.51 1.79 1.50

2.32 2.39 2.29

2.86 2.86

0.1

550

90% 60%
1.50

71%

0.13

407

10% 40%2.05

5.50

PolandNorway
65%

0.12

380

443

584
65%

0.08

580

85%
1.40

65%

0.11

400

1.34

2.10

2.23 2.20

Slovakia

300

1 200

600

640

0.05

280

450

1 120 1 100 1 100

2.20

0.080 0.080 0.070

670

0.13
0.08 0.10
6.00 6.40 5.70

315

380

1.54

650

Slovenia
15%
2.00

Spain

1 120 1 070 1 100 1 010

2.27 2.00

65%

0.1

500

85% 96% 49%
1.06 1.11

400

15% 4% 51%
1.28 1.25

Sweden350

49

Source: FAO/ITTO/UNECE Forest product conversion factors questionnaire, 2018.

UnitedKingdom
677

0.13

462

410
0.12

0.12

557
0.09

563
0.10

2.19
1.52

2.24
1.51

650

649

1 100 1 081

2.38

2.23

65% 66%

1.21

1.11

65% 67%

1.65

400Median
1.64

Average

6.00

192

152

1.83

1.96

373
265
0.12
5.93
8.62

397
280
0.11
6.00
8.62

900 9540.080 0.088

1 080 1 069

2.30

2.32

0.082 0.080 0.080 0.083

650

1 100

1.53

2.36

UkraineNotes: The ratios shown for wood pellets assumes only the wood fibre input into the manufacture of pellets and does not include any wood fibre that may have been
burned by heat dryers to remove moisture from the wood fibre. Note that, as for all ratios involving roundwood, volume is measured underbark.

Higher heating value (bulkvolume)Pressed logs and briquettes
Solid wood input to tonne
product
Product basic density (solid
volume, oven dry)
Bulk density (loose volume)
Higher heating value
Bark and chipped fuelProduct basic density (solid
volume, oven dry)
Bulk density (loose volume at
50% mcw)
Higher heating value
Charcoal (average 3-4% mcd)
Wood-based ethanol

Fuelwood
Conifer(typical shipping weight)
Wood basic density (dryweight/green m3)
Higher heating value
Solid wood volume / stacked
volumeNon-conifer(typical shipping weight)
Wood basic density (dryweight/green m3)
Higher heating value
Solid wood volume / stacked
volumePellets
Solid wood m3 per tonnepellets
Solid wood input to bulk m3
pellets
Product basic density (solid
volume, oven dry)
Bulk density (loose volume,
5–10% mcw)

Moldova

9.4.2

Netherlands

Europe9. ENERGY WOOD PRODUCTS AND PROPERTIES

Europe©iStockReferences
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52

REFERENCES©iStock

53

©UNECEAnnexANNEX TABLE 1

LIST OF EQUIVALENTS

To convert fromTo

Multiply bycentimetre
inch
foot
metre
millimetre
inch
foot
metre
millimetre
centimetre
foot
metre
millimetre
centimetre
inch
metre
millimetre
centimetre
inch
foot

0.1
0.03940.00328
0.001
10
0.394
0.0328
0.01
25.4
2.54
0.08330.0254
304.8
30.48
12
0.3048
1,000
100
39.37
3.281

square inchsquare footsquare metre
square centimetre
square footsquare metre
square centimetre
square inchsquare metre
square centimetre
square inchsquare foot0.155
0.001076
0.0001
6.452
0.0069444
0.0006452
929
144
0.092910 000
1 550
10 764

basic density
specific gravity

1 000
0.001

stere
cord
stere
cord
cubic footcubic metrestere
cubic footcubic metre
cord

0.02832
0.0078125
10.2759128
3.62453.624535.31510.2759Lengthmillimetre
millimetre
millimetre
millimetre
centimetre
centimetre
centimetre
centimetre
inch
inch
inch
inch
foot
foot
foot
foot
metre
metre
metre
metre

Densityspecific gravity
basic density

Stacked measure
cubic footcubic footcubic metre
cubic metre
cord
cord
cord
stere
stere
stere

To

Multiply bypound
kilogramgram
kilogram
ton
tonne
gram
poundstontonnekilogram
pound
tonne
poundskilogramton

0.002205
0.001
454
0.454
0.00050.0004541000
2.205
0.0011023
0.001
907
2000
1.1023
2 205
1 000
0.907

square metre (1 mm basis)
cubic footcubic metre
cunit
square foot (3/8 inch basis)
cubic footcubic metre
cunit
square foot 3/8
square metre (1 mm basis)
cubic metre
cunit
square foot (3/8 inch basis)square metre (1 mm basis)
cubic footcunit
square foot (3/8 inch basis)square metre (1 mm basis)
cubic footcubic metre

0.885
0.031250.000885
0.0003125
1.13008
0.353150.001
0.00035315
32
28.32
0.028320.01
1 130.08
1 000
35.315
2.832
3 200
2 832
100
2.832

joule
British thermal unit

1 055
0.0009479

kg per cubic metre
pounds per cubic foot16.0190.06243

WeightAreasquare centimetre
square centimetre
square centimetre
square inchsquare inchsquare inchsquare footsquare footsquare footsquare metre
square metre
square metre

To convert from
gram
gram
poundspoundspoundspoundskilogramkilogramkilogramkilogram
ton
ton
ton
tonne
tonne
tonne

Volumesquare foot (3/8 inch basis)square foot (3/8 inch basis)square foot (3/8 inch basis)square foot (3/8 inch basis)square metre (1 mm basis)square metre (1 mm basis)square metre (1 mm basis)square metre (1 mm basis)
cubic footcubic footcubic footcubic footcubic metre
cubic metre
cubic metre
cubic metre
cunit
cunit
cunit
cunit

Heat
British thermal unit
joule

Weight to volume ratios
pounds per cubic footkg per cubic metre

Source: Fonseca, 2005.

55

Forest product conversion factors

EXAMPLE OF WOOD BALANCE USING CONVERSION FACTORSANNEX FIGURE 1

Conversion Factors

Products in unitof output

Forest Products (1 000 m3 swe)
1 593 Roundwood needed(1 000 m3)

Material Primarybalance product

Chips

Sawdust,shavings,
sanding
dust
Losses

Bark*

Total
Product
swe m3/
excluding product
unit
bark
unit
Quantity (1 000)

Sawnmilling Sector
Roundwood in

1,000

Sawnwood
Shrinkage
Chips
Sanding and sawdust
Loss
Recoverable bark

50%
3%
33%
10%
4%
7%

} 530

53%
4%
37%
3%
3%
7%

} 113

60%
69%
1%
0.3%
7%

} 39.4

95%
5%
7%

720

67%
33%

} 106.5

100%

116

330

100

40

73

1.06

500

m3

2.4
2.4

138
42

odmt
odmt

2.6

28

odmt

1.08

105

m3

2.4
2.4

31.1
2.5

odmt
odmt

2.6

5.6

odmt

1.64

24

m3

2.4

0.2

odmt

2.6

1.1

odmt

2.4

300

m3

2.6

9.9

odmt

106.5

1.5

71

m3

116

0.1824

636

gj

1000

Plywood/Veneer Mill
Roundwood in200

Plywood and veneer
Shrinkage
Chips
Sanding and sawdust
Loss
Recoverable bark

75

6

6

15

200

OSB MillRoundwood in

40

PanelsShrinkage (densification)
Sanding and sawdust
Loss
Recoverable bark

0.5

0.1

3

40

Pulp and paper Mill
Roundwood in
Chips in
Pulp and paper
Loss
Recoverable bark

353
405

38

26

758

Particle board Mill
Sawdust in

106

Particle board
Shrinkage (densification)

Biomass power plant*
Bark in

116

Power out

1 509 m3
Wood
products

Energyout

84 m3

Losses

Notes: odmt = oven-dry tonne; swe = solid wood equivalent. Conversion factors are used in outlook studies to predict the amount of raw material needed fromthe forest to supply a given quantity of manufactured forest products and vice-versa. A wood balance can check the accuracy of conversion factors and assist in
predicting the flow and availability of wood residues. This figure is an example of a simple wood balance using conversion factors and could represent a nationalor subregional balance. In the example, 500 000 m3 of sawnwood is predicted to be produced from 1 000 000 m3 of roundwood using the 2.0 input/output
factor, which is represented in the reciprocal format of 50%. One might assume that 500 000 m3 of sawnwood would have the same solid wood equivalent
volume but this is not the case because wood products (including sawnwood) are often more or less dense than the parent wood used as the raw material. The
500 000 m3 of dried sawnwood was 530 000 m3 in the green state (prior to shrinkage), so a 1.06 factor is used to determine swe. Note that the total productionof wood products in swe plus the losses (1 593 000 m3) balances with the roundwood consumed (excluding bark volume and wood energy produced).
* The biomass power plant in this example is assumed to be operated entirely from bark volume, which is excluded from the balance.
Source: UNECE/FAO, 2010a.

56

Forest product conversion factors provides, for 37 countries
around the world, ratios of raw-material input to output for eightcategories of wood-based forest products. Analysts, policymakers,
forest practitioners and forest-based manufacturers often needthese conversion factors to understand sectoral drivers of efficiency,
feasibility and economics. In addition, such factors are used forconversions from one unit of measure to another. The publication
includes explanations of the units of measure and determinants of
the ratios, as well as information on some of the physical properties
of wood-based forest products. Finally, where reported factors areunavailable, factors from other sources are given.

ISBN 978-92-5-132247-5

9789251322475
CA7952EN/1/03.20