United States

Department of

Agriculture

Forest Service

Pacific Northwest

Research Station

General Technical

Report

PNW-GTR-810

April 2010

Fuelwood Characteristics

of Northwestern Conifers

and Hardwoods (Updated)

Pamela L. Wilson, James W. Funck, and Robert B. Avery
The Forest Service of the U.S. Department of Agriculture is dedicated to the

principle of multiple use management of the Nation’s forest resources for sustained yields of wood, water, forage, wildlife, and recreation. Through forestry

research, cooperation with the States and private forest owners, and management of the national forests and national grasslands, it strives—as directed by

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Authors

Pamela L. Wilson and Robert B. Avery were research assistants, and James W.

Funck was an associate professor, Department of Forest Products, Oregon State

University, Corvallis, OR 97331.

Editors

Daniel J. Parrent is a wood utilization specialist, Juneau Economic Development

Council, 204 Siginaka Way, Sitka, AK 99835; James W. Funck is a manager,

Weyerhaeuser Company, P.O. Box 9777, Federal Way, WA 98063; James Reeb is

an associate professor, Forestry and Natural Resources, Oregon State University

Lincoln County Extension, Newport, OR 97365; and Allen M. Brackley is a

research forester, U.S. Department of Agriculture, Forest Service, Alaska Wood

Utilization Research and Development Center, 204 Siginaka Way, Sitka, AK 99835.

Research and publishing were accomplished under agreements PNW-07-JV11261935-040, PNW-07-JV-1126935-041, and Cooperative State Research, Education, and Extension Service grant (WUR Year 08).
Fuelwood Characteristics of Northwestern

Conifers and Hardwoods (Updated)

Pamela L. Wilson, James W. Funck, and Robert B. Avery

Updated, Reformatted, and Edited by:

Daniel J. Parrent, James W. Funck, James Reeb, and Allen M. Brackley

U.S. Department of Agriculture, Forest Service

Pacific Northwest Research Station

Portland, Oregon

General Technical Report PNW-GTR-810

April 2010

Published in cooperation with:

Oregon State University
Abstract

Wilson, Pamela L.; Funck, James W.; Avery, Robert B. 2010. Fuelwood

characteristics of northwestern conifers and hardwoods. Updated by Parrent,

Daniel J.; Funck, James W.; Reeb, James; Brackley, Allen M., eds. Gen. Tech.

Rep. PNW-GTR-810. Portland, OR: U.S. Department of Agriculture, Forest

Service, Pacific Northwest Research Station. 50 p. (First published 1987, Res.

Bull. 60, Forest Research Laboratory, College of Forestry, Oregon State University, Corvallis, OR).

This report is an update of the original publication by Oregon State University in

1987 (Resource Bulletin 60). According to agreements, researchers at the U.S.

Department of Agriculture, Forest Service, Pacific Northwest Research Station and

the Juneau Economic Development Council worked with Oregon State University to

update this reference concerning wood energy properties. The fuelwood characteristics were reformatted and presented in tabular form, and a literature review was

conducted to check for additional information published since 1987. This report

provides fuelwood values for 34 conifer and 20 hardwood species found in the

Pacific Northwest and Alaska. Values are presented for the following characteristics:

specific gravity of wood and bark, percentage moisture content of wood and bark,

higher heating value of wood and bark, percentage ash of wood and bark, percentage bark by volume, and ultimate analysis of wood and bark (percentage of carbon,

hydrogen, oxygen, nitrogen, and sulfur).

Keywords: Fuelwoods, heating value, British thermal unit values, Pacific

Northwest.

Preface

British thermal unit (Btu) is a standard measure of energy used in the United States

to evaluate the potential of fuel. As personnel from the U.S. Department of Agriculture, Forest Service, Alaska Wood Utilization Research and Development Center

(WUC) and Juneau Economic Development Council (JEDC) worked on projects to

review renewable energy use, there was a constant need for this information. In the

search to locate sources that provided Btu values for Pacific Northwest species, the

researchers found references to Oregon State University (OSU), College of Forestry, Research Bulletin 60, published in September 1987.
It rapidly became a standard reference used by Daniel Parrent of JEDC and

Allen Brackley of WUC for research projects concerned with wood energy use and

systems. Both users recognized that although the existing publication was comprehensive and the best source that either had located, it was difficult to use. Parrent

took it upon himself to reformat the information into tables that allowed easier

access to the data. Almost simultaneously, Brackley contacted Jim Funck at OSU

and suggested that the publication contained very timely and valuable information

and, therefore, should be reprinted and made more generally available to anyone

working with wood energy systems. Funck and James Reeb at OSU conducted a

literature review to check for any additional information published since 1987, and

worked with Parrent and Brackley to publish the updated tables.

The original version of the OSU report contained fuelwood values for species in

the Pacific Northwest. This report adds black spruce (Picea mariana [Mill.] Britton,

Sterns & Poggenb.), a species in the boreal forest of northern Alaska. Some of the

information for black spruce resulted from research at the University of Alaska

Fairbanks, Agriculture and Forestry Experiment Station.

It was agreed that the reprint would publish the text in the original form, taking

into consideration any new reference material and presenting fuelwood characteristics in tabular form. The original authors (Pamela L. Wilson, James W. Funck, and

Robert B. Avery) would be credited as authors of the updated version. The work of

the above-mentioned individuals would be recognized by adding their names to the

formal title page and citation for the updated version of Fuelwood Characteristics of

Northwestern Conifers and Hardwoods (originally published by the Forest Research

Laboratory, Oregon State University as Research Bulletin 60 in September 1987).

In response to peer reviews, moisture and ash contents on wet basis were added

along with tables in the International System of units (metric).

Updated, reformatted, and edited by:

Daniel J. Parrent

James W. Funck

James Reeb

Allen M. Brackley
Contents

1 Introduction

5 Conifers

25 Hardwoods

36 Acknowledgments

36 Metric Equivalents

37 Literature Cited

47 Appendix
1

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Introduction

This report is intended to provide a convenient summary of fuelwood values for

tree species of the Pacific Northwest. It collates the published values and gives

accurate ranges by species for each fuelwood characteristic.

Species selected are those that were inventoried by the Pacific Northwest Forest and Range Experiment Station for Washington, Oregon, Idaho, and northern

California. We included only species that appear in the inventory for which fuelwood information was found in the literature. Thirty-three conifer and 20 hardwood species appeared in the original report. An additional conifer, black spruce

(Picea mariana [Mill.] B.S.P.), was added to this updated version. In the original

work, scientific names were verified using Little (1979) if the scientific name in

the original reference differed from current usage at that time. If the scientific

name could not be verified as either a current or a former name, the reference was

not included. This update included checking the species list with the names found

in the U.S. Department of Agriculture’s PLANTS Database (USDA NRCS 2009).

Current synonyms were added to the list for some species, and common names

were also updated.

The following fuelwood characteristics are included in this report:

• Specific gravity of wood and bark

• Percentage moisture content of wood and bark

• Higher heating value of wood and bark

• Percentage ash of wood and bark

• Percentage bark by volume

• Ultimate analysis of wood and bark:

– Percentage carbon

– Percentage hydrogen

– Percentage oxygen

– Percentage nitrogen

– Percentage sulfur

The range of values found for each category is given, as well as any finer

breakdown supplied in the published reports. For example, for some species,

the moisture content is given for heartwood and sapwood or for inner and outer

bark. Not all categories appear for all species, as pertinent values often were not

available.

We used original sources whenever possible. Literature reviews are cited only

when values given differ from any other published values and the original source is
2

GENERAL TECHNICAL REPORT PNW-GTR-810

not easily available. We made no attempt to go back to the original references from

Isenberg (1980, 1981). The values we list are as published; they were not necessarily determined according to accepted procedures, and the original authors did not

convert units.1

Hale (1933) listed the gross calorific value of wood in British thermal units

(Btu) per air-dry (AD) cord. The wood was burned in a coal-fired, domestic hotwater heater. In calculating the heating values, we assumed that one cord of split

wood cut into 1-ft lengths contained 90 ft3 of solid material and that the moisture

content of the split wood was 20 percent on a total-weight (TW) basis (green

weight basis). Weights per cubic foot of different species of wood were taken

from the records of the Forest Products Laboratories of Canada (Smith 1970).

Other references give heating values in Btu per AD pound, Btu per oven-dry

(OD) pound, or kilocalorie (kcal) per kilogram. If heating values originally were

given in both Btus and other units, we list only the Btu heating value.

The values provided by Sargent (1885) were listed in this publication for

percentage of ash from wood, but his specific gravity values were listed only when

no other information was available. Sargent’s values for specific gravity were

determined on an OD-volume basis, whereas this paper generally reports specific

gravity on a green-volume basis.

Specific gravity of wood and bark can be determined on the basis of green,

AD, or OD volume. The calculation for specific gravity is shown in equation 1.

Specific Weight (green, AD, or OD)

gravity = (1)

Weight of displaced water at 4 °C

In green wood or bark, the cell walls are saturated, giving the largest possible

volume, the largest water displacement, and therefore, the lowest specific gravity.

Determination of specific gravity with OD volume results in the least displacement

of water and gives the highest specific gravity. The density of OD wood in pounds

per cubic feet can be estimated by multiplying the specific gravity by the weight of

1 ft3 of water at 4 °C (62.4 lb/ft3

). The higher the density (or specific gravity), the

more Btus per cubic foot of wood are available for combustion.

The moisture content of wood and bark is very important to combustion.

Moisture reduces both heating value and furnace efficiency. Maintaining combustion at moisture contents over 60 percent (TW basis) is very difficult, if not

1

 Metric conversion factors are provided at the end of the report. In this update, English

measurements have been converted to metric units, and these are shown in the tables.
3

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

impossible (Karchesy and Koch 1979). Combustion can be divided into three

processes: (1) moisture is evaporated, requiring approximately 1,100 Btu per pound

of water, (2) the fuel temperature rises until the volatiles are driven off and burned,

(3) the remaining carbon is burned (Karchesy and Koch 1979). Thus, much available heat is used to evaporate the moisture in the fuel. The minimum amount of air

needed for combustion (the theoretical air) does not depend on the moisture content

and can be calculated from the ultimate analysis (percentage of carbon, hydrogen,

oxygen, nitrogen, and sulfur); Karchesy and Koch (1979) provided a good description of this calculation.

In the forest industry, moisture content is generally given on the OD basis,

whereas combustion engineers generally use the wet basis. In the original report,

moisture contents were given on an OD basis. Methods for calculating the moisture content and for converting between the two bases are shown in equations (2)

through (5) (table 1). This update provides these converted moisture contents on a

wet basis in the tables. Additional details on these conversions can be found in the

appendix.

The higher heating value (HHV) of wood and bark (the maximum energy that

can be produced) is determined with an oxygen bomb calorimeter and is calculated

at zero percent moisture content. Any moisture in the wood or bark reduces that

maximum value proportionately. If the moisture content on a wet basis is known,

the heating value at that moisture content can be calculated according to equation

(6) (see table 1). For example, for a moisture content of 50 percent on a TW basis

(100 percent based on OD weight) and a HHV of 8,500 Btu/lb,

Heating value = 100 - 50 (8,500) = 4,250 Btu/lb

 100

Neither HHV (Btu per OD pound) nor percentage ash content differs widely

between species. In nearly all species, the HHV can be considered to be 9,000 Btu/

OD lb ± 10 percent.2 The ash content generally ranges from 0.1 to 1 percent for

wood and from 1 to 3 percent for bark (see footnote 2). If ash content in excess of

these values is obtained, it can reasonably be assumed that the material has been

contaminated during handling and processing. The reported values for the species

in this publication could have come from samples with extraneous material, and

final values cannot be adjusted for this condition.

2

 Zerbe, J.I. 1987. Personal communication. Energy specialist, Forest Products Laboratory,

One Gifford Pinchot Drive, Madison, WI 53726.
4

GENERAL TECHNICAL REPORT PNW-GTR-810

Neither ultimate nor proximate (moisture, volatile, carbon, and ash content and

HHV) analyses differ much between species in Btu per OD weight. Arola (1976)

gave typical ultimate and proximate analysis results by softwood (conifer) and

hardwood for wood and bark (table 2).3

 Some totals are not 100 percent, because

different sources of data for ash content were averaged. The ultimate analyses in

this publication also may not add up to 100 percent, because the ultimate analysis

includes ash, and the range of ash content is listed separately.

3 A comparison of table 2 to the general ash content ranges mentioned previously shows

higher values in table 2. The source for the general values, Zerbe, has concerns with

Arola’s methods and does not think the values in table 2 are realistic. Zerbe believes that

the proximate analysis had to be based on something other than the OD condition (which

standard methods require). If the original weight of the material is not taken at the OD

condition, then the excess moisture is driven off as volatile matter; although there is the

same absolute amount of fixed carbon, it is a reduced percentage of the original weight.

Arola also mentioned a connection between ultimate analysis and quantifying potential

pollutants. Zerbe, however, believes that comparing fixed carbon and ultimate carbon by the

two methods of analysis and inferring that the difference is the contribution of pollution is

not necessarily valid.

Table 1—Equations for calculating percentage moisture content (equations [2] through [5]) and heating value

(equation [6]) of wood and bark

Equation

Equation number

Percentage moisture content = wet weight – OD weight x 100 (2) (OD basis) OD weight

Percentage moisture content = wet weight – OD weight x 100 (3) (TW basis) wet weight

Percentage moisture content = percentage moisture content (TW basis) x 100 (4) (OD basis) 100 – percentage moisture content (TW basis)

Percentage moisture content = percentage moisture content (OD basis) x 100 (5) (TW basis) 100 + percentage moisture content (OD basis)

Gross heating value = 100 – percentage moisture content (TW basis) x HHV (6) 100

Note: OD = oven-dry; TW = total weight or green basis; HHV = higher heating value.
5

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Conifers

The data for northwestern conifers listed below are presented in six tables. The

physical properties are given in table 3 for the bark and table 4 for the wood. Table

5 provides the heating values, ash content, and analysis of the bark of the conifers

as per the original publication. Table 6 provides these same properties but converted into metric units and ash content on wet basis. Table 7 provides the heating

values and ash content of the wood of the conifer species. Like table 6, table 8

shows the data converted into metric units and ash content on wet basis.

Conifer species

Scientific name Common name

Abies amabilis (Douglas ex Louden) Pacific silver fir

Douglas ex Forbes

Abies concolor (Gord. & Glend.) Lindl. White fir

ex Hildebr.

Abies grandis (Douglas ex D. Don) Lindl. Grand fir

Abies lasiocarpa (Hook.) Nutt. Subalpine fir

Abies magnifica A. Murray California red fir, Shasta

red fir

Abies procera Rehder Noble fir

Table 2—Typical proximate and ultimate analyses of wood and bark

Proximate Ultimate

Volatile Fixed

matter carbon Asha C H O N S Asha

Percent

Hardwood

Wood 77.3 19.4 3.4 50.8 6.4 41.8 0.4 — 0.9

Bark 76.7 18.6 4.6 51.2 6.0 37.9 0.4 — 5.2

Softwood

Wood 77.2 22.0 1.6 52.9 6.3 39.7 0.1 — 1.0

Bark 73.3 23.7 3.0 53.1 5.9 37.9 0.2 — 2.3

Note: C = carbon, H = hydrogen, O = oxygen, N = nitrogen, S = sulfur.

It appears that in the reported proximate analysis, the weight of the tested material was not taken at the oven-dry

condition. The calculation of percentage of fixed carbon in this situation results in a value that is lower than

would be obtained from application of standard methods (original weight taken at the oven-dry condition).

a

 Ash percentages may differ because different data sources were averaged.

Source: Arola 1976.
6

GENERAL TECHNICAL REPORT PNW-GTR-810

Scientific name Common name

Calocedrus decurrens (Torr.) Florin Incense cedar

Chamaecyparis lawsoniana (A. Murray) Parl. Port Orford cedar

Cupressus nootkatensis (D. Don) Spach Alaska yellow-cedar,

Alaska cedar

Chamaecyparis nootkatensis D. Don Alaska yellow-cedar,

Alaska cedar

Juniperus occidentalis Hook. Western juniper

Larix occidentalis Nutt. Western larch

Libocedrus decurrens Torr. Incense cedar

Picea engelmannii Parry ex Engelm. Engelmann spruce

Picea glauca (Moench) Voss White spruce

Picea mariana (Mill.) Britton, Sterns & Black spruce

Poggenb.

Picea pungens Engelm. Blue spruce

Picea sitchensis (Bong.) Carr. Sitka spruce

Pinus albicaulis Engelm. Whitebark pine

Pinus aristata Engelm. Bristlecone pine

Pinus attenuata Lemmon Knobcone pine

Pinus contorta Douglas ex Loud. Lodgepole pine

Pinus jeffreyi Balf. Jeffrey pine

Pinus lambertiana Douglas Sugar pine

Pinus monticola Douglas ex D. Don Western white pine

Pinus muricata D. Don Bishop pine

Pinus ponderosa C. Lawson Ponderosa pine

Pinus radiata D. Don Monterey pine, radiata pine

Pinus sabiniana Douglas ex Douglas California foothill pine,

digger pine, gray pine

Pseudotsuga menziesii (Mirb.) Franco Douglas-fir

Sequoia sempervirens (Lamb. ex D. Don) Endl. Redwood

Sequoiadendron giganteum (Lindl.) J. Buchholz Giant sequoia

Taxus brevifolia Nutt. Pacific yew

Thuja plicata Donn. ex D. Don Western redcedar

Tsuga heterophylla (Raf.) Sarg. Western hemlock

Tsuga mertensiana (Bong.) Carr. Mountain hemlock
7

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Table 3—Physical properties of northwestern conifers (bark)

Specific gravity Moisture content Bark by volume

Citation Oven-dry Total-weight Citation Citation

Scientific name Common name Valuea number basis basis number Value number

– – – – Percent – – – – Percent

Abies amabilis Pacific silver fir 12 85

Inner bark 0.53 73 77.4 43.6 73Outer bark .58 73 39.6 28.4 73Mixed .44 74Mixed .68b 27

Abies concolor White fir 9.7-28.6 28,85

Inner bark .69c 7Outer bark .60c 7Mixed .62b 27

Abies grandis Grand fir

Inner bark .63 73 81 44.8 73Outer bark .70 73 51.4 34.0 73Mixed .57-.64b 27 50.8 33.4 53

Abies lasiocarpa Subalpine fir .50-.55b 27Abies magnifica California red fir 22.2 18.2 53

Inner bark .69c 7

Outer bark .50c 7Mixed .50b 27

Abies procera Noble fir .56b 27Chamaecyparis Port Orford cedar .33-.52b 27

lawsoniana

Chamaecyparis Alaska yellow-cedar 11-13.1 16,74

nootkatensis Inner bark .41 73 145 59.2 73

Outer bark .38 73 79.4 44.3 73Mixed .63b 27

Juniperus occidentalis Western juniper .48b 27Larix occidentalis Western larch 21 ± 6.5 76

Inner bark .37-.43 29,73 98.6 49.6 73Outer bark .33-.35 29,73 44.0 30.6 73Mixed .32-.33 25,29,74
8

GENERAL TECHNICAL REPORT PNW-GTR-810 Table 3—Physical properties of northwestern conifers (bark) (continued) Specific gravity Moisture content Bark by volume Citation Oven-dry Total-weight Citation Citation Scientific name Common name Valuea number basis basis number Value number – – – – Percent – – – – Percent Libocedrus decurrens Incense cedar 25 20 53 29 ± 9.6 76 Outer bark .30c 7 Mixed .27b 27 Picea engelmannii Engelmann spruce Inner bark .41-.45 29,73 121 55 73 Outer bark .52-.53 29,73 60.5 37.7 73 Mixed .43-.51 25,29,73,74 Mixed .80b 27

Picea glauca White spruce

Inner bark .45 73 104 51 73 8.6-11.7 85Outer bark .43-.50 29,73 50 33 73Mixed .39 25,29Mixed .62-.68b 27

Picea mariana Black spruce 45.6 31.3 77Picea pungens Blue sprucePicea sitchensis Sitka spruce

Inner bark .44 73 112 53 73Outer bark .62 73 55.3 35.6 73Mixed .63b 27

Pinus albicaulis Whitebark pinePinus aristata Bristlecone pinePinus attenuata Knobcone pine 11.1 43Pinus contorta Lodgepole pine 10 ± 2.4 16,74,76

Inner bark .32-.34 29,73 128 56 73

Outer bark .45-.51 29,73 42 29 73At 1.0 foot .42 74At 4.5 feet .40 74Mixed .38 25,29Mixed .60b 27

Pinus jeffreyi Jeffrey pine

Outer bark .36c 7

Pinus lambertiana Sugar pine

Outer bark .34c 7

Mixed .38b 27
9

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Table 3—Physical properties of northwestern conifers (bark) (continued)

Specific gravity Moisture content Bark by volume

Citation Oven-dry Total-weight Citation Citation

Scientific name Common name Valuea number basis basis number Value number

– – – – Percent – – – – Percent

Pinus monticola Western white pine 17 ± 8.3 16,21,76

Inner bark .31 73 118 54 73Outer bark .54 73 75 43 73Mixed .51 21 64-82 39-45 21,60Mixed .63b 27

Pinus muricata Bishop pinePinus ponderosa Ponderosa pine 5.9-27.2 16,50,76,82

Inner bark .34-.36 29,73 77.8 43.8 73Outer bark .34-.35 29,73 21 17 73Outer bark .27c 7

Mixed .28-.35 25,29,74 15.3-40.4 13.3-28.8 53,60

Pinus radiata Monterey pinePinus sabiniana California foothill pine 18.3 43

Pseudotsuga menziesii Douglas-fir 9.4-35 16,21,74,76,

83,85

Inner bark .42-.46 29,73,74 133 57.1 73Outer bark .40-.46 29,73,74 80.3 44.5 73Outer bark .48c 7

Mixed .41-.51 21,25,74Mixed .41-.54b 27

Old growth 8.9 8.2 53Second growth 97.2 49.3 53At test 48-80.2 32-44.5 14,21

Sequoia sempervirens Redwood 13.9 12.2 53

Inner bark .48c 7

Outer bark .43c 7Mixed .46b 27

Old growth 14-16 58Second growth 12.6-13 58

Sequoiadendron Giant sequoia

giganteum

Taxus brevifolia Pacific yew .35 21 97.2 49.3 21 3.4 21

Pacific yew .62b 27
10

GENERAL TECHNICAL REPORT PNW-GTR-810 Table 3—Physical properties of northwestern conifers (bark) (continued) Specific gravity Moisture content Bark by volume Citation Oven-dry Total-weight Citation Citation

Scientific name Common name Valuea number basis basis number Value number

– – – – Percent – – – – Percent

Thuja plicata Western redcedar

Inner bark .36 73 88.5 46.9 73Outer bark .38 73 37.4 27.2 73Mixed .35-.37 21,74 44.7-47.4 30.9-32.2 21,53 9 ± 4.1 21,76

Mixed .44b 27

Coastal 13.9 16Interior 15.2 16

Tsuga heterophylla Western hemlock

Inner bark .38-.46 29,51,73,74 86-134 46-57 51,73

Outer bark .45-.56 29,51,73,74 38-65.2 28-39.5 51,73

Mixed .44-.46 21,25,29,74 65-74 39-43 14,21 6.3-16.3 21,76,85Mixed .59b 27

Coastal 16.3 16Interior 17.9 16

Tsuga mertensiana Mountain hemlock .46b 27

a Green volume, oven-dry weight unless otherwise noted.b Oven-dry volume, oven-dry weight.c Volume at 13 percent ± 2 percent moisture content, oven-dry weight.
11

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Table 4—Physical properties of northwestern conifers (wood)

Moisture content

Specific gravity Sapwood Heartwood Mixed

Citation OD TW Cita- OD TW Cita- TW CitaScientific name Common name Valuea number basis basis tion basis basis tion OD basis basis tion

– – – Percent – – – – – – Percent – – – – – – – Percent – – – –

Abies amabilis Pacific silver fir 0.28-0.55 20,47,48, 164 62.1 16,57 55 35 57,16 66-74 40-43 16,20

75,85 49,75

Abies concolor White fir .26-.54 22,47,49, 98 49 57 160 62 57 110-154 52-61 29,49,90

85,86,90

Abies grandis Grand fir .24-.55 47,49 136 58 57 91 48 57 94 48 49

Abies lasiocarpa Subalpine fir .30-.38 4,49,75,83 153 60 16 56 36 16 47-67 32-40 16,49,57,75Abies magnifica California red fir .31-.46 47,49,68 108 52 49,57Abies procera Noble fir .26-.44 47,49,56 115 53 57 34 25 57 36-70 26-41 49,56Chamaecyparis Port Orford cedar .39-.40 49,78,87 98-200 49-67 57,78 40-50 29-33 57,78 43 30 49

lawsoniana

Chamaecyparis Alaska yellow- .42 20,49 166 62 57 32 24 57 34-52 25-34 16,20,49

nootkatensis cedar

Juniperus occidentalis Western juniper .58b 64 128-216 56-68 39 46-87 32-47 39 64-178 39-64 39

Larix occidentalis Western larch .37-.55 20,21,47, 110-119 52-54 16,57, 35-54 26-35 16,56,57 49.4-63.9 33.1-39.0 20,21,

49,75,83 87 49,75

Libocedrus decurrens Incense cedar .35 49 213 68 57 40 29 57 108 52 49Picea englemannii Englemann spruce .23-.58 5,20,47,49, 173 63 57 51 34 57 58-100 37-50 20,49,75

75,83

Picea glauca White spruce .35-.46 20,49,75,83,85 163 62 16 51 34 16 50-75 33-43 16,20,49,75Picea mariana Black spruce .5-.55 77Picea pungens Blue spruce .37b 64

Picea sitchensis Sitka spruce .35-.37 20,49,83 142 59 57 41 29 57 42-43 29-30 16,20,49

Pinus albicaulis Whitebark pine .42b 33,34,64

Pinus aristata Bristlecone pine .56b 64

Pinus attenuata Knobcone pine .35-.42 43,72

Pinus contorta Lodgepole pine

Sapwood

Green .36 44 163 62 44Dead down .36 44 15 13 44Dead standing .37 44 18 15 44At test 115-120 53-55 16,57

Heartwood

Green .38 44 35 26 44Dead down .36 44 20 17 44Dead standing .38 44 12 11 44At test 38-41 28-29 16,57

Mixed (at test) .26-.55 20,44,47, 49-65 33-39 16,20,49,75

49,75,82
12

GENERAL TECHNICAL REPORT PNW-GTR-810 Table 4—Physical properties of northwestern conifers (wood) (continued) Moisture content Specific gravity Sapwood Heartwood Mixed Citation OD TW Cita- OD TW Cita- TW Cita- Scientific name Common name Valuea number basis basis tion basis basis tion OD basis basis tion – – – Percent – – – – – – Percent – – – – – – Percent – – – Pinus jeffreyi Jeffrey pine .37 49 101 50 49 Pinus lambertiana Sugar pine .28-.45 47,49 219 69 57 98 49 57 137 58 49 Pinus monticola Western white pine Sapwood Green .46 44 27 21 44 Dead down .35 44 34 25 44 Dead standing .34 44 14 12 44 At test 148 60 57 Heartwood

Green .43 44 28 22 44Dead down .38 44 35 26 44Dead standing .39 44 17 15 44At test 62 38 57

Mixed (at test) .29-.45 20,21,44, 54-127 35-56 16,20,21,

47,49 49,60

Pinus muricata Bishop pine .45 71Pinus ponderosa Ponderosa pine .27-.54 20,29,47,49, 148 60 16,57 40 29 16,57 71-149.2 42-59.9 6,20,49,

50,75,82 53,60,75

Pinus radiata Monterey pine .40-.53 11 90-145 47-59 11 35 26 11Pinus sabiniana California foothill .37-.43 43,70 102 51 70

pine

Pseudotsuga menziesii Douglas-fir .33-.59 20,21,47,49, 115-154 53-61 16,57 31-39 24-28 16,57 36-65.6 26-39.6 16,20,

75,83,85 21,49,

Sequoia sempervirens Redwood

Open grown .28 49 146 59 49

Close grown .32 49 112 53 49Old growth .36-.38 29,83 210 68 57 86 46 57Second growth .33-.34 29,83 127 56 57

Mixed .24-.36 3 75-155 43-61 3,29,53

Sequoiadendron giganteum Giant sequoia

Young growth .35 59Old growth .30 59Mixed .34 12 180 64 12

Taxus brevifolia Pacific yew .59-.60 21,49 44-50.2 31-33.4 21,49Thuja plicata Western redcedar .27-.42 20,21,47,49,75 249 71 57 58 37 57 34.1-62 25.4-38 16,20,21,

49,75

Tsuga heterophylla Western hemlock .30-.52 20,21,23,47, 143-170 59-63 16,57 55-85 35-46 16,57 64.6-92 39.3-48 6,20,21,

49,75,83,85 23,49,75

Tsuga mertensiana Mountain hemlock .37-.45 49,93 62-68 38-40 49,93

Note: OD = oven dry, TW = total weight.a Green volume, oven-dry weight unless otherwise noted.b Oven-dry volume, oven-dry weight.
13

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Table 5—Higher heating values and ash content of northwestern conifers (bark)

Analysis

Carbon

Hydrogen

Heating value Oxygen

Citation Citation Nitrogen Citation

Scientific name Common name Value number Asha number Sulfur number

Btu/OD lb Percent Percent

Abies amabilis Pacific silver firAbies concolor White firAbies grandis Grand fir 9,641 36 2.5 53Abies lasiocarpa Subalpine firAbies magnifica California red fir 2.6 53Abies procera Noble firChamaecyparis Port Orford cedar

lawsoniana

Chamaecyparis Alaska yellow-cedar

nootkatensis

Juniperus Western juniper

occidentalis

Larix occidentalis Western larch 8,280-9,162 9,25,36,61 1.6-2.4 8,29

8,204b 8

4,860c 29

Libocedrus decurrens Incense cedar .6 53

Picea englemannii Englemann spruce 8,420-9,616 9,25,36,61 2.5-2.6 8,29

8,359d 8

Picea glauca White spruce 8,340-8,913 25,52 3.0-4.2 29,52 52.4 (C) 52

6.4 (H)

38.1 (O)

.1 (N)

0 (S)

Picea mariana Black spruce 8,377 77 .27-.46 77 46.4 (C) 77

2.0 8 5.9 (H)

.19 (N)
14

GENERAL TECHNICAL REPORT PNW-GTR-810 Table 5—Higher heating values and ash content of northwestern conifers (bark) (continued) Analysis Carbon Hydrogen Heating value Oxygen Citation Citation Nitrogen Citation

Scientific name Common name Value number Asha number Sulfur number

Btu/OD lb Percent Percent

Picea pungens Blue sprucePicea sitchensis Sitka sprucePinus albicaulis Whitebark pinePinus aristata Bristlecone pinePinus attenuata Knobcone pinePinus contorta Lodgepole pine 9,310-10,760 9,16,25,31,36 .5-2.2 8,29,31 55.0 (C) 31

10,190e 8 5.8 (H)

38.7 (O+N)

trace (S)

Pinus jeffreyi Jeffrey pinePinus lambertiana Sugar pine .6 8Pinus monticola Western white 8,904-9,335 21,27,36 1.3-2.6 21,27

pine 5,040c 29

Pinus muricata Bishop pine 9,415-9,616 25,36,89 .7 29,53Pinus ponderosa Ponderosa pine

Pinus radiata Monterey pinePinus sabiniana California foothill

pine

Pseudotsuga Douglas-fir 51.2-56.2 (C) 9,14,31,38

menziesii 5.8-6.2 (H) 9,14,31,38

Old growth 10,100 92 2.2 53 38.8-39.3 (O) 9,14,38Second growth 10,150 92 1.2 53 0-.2 (N) 9,14,38

At test 9,373-10,845 9,14,16,21,25, 1.0-3.7 9,14,21,29, 36.7 (O+N) 31

31,36,60,89 31,38,41 0.0-trace (S) 9,14,31,38
15

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Table 5—Higher heating values and ash content of northwestern conifers (bark) (continued)

Analysis

Carbon

Hydrogen

Heating value Oxygen

Citation Citation Nitrogen Citation

Scientific name Common name Value number Asha number Sulfur number

Btu/OD lb Percent Percent

Sequoia sempervirens Redwood 8,350 2 .4-.8 2,31,53 51.9 (C) 2,3

5.1 (H) 2

42.4 (O) 2

42.6 (O+N) 31

.1 (N) 2

trace-.1 (S) 2,31

Sequoiadendron Giant sequoia

giganteum

Taxus brevifolia Pacific yew 6,961 21 8.1 21Thuja plicata Western redcedar 8,694-9,014 9,16,21,36,60 1.95-2.25 21,29,53

4,830c 29

Tsuga heterophylla Western hemlock 8,900-9,943 9,14,16,21,25, 1.5-3.7 9,14,21,29 51.2-53.0 (C) 9,14

29,36,60 5.8-6.2 (H)

39.2-39.3 (O)

0-.1 (N)

0-trace (S)

Tsuga mertensiana Mountain hemlock

a Ash content on oven-dry basis.b British thermal units per pound, at 6.7 percent moisture content.c Kilocalories per kilogram; moisture content not stated.d British thermal units per pound, at 5.5 percent moisture content.e British thermal units per pound, at 5.6 percent moisture content.
16

GENERAL TECHNICAL REPORT PNW-GTR-810 Table 6—Higher heating values and ash content of northwestern conifers (bark) in International System of Units (SI) Analysis Carbon Hydrogen Oxygen Heating value Citation Nitrogen Citation Scientific name Common name Value Citation number Asha number Sulfur number Megajoule Percent Percent per kilogram Abies amabilis Pacific silver fir

Abies concolor White firAbies grandis Grand fir 22.42 36 1.25 53Abies lasiocarpa Subalpine firAbies magnifica California red fir 1.3 53Abies procera Noble firChamaecyparis Port Orford cedar

lawsoniana

Chamaecyparis Alaska yellow-cedar

nootkatensis

Juniperus Western juniper

occidentalis

Larix occidentalis Western larch 19.26-21.31 9,25,36,61 .8-1.2 8,29

19.08 820.35 29

Libocedrus decurrens Incense cedar .3 53Picea englemannii Englemann spruce 19.58-22.37 9,25,36,61 1.25-1.3 8,29

19.44 8

Picea glauca White spruce 19.40-20.73 25,52 1.5-2.1 29,52 52.4 (C) 52

6.4 (H)

38.1 (O)

.1 (N)

0 (S)

Picea mariana Black spruce 19.48 77 .135-.23 77 46.4 (C) 77

1.0 8 5.9 (H)

.19 (N)

Picea pungens Blue sprucePicea sitchensis Sitka spruce
17

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Table 6—Higher heating values and ash content of northwestern conifers (bark) in International System of units (SI) (continued)

Analysis

Carbon

Hydrogen

Oxygen

Heating value Citation Nitrogen Citation

Scientific name Common name Value Citation number Asha number Sulfur number

Megajoule Percent Percent

per kilogram

Pinus albicaulis Whitebark pinePinus aristata Bristlecone pinePinus attenuata Knobcone pinePinus contorta Lodgepole pine 21.66-25.03 9,16,25,31,36 .25-1.1 8,29,31 55.0 (C) 31

23.70 8 5.8 (H)

38.7 (O+N)

trace (S)

Pinus jeffreyi Jeffrey pinePinus lambertiana Sugar pine .3 8Pinus monticola Western white 20.71-21.71 21,27,36 .65-1.3 21,27

pine 21.10 29

Pinus muricata Bishop pine 21.90-22.37 25,36,89 .35 29,53Pinus ponderosa Ponderosa pinePinus radiata Monterey pinePinus sabiniana California foothill

pine

Pseudotsuga menziesii Douglas-fir 51.2-56.2 (C) 9,14,31,38

5.8-6.2 (H) 9,14,31,38

Old growth 23.49 92 1.1 53 38.8-39.3 (O) 9,14,38Second growth 23.61 92 .6 53 0-.2 (N) 9,14,38

At test 21.80-25.23 9,14,16,21,25, .5-1.85 9,14,21,29, 36.7 (O+N) 31

31,36,60,89 31,38,41 0-trace (S) 9,14,31,38
18

GENERAL TECHNICAL REPORT PNW-GTR-810 Table 6—Higher heating values and ash content of northwestern conifers (bark) in International System of units (SI) (continued) Analysis Carbon

Hydrogen

Oxygen

Heating value Citation Nitrogen Citation

Scientific name Common name Value Citation number Asha number Sulfur number

Megajoule Percent Percent

per kilogram

Sequoia sempervirens Redwood 19.42 2 .2-.4 2,31,53 51.9 (C) 2,31

5.1 (H) 2,31

42.4 (O) 2

42.6 (O+N) 31

.1 (N) 2

trace-.1 (S) 2,31

Sequoiadendron Giant sequoia

giganteum

Taxus brevifolia Pacific yew 16.19 21 4.05 21

Thuja plicata Western redcedar 20.22-20.97 9,16,21,36,60 .975-1.125 21,29,53

20.22 29

Tsuga heterophylla Western hemlock 20.70-23.13 9,14,16,21,25, .75-1.85 9,14,21,29 51.2-53.0 (C) 9,14

29,36,60 5.8-6.2 (H)

39.2-39.3 (O)

0-.1 (N)

0-trace (S)

Tsuga mertensiana Mountain hemlock

a Ash content on total weight or green basis. This value was calculated by assuming an increase in mass from oven-dry to 50-percent moisture content green

basis. This mass increase would all be water and the amount of ash would remain the same (e.g., doubling the number of pounds of mass in relation to theash). Thus, to get the ash content on green basis, the value for the oven-dry basis is divided by half. Actual moisture content of green material may differfrom a moisture content of 50-percent green basis.
19

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Table 7—Higher heating values and ash content of northwestern conifers (wood)

By volume By weight Ash

Citation Citation Citation

Scientific name Common name Value number Value number Value number

Million Btu Btu/OD lb Percent

per AD cord

Abies amabilis Pacific silver fir 16.5 24 0.23-0.47 6,29,64

Abies concolor White fir 8,795 89 .4-.85 29,64,83

4,440a 29

Abies grandis Grand fir 17.4 24 8,664 89 .25-.49 18,42,64Abies lasiocarpa Subalpine fir .4-.5 64,83Abies magnifica California red fir .30 64Abies procera Noble fir .34-.71 29,42,64Chamaecyparis Port Orford cedar .10 64

lawsoniana

Chamaecyparis Alaska yellow-cedar 9,900 16 .22-.34 42,64

nootkatensis

Juniperus Western juniper .12-.36 40,64

occidentalis

Larix occidentalis Western larch 26.5 24 8,370-8,431 21,36 .09-.80 21,29,61,64,83Libocedrus decurrens Incense cedar

Sapwood .47 29Heartwood 10,668 89 .30 29Mixed .08-.34 29,64

Picea englemannii Englemann spruce 17.6 24 .20-2.0 29,61,64,83Picea glauca White spruce 16.2 24 8,890 78 .22-.30 10,29Picea mariana Black spruce 19.1 24 8,377-8,551 77 77

8,246 8

Picea pungens Blue spruce .38 64Picea sitchensis Sitka spruce 15.9 24 8,100 16 .17-.45 29,64

4,500a 29

Pinus albicaulis Whitebark pine .27 64Pinus aristata Bristlecone pine .30 64Pinus attenuata Knobcone pine .20-.33 43,64Pinus contorta Lodgepole pine

Sapwood

Green 19.9b 44 .36 44Dead down 19.5 b 44 .51 44Dead standing 19.6 b 44 .53 44
20

GENERAL TECHNICAL REPORT PNW-GTR-810 Table 7—Higher heating values and ash content of northwestern conifers (wood) (continued) By volume By weight Ash Citation Citation Citation Scientific name Common name Value number Value number Value number Million Btu Btu/OD lb Percent per AD cord Heartwood Green 20.0 b 44 .34 44 Dead down 19.9 b 44 .43 44 Dead standing 20.1 b 44 .55 44 Mixed 20.1 24 8,600 16 4,870a 29

Mixed (at test) .19-.50 29,42,44,61,64,82

Pinus jeffreyi Jeffrey pine .26 64Pinus lambertiana Sugar pine

Sapwood .20 29Heartwood .20 29Mixed .22-.50 61,64

Pinus monticola Western white pine

Sapwood

Green 19.8b 44 .29 44Dead down 19.8 b 44 .29 44Dead standing 19.5 b 44 .23 44At test .20 29

Heartwood

Green 20.3 b 44 .36 44

Dead down 20.4 b 44 .28 44Dead standing 20.2 b 44 .30 44At test .20 29

Mixed 18.6 24 8,366-8,620 21,35

Mixed (at test) .20-.33 21,29,44,64,82

Pinus muricata Bishop pine .26 64Pinus ponderosa Ponderosa pine

Sapwood .30 29Heartwood 8,920-8,992 89 .20 29Mixed 22.1 24 9,100-9,140 9,16,29,92 .18-.50 29,53,61,64,82

Pinus radiata Monterey pine .30 64Pinus sabiniana California foothill 1.10-.40 43,64

pine
21

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Table 7—Higher heating values and ash content of northwestern conifers (wood) (continued)

By volume By weight Ash

Citation Citation Citation

Scientific name Common name Value number Value number Value number

Million Btu Btu/OD lb Percent

per AD cord

Pseudotsuga menziesii Douglas-fir .08-.80 6,15,21,29,40,53,

64,83

Sapwood 8,500 92Heartwood 7,500-9,000 29,89,92Mixed 22.2c 8,318-9,200 9,15,16,

21,61,89

Mixed 24.3 24

Sequoia sempervirens Redwood 8,840-9,220 15,60

5,020a 29

Second growth .10 83Old growth .10 83Mixed .14-.40 15,29,53,64

Sequoiadendron Giant sequoia .50 64

giganteum

Taxus brevifolia Pacific yew 9,322 21 .22-.32 21,40,64Thuja plicata Western redcedar 16.8 24 8,588-9,700 16,21,92 .27-.42 21,35,29Tsuga heterophylla Western hemlock 19.3 24 8,410-8,620 9,15,16,21,92

Sapwood .37 29Heartwood .51 29Mixed .30-2.2 15,21,29,35,83

Tsuga mertensiana Mountain hemlock .50 29

Note: AD = air-dry, OD = oven-dry.a Kilocalories per kilogram (kcal/kg).b Megajoules per kilogram (mJ/kg).c No citation was listed in the original publication.
22

GENERAL TECHNICAL REPORT PNW-GTR-810 Table 8—Higher heating values and ash content of northwestern conifers (wood) in International System of units (SI) By volume By weight Asha Citation Citation Citation Scientific name Common name Valueb number Value number Value number Megajoules Megajoules Percent per solid AD per kilogram cubic meter Abies amabilis Pacific silver fir 6822.3 24 0.115-0.235 6,29,64 Abies concolor White fir 20.46 89 .2-.425 29,64,83 18.59 29 Abies grandis Grand fir 7194.4 24 20.15 89 .125-.245 18,42,64

Abies lasiocarpa Subalpine fir .2-.25 64,83

Abies magnifica California red fir .15 64Abies procera Noble fir .17-.355 29,42,64Chamaecyparis Port Orford cedar .05 64

lawsoniana

Chamaecyparis Alaska yellow-cedar 23.03 16 .11-.17 42,64

nootkatensis

Juniperus occidentalis Western juniper .06-.18 40,64Larix occidentalis Western larch 10 957.0 24 19.47-19.61 21,36 .045-.40 21,29,61,64,83Libocedrus decurrens Incense cedar

Sapwood .235 29Heartwood 24.81 89 .15 29Mixed .04-.17 29,64

Picea englemannii Englemann spruce 7277.1 24 .10-1.0 29,61,64,83

Picea glauca White spruce 6698.2 24 20.68 78 .11-.15 10,29Picea mariana Black spruce 7897.3 24 19.48-19.89 77 .195 77

19.18 8

Picea pungens Blue spruce .19 64Picea sitchensis Sitka spruce 6574.2 24 18.84 16 .085-.225 29,64

Pinus albicaulis Whitebark pine .135 64

Pinus aristata Bristlecone pine .15 64Pinus attenuata Knobcone pine .10-.165 43,64Pinus contorta Lodgepole pine

Sapwood

Green 19.9 44 .18 44

Dead down 19.5 44 .255 44Dead standing 19.6 44 .265 44
23

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Table 8—Higher heating values and ash content of northwestern conifers (wood) in International System of Units (SI) (continued)

By volume By weight Asha

Citation Citation Citation

Scientific name Common name Valueb number Value number Value number

Megajoules Megajoules Percent

per solid AD per kilogram

cubic meter

Heartwood

Green 20.0 44 .17 44Dead down 19.9 44 .215 44Dead standing 20.1 44 .275 44

Mixed 8310.8 24 20.00 16Mixed 20.39 29

Mixed (at test) .095-.25 29,42,44,61,64,

Pinus jeffreyi Jeffrey pine .13 82,64

Pinus lambertiana Sugar pine

Sapwood .10 29Heartwood .10 29Mixed .11-.25 61,64

Pinus monticola Western white pine

Sapwood

Green 19.8 44 .145 44Dead down 19.8 44 .145 44Dead standing 19.5 44 .115 44At test .10 29

Heartwood

Green 20.3 44 .18 44Dead down 20.4 44 .14 44Dead standing 20.2 44 .15 44At test .10 29

Mixed 7690.6 24 19.46-20.05 21,35Mixed (at test) .10-.165 21,29,44,64,82

Pinus muricata Bishop pine .13 64Pinus ponderosa Ponderosa pine

Sapwood .15 29Heartwood 20.75-20.92 89 .10 29Mixed 9137.7 24 21.17-21.26 9,16,29,92 .09-.25 29,53,61,64,82

Pinus radiata Monterey pine .15 64
24

GENERAL TECHNICAL REPORT PNW-GTR-810 Table 8—Higher heating values and ash content of northwestern conifers (wood) in International System of Units (SI) (continued) By volume By weight Asha Citation Citation Citation Scientific name Common name Valueb number Value number Value number Megajoules Megajoules Percent per solid AD per kilogram cubic meter Pinus sabiniana California foothill .55-.20 43,64 pine Pseudotsuga Douglas-fir .04-.40 6,15,21,29,40,53, menziesii 64,83

Sapwood 19.77 92Heartwood 17.44-20.93 29,89,92Mixed 9179.0c 19.35-21.40 9,15,16,21,

61,89

Mixed 10 047.3 24

Sequoia sempervirens Redwood 20.56-21.45 15,60

21.02 29

Second growth .05 83Old growth .05 83Mixed .07-.20 15,29,53,64

Sequoiadendron Giant sequoia .25 64

giganteum

Taxus brevifolia Pacific yew 21.68 21 .11-.16 21,40,64Thuja plicata Western redcedar 6946.3 24 19.98-22.56 16,21,92 .135-.21 21,35,29Tsuga heterophylla Western hemlock 7980.0 24 19.56-20.05 9,15,16,21,92

Sapwood .185 29Heartwood .255 29Mixed .15-1.1 15,21,29,35,83

Tsuga mertensiana Mountain hemlock .25 29

a Ash content on total weight or green basis. This value was calculated by assuming an increase in mass from oven-dry to 50-percent moisture content green

basis. This mass increase would all be water and the amount of ash would remain the same (e.g., doubling the number of pounds of mass in relation to the ash).Thus, to get the ash content on green basis, the value for the oven-dry basis is divided by half. Actual moisture content of green material may differ from amoisture content of 50-percent green basis.

b The conversion to standard international units was made by multiplying the value of British thermal units by 1054.35 to get the value of megajoules. This

number was then divided by 2.55 to convert from a cord to cubic meters of solid material. One cord contains 3.62 m3, based on 90 ft3 of solid material. AD =

air-dry.

c No citation was listed in the original publication.
25

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Hardwoods

The data for northwestern hardwoods listed below are presented in six tables. The

physical properties are given in table 9 for the bark and table 10 for the wood.

Table 11 provides the heating values, ash content, and analysis of the bark of the

hardwoods as per the original publication. Table 12 provides these same properties

but converted into metric units and ash content on wet basis. Table 13 provides the

heating values and ash content of the wood of the hardwood species. Like table 12,

table 14 shows the data converted into metric units and ash content on wet basis.

Hardwood species

Scientific name Common name

Acer macrophyllum Pursh Bigleaf maple

Alnus rhombifolia Nutt. White alder

Alnus rubra Bong. Red alder

Arbutus menziesii Pursh Pacific madrone

Betula papyrifera Marsh. Paper birch

Chrysolepis chrysophylla (Douglas Giant chinquapin, golden

ex Hook.) Hjelmqvist chinquapin

Castanopsis chrysophylla Giant chinquapin, golden

(Douglas ex Hook.) Hjelmqvist chinquapin

var. chrysophylla

Cornus nuttallii Audubon ex Torr. & A. Gray Pacific dogwood

Fraxinus latifolia Benth. Oregon ash

Lithocarpus densiflorus (Hook. & Arn.) Rehder Tanoak

Populus balsamifera L. ssp. trichocarpa Black cottonwood

(Torr. & A. Gray ex Hook.) Brayshaw

Populus fremontii S. Watson Fremont cottonwood

Populus tremuloides Michx. Quaking aspen

Populus trichocarpa Torr. & A. Gray ex Hook. Black cottonwood

Quercus agrifolia Nee California coastal live oak

Quercus chrysolepis Liebm. Canyon live oak

Quercus douglasii Hook. & Arn. Blue oak

Quercus garryana Douglas ex Hook. Oregon white oak

Quercus kelloggii Newberry California black oak

Quercus lobata Nee Valley oak, California

white oak

Quercus wislizeni A. DC. Interior live oak

Umbellularia californica (Hook. & Arn.) Nutt. California laurel, Oregon

myrtle, California bay
26

GENERAL TECHNICAL REPORT PNW-GTR-810 Table 9—Physical properties of northwestern hardwoods (bark) Specific gravity Moisture content Bark by volume Citation Oven-dry Total-weight Citation Citation Scientific name Common name Valuea number basis basis number Value number – – – – – Percent – – – – – Percent Acer macrophyllum Bigleaf maple 7.8-10.5 16,21

Inner bark 0.66 73 134 57 73Outer bark .45 73 70.1 41.2 73Mixed .56 21 60.5 37.7 21Mixed .55b 27

Alnus rhombifolia White alderAlnus rubra Red alder 13.5 16

Inner bark .52 73 87.8 46.8 73Outer bark .62 73 66.0 39.8 73Mixed .58 26

Arbutus menziesii Pacific madroneBetula papyrifera Paper birch 8.0-15.7 16,74,84

Inner bark .57-.63 30,73 67.7 40.4 73

Outer bark .54-.66 30,73 22.5 18.4 73

Mixed .56 30Mixed .69b 27

Castanopsis Giant chinquapin 11.1 84

chrysophylla

Cornus nuttallii Pacific dogwoodFraxinus latifolia Oregon ash .50b 27

Lithocarpus Tanoak .75b 27 15.7 81

densiflorus

Populus fremontii Fremont cottonwoodPopulus tremuloides Quaking aspen 65.1-67.2 39.4-40.2 48 8.9-16.5 16,48,81

Inner bark .4 30Outer bark .55 30Mixed .50 25,30Mixed .61-.73b 27
27

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Table 9—Physical properties of northwestern hardwoods (bark) (continued)

Specific gravity Moisture content Bark by volume

Citation Oven-dry Total-weight Citation Citation

Scientific name Common name Valuea number basis basis number Value number

– – – – – Percent – – – – – Percent

Populus tricocarpa Black 18.3 16

cottonwood

Inner bark .38-.41 30,73 130 57 73Outer bark .42-.44 30,73 77.4 43.6 73Mixed .40-.46 26,30,74Mixed .60b 27

Quercus agrifolia California coastal

live oak

Quercus chrysolepis Canyon live oakQuercus douglasii Blue oakQuercus garryana Oregon white oak .80b 27Quercus kelloggii California black oakQuercus lobata Valley oak .66b 27Quercus wislizeni Interior live oakUmbellularia California laurel californica

a Green volume, oven-dry weight unless otherwise noted.b Oven-dry volume, oven-dry weight.
28

GENERAL TECHNICAL REPORT PNW-GTR-810 Table 10—Physical properties of northwestern hardwoods (wood) Moisture content Specific gravity Sapwood Heartwood Mixed or unspecified Citation OD TW Citation OD TW Citation OD TW Citation Scientific name Common name Valuea number basis basis number basis basis number basis basis number – – Percent – – – – Percent – – – – Percent– – Acer macrophyllum Bigleaf maple 0.44-0.62 20,21,49 39-72 28-42 16,20,21,49 Alnus rhombifolia White alder .41b 64 Alnus rubra Red alder .37-.41 20,49,81 97 49 57 98-101 49-50 16,20,49 Arbutus menziesii Pacific madrone .54-.58 49,65,80 68-93 40-48 49,57,65,80 Betula papyrifera Paper (white) 48-.52 16,20,37, 72 42 16,57 74-89 43-47 16,57 65-73 39-42 16,20,49 birch 49,84

Castanopsis Giant 111-166 53-62 49,57,63,80

chrysoplylla chinquapin

Sapwood .40-.41 63Heartwood .42 63Mixed .41-.43 49,63,80,84

Cornus nuttallii Pacific dogwood .58 49 52 34 49

Fraxinus latifolia Oregon ash .50 49 48 32 49

Lithocarpus densiflorus Tanoak .48-.62 19,54,62, 43.6-120 30.4-55 19,54,57,

67,80,81,86 62,67,80,86

Populus fremontii Fremont .41 17 139 58 17

cottonwood

Populus tremuloides Quaking aspen .33-.39 20,37,49,81 113 53 57 95 49 57 90-123 47-55 20,46,48,49

Populus trichocarpa Black .28-.40 37,47,49 146 59 57 162 62 57 132-175 57-64 16,49

cottonwood

Quercus agrifolia California .83b 64

coastal live oak

Quercus chrysolepis Canyon live oak .70 49 62 38 49

Quercus douglasii Blue oak .64 81Quercus garryana Oregon .63-.64 49,55 67-72 40-42 49,55

white oak

Quercus kelloggii California .46-.51 49,66,81 75 43 57 76 43 57 106-108 51-52 49,66

black oak

Quercus lobata Valley oak .53-.58 55,69,81 91-103 48-51 55,69Quercus wislizeni Interior .79b 64

live oak

Umbellularia californica California .51-.59 49,80 59.8-70 37.4-41 49,57,80

laurel

Note: OD = oven-dry, TW = total weight.a Green volume, oven-dry weight unless otherwise noted.b Oven-dry volume, oven-dry weight.
29

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Table 11—Higher heating values and ash content of northwestern hardwoods (bark)

Analysis

Carbon

Hydrogen

Heating value Oxygen

Citation Citation Nitrogen Citation

Scientific name Common name Value number Asha number Sulfur number

Btu/OD lb Percent Percent

Acer macrophyllum Bigleaf maple 8,277 21 6.9 21Alnus rhombifolia White alderAlnus rubra Red alder 8,406-8,760 9,26,60 2.4-5.9 8,30,61 46.03 (C) 77

7,947b 8 5.94 (H)

.6 (N)

Arbutus menziesii Pacific madroneBetula papyrifera Paper birch 9,490- 9,52 1.5-2.4 8,30,52 57.4 (C) 52

10,310 6.7 (H)

9,434c 8 33.8 (O)

.3 (N)

0 (S)

Castanopsis Giant chinquapin

chrysophylla

Cornus nuttallii Pacific dogwoodFraxinus latifolia Oregon ashLithocarpus Tanoak

densiflorus

Populus fremontii Fremont

cottonwood

Populus tremuloides Quaking aspen 8,430-8,712 9,25,30 2.8 8

8,433d 8
30

GENERAL TECHNICAL REPORT PNW-GTR-810 Table 11—Higher heating values and ash content of northwestern hardwoods (bark) (continued) AnalysisCarbon

Hydrogen

Heating value Oxygen

Citation Citation Nitrogen Citation

Scientific name Common name Value number Asha number Sulfur number

Btu/OD lb Percent Percent

Populus trichocarpa Black cottonwood 8,765-9,000 16,26,60 5.0 30Quercus agrifolia California coastal

live oak

Quercus chrysolepis Canyon live oakQuercus douglasii Blue oakQuercus garryana Oregon white oakQuercus kelloggii California black oakQuercus lobata Valley oakQuercus wislizeni Interior live oakUmbellularia California laurel

caifornica

a Ash content on oven-dry basis.b British thermal units per pound, at 5.8 percent moisture content.c British thermal units per pound, at 4.8 percent moisture content.d British thermal units per pound, at 5.5 percent moisture content.
31

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Table 12—Higher heating values and ash content of northwestern hardwoods (bark) in International System of units (SI)

Analysis

Carbon

Hydrogen

Heating value Oxygen

Citation Citation Nitrogen Citation

Scientific name Common name Value number Asha number Sulfur number

Megajoules Percent Percent

per kilogram

Acer macrophyllum Bigleaf maple 19.25 21 3.45 21Alnus rhombifolia White alderAlnus rubra Red alder 19.55-20.38 9,26,60 1.2-2.95 8,30,61 46.03 (C) 77

18.48 8 5.94 (H

.6 (N)

Arbutus menziesii Pacific madroneBetula papyrifera Paper birch 22.07-23.98 9,52 .75-1.2 8,30,52 57.4 (C) 52

21.94 8 6.7 (H)

33.8 (O)

.3 (N)

0 (S)

Castanopsis Giant chinquapin

chrysophylla

Cornus nuttallii Pacific dogwoodFraxinus latifolia Oregon ashLithocarpus Tanoak

densiflorus

Populus fremontii Fremont

cottonwood

Populus tremuloides Quaking aspen 19.61-20.26 9,25,30 1.4 8

19.62 8
32

GENERAL TECHNICAL REPORT PNW-GTR-810 Table 12—Higher heating values and ash content of northwestern hardwoods (bark) in International System of units (SI) (continued) AnalysisCarbon

Hydrogen

Heating value Oxygen

Citation Citation Nitrogen Citation

Scientific name Common name Value number Asha number Sulfur number

Megajoules Percent Percent

per kilogram

Populus trichocarpa Black 20.39-20.93 16,26,60 2.5 30

cottonwood

Quercus agrifolia California

coastal live oak

Quercus chrysolepis Canyon live oakQuercus douglasii Blue oakQuercus garryana Oregon white oakQuercus kelloggii California black

oak

Quercus lobata Valley oakQuercus wislizeni Interior live oakUmbellularia California laurel

caifornica

a Ash content on total weight or green basis. This value was calculated by assuming an increase in mass from oven-dry to 50-percent moisture content green

basis. This mass increase would all be water and the amount of ash would remain the same (e.g., doubling the number of pounds of mass in relation to theash). Thus, to get the ash content on green basis, the value for the oven-dry basis is divided by half. Actual moisture content of green material may differ froma moisture content of 50-percent green basis.
33

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Table 13—Higher heating values and ash content of northwestern hardwoods (wood)

By volume By weight Asha

Citation Citation Citation

Scientific name Common name Value number Value number Value number

Million Btu Btu per OD lb Percent

per AD cord

Acer macrophyllum Bigleaf maple 8,140-8,410 13,16,21 0.26-0.54 21,42,64Alnus rhombifolia White alder .31 64Alnus rubra Red alder 17.4 24 7,990-8,000 9,16 .23-2.00 30,42,61,64

Arbutus menziesii Pacific madrone .09-.40 40,64Betula papyrifera Paper birch 23.4 24 8,334 79

Sapwood .24 30

Heartwood .21 30Mixed .2-.4 30,64,81

Castanopsis Giant chinquapin .30-.35 42,64

chrysophylla

Cornus nuttallii Pacific dogwood .22-.50 40,64Fraxinus latifolia Oregon ash 8,200 92 .34 64Lithocarpus densiflorus Tanoak .31-1.49 42,64,81Populus fremontii Fremont .77-1.13 64

cottonwood

Populus tremuloides Quaking aspen 17.7 24 5,785b 30 .2-2.1 10,30,64,91

.09-.15 (N)c 91

Populus trichocarpa Black cottonwood 15.5 24 8,800 16 .3-1.27 30,64Quercus agrifolia California coastal 1.28 64

live oak

Quercus chrysolepis Canyon live oak .60 64Quercus douglasii Blue oak .84-1.4 64,81Quercus garryana Oregon white oak 8,110 13 .39 64Quercus kelloggii California black oak .26-.40 64,81Quercus lobata Valley oak .3-.9 64,81Quercus wislizeni Interior live oak 1.02 64Umbellularia California laurel .16-.39 40,64

californica

Note: AD = air-dry, OD = oven-dry.a Ash content on oven-dry basis.b British thermal units per air-dry pound.c Percentage nitrogen also provided for quaking aspen.
34

GENERAL TECHNICAL REPORT PNW-GTR-810 Table 14—Higher heating values and ash content of northwestern hardwoods (wood) in International System of units (SI) By volume By weight Asha Citation Citation Citation

Scientific name Common name Valueb number Value number Value number

Megajoules Megajoules Percent

per solid AD per kilogram

cubic meter

Acer macrophyllum Bigleaf maple 18.93-19.56 13,16,21 0.13-0.27 21,42,64Alnus rhombifolia White alder .155 64Alnus rubra Red alder 7194.4 24 18.58-18.61 9,16 .115-1.00 30,42,61,64Arbutus menziesii Pacific madrone .045-.20 40,64

Betula papyrifera Paper birch 9675.2 24 19.38 79

Sapwood .12 30

Heartwood .105 30Mixed .1-.2 30,64,81

Castanopsis Giant chinquapin .15-.175 42,64

chrysophylla

Cornus nuttallii Pacific dogwood .11-.25 40,64Fraxinus latifolia Oregon ash 19.07 92 .17 64Lithocarpus Tanoak .155-.745 42,64,81

densiflorus

Populus fremontii Fremont .385-.565 64

cottonwood

Populus tremuloides Quaking aspen 7318.4 24 13.46 30 .1-1.05 10,30,64,91

.09-.15 (N)c 91

Populus trichocarpa Black cottonwood 6408.8 24 20.47 16 .3-1.27 30,64Quercus agrifolia California coastal .64 64

live oak
35

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Table 14—Higher heating values and ash content of northwestern hardwoods (wood) in International System of units (SI) (continued)

By volume By weight Asha

Citation Citation Citation

Scientific name Common name Valueb number Value number Value number

Megajoules Megajoules Percent

per solid AD per kilogram

cubic meter

Quercus chrysolepis Canyon live oak .30 64Quercus douglasii Blue oak .42-.7 64,81Quercus garryana Oregon white oak 18.86 13 .195 64Quercus kelloggii California black oak .13-.20 64,81

Quercus lobata Valley oak .15-.45 64,81

Quercus wislizeni Interior live oak .51 64Umbellularia California laurel .08-.195 40,64

californica

a Ash content on total weight or green basis. This value was calculated by assuming an increase in mass from oven-dry to 50-percent moisture content green

basis. This mass increase would all be water and the amount of ash would remain the same (e.g., doubling the number of pounds of mass in relation to the ash).Thus, to get the ash content on green basis, the value for the oven-dry basis is divided by half. Actual moisture content of green material may differ from amoisture content of 50-percent green basis.

b The conversion to standard international units was made by multiplying the value of British thermal units by 1054.35 to get the value of megajoules. This

number was then divided by 2.55 to convert from a cord to cubic meters of solid material. AD = air-dry.

c Percentage nitrogen also provided for quaking aspen.
36

GENERAL TECHNICAL REPORT PNW-GTR-810

Acknowledgments4

The editors acknowledge the authors, the original research, and the publication by

the Forest Research Laboratory at Oregon State University. Their work provided

the basis for this update.

The authors thank the following reviewers: R.M. Kellogg, Wood Science

Department, Forintek Canada Corp., Vancouver, British Columbia, Canada; J.J.

Karchesy, R.L. Krahmer, M.L. Laver, and M.D. McKimmy, College of Forestry,

Oregon State University, Corvallis; J.I. Zerbe, Forest Products Laboratory, USDA

Forest Service, Madison, Wisconsin; J.O. Howard and W.Y. Pong, Pacific Northwest Forest and Range Experiment Station, USDA Forest Service, Portland,

Oregon; D.G. Arganbright, W.A. Dost, and A.P. Schniewind, Forest Products

Laboratory, University of California, Richmond; L.R. Johnson and A.A. Moslemi,

College of Forestry, Wildlife, and Range Sciences, University of Idaho, Moscow;

R.W. Smith, College of Forest Resources, University of Washington, Seattle.

Metric Equivalents

When you know: Multiply by: To find:

British thermal units (Btu) 0.252 Kilocalories

British thermal units (Btu) 1054.35 Joule

British thermal units per .002326 Megajoules per

pound (Btu/lb) kilogram

British thermal units per 413.47 Megajoules per

air-dry cord (Btu/AD cord) AD cubic meter

Feet (ft) .305 Meters

Cubic feet (ft3

) .0283 Cubic meters

Pounds (lb) .454 Kilograms

Pounds per cubic foot (lb/ft3) 16.02 Kilograms per

cubic meter

Degrees Fahrenheit (°F) .56(°F - 32) Degrees Celsius

4

 The second paragraph gives the original Acknowledgments; thus, some of the affiliations

and employments have changed since 1987.
37

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

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Orford white-cedar. Journal of Forestry. 51(8): 555–559.

79 Tillman, D.A. 1978. Wood as an energy resource. New York: Academic

Press. 266 p.

80 Torgeson, O.W. 1950. Kiln drying schedules for 1-inch laurel, madrone, tanoak,

and chinquapin. Rep. No. 1684. Madison, WI: U.S. Department of Agriculture,

Forest Service, Forest Products Laboratory. 24 p.

81 U.S. Department of Agriculture, Forest Service. [N.d.a]. Physical characteristics and chemical analysis of certain domestic hardwoods received at the Forest

Products Laboratory for pulping October 1948 to November 1957. Res. Note

PP-110. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest

Products Laboratory. [Pages unknown].

82 U.S. Department of Agriculture, Forest Service. [N.d.b]. Physical characteristics and chemical analysis of certain domestic pine woods received at the

Forest Products Laboratory for pulping from October 1, 1948 to September 4,

1956. Res. Note PP-112. Madison, WI: U.S. Department of Agriculture, Forest

Service, Forest Products Laboratory. [Pages unknown].

83 U.S. Department of Agriculture, Forest Service. [N.d.c]. Physical characteristics and chemical analysis of certain softwoods (other than pine) received at the

Forest Products Laboratory October 1, 1948 to August 7, 1957. Res. Note PP114. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest

Products Laboratory. [Pages unknown].

84 U.S. Department of Agriculture, Forest Service. [N.d.d]. Summary of certain

physical properties of domestic hardwoods and foreign woods used in pulping

experiments at the Forest Products Laboratory–July 1927 to December 1940.

Rep. PP-107. Madison, WI: U.S. Department of Agriculture, Forest Service,

Forest Products Laboratory. [Pages unknown].
45

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

85 U.S. Department of Agriculture, Forest Service. [N.d.e]. Summary of certain

physical properties of softwoods (except pines) used in pulping experiments at

the Forest Products Laboratory–July 1927 to July 1935. Rep. PP-108. Madison,

WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. [Pages unknown].

86 U.S. Department of Agriculture, Forest Service. 1967. Veneer cutting and

drying properties of tanoak. Res. Note FPL-RN-0164. Madison, WI: U.S.

Department of Agriculture, Forest Service, Forest Products Laboratory.

[Pages unknown].

87 U.S. Department of Agriculture, Forest Service [USDA FS]. 1999. Wood

handbook—wood as an engineering material. Gen. Tech. Rep. FPL-GTR-113.

Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products

Laboratory. 463 p.

88 U.S. Department of Agriculture, Natural Resources Conservation Service

[USDA NRCS]. 2009. The PLANTS database. Baton Rouge, LA: National

Plant Data Center. http://plants.usda.gov. (3 April 2009).

89 Voorhies, G.; Huntsberger, T.G. 1983. Heat and combustion of ponderosa pine

and selected associated species indigenous to the Rocky Mountain region.

Arizona Forestry Notes 19. Flagstaff, AZ: Northern Arizona University. 14 p.

90 Wilcox, W.W.; Pong, W.Y. 1971. The effects of height, radial position, and

wetwood on white fir wood properties. Wood and Fiber. 3(1): 47–55.

91 Wilde, S.A.; Paul, B.H. 1959. Growth, specific gravity, and chemical composition of quaking aspen on different soil types. Rep. No. 2144. Madison, WI:

U.S. Department of Agriculture, Forest Service, Forest Products Laboratory.

10 p.

92 Willey, E.C. 1942. Saving fuel in Oregon homes. Circular Series 7. Corvallis,

OR: Engineering Experiment Station, Oregon State College. 36 p.

93 Youngs, R.L. 1963. Strength and related properties of mountain hemlock. Res.

Pap. FPL-3. Madison, WI: U.S. Department of Agriculture, Forest Service,

Forest Products Laboratory. 12 p.
46

GENERAL TECHNICAL REPORT PNW-GTR-810
47

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

Appendix

Explanation of Conversions Made in the Updated Report and

Editors Comment

In the original publication, the term total weight (TW) was used to define the

initial (fresh or green) weight of the sample before drying, and all moisture contents were reported by using an oven-dry (OD) basis. Given that energy-related

conversions use green-weight moisture contents, this revised publication provides

OD moisture contents converted to green basis (assumed to be 50-percent moisture

content TW) in the tables. It was determined that having ash content reported as a

percentage of green weight as well as a percentage of OD weight would also be

helpful.

Wood is hygroscopic, meaning it has the ability to exchange (absorb or desorb)

moisture with its surrounding environment. Once the wood has been converted

from the living tree to product form (e.g., firewood, chips, lumber, or veneer), the

inorganic components that create ash are fixed and, for most analytical purposes,

constant for a given piece of material. The weight of the material per unit of

volume, however, will fluctuate as moisture is exchanged with the atmosphere.

Determination of moisture content (MC) of wood and bark is a relatively

simple matter of taking a sample, weighing it, drying it in an oven at a temperature

of 103 ± 2 °C (217 ± 4 °F), and periodically reweighing the material until a stable

weight is obtained. At the point the material is referred to as “bone” or “oven” dry,

all of the free water between cells and bound water from the interior of the cells

has been removed. This condition is also referred to as zero percent MC. There is

still water that is bound to the chemical structure of the wood, but removal of this

material requires temperatures above the boiling point of water; as the material is

removed, the chemical structure of the wood material is altered. This process is

referred to as destructive distillation and is often accompanied by a charring of the

material.

Moisture meters can also be used to measure the moisture content of wood.

These meters, however, are based on resistance, dielectric constant, or power loss

factor. The point in drying where resistance starts to increase is referred to as the

fiber saturation point (fsp). In changes in moisture content above the fsp, there is

no shrinkage or expansion in the physical dimensions of a piece of solid wood,

lumber, veneer, or bark. As changes take place below the fsp, the physical dimensions of the material will change. These changes in dimension, however, are

relatively minor and inconsequential in relation to the changes in mass, unless
48

GENERAL TECHNICAL REPORT PNW-GTR-810

the material is being used for finish in a heated or air conditioned building. In such

situations, material should be conditioned so that the material has an MC very near

the equilibrium conditions where it will be put into service. Note that meters do not

accurately measure the MC of wood material that is saturated with water. The

meter indicates that the wood is saturated but does not really provide a valid

estimate of how much water it contains.

Given the hygroscopic nature of wood, once it is removed from the stump, the

wood is always changing moisture content to reach equilibrium with the surrounding atmosphere. In the fresh-cut condition, the weight of water can be greater than

the weight of the wood substance in a piece of wood, but the instant the material is

cut from the stump, the process of moving to equilibrium conditions begins. The

Wood Handbook (USDA FS 1999) published tables showing average equilibrium

MC at various locations in the United States. Users of these tables should be aware

that there is a difference between how wood scientists interested in forest products

and engineers concerned with energy relationships calculate MC of wood material.

Owing to the ever-changing moisture content of the material to equilibrium

conditions, wood technologists calculate moisture content as a percentage of the

OD condition. This condition is absolute and a piece of wood can repeatedly be

returned to it. Engineers concerned with energy values use the original, initial

sample (total or green weight) as the basis for determining MC. In all manipulations of MC, users are reminded that the OD condition may be repeatedly obtained.

The green condition is a function of many factors and is often referenced to such

terms as “the living tree,” “fresh cut,” or “undried.” In the living tree, there is

usually a major difference between wood from the sapwood and heartwood portions of the tree. In the commerce of the forest products industry, the term “fresh

cut” implies that the material has recently been harvested and with minimal delays

transported to a mill where the amount harvested and delivered is based on weight

at the stated condition. In cold climates, “fresh weight” may include ice and snow,

and in any climate, it may include contamination in the form of dirt, mud, and

rocks. Given an awareness of all of these problems, the editors have used an MC of

50 percent (TW or green basis) as the best estimate for the original condition soon

after harvest. Depending on the time of year, the MC of chips, sawdust, and bark,

singularly or in combination, may be above or below the 50 percent green basis

MC, depending on exposure to rain or snow. Therefore, a piece of wood that has an

MC of 100 percent (OD basis) is considered to have an MC of 50 percent (TW or

green basis). The formulas for calculating MC by the two methods are shown in

table 1 of the text (equations (2) and (3)). Once calculated, an MC value from one
49

Fuelwood Characteristics of Northwestern Conifers and Hardwoods (updated)

basis can be converted to the alternative basis using equations (4) and (5) in table 1.

In a similar manner, these equations can be manipulated so the material weights

at any stated MC can be adjusted to some other desired MC. Frequently, engineers

working on the design of combustion systems want to convert OD weight basis

values to TW or green values. To convert the weight of material from one MC basis

to another, view the conversion as a two-stage process. First, if the material is not

oven dry, convert it to the oven-dry condition.

If the starting MC is a percentage of OD weight, then the formula is:

OD weight = weight at the specified MC /

 (1 + percentage MC at OD basis / 100) (7)

If the starting MC is a percentage of green weight, then the formula is:

OD weight = weight at the specified MC x

 (1 - percentage MC at wet weight / 100) (8)

For example, assume you have 100 lb of material at an MC of 25 percent (OD

basis). Equation (7) can then be used to calculate an OD weight of 80 lb (100 /

(1 + 25/100)). Likewise, for 100 lb of material at 20 percent MC (wet or green

basis), equation (8) can be used to calculate an OD weight of 80 lb (100 x (1 - 20/

100)). Once the OD weight is calculated, equation (8) can be used to calculate the

weight of the sample at any other moisture content.

Ash, a residual material left after burning, results from inorganic compounds

that remain after high-temperature combustion takes place. Such chemicals include

calcium, potassium, magnesium, manganese, and silicon. Ash content is usually

reported as a percentage of the oven-dry weight of wood. The formula for converting from dry basis to green basis is almost exactly the same as that for moisture

content. Equations (7) and (8) can be used to convert ash content at a specified

MC to a second MC. Note that the weight of the inorganic material is constant,

regardless of the MC. Thus, as MC changes, it is the gain or loss of water and not

the basic chemical composition of the wood that changes. If the ash content of an

oven-dry sample of 10 lb of wood is 1.8 percent (0.018), then the ash resulting

from burning will be 0.18 lb (10 lb x 0.018). If the ash content is desired in relation to some other MC, use equations (7) and (8) to calculate the weight of the

10-lb sample at the second MC. If ash content is desired in relation to the green

condition, assumed as 50 percent MC (TW or green basis) or 100 percent MC

(OD basis), then the green weight of the sample increases to 20 lb (increase in

weight is all water) and the new percentage is 0.18 lb divided by 20 lb (0.009 or

0.9 percent ash).
50

GENERAL TECHNICAL REPORT PNW-GTR-810

Conversions made in this updated report were based on the above information.

In tables 3, 4, 9, and 10, we reported MC in both the original OD basis and the

converted TW or green basis, assumed as an MC of 50 percent TW or 100 percent

dry basis. The conversions were made by using equation (5) in table 1. In the

calculated green basis value, we carried the same number of decimal places as the

original report. All other data are reported as per the original publication.

Tables 5 and 11 show the heating values and ash contents using units reported

in the original publication. Tables 6 and 12 show the heating values converted to

the metric or International System of units. Values originally reported in metric

units were not changed. Ash contents were converted from OD basis to wet basis

based on the discussion above.

Likewise, tables 7 and 13 show the higher heating values and ash contents using

the units reported in the original publication. Tables 8 and 14 show the higher

heating values converted to SI units and ash content based on wet weight. To make

the conversion for the higher heating value by volume, we assumed that a cord is a

pile of wood 4 ft by 4 ft by 8 ft that includes wood, bark, and air. Thus, one cord

contains 128 ft3

 of stacked roundwood, which is about 90 ft3 of solid material. If a

cord is converted to stacked meters, then this converts to about 2.55 m3

 of solid

material. Thus, the conversion from British thermal units per air-dried cord to

megajoules per cubic meter was made by multiplying the original value by

1,054.35 and dividing by 2.55 (or simply multiplying by 413.47).

The word “clean” can be used to describe residual products (chips, sawdust,

bark, and hog fuel) that have been moved (blown or conveyed) from the production

process to vans or railcars for transport or a clean asphalt or cement pad for temporary storage. If the material is in temporary storage, dedicated equipment (e.g.,

dozers, loaders) that is kept completely free of mud, rocks, and dirt is used to

handle the material and prevent contamination. Energy systems may have less

stringent material requirements than the pulp and paper industry, but most of the

basic rules of the pulp and paper industry apply. It is observed that many firms

interested in converting to renewable energy systems have initially focused on the

burning technology, only to discover during the startup operation that most of the

problems are associated with fuel characteristics and handling. The major problems

with burning biomass material are contamination and moisture not associated with

the basic MC and ash content of the material, but resulting from poor handling,

storage, and delivery to the burning site.
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