Forest Products 

Laboratory Research 

Program on 

Small-Diameter 

Material 

United States

Department of 

Agriculture 

Forest Service 

Forest 

Products 

Laboratory 

General 

Technical 

Report 

FPL−GTR−110 (Rev.) 
Abstract 

Forests in the United States contain a significant amount of small-diameter and underutilized material. These overstocked 

stands not only increase the risk of insect, disease, fire, and drought damage, but also are costly to remove. Finding 

economical and marketable uses for small-diameter and underutilized material would alleviate these problems while improving watershed health and providing economic opportunities for local communities to help offset forest management 

costs. An extensive research program at the Forest Products Laboratory of the USDA Forest Service is focused on 

searching for economical and marketable uses for small-diameter material. The projects described in this report range from 

conserving timber through improving sawing technology to developing businesses for using small-diameter material. 

Keywords: small-diameter timber, research, value-added, wood utilization, products 

Revised December 2000 

Forest Products Laboratory. 2000. Forest Products Laboratory research program on small-diameter material. Gen. Tech. Rep. FPL–GTR–110 (Rev.). 

Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 31 p. 

A limited number of free copies of this publication are available to the public from the Forest Products Laboratory, One Gifford Pinchot Drive, 

Madison, WI 53705–2398. Laboratory publications are sent to hundreds of libraries in the United States and elsewhere. 

The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin. 

The use of trade or firm names is for information only and does not imply endorsement by the U.S. Department of Agriculture of any product or service. 

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Room 326-W, Whitten Building, 14th and Independence Avenue, SW, Washington, DC 20250–9410, or call (202) 720–5964 (voice and TDD). USDA is 

an equal employment opportunity employer. 
Contents 

Page

Regional Index of Projects ..................................................................................................................................................iii

Background .......................................................................................................................................................................... 1

Conservation Through Best Opening Face Technology....................................................................................................... 2

Sustaining Rural Communities Through Improving Quality of Forest Products ................................................................. 3

Wood Utilization for Ecosystem Management: The Colville Study .................................................................................... 4

Economic Feasibility of Small-Diameter Timber ................................................................................................................ 6

Quality of Pulp From Small-Diameter Trees ....................................................................................................................... 7

Biopulping of Small-Diameter Material............................................................................................................................... 9

Polyoxometalates for Pulping and Bleaching of Mixed Species........................................................................................ 10

Structural Use of Small-Diameter Round Timbers ............................................................................................................ 11

Air-Drying of Small-Diameter Round Timbers ................................................................................................................. 13

Connectors for Roundwood Structural Applications.......................................................................................................... 14

Measurement of Roundwood Material Properties.............................................................................................................. 15

Use of Roundwood in a Demonstration Structure.............................................................................................................. 16

Use of Sound to Evaluate Standing Timber ....................................................................................................................... 17

Veneer Recovery From Small-Diameter Stands in Southwestern Oregon......................................................................... 18

Nontraditional and Underutilized Species for Timber Bridge Design ............................................................................... 19

Lumber Recovery From Ponderosa Pine............................................................................................................................ 21

Properties of Small-Diameter Inland Species Important for Truss Design ........................................................................ 22

Mechanical Grading of Structural Logs for Log Homes.................................................................................................... 23

Utilization Options for Suppressed Douglas-fir ................................................................................................................. 24

Debarking of Softwood With Fungi to Improve Marketing Options ................................................................................. 26

Composting of Wood Waste .............................................................................................................................................. 27

Wood Fiber–Plastic Composites From Underutilized Species........................................................................................... 28

Development of Businesses for Utilizing Small-Diameter Material.................................................................................. 30

Log-Sort Yards................................................................................................................................................................... 31

 iii 

Regional Index of Projects 

 Projects by Forest Service Region 

 1 2 3 4 5 6 8 9 10 

Project 

Page 

no. 

Northern Rocky 

Mt. 

Southwestern Inter 

mount. 

Pacific 

SW 

Pacific 

NW 

Southern Eastern Alaska 

Conservation through BOF technology 4 9 9 9 9 9 9 9 9 9

Improving forest products for rural 

communities 

5 9 9 9 9 9 9 9 9 9

Colville study: ecosystem management 6 — — — — — 9 — — — 

Economic feasibility of small-diameter 

timber 

8 — — 9 9 9 9 — — — 

Quality of pulp from small-diameter trees 9 — — — 9 — 9 — — — 

Biopulping of small-diameter material 11 — — — — — — — 9 — 

Polyoxometalates for pulping and 

bleaching 

12 — — — — — — — 9 — 

Structural use of small-diameter round 

timbers 

13 — — 9 9 — 9 — — — 

Air-drying of small-diameter round timbers 15 — — 9 — — — — — — 

Connectors for roundwood structural 

applications 

16 — — 9 — — — — 9 — 

Measurement of roundwood properties 17 — 9 9 9 — — — — — 

Use of roundwood in a demonstration 

structure 

18 — — — — — — — 9 — 

Use of sound to evaluate standing timber 19 9 — — 9 — 9 — 9 9

Veneer recovery in southwestern Oregon 20 — — — — — 9 — — — 

Nontraditional species for timber bridges 21 9 9 9 9 9 9 9 9 9

Lumber recovery from ponderosa pine 23 — 9 9 9 — — — — — 

Properties of inland species for truss 

design 

24 9 — 9 9 — — — — — 

Mechanical grading of logs for homes 25 9 — — 9 — — — — — 

Utilization options for suppressed 

Douglas-fir 

26 — — — — 9 — — — — 

Debarking of softwood to improve 

marketing 

28 — 9 — — — — — — — 

Composting of wood waste 29 — — — — — — — — 9

Wood fiber–plastic composites 30 — — 9 — — — — — — 

Businesses for small-diameter material 32 9 9 9 — 9 9 9 9 9

Log-sort yards 33 9 9 9 9 9 9 9 9 9

Forest Products Laboratory Research 

Program on Small-Diameter Material 

Background 

Over the past several years, the Forest Products Laboratory has refocused a significant part of its research program on the 

use of small-diameter and thinning material. The primary reason for this shift is the vast amount of small-diameter and 

underutilized material in the national forests. These forest stands cannot resist drought and insect attack, and the buildup 

of dead woody debris is increasing the risk of extensive wildfire. Costs associated with removal of this forest biomass 

understory are high, ranging from approximately $150 to $500 per acre ($370 to $1,235 per hectare), whether removal is 

done mechanically or through prescribed fires. Forest Service estimates indicate that approximately 56 million acres 

(15.6 × 106 ha) of national forests need some kind of removal treatment to reduce the risk of infestation by insects and 

diseases and to reduce high concentrations of fuel buildup. These treatments would also restore watershed health and 

maintain biodiversity. Economical and value-added uses for small-diameter material can help offset forest management 

costs while providing economic opportunities for many small, forest-based communities. 

Previous attempts to support proactive management of underutilized and low-valued timber focused on large industrial 

forestry approaches that require prohibitive capitalization and infrastructure considering the value returned by the 

products. These capital-intensive investments require a continuous supply of timber from public lands for long periods. 

The current strategy focuses on using rural-community-based approaches to generate small businesses that can serve 

local markets with value-added forest products that can be created from the material removed under ecosystem 

management principles. 

The research program at the Forest Products Laboratory (FPL) is aimed at overcoming some technical and economic 

barriers associated with value-added forest products made from small-diameter materials. Since 1993, as budgets have 

declined, FPL has shifted some of its research effort to focus on characterizing small-diameter and thinning material, 

identifying potential uses, and providing technology that can help rural forest-based communities to create successful 

businesses from the byproducts of ecosystem management. For example, research projects are exploring the potential 

of small-diameter material in pulp and papermaking, studying the use of roundwood as a structural material for bridges, 

boardwalks, trail structures, picnic shelters, storage sheds, and other buildings, and evaluating the distribution of lumber 

grades from small-diameter material. 

The following report summarizes past and present research studies on the use of small-diameter material. These studies 

involve many different regions and rural communities. The information gained in any specific location can usually be 

applied nationally. 
2 

 Conservation Through Best Opening Face Technology 

Location Nationwide 

Approach The purchase of standing timber 

(stumpage) is the biggest cost of 

manufacturing softwood dimension 

lumber. Stumpage can account for 

as much as 80% of the total cost of 

manufacturing. To decrease costs, 

processing efficiencies need to be 

dramatically improved; industry has 

responded by automating and increasing production speeds. An unfortunate side effect has been inaccurately manufactured lumber and 

poor lumber recovery. In addition, 

higher processing speeds make it 

impossible for machine operators to 

make consistently good breakdown 

decisions. This has a severe impact 

on recovery because poor sawing 

decisions have a more adverse 

effect on lumber from small logs 

than they do on lumber from large logs. 

 To satisfy increased demands for more efficient conversion of logs to lumber, the Best Opening Face 

(BOF) system was developed at the Forest Products Laboratory (FPL) in the early 1970s. The BOF system 

is a computer simulation model of the sawing process for recovering dimension lumber from sound smalldiameter logs. The BOF model simulates the actual sawing process and determines the best opening face 

for the log. The BOF model helps sawmill operators recover the most lumber from any given log, 

especially small-diameter logs. 

Status Since its development, the BOF program has become the most widely adapted sawmill model for simulating the process of recovering dimension lumber from sound small-diameter softwood logs. 

Results The BOF has proven itself to be an effective aid in sawmill efficiency and forest conservation. This FPLdeveloped technology has aided the automation of West Coast sawmills since the 1970s. Industries incorporated BOF algorithms into computerized optical log scanners and sawing systems to maximize recovery 

of softwood dimension lumber. The BOF and related sawmill computer automation helped prevent industry collapse in the 1970s and 1980s as sawmills shifted from old-growth to small-diameter second-growth 

timber supplies in the Pacific Northwest. In addition to being adopted by industry, BOF provided the basis 

for State and Private Forestry’s national Sawmill Improvement Program (SIP). 

 A vast portion of softwood dimension production in the United States and Canada is manufactured today 

with the help of BOF-based technology. The SIP has improved sawmill efficiency by about 31⁄2%, which 

equates to annual conservation of 1 billion board feet of lumber. This is enough lumber to build all the 

houses in Madison, Wisconsin. 

Contact John “Rusty” Dramm, Forest Products Utilization Specialist, USDA Forest Service, Forest Products 

Laboratory, Madison, WI (608) 231–9326, Fax (608) 231–9592, jdramm@fs.fed.us 
3 

Sustaining Rural Communities Through Improving 

Quality of Forest Products 

Location Nationwide and international

Approach Rural America has been experiencing high unemployment and a 

declining tax base as forest products 

firms close their doors in response 

to the changing structure and availability of timber supply on public 

lands. To overcome these problems, 

the forest products industry has 

made improved quality, productivity, and efficiency key objectives. 

Quality improvement is particularly 

important because it has effects on 

productivity, competitiveness, and 

business survival. Improved quality 

results in lower costs because of 

less scrap and rework, fewer mistakes and delays, and better use of 

machines and materials. Productivity increases in response to lower costs, which allows a company to capture the market with better quality at a lower price. Capturing the market improves competitive position 

and helps companies stay in business, retaining jobs and providing for economic growth. In addition to the 

economic benefits, quality improvement promotes better utilization and conversion efficiency, which helps 

to conserve and extend timber resources and to mitigate impacts on water quality, endangered species, and 

biodiversity. 

Forest Service efforts are helping industry reach their objectives and adapt to the increasing supply of 

small-diameter and underutilized material by implementing quality improvement technology. Quality and 

productivity are improved through informed decision-making provided by the adoption of tools such as 

Statistical Process Control (SPC). Documented case studies where SPC has been implemented have 

demonstrated positive results in controlling lumber size variation and improving manufacturing efficiency, 

quality, and productivity. 

Status The project has been completed. Although no further development is planned, technology transfer 

continues through conferences, clinics, and workshops. 

Results Quality improvement technology is improving industry’s competitive position and helping to sustain rural 

communities by retaining jobs based on the forest industry. In one example, the use of SPC technology 

helped a sawmill owner in the Upper Midwest gain a competitive position in the hardwood market by controlling lumber size variation and reducing target lumber sizes. The size reduction resulted in improved 

lumber recovery and annual savings of $250,000. The properly adjusted target sizes allowed for greater 

lumber dry kiln capacity and shorter drying times that brought an additional $500,000 in energy savings 

and increased productivity. In another example, the use of SPC helped a sawmill in the Intermountain 

West stay in business by identifying and correcting processing problems and bringing lumber size variation under control. These changes lowered cost per unit of output and allowed the mill to purchase logs 

and continue operating, retaining 80 jobs that otherwise would have been lost. 

Contact John “Rusty” Dramm, Forest Products Utilization Specialist, USDA Forest Service, Forest Products 

Laboratory, Madison, WI (608) 231–9326, Fax (608) 231–9592, jdramm@fs.fed.us 
4 

 Wood Utilization for Ecosystem Management: 

The Colville Study 

Location Colville National Forest, Washington 

Approach The Colville Study was initiated in 

1994 to identify and evaluate management options for achieving ecosystem objectives in dense stands 

of small-diameter trees with the aid 

of removing some wood for products. Dense stands of smalldiameter trees are common in the 

forests of the Intermountain West 

and east of the crest of the Cascade 

Range in Oregon and Washington. 

The Colville National Forest (NF) 

selected the Rocky II timber sale 

as an example of the type of stand 

that needs management to achieve 

late successional forest structure, 

decrease forest health risk from 

fire, insects, and disease, improve 

wildlife habitat, and improve aesthetics. A series of research studies were conducted to aid managers in 

understanding how stands may be treated and how products are used. Research was conducted on 

silviculture and ecology, forest operations, timber conversion, and economics. 

Status Studies are complete and results are being transferred to National Forests of Region 6. Some results are in 

the form of a software program called Financial Evaluation of Ecosystem Management Activities 

(FEEMA) to aid in management decisions. 

Results Silvicultural simulations confirm that dense small-diameter stands are unlikely to meet desired conditions 

without treatment. The cost of harvesting is very sensitive to the average diameter of stems and is a key influence on overall economic return from the manufacture of various products. Strength properties of smalldiameter wood were tested for the production of lumber, veneer, composite products, mechanical pulp, and 

chemical pulp; strength was found to be adequate, with some variation by species. Summaries of studies 

on the pulp quality of small-diameter trees from the Rocky II timber sale and the economic return for various small-diameter processing options can be found on subsequent pages. FEEMA is used to evaluate the 

potential return (stumpage prices) possible for given treatments of given small-diameter stands, which are 

presumed to be made into specified products. This program can aid in evaluating the combinations of 

stems offered for sale that should obtain given prices for stumpage. FEEMA is being adopted by National 

Forests in Region 6 to aid in planning management treatments. 

Publications Barbour, R.J.; Fight, R.D. 1998. It’s not easy being green: The tricky world of small-diameter timber. 

Science Findings. 1998(4). Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific 

Northwest Research Station. 6 p. (http://www.fs.fed.us/pnw/sfmay.pdf) 

Barbour, R.J.; Tesch, S.; McNeel, J. [and others]. 1997. Objectives and study design of the Colville Study: 

Silviculture, ecology, utilization, and economics of small-diameter densely stocked stands. In: Barbour, 

R.J.; Skog, K.E., eds. Role of wood production in ecosystem management: Proceedings of the sustainable 

forest working group at the IUFRO All Division 5 Conference; 1997 May 6–8; Pullman, WA. Gen. Tech. 

Rep. FPL–GTR–100. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products 

Laboratory: 67–72. (http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr100.pdf) 
5 

Fight, R.D. 1997. Financial analysis of ecosystem management activities in stands dominated 

by small-diameter trees. In: Barbour, R.J.; Skog, K.E., eds. Role of wood production in ecosystem 

management. Proceedings of the sustainable forest working group at the IUFRO All Division 5 

Conference; 1997 May 6–8; Pullman, WA. Gen. Tech. Rep. FPL–GTR–100. Madison, WI: 

U.S. Department of Agriculture, Forest Service, Forest Products Laboratory: 90–94. 

(http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr 100.pdf) 

Fight, R.D.; Chmelik, J.T. 1998. Analysts guide to FEEMA for financial analysis of ecosystem 

management activities. Gen. Tech. Rep. FPL–GTR–111. Madison, WI: U.S. Department of Agriculture, 

Forest Service, Forest Products Laboratory. 5 p. (http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr111.pdf) 

U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. FEEMA: Financial 

evaluation of ecosystem management activities. Portland, OR: U.S. Department of Agriculture, Forest 

Service, Pacific Northwest Research Station. (http://www.fs.fed.us/pnw/data/feema.htm) 

Willits, S.; Barbour, R.J.; Tesch, S. [and others]. 1996. The Colville study: Wood utilization for ecosystem 

management—Preliminary results of study of product potential from small-diameter stands. Res. Pap. 

FPL–RP–559. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 

11 p. (http://www.fpl.fs.fed.us/documnts/fplrp/fplrp559.pdf) 

Contacts Kenneth Skog, Research Forester, USDA Forest Service, Forest Products Laboratory, Madison, WI 

(608) 231–9360, Fax (608) 231–9508, kskog@fs.fed.us; Jamie Barbour, Research Forest Products 

Technologist, USDA Forest Service, Pacific Northwest Research Station, Portland, OR (503) 808–2074, 

Fax (503) 808–2020, jbarbour01@fs.fed.us
6 

 Economic Feasibility of Small-Diameter Timber 

Location Colville National Forest, Washington 

Approach An economic analysis was 

conducted on various industrial 

processes that use small-diameter 

timber to manufacture products, 

some of which were produced from 

large-diameter trees in the past. 

The products were pulp, oriented 

strandboard (OSB), and dimension, 

stud, machine-stress-rated, and veneer laminated lumber. Each technology was analyzed in terms of 

standard industrial-scale operations 

and its per-unit operating and capital costs, along with unit operating 

revenues at prevailing product 

prices. Researchers calculated the 

timber inputs required to feed such 

operations and a return-to-wood 

figure for each operation, which was expressed as the difference between gross operating revenues and 

costs divided by timber requirements. These calculations set benchmarks for what such operations could 

afford to pay for delivered timber of the type generated by the thinning operations, or, alternatively, what 

the forests could expect to recoup for the expense of undertaking these treatments. 

Status The project was completed in May 1996. 

Results Researchers conclude that pulping, followed by veneer laminated lumber and OSB, provides the highest 

returns to wood, $2.23 to $1.24/ft3

 ($78.72 to $43.77/m3). The lumber options provide lower returns of 

$1.24 to $1.10/ft3

 ($43.77 to $38.83/m3). For all options, considerable capital investments were found to 

be required to achieve these rates of return to wood. This implies that industrial concerns would need to 

be assured of dependable supplies of wood before committing the large sums required. 

Publication Spelter, H.; Wang, R.; Ince, P. 1996. Economic feasibility of products from Inland West small-diameter 

timber. Gen. Tech. Rep. FPL–GTR–92. Madison, WI: U.S. Department of Agriculture, Forest Service, 

Forest Products Laboratory. 17 p. 

Contact Henry Spelter, Economist, USDA Forest Service, Forest Products Laboratory, Madison, WI 

(608) 231–9380, Fax (608) 231–9592, hspelter@fs.fed.us 
7 

 Quality of Pulp From Small-Diameter Trees 

Location Colville National Forest, Washington 

Approach A research study is evaluating the 

chemical and mechanical pulping 

of small-diameter resources harvested on the Colville National 

Forest. Raw materials assessed in 

these pulping trials include sawmill residue chips, submerchantable logs, and small trees from 

Douglas-fir, western larch, and 

lodgepole pine. Vaagen Bros. 

Lumber (Colville, Washington) 

supplied the sawmill residue chips 

and submerchantable logs. The 

small trees were obtained directly 

from the Colville National Forest. 

All roundwood was shipped to 

Forest Products Laboratory (FPL), 

where it was peeled, chipped, and 

screened. Chip samples were sent to the University of Washington, Seattle, for chemical (kraft) pulping 

research. The FPL used the remaining chips for mechanical pulping research by thermomechanical pulping 

(TMP) and chemithermomechanical pulping (CTMP) processes. 

Status Researchers have completed all kraft, TMP, and CTMP trials. 

Results The results of the kraft pulping trials showed that all small trees and submerchantable logs can be used as 

potential raw materials in kraft pulp mills. These wood sources (except Douglas-fir submerchantable logs) 

produce pulps with a kappa number comparable to that of pulps from sawmill residue chips. (Kappa number indicates the extent of delignification during pulp processing.) Pulping large quantities of Douglas-fir 

submerchantable logs with sawmill residue chips produces pulp with inherent chemical nonuniformity. 

Pulping small trees raw materials with sawmill residue chips in linerboard mills (70 to 100 kappa number 

range) may produce pulp with significant chemical nonuniformity. All western larch raw materials had low 

kraft pulp yields. 

The results show that four of the evaluated resources were equal to or better than corresponding sawmill 

residue chips in TMP trials. Lodgepole pine and Douglas-fir small trees produced a better quality pulp, and 

the quality of Douglas-fir and western larch submerchantable logs pulp was the same as that of sawmill 

residue chip pulp. Lodgepole pine submerchantable logs and western larch small trees produced a lower 

quality TMP pulp than that obtained from sawmill residue chips. 

In the initial CTMP trials, which used a higher concentration of sodium sulphite liquor, the quality of 

Douglas-fir small trees and submerchantable logs pulp and lodgepole pine small trees pulp was better than 

that of sawmill residue chips pulp; the quality of lodgepole pine submerchantable logs pulp was comparable to that of sawmill residue chips pulp. Western larch submerchantable logs and small trees and lodgepole pine submerchantable logs were damaged during pulp preparation and thus produced a lower quality 

pulp than that obtained from sawmill residue chips. In the second CTMP trial, which used a lower concentration of sodium sulphite liquor, the quality of Douglas-fir submerchantable logs and western larch small 

trees pulp was better than that of sawmill residue chips pulp; the quality of Douglas-fir small trees pulp 

was comparable to that of sawmill residue chips pulp. 

The same fiberization and refining conditions were used for all raw materials in both TMP and CTMP 

processes. Optimizing these processes for each species would probably improve pulp and paper quality. 
8 

Publications Myers, G.C.; Barbour, R.J.; Abubakr, S. 1997. Utilization of nontraditional species. In: Proceedings, 

TAPPI Environmental Conference; 1997 May 5–7; Minneapolis, MN. Atlanta, GA: TAPPI Press: 

131–138.

Myers, G.C.; Kumar, S.; Gustafson, R.R. [and others]. 1997. Pulp quality from small-diameter trees. 

In: Barbour, R.J.; Skog, K.E., eds. Role of wood production in ecosystem management. Proceedings of the 

sustainable forest working group at the IUFRO All Division 5 Conference; 1997 May 6–8; Pullman, WA. 

Gen. Tech. Rep. FPL–GTR–100. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest 

Products Laboratory: 113–115. (http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr100.pdf) 

Myers, G.C.; Barbour, R.J.; Abubakr, S. 1999. Small-diameter trees used for thermomechanical pulps. 

TAPPI Journal 82(10):105–110. 

Myers, G.C.; Barbour, R.J.; Abubakr, S. 1999. Small-diameter trees used for chemithermomechanical 

pulps. In: Proceedings, TAPPI Environmental Conference; 1999 April 18–21; Nashville, TN. Atlanta, GA: 

TAPPI Press: 481–490. 

Contact Gary C. Myers, Research Forest Products Technologist, USDA Forest Service, Forest Products 

Laboratory, Madison, WI (608) 231–9425, Fax (608) 231–9262, gcmyers@fs.fed.us 
9 

Biopulping of Small-Diameter Material 

Location Forest Products Laboratory, Madison, Wisconsin

Approach Biopulping, the fungal treatment of 

wood chips prior to mechanical 

pulping, decreases energy consumption by a minimum of 30% 

and significantly increases paper 

strength properties. Its commercial 

feasibility has been demonstrated 

by large-scale trials. Currently, 

biopulping technology tends to use 

specialized equipment within or 

near a mechanical pulping mill to 

steam, inoculate, and aerate chips 

from a common pulpwood species. 

Biopulping of small-diameter material presents unique challenges because it would involve alternative 

wood species and, in most cases, 

shipping to distant mills. 

The Colville Study found that mechanical and chemical pulping were suitable uses for small-diameter 

timber, but it did not include biopulping in its investigation. In a two-phase project, Forest Products 

Laboratory researchers are studying the use of biopulping on small-diameter materials from the Colville 

National Forest. First, laboratory experiments are identifying efficient biopulping strains suitable for a 

variety of wood species. Biopulping of nonsterile chips with reduced aeration are being evaluated. In the 

second phase, biopulping trials will be scaled up under field conditions. Results will contribute to the 

development of biomechanical pulping processes for small-diameter timber.

Status The project is in the first phase. Comparative analyses of fungal strains have revealed substantial physiological adaptations to changes in wood species. A genetically altered fungal strain has been isolated, and 

laboratory experiments have demonstrated significantly increased energy savings for wood chips derived 

from small-diameter material. 

Contacts Daniel Cullen, Supervisory Microbiologist, Institute for Microbial and Biochemical Technology, USDA 

Forest Service, Forest Products Laboratory, Madison, WI (608) 231–9468, Fax (608) 231-9488, dcullen01@fs.fed.us; Gary C. Myers, Research Forest Products Technologist, Forest Products Laboratory 

(608) 231–9425, Fax (608) 231–9262, gcmyers@fs.fed.us; Thomas W. Jeffries, Director, Institute of Microbial and Biochemical Technology, Forest Products Laboratory (608) 231–9453, Fax (608) 231–9262, 

twjeffries@fs.fed.us 
10

Polyoxometalates for Pulping and Bleaching 

of Mixed Species 

Location Forest Products Laboratory, Madison, Wisconsin 

Approach Pulping for papermaking provides a 

potential market for small-diameter 

mixed species timber. However, 

conventional pulping is not feasible 

for small-diameter mixed species 

because chemical pulping rates are 

not uniform. Some species are more 

difficult to delignify than are others, 

so they cannot be pulped together; 

easy-to-delignify species would be 

overcooked, while hard-to-delignify 

species would be undercooked. This 

kind of pulping would result in a 

pulp with inferior properties. 

This project investigates the use of 

polyoxometalates (POMs) in the 

pulping and bleaching of smalldiameter mixed species. POMs, a class of nontoxic, environmentally friendly chemical compounds, mimic 

the action of enzymes used by naturally occurring white-rot fungi to metabolize wood components. These 

systems are selective—they remove lignin without damaging the cellulose. POMs have an advantage over 

fungi because they are inorganic and can be used at elevated temperatures to speed up the reaction rates to 

commercially feasible levels. POMs produce no environmentally troublesome byproducts in either pulping 

or bleaching. Researchers are pulping and bleaching small-diameter mixed species with POMs to determine the advantages of these chemical compounds over other delignifying techniques that are not as 

selective. 

Status Phase 1 of the study has been completed. Phase 1 was a small-scale study that investigated the feasibility 

of using POMs to delignify small-diameter mixed species. Phase 2 will be conducted on a larger scale to 

allow more comprehensive testing of pulp properties. 

Results Exploratory work has shown that POM-based systems are effective at pulping and bleaching smalldiameter mixed species. 

Contact James Bond, Project Leader, Chemistry and Pulping Research, USDA Forest Service, Forest Products 

Laboratory, Madison, WI (608) 231–9457, Fax (608) 231–9262, jbond@fs.fed.us

mix

press

wash

wash

brownstock

POM

m ake-up

C O2

O 2

w ater

removal

technology

NPE

removal

metal

recovery

and POM

reprocessing

bleached

pulp

wash

water

recycle

purified POM

stream

polyoxometalate

delignification

POM

reoxidation

&

wet

oxidation

of

dissolved

organics
11

Structural Use of Small-Diameter Round Timbers 

Location Intermountain West, particularly Flagstaff, Arizona, and selected sites in New Mexico 

Approach Developing value-added structural 

uses for round timber will significantly improve the efficient use of 

forest resources. Such uses include 

space frames, trusses, and segmental 

arches for roof assemblies, beam–

column elements for post-frame 

building systems, and pile foundations for residential structures in 

flood- or surge-prone areas. Increasing the value of this material could 

provide an incentive to increase 

selective thinning. Eliminating the 

need for added processing and 

generating low-value materials, 

such as chips, slabs, and sawdust, 

will reduce the unit cost of 

producing structural elements. 

 Compared with lumber and sawn timbers, small-diameter logs have the advantage for a variety of structural applications. The strength of roundwood has been shown to be less variable than that of sawn timber, 

giving a potential advantage in the derivation of allowable stresses. Fiber continuity on the surface of a log 

is less likely to produce splinters than does the “diving” grain common to sawn lumber, giving some 

advantage in applications involving repeated human contact (for example, playground equipment). The 

natural taper of roundwood makes it appropriate for use in column applications where moments and axial 

force increase from tip to butt. With respect to the presence of juvenile and mature wood, the symmetry of 

roundwood makes it less susceptible to warp, more dimensionally stable, and stronger than most lumber 

sawn from it. The round section is better suited to applications where members must carry axial loads in 

combination with multidirectional bending moments. These advantages, coupled with the low processing 

cost, make small-diameter logs an attractive alternative to sawn lumber for many applications. 

Status Researchers have completed pilot studies and identified connections as the aspect of roundwood structural 

use most in need of further investigation. To encourage structural applications of round timbers, connectors must be inexpensive, be easy to apply, and provide consistent, reliable strength and stiffness. These 

characteristics rely on details of the connector as well as moisture conditions and quality of the material at 

the site of attachment. Current research projects are therefore focused on connection performance, air drying, and material properties of roundwood. Another important issue is the lack of information about 

roundwood use in structures. A major obstacle to acceptance of this material centers on necessary deviation from conventional construction practice. Consequently, demonstrations of small-diameter round timber in structural assemblies are being planned. Summaries of these projects can be found in this report. 

Future efforts will focus on developing span tables as well as design guidelines and connection details 

for this type of timber. 
12

Results This study has demonstrated the potential for roundwood use as an alternative to sawn dimension lumber. 

Mean strength and modulus of elasticity of small-diameter timber are comparable to published values from 

tests on clear wood. Strength variability for a given species is low enough to make incremental stress 

grades unnecessary. Using the full section of roundwood reduces processing costs and waste. Loadcarrying capacities of small-diameter timber elements are three to six times that of any prismatic sawn 

timber that could be obtained from them. These findings suggest that it is more efficient to use smalldiameter timber as roundwood than as sawn dimension lumber. 

Contact Ronald Wolfe, Research Engineer, USDA Forest Service, Forest Products Laboratory, Madison, WI (608) 

231–9223, Fax (608) 231–9592, rwwolfe@fs.fed.us 
13

 Air-Drying of Small-Diameter Round Timbers 

Location Vallecitos and Glenwood, New Mexico; Eagar, Flagstaff, Holbrook, Tombstone, and Winslow, Arizona 

Approach Structural applications of smalldiameter timber rely heavily on the 

performance and predictability of 

connections. To optimize the design 

of small-diameter connections, the 

timber should be dried in a manner 

that minimizes drying degrade, especially in the region of the connection.

The drying of round small-diameter 

timber presents different challenges 

than those found in the drying of 

sawn lumber. The symmetry of juvenile wood in small-diameter logs 

means that they are less likely to 

warp compared with lumber cut from 

these logs. Nevertheless, roundwood 

is more difficult to dry because it has 

a lower surface to volume ratio, has 

less exposed end-grain compared with sawn lumber, and is more prone to splitting. Some kiln-drying has 

been used to lower the weight of roundwood poles and piles. Nevertheless, the market for round timber is 

too small for kiln-drying to be an economical option. Air-drying of roundwood requires less energy cost 

than does kiln-drying, but it takes more time and space. A number of air-drying test sites have been established in the arid U.S. Southwest to assess the viability of air-drying small-diameter timber. Cooperators 

monitoring these sites include a lumber company, a university, and a community cooperative. These airdrying studies are considering the effects of shading cloths, end coatings, machining on timber ends, and 

log size on the time needed for drying, the rate of drying, and the degrade of the round timbers. 

Status Three drying studies have been completed and two will be initiated in the fall of 2000. The University of 

Idaho and the Rogue Institute in southwestern Oregon have expressed interest in this project, but economic 

constraints have kept them from participating. Researchers would like to expand the project into Idaho and 

southwestern Oregon because they could then study the effects of a different climate on air-drying smalldiameter timber. Whereas some mills in the southwest might need to slow down the drying process to 

minimize splitting, mills in the northwest might need to accelerate the process. Results of this study will 

form the basis of a published guideline for assessing the feasibility of air drying as a means of producing 

a stable small-diameter timber product of acceptable quality for structural applications. 

Results The primary purpose of air drying logs is to reduce transportation hauling weight. On average, peeled logs 

lose moisture at a rate of roughly 2.5% per day until they reach the fiber saturation point, where wood 

moisture content equilibrates at 8%. Drying below the fiber saturation point proceeds at a slower rate; 

wood moisture content drops from 35% to 15% over a period of 2 months. Unpeeled logs dry at about 1/10

the drying rate of peeled logs. Therefore, air drying unpeeled logs is probably not effective.

Contacts William Simpson, Forest Products Technologist, USDA Forest Service, Forest Products Laboratory, 

Madison, WI (608) 231–9357, Fax (608) 231–9508, wtsimpson@fs.fed.us; Ronald Wolfe, Research 

Engineer, Forest Products Laboratory (608) 231–9223, Fax (608) 231–9592, rwwolfe@fs.fed.us
14

Connectors for Roundwood Structural Applications 

Location Forest Products Laboratory, Madison, Wisconsin 

Approach Previous research on the structural applications of 

small-diameter round timber showed that available 

connectors control the use of this resource in most 

structural applications. Most commercial connectors 

are intended for use with sawn lumber. Two types of 

connectors are made specifically for round timber: 

connectors used for utility poles and those used in custom-built structures. The former are not suitable for 

small-diameter timber, and the latter are designed on 

the basis of proprietary information. Published information about small-diameter timber connectors is limited. Any connectors developed for this kind of resource will have to be able to transfer axial bending 

and/or shear loads, be economically feasible, demonstrate a preference for ductile failure over brittle failure, and compete against conventional construction. 

This project involves pilot testing a variety of connection details to determine relative capacities and material costs. The connectors tested include dowel-nut 

connectors, finger joints, nailed metal plates, wood 

shear keys, and threaded dowel rods. Dowel-nut 

connectors were adapted from the furniture industry 

and finger joints were modeled after the glulam 

industry. Metal plates have been used for heavy timber. 

The threaded dowel rod is an adaptation of the concrete 

post tensioning rod. Forest Products Laboratory researchers are selecting the most promising details to 

develop a data base for deriving design values that will be applied in demonstration structures. 

Status The dowel-nut connector has been evaluated for use with Douglas-fir peeler cores as well as smalldiameter round ponderosa pine. A combination of peeler core and dowel-nut was used to construct a 60-ft- 

(18-m-) span space-frame roof system in Ferndale, Washington. Preliminary results show that the performance of the dowel-nut connection in ponderosa pine round timber is superior to that in the peeler core. 

Flitch and gusset plate connections fabricated using power-driven nails show potential as a low-cost connection that exhibits a very ductile failure mode. 

 Shear keys performed as expected and can be designed for a shear parallel-to-grain failure mode following 

guidelines in the National Design Specification for Wood Construction. The finger joints have not been 

tested to date. 

Results At present, test connections show design capacities in the range of 10,000 to 30,000 lb (44.5 to 133.5 kN) 

for 5- to 7-in.- (127- to 178-mm-) diameter round timbers. 

Contact Ronald Wolfe, Research Engineer, USDA Forest Service, Forest Products Laboratory, Madison, WI 

(608) 231–9223, Fax (608) 231–9592, rwwolfe@fs.fed.us 
15

 Measurement of Roundwood Material Properties 

Location South Dakota, southern Colorado, New Mexico, and Arizona 

Approach Limited knowledge of the strength 

and stiffness of small-diameter timber presents an obstacle to its acceptance as a structural component. 

Existing data from test results for 

small clear specimens, full-size 

lumber, and utility poles do not adequately represent the proportion of 

juvenile wood likely to be found in 

most small-diameter round timber. 

There is also some question as to 

how well the existing data base 

applies to suppressed-growth smalldiameter timber, in which the portion of juvenile wood is not a 

major consideration. 

This project seeks to obtain data needed to characterize the strength and stiffness of small-diameter round 

timber for use in design. A mobile test machine has been designed specifically for this purpose. The 

machine is being used to test logs shortly after harvest to characterize strength and stiffness distributions, 

including variations in these values along the stem length. Because the influence of juvenile wood is likely 

to be most obvious for axial stiffness and strength, the machine was designed to test log sections in axial 

compression. It has a half-million-pound (2.2 MN) load capacity, enough to test a 10-in.- (25-cm-) 

diameter Douglas-fir timber to failure. 

The primary reason for building a mobile test machine was to minimize the influence of moisture variations on timber strength. Wood tested at or above the fiber saturation point, roughly 35% moisture content, 

should exhibit little variability as a result of moisture. As moisture drops below this point, however, wood 

strength and stiffness increase. Until the log section reaches a uniform equilibrium moisture content, moisture gradients will add to the variability. The time required to dry small-diameter timber to a uniform equilibrium moisture content therefore makes it preferable to test in the green condition and then derive a dryuse adjustment. Testing in the green condition, shortly after harvest, will eliminate the variable influence 

of moisture and expedite data collection. 

Log samples are being collected for laboratory testing in bending and compression as a check on correlation and calibration. These results will be compared to the results of field tests on end-matched specimens. 

The bending and compression results should offer a basis for checking the correlation between compression and bending as well as a basis for moisture adjustment and mobile test machine calibration. 

Results obtained from this project will be used to develop standards for deriving design stresses for smalldiameter round timber. These values will also be incorporated in the design of experimental structures 

used to demonstrate the capabilities for round timber use in construction. 

Status The mobile test machine has been calibrated and used twice in field tests. The first test was conducted in 

the Black Hills of South Dakota, close to the eastern limit of the range of ponderosa pine, and in New 

Mexico. Future tests will be conducted in Arizona, Oregon, and Idaho. 

Contact Ronald Wolfe, Research Engineer, USDA Forest Service, Forest Products Laboratory, Madison, WI 

(608) 231–9223, Fax (608) 231–9592, rwwolfe@fs.fed.us
16

Use of Roundwood in a Demonstration Structure 

Location Forest Products Laboratory, Madison, Wisconsin 

Approach A lack of familiarity with the use of 

small-diameter round timber in 

structures and a lack of information 

on drying processes, wood properties, and connectors for this material 

present an obstacle to the acceptance of roundwood in structures. 

The construction of a demonstration 

structure shows the potential of 

roundwood to provide strength and 

stability as well as the creative possibilities that the shape of this resource bring to wood structures. The 

objective of this study is to demonstrate potential applications of structural components made from smalldiameter round timber. Such applications provide value-added markets 

that could help small businesses 

profit from processing this “low 

value” resource. 

For this project, the Forest Products Laboratory (FPL) constructed a demonstration structure framed with 

posts, beams, and trusses made from small-diameter ponderosa pine. Five types of roundwood connectors 

were used. In addition to demonstrating the structural uses of round timber, this structure provides a basis 

for comparing various applications of wood shingles. Researchers detailed the types of connections, treatments, and materials. This experimental structure demonstrates the practical applications of many findings 

from studies on connectors and material properties. 

Researchers are monitoring the performance of the demonstration structure. The structure serves as a demonstration of the benefits of wood research for FPL visitors. It also provides a basis for the development of 

construction guidelines for working with this resource and for making architects and contractors more 

aware of the possibilities for small-diameter roundwood use in structures. 

Status The structure was completed in July 2000. The FPL is providing some technical guidelines to cooperators 

who want to use small-diameter round timber in structures. Examples include roofs for a school gym, a log 

barn, and a Navaho dwelling (hogan).

Contact Ronald Wolfe, Research Engineer, USDA Forest Service, Forest Products Laboratory, Madison, WI 

(608) 231–9223, Fax (608) 231–9592, rwwolfe@fs.fed.us 
17

 Use of Sound to Evaluate Standing Timber 

Location Alaska, Arizona, Idaho, Michigan, Minnesota, and Washington 

Approach Differences in genetics, the environment, and responses to human 

intervention create a wide variability in wood as a material. Consequently, manufacturers and users 

of wood products become frustrated by processing difficulties 

and performance variability in 

finished products. Nondestructive 

evaluation (NDE) technologies 

have contributed significantly 

towards eliminating the cause of 

these frustrations. NDE is the science of identifying the physical 

and mechanical properties of a 

material without altering its enduse capabilities and using this 

information to make decisions on 

appropriate applications. In the forest products industry, NDE technologies are currently used in lumber 

and veneer grading programs and result in engineered materials with well-defined performance 

characteristics. 

NDE includes various technologies, such as x-rays, chemical analyses, vibration properties, and sound 

wave transmission. The use of sound wave transmission characteristics has received considerable attention 

because of its potential to evaluate the quality of wood in standing timber. Two properties commonly 

measured by sound wave NDE are speed-of-sound transmission and sound wave attenuation, the rate at 

which a wave loses energy as it travels through wood. Speed-of-sound transmission depends on fiber 

(grain) angle and is significantly influenced by the presence of certain types of decay or deterioration. Previous research has found that sound travels at a lower speed through deteriorated stems. Sound wave attenuation correlates with wood properties such as modulus of elasticity (MOE). Better knowledge of the 

properties of standing small-diameter timber will help identify more value-added uses for this resource. 

The USDA Forest Service has initiated a series of studies with various cooperators to investigate NDE 

technologies for standing timber. The studies represent a wide range of species as well as forest ecosystems. Wood is evaluated for the presence of decay as well as MOE. To detect the presence of decay, researchers measure speed-of-sound transmission across the diameter of the tree stem. To determine MOE, 

they place accelerometers approximately 1.6 ft (0.5 m) apart along the tree stem, with the upper accelerometer 3.3 ft (1.0 m) above the groundline. They then use an impact hammer to strike a nail inserted into 

the stem to induce a stress wave into the stem. The characteristics of the resulting wave are related to the 

mechanical properties of lumber obtained from the tree. 

Status The studies are in their beginning phases.

Results Preliminary results are encouraging. Researchers have observed a very good correlation between sound 

transmission characteristics and the presence of decay in small-diameter balsam fir trees. Results from 

studies on Douglas-fir trees indicate a relationship between sound transmission characteristics and the 

mechanical properties (MOE) of structural lumber obtained from these trees. 

Contact Robert Ross, Project Leader, USDA Forest Service, Forest Products Laboratory, Madison, WI 

(608) 231–9221, Fax (608) 231–9592, rjross@fs.fed.us 
18

 Veneer Recovery From Small-Diameter Stands 

in Southwestern Oregon 

Location Applegate Watershed, southwestern Oregon 

Approach The Applegate Watershed consists 

of dense, overstocked stands of 

ponderosa pine, Douglas-fir, white 

fir, and Shasta red fir. By finding 

economical and value-added uses 

for this material, foresters can offset 

management costs. 

The USDA Forest Service, Pacific 

Northwest Experiment and Range 

Research Station, with cooperation 

from both the Forest Products Laboratory and State and Private Forestry in Region 6, examined the 

relationship between nondestructive 

evaluation of small-diameter timber 

in the Applegate Watershed and 

wood product quality. Researchers also examined the potential of producing veneer from this resource. 

They concluded that the properties of this veneer make it suitable for the manufacture of engineered wood 

products, such as laminated veneer lumber (LVL). 

 Collaborators selected sample sites and 25 sample trees of each of three species (ponderosa pine, Douglasfir, and white fir). The sound wave characteristics of both tree-length and short logs were nondestructively 

measured. The logs were then taken to a mill where they were cut into veneer and processed into LVL. 

The quality of the veneer, as determined by ultrasonic grading, was compared to the quality of the logs 

from which the veneer was made. 

Status The ponderosa pine portion of the study has been completed. Data analysis for Douglas-fir and white fir is 

in progress. 

Results Information to date indicates that the quality of the veneer produced from small-diameter trees is similar to 

the quality of veneer produced from old growth. Measurements from both short and tree-length logs correlate strongly to comparable measurements made on veneer obtained from those logs. These findings suggest that small-diameter timber is suitable for the manufacture of LVL. In addition, the collaborators have 

shown that the quality of logs can be assessed more accurately before they are processed into veneer. This 

results in more efficient use of the resource and a cost savings to LVL manufacturers. 

Contacts Susan Willits, Program Manager, USDA Forest Service, Pacific Northwest Research Station, Portland, OR 

(503) 808–2066, Fax (503) 808–2020, swillits@fs.fed.us; Robert Ross, Project Leader, USDA Forest Service, Forest Products Laboratory, Madison, WI, (608) 231–9221, Fax (608) 231–9592, rjross@fs.fed.us 
19

 Nontraditional and Underutilized Species 

for Timber Bridge Design 

Location Nationwide 

Approach The transportation infrastructure in 

the United States is in disrepair. 

Approximately 50% of highway 

bridges are structurally deficient or 

functionally obsolete. The majority 

of these bridges are located on rural 

roads where local economies 

depend heavily on the highway 

system. 

Timber bridges have proven their 

durability, and many bridges more 

than 50 years old are still in service. 

Forest Service efforts during the 

past decade have done much to advance the acceptance and use of 

timber bridges, and the potential for 

improved wood utilization in bridge 

applications continues to grow. 

Many timber highway bridges are currently being constructed from glued-laminated timber (glulam), 

which is manufactured by gluing together relatively small sawn lumber members to form large structural 

components. Small-diameter material is especially suited to the construction of glulam stress-laminated 

decks and deck panels. Stress-laminated bridge decks are constructed from a series of small glulam beams 

manufactured from nominal 2- by 4-in. (standard 38- by 89-mm) lumber. By placing the beams side by 

side and connecting them with tensioned steel bars, bridges can be built with spans up to 50 ft (15 m). 

Glulam deck panels are typically placed on top of glulam or steel beams to form a bridge deck. Nominal 

6- or 8-in. (standard 140- or 184-mm) material is required for these panels; nominal 6-in. (standard 

140-mm) material is used in most cases. Some species, such as ponderosa pine, are excellent for glulam 

bridge applications because the material is easily glued and treated with wood preservatives. These applications are also well suited for low-strength material, which is typical of several small-diameter species. 

Status The Forest Products Laboratory has been involved in developing timber bridge systems for secondary 

wood species for more than a decade. Many stress-laminated bridges have been built using red pine 

glulam, and extensive field evaluations have been completed. Five bridges have been built from new designs using cottonwood glulam deck panels: four bridges have cottonwood decks on steel stringers, and 

one is a cottonwood girder bridge with a cottonwood glulam deck. Several more bridges will be built using 

cottonwood during the next 2 years. Two ponderosa pine bridges were built on the Tonto National Forest 

in Arizona. 

Much basic research has been directed toward adapting these bridge designs to other small-diameter 

species. Future work will include the development of economical standardized designs using smalldiameter species. 

Results Red pine glulam bridges have shown good performance in field evaluations, as have demonstration structures built with small-diameter material. Efficient manufacture of glulam from combinations of yellowpoplar, red oak, and red maple lumber has led to a revision of industry standards. 
20

Publications Ritter, M.A.; Duwadi, S.R. 1998. Research accomplishments for wood transportation structures based on a 

national research needs assessment. Gen. Tech. Rep. FPL–GTR–105. Madison, WI: USDA Forest Service, 

Forest Products Laboratory. 30 p. 

Ritter, M.A.; Wacker, J.P.; Duwadi, S.R. 1995. Field performance of stress-laminated timber bridges on 

low-volume roads. In: Proceedings, 6th international conference on low-volume roads, 1995 June 25–29, 

Minneapolis, MN. Washington, DC: National Academy Press; Vol. 2: 347–356. 

Ritter, M.A.; Wacker, J.P.; Tice, E.D. 1995. Field performance of timber bridges. 2. Cooper Creek stresslaminated deck bridge. Res. Pap. FPL–RP–536. Madison, WI: USDA Forest Service, Forest Products 

Laboratory. 17 p. 

Wacker, J.P.; Ritter, M.A. 1992. Field performance of timber bridges. 1. Teal River stress-laminated deck 

bridge. Res. Pap. FPL–RP–515. Madison, WI: USDA Forest Service, Forest Products Laboratory. 19 p. 

For a list of additional publications on this topic, visit the FPL Wood Transportation Structures Research 

Publications website (http://www.fpl.fs.fed.us/wit/pubs.htm). 

Contact Michael Ritter, Assistant Director, USDA Forest Service, Forest Products Laboratory, Madison, WI 

(608) 231–9229, Fax (608) 231–9592, mritter@fs.fed.us 
21

 Lumber Recovery From Ponderosa Pine 

Location Flagstaff, Arizona; Forest Products Laboratory, Madison, Wisconsin

Approach More than 5.5 million acres 

(2.23 million hectares) of densely 

stocked ponderosa pine are in the 

southwest. Thinning these stands 

would improve forest health and 

reduce the risk of catastrophic wildfire. The cost of such management 

is high, but cost could be defrayed 

by converting the removed wood 

into products. Past research to 

evaluate product recovery from 

small-diameter ponderosa pine trees 

has generally not been specific to 

suppressed stands and has been 

limited to a few grading options. 

Approximately 150 ponderosa pine 

trees were selected from a stand near Flagstaff, Arizona. The trees were about 100 years old and 6 to 16 in. 

(15 to 41 cm) diameter at breast height. The forest management objectives were to return these dense overstocked stands to stock levels similar to presettlement conditions. The trees were measured and cut into 

logs. Half of each log was sawn into appearance grade lumber and the other half into nominal 2- by 4-, 2- 

by 6-, and 2- by 8-in. lumber (standard 38- by 89-, 38- by 140-, and 38- by 184-mm lumber). A total of 

14,000 board feet (33 m3

) of lumber was processed. The structural lumber was graded into structural light 

framing, machine stress rated, and lamstock grades. 

Results The cubic volume (percentage of gross cubic log volume) of dried and surfaced lumber increased with log 

diameter. The recovery of dimension lumber was slightly higher than that of appearance grade lumber. The 

recovery of No. 2 Common and better appearance-grade lumber was about 25%, with a majority of lumber 

(66%) graded as No. 3 Common. A previous study showed that the value of No. 3 Common lumber can be 

improved with further processing as cut stock. 

Preliminary analysis of the data by visual grade for the Structural Light Framing grading system showed 

that about 50% of the lumber is No. 2 or better grade. However, very little lumber is Select Structural (the 

highest grade), and very little is below No. 3 (Economy) grade. Value recovery depends upon both the 

volume and grade of the lumber recovered from the log. The value of both appearance-grade and dimension lumber increased with log diameter. Even though logs of equal size sawn for appearance grade had 

similar volume recovery to those sawn for dimension lumber, the logs sawn for appearance grades would 

be worth more than those sawn for dimension lumber (based on 1999 Western Wood Products Association 

year-to-date prices). 

Wane on the edges of the pieces and warp caused by drying degrade were the two most common gradelimiting factors for the dimension lumber. The grade of about half the pieces was limited by drying degrade. The top loading used to weigh down half the dimension lumber did not reduce warp. To better 

understand this anomalous result and to investigate other drying alternatives, an independent study on 

the drying of small-diameter ponderosa pine has been initiated at the Forest Products Laboratory. 

Status Testing and evaluation are almost complete. 

Contacts David Green, Research Engineer, USDA Forest Service, Forest Products Laboratory, Madison, WI 

(608) 231–9261, Fax (608) 231–9303, dwgreen@fs.fed.us; Eini Lowell, Research Scientist, USDA Forest 

Service, Pacific Northwest Research Station, Portland, OR (503) 808–2072, Fax (503) 808–2020, 

elowell@fs.fed.us 
22

 Properties of Small-Diameter Inland Species 

Important for Truss Design 

Location Idaho, western Montana, Four Corners region of Arizona and New Mexico, Flagstaff area of 

northern Arizona 

Approach A research study is in progress to 

evaluate the yield of structurally 

graded nominal 2- by 4-in. 

(standard 38- by 89-mm) lumber 

(2 by 4) from several locations in 

the Inland West. Species being 

evaluated include ponderosa pine, 

lodgepole pine, white fir, and grand 

fir, where available. Smalldiameter trees are sawn into 2 by 4s 

for each location. Researchers then 

determine the grade of the wood 

using mechanical and visual grading systems. Some lumber is used 

to determine the properties of 

manufactured metal-plate connections when used with smalldiameter timber. Production of 

structural lumber for use in metal-plate-connected wood trusses is an attractive option for using lumber 

from small-diameter trees. However, little information is available on the mechanical properties of this 

material. The information obtained in this study, when combined with historical data and independent 

studies on other uses, is helping to define utilization options for wood from small-diameter trees in the 

Inland West. 

Status Results from the Idaho and Montana locations indicate that excellent yields of visually graded structural 

lumber can be obtained from lodgepole pine and grand fir. Ponderosa pine thinnings show little potential 

for direct use as structural lumber, since these trees grow below the canopy and the wood has many knots. 

Additional ponderosa pine samples obtained from co-dominant trees are expected to produce better yields. 

Mechanical grading of lodgepole pine and grand fir offered even better grade yield of structural products 

than did visual grading. Machine–stress-rated (MSR) lumber can produce an estimated $27 per thousand 

board feet ($11.44/m3

) premium over the value of visually graded lumber for lodgepole pine and a $15 per 

thousand board feet ($6.36/m3

) premium for grand fir. Testing and analysis of material from Colorado and 

Arizona are in progress. 

Contact David Green, Research Engineer, USDA Forest Service, Forest Products Laboratory, Madison, WI 

(608) 231–9261, Fax (608) 231–9303, dwgreen@fs.fed.us 
23

Mechanical Grading of Structural Logs for Log Homes 

Location Idaho, Montana 

Approach In the West, 80% to 90% of the logs used to make 

log homes come from standing dead trees, primarily 

trees killed during wildfires. Dead trees that are left 

in the forest contribute to fire risk and often have 

little value in traditional markets. Log homes provide a high-value use for such material as well as 

employment opportunities for local communities. 

Current structural grading methods for logs to be 

used in log homes are based solely on visual methods. Property assignments with this process are not 

very precise and are probably overconservative. 

Previous Forest Products Laboratory research on 

structural timbers demonstrated that a mechanical 

grading system based on a combination of visual 

grading and nondestructive testing is more precise 

than standard structural grading methods and can 

lead to more efficient use of the available resource. Such a grading system for structural logs can potentially allow the use of small-diameter members in log homes and thus increase the use of dead timber. In 

this two-phase study, a mechanical grading system is being developed for logs from dead trees. 

Status Phase I of the study is nearing completion. Logs with a uniform diameter of 9 in. (23 cm) were obtained 

from dead subalpine fir and lodgepole pine trees. To provide the modulus of rupture to modulus of elasticity relationship needed to develop grade boundaries for mechanical sorting, 60 logs were tested at the 

University of Montana in third-point bending. To determine the relationship between compression and 

bending, an additional 60 logs are being tested as short columns at the Forest Products Laboratory. Analysis of these bending tests is in progress. In Phase II, researchers will sort logs into one or more mechanical 

grades, then subject the logs to bending tests to assess the accuracy of the property assignments. 

Contact David Green, Research Engineer, USDA Forest Service, Forest Products Laboratory, Madison, WI 

(608) 231–9261, Fax (608) 231–9303, dwgreen@fs.fed.us
24

 Utilization Options for Suppressed Douglas-fir 

Location Shasta–Trinity National Forest, California; Forest Products Laboratory, Madison, 

Wisconsin

Approach Problems associated with densely 

stocked small-diameter stands are 

common in the West. Such stands 

cannot resist drought and insect attack, and the buildup of woody debris increases the risk of catastrophic wildfire. The stands must be 

thinned to maintain or improve forest health and to reduce the risk of 

wildfire. Historically, smalldiameter trees have been considered 

nonmerchantable and treated as 

waste. To help pay the estimated 

$150 to $500 per acre ($375 to 

$1,250 per hectare) associated with 

thinning, economical uses must be 

found for these trees. Douglas-fir 

(Pseudotsuga menziesii) is the most 

important commercial species in western United States and a major component in many stands of suppressed trees. Although there are extensive data on expected yields of lumber products from large 

Douglas-fir trees and from intensively managed plantations, little information is available on properties 

and grade yield from suppressed trees. 

Trees were selected from a 67-acre (26.8-hectare) stand of even-aged Douglas-fir on the Shasta–Trinity 

National Forest that was being thinned to reduce ladder fuels and to maintain forest health. Most trees 

sampled were 60 to 80 years old, with diameter at breast height ranging from 4 to 10 in. (10.2 to 25.4 cm). 

The average size of the worst knot in butt and middle logs was 0.2 to 0.3 in. (0.5 to 0.8 cm). Generally, 

the logs had less taper than might be expected in small-diameter trees and a low occurrence of juvenile 

wood in the butt logs. The logs were cut into nominal 2- by 4-in. (standard 38- by 89-mm) and nominal 

2- by 6-in. (standard 38- by 140-mm) lumber and dried in a dehumidification kiln. Some lumber was 

scanned to estimate the recovery of clear cuttings. The rest of the lumber was graded as Structural Light 

Framing, Light Framing, or LamStock (Stud grade). 

Results The results of visual grading are shown in the following table. Based on visual characteristics, 82% of the 

lumber might qualify for the highest machine-stress-rated grades and 30% for tension lamination grades of 

glulam. Mechanical testing must be completed before final grade assignments can be made for these grading systems. Some lumber is also being finger jointed for determining finger-joint strength for glulam 

beams. 
25

Status Mechanical testing and evaluation of results are nearing completion. 

Contacts David Green, Research Engineer, USDA Forest Service, Forest Products Laboratory, Madison, WI 

(608) 231–9261, Fax (608) 231–9303, dwgreen@fs.fed.us; Eini Lowell, Research Scientist, USDA Forest 

Service, Pacific Northwest Research Station, Portland, OR (503) 808–2072, Fax (503) 808–2020, 

elowell@fs.fed.us

Results of visual grading 

Grade and rejects Yield (%) 

Structural Light Framing 

Select Structural 68 

No. 1 7 

No. 2 17 

No. 3 5 

Rejects 3 

Light Framing 

Construction 74 

Standard 17 

Utility 5 

Rejects 4 

Stud 

Grade 88 

Rejects 11 
26

Debarking of Softwood With Fungi to 

Improve Marketing Options 

Location Rocky Mountain Region 

Approach One barrier to using smalldiameter, slow-growth timber is 

the lack of a practical, economical 

way to remove the bark. Removing 

the bark of dormant or slowgrowing timber is very difficult 

because the cambial layer, which 

lies just under the bark, is resistant 

to shearing. Since the cambial 

layer is very thin and susceptible to 

microbial degradation, it is possible to harness the use of natural 

fungi to aid in debarking. Fungi 

debark timber biologically by attacking the cambial layer and loosening the bark. Some fungi are detrimental because they discolor the wood (sapstain). Other fungi can 

debark timber and prevent the incursion of detrimental fungi. 

To investigate the potential of fungi for debarking small-diameter timber, fungi that naturally colonize 

the cambial layer will be isolated from felled and exposed logs. The fungi will be identified and used to 

inoculate new logs in the cambial region. Various treatments will be tested that might facilitate growth 

of the fungi, such as wetting the log or sealing the exposed ends. After appropriate incubation times, 

the bark will be removed mechanically and the amount of energy required for debarking will be measured. 

Researchers will investigate several variables: species of fungi and tree, age and growth rate of wood, 

type and method of inoculation, incubation time required, and season of harvest. Sampling for new 

fungi and analysis of fungal application will be conducted on a quarterly basis for approximately 

2 years. Researchers hope to identify the most efficient fungi for debarking and the optimum conditions 

for inoculation and colonization. The final product will be a biological debarking process that is suitable for commercial use. This project will increase forest health and productivity by lowering the cost 

of removing bark from slow-growing, overcrowded small-diameter timber, thus making this resource 

more commercially desirable.

Status The project is in progress. 

Contacts Thomas W. Jeffries, Director, Institute of Microbial and Biochemical Technology, USDA Forest Service, Forest Products Laboratory, Madison, WI (608) 231–9453, Fax (608) 231–9262, 

twjeffries@fs.fed.us; Jessie A. Micales, Project Leader, Forest Products Laboratory (608) 231–9215, 

Fax (608) 231–9592, jmicales@fs.fed.us; Robert Dettman, Branch Chief, Rural Development, USDA 

Forest Service, Rocky Mountain Region, Golden, CO (303) 275–5741, Fax (303) 275–5754, 

bdettmann@fs.fed.us 
27 

 Composting of Wood Waste 

Location Ketchikan, Alaska 

Approach The disposal of woody residues, 

whether from thinning overstocked 

small-diameter stands or from the 

forest product industry, has 

become a costly problem. In the 

past, this material was burned or 

allowed to accumulate in huge 

piles on low-value land behind 

mills or within the forest. Tighter 

environmental regulations 

designed to reduce the runoff of 

organic residues into groundwater 

supplies have necessitated the 

development of different disposal 

systems. Composting transforms 

wood waste into a value-added 

product. It is a microbial process 

that converts carbonaceous and nitrogenous materials into a stable, often nutrient-rich, organic soil 

supplement that can be sold to consumers or returned to the forest to increase soil fertility and improve 

forest health. 

Large-scale, commercial composting operations require substantial amounts of capital investment. The 

small-scale producer of forest products residues cannot afford this type of investment. The Forest Service is therefore exploring smaller-scale alternatives that will be efficient at compost production but do 

not require a large investment of capital. Increasing the efficiency of composting woody materials 

would also decrease costs by allowing faster turnover of woody residues. Passive aeration of compost 

piles and windrows does not require investment in large air-handling systems and is one possibility for 

reducing costs. This system has not yet been thoroughly evaluated for the composting of forestry 

residues. 

The objective of this study is to develop cost-effective and efficient composting technologies for the 

materials and conditions found in southeastern Alaska that have universal applications and can be used 

throughout the United States. Specific objectives include the following: 

• Determining whether passive aeration composting is as effective as active aeration for composting 

a variety of forestry residues 

• Determining how much residue from decay-resistant wood species, such as cedar, can be incorporated into compost without decreasing its quality 

• Determining whether the addition of wood-decay fungi or commercially available bacterial preparations to the curing stage of composting will accelerate the decomposition of recalcitrant woody 

materials 

Status The study is in its initial phase, the construction of passively aerated compost windrows. 

Contacts Jessie A. Micales, Project Leader, Center for Forest Mycology Research, USDA Forest Service, Forest 

Products Laboratory, Madison, WI (608) 231–9215, Fax (608) 231–9592; jmicales@fs.fed.us; Paul 

McIntosh, Community Liason Officer, USDA Forest Service, Alaska Region, Ketchikan, AK 

(907) 228–6201, Fax (907) 228–6215, pmcintosh@fs.fed.us 
28

 Wood Fiber–Plastic Composites 

From Underutilized Species 

Location Albuquerque and Mountainair, New Mexico; 

Phoenix, Arizona; northern California 

Approach Utilization research on composite materials 

conducted at the Forest Products Laboratory 

(FPL) is helping to justify and provide a return for removal of the present biomass 

buildup. The technology used to assemble 

composites from small pieces of wood is 

adaptable to a changing resource base. Composites can be made from a variety of wood 

and wood-based raw materials, including fibers, particles, flakes, and strands. Current 

research focuses on developing wood fiber–

plastic composites from blends of thermoplastics and various species of wood fibers 

(pinyon pine, juniper, insect-killed white fir, 

and guayule wood). More than 3.4 ×109

 lb 

(1.5 ×109

 kg) of filled thermo- plastic composite materials are used annually in the 

United States to produce a wide range of 

products. Fillers improve the stiffness, 

strength, and dimensional stability of thermoplastics. At FPL, wood fiber is being used 

as a filler in wood–plastic composites. The 

benefits to using this technology include reducing the overall amount of material used through better engineering, increasing the strength and life 

of the product, and reducing the weight of the product. 

Status One study is exploring the properties of thermoplastics filled with wood fibers from small-diameter and 

insect-killed white fir. Fibers from insect-killed white fir have slightly better notched impact, tensile, 

and flexural properties than that of commercially available wood flour fillers. Other small-diameter 

species are being investigated. 

Another study centers on expanding the potential uses of juniper and developing technology for industrial application of juniper fiber materials. This study focuses on determining current environmental 

management needs for juniper rangelands, improving rural community economic sustainability, and 

providing a competitive and efficient alternative for a high-value durable exterior panel products. The 

goal is to develop and demonstrate the technical and market feasibility for a juniper–polymer material 

system engineered for highway signage. Prototype signs were made from whole juniper trees and others from juniper stems. Samples from these sign panels are being tested for stiffness, strength, durability, fastener performance, and puncture resistance. Samples have also been installed at various Forest 

Service sites in New Mexico. After 12 months of exposure, the samples will be evaluated for weatherability, animal damage, and general evidence of continued serviceability. Mixing juniper fiber with a 

controlled blend of waste plastics will allow FPL scientists to create a material with the needed mechanical properties and weather resistance for the sign industry. 
29 

A third study involves expanding the potential uses of wood fiber–thermoplastic composites to a host 

of exterior applications by incorporating a naturally occurring preservative and termicide into the composites. Limited research data indicate that when the naturally occurring resin of guayule (Parthenium 

argentatum) combines with wood in a composite, it provides protection against termites, molluscan 

borers, and fungi. The objective of this research is to use guayule as a natural wood preservative in 

wood fiber–plastic composites. Termite tests are ongoing in Arizona, and the University of Illinois is 

conducting decay tests. This research and development should lead to many markets for durable exterior materials. 

Contact James Muehl, Scientist, USDA Forest Service, Forest Products Laboratory, Madison, WI 

(608) 231–9398, Fax (608) 231–9582, jmuehl@fs.fed.us 
30

 Development of Businesses for Utilizing 

Small-Diameter Material 

Location Nationwide 

Approach Attempts to find ways to support 

proactive management of underutilized and undervalued timber have 

previously focused on large industries, which require a high amount 

of capital and infrastructure compared to the value returned by the 

products. Recent efforts by the 

State & Private Forestry Technology Marketing Unit at the Forest 

Products Laboratory focus on rural 

community-based approaches to 

generate small businesses that can 

serve local markets with lower 

costs. Information is being developed for small forest-dependent 

communities to evaluate the uses 

of small-diameter material in various markets and their economic 

feasibility. 

 This work is being developed and tested within the Intermountain West and Southwest. These regions 

consists of many dense stands of overstocked small-diameter material that are at risk from insect infestation and catastrophic wildfire. Although current efforts focus on this particular region, the results are 

applicable to any available forest biomass; they are specifically targeted to a community-based 

approach to generating market pull to remove excess biomass. The results from this work will be 

applicable to areas with forest-based communities and undervalued overstocked timber. 

Status A bibliography of information relevant to utilization of small-diameter and underutilized material is 

available. Computerized software programs are under development that will estimate capitalization, labor, and raw material requirements for appropriate combinations of harvesting and processing systems 

and associated product markets. Model outputs will be based on available resource characteristics and 

supplies. This software assesses the economic feasibility of new investments and develops detailed 

business pro-forma statements. Various investment feasibility scenarios are also under development, 

representing technologies that could contribute to the complete and economic use of small-diameter 

and underutilized material. 

Contact John “Rusty” Dramm, Forest Products Utilization Specialist, USDA Forest Service, 

Forest Products Laboratory, Madison, WI (608) 231–9326, Fax (608) 231–9592, jdramm@fs.fed.us 
31 

Log-Sort Yards 

Location Nationwide 

Approach In the past 10 years, the amount 

and type of Federal timber 

available for the traditional forest 

products industry has changed 

dramatically. As a result, many 

large timber firms have shut down, 

causing unemployment problems 

in several forest-dependent rural 

communities. The establishment of 

log-sort yards in these areas would 

provide an opportunity to improve 

the marketing of small-diameter 

timber by offering a location where 

purchasers could bring small 

quantities of timber for sorting for 

the best market niche. Improved 

marketing of this resource could 

improve rural economies. 

Log-sort yards are heterogeneous and have different functions. Some manufacture value-added products such as debarked logs and utility poles, and others simply sort logs according to different grades 

and species. In general, log-sort yards manufacture and sort logs into higher-value products and broker 

them to the best market. They thus provide a market for large and small timber producers and for 

supply firms with raw materials. Successful log-sort yards are self-sufficient and have a good business 

plan, well-established markets, a steady supply of wood, and adequate capital. 

This project investigates the log-sort yard as a feasible outlet for small-diameter timber utilization and 

marketing by determining how to plan, develop, and operate such a yard successfully. Many aspects of 

these enterprises are being studied, including design, technology, grading and scaling procedures, and 

markets. This analysis will provide knowledge about the business planning and management skills 

needed to operate a small-diameter processing center. A good business plan is particularly important 

for obtaining financing and increasing the odds of success. 

After reviewing current information on log-sort yards, project team members visited existing and 

planned log-sort yards in the United States that represent a variety of management situations; some 

log-sort yards were commercially owned, and others were run by the community or government. The 

aim of the project is to produce a log-sort yard guidebook applicable to both small-diameter softwoods 

in the West and underutilized material in forests nationwide. Developing successful log-sort yards 

promotes better utilization and improved value recovery of available timber resources. 

Status Team members are currently analyzing the information collected and preparing the guidebook. 

Contact John “Rusty” Dramm, Forest Products Utilization Specialist, USDA Forest Service, Forest Products 

Laboratory, Madison, WI (608) 231–9326, Fax (608) 231–9592, jdramm@fs.fed.us