## Wood Use: U.S. Competitiveness and Technology—Vol. II

November 1984

NTIS order #PB85-156081Recommended Citation: Wood Use: U.S. Competitiveness and Technology—Volume II-Technical Report (Washington, DC: U.S. Congress, Office of Technology Assessment, OTA-M-224, November 1984).

Library of Congress Catalog Card Number 83-600567

For sale by the Superintendent of Documents U.S. Government Printing Office, Washington, DC 20402

# Preface

The Office of Technology Assessment assessed the role of wood in the U.S.economy at the request of Senator Mark Hatfield, Chairman of the Senate Committee on Appropriations, and Senator Thad Cochran, Chairman of the Subcommittee on Agriculture, Rural Development, and Related Agencies, Representative James Weaver, Chairman of the Subcommittee on Forests, Family Farms, and Energy, joined in support of the assessment in the House of Representatives. Thefinal report of this assessment was published as volume I of Wood Use: U.S. Competitiveness and Technology, Representative Weaver requested that this second volume, a technical report on wood technologies and wood use, be prepared. Volume II reviews the status of wood manufacturing technologies and surveysthe current and future uses of wood products. It explores the existing or developing technologies and manufacturing processes that can enable the United States to benefit from its vast timber resource. Technologies for increasing the growth and production from the forest and the efficiency of harvesting and transporting timber were treated in volume I.

- JOHN H. GIBBON S Director

,., ///

### Wood Use: U.S. Competitiveness and Technology Advisory Panel

Larry Tombaugh, Chairman Department of Forestry, Michigan State University

Darius Adams Carter Keithley Department of Forest Management Wood Heating Alliance Oregon State University Clark S. Binkley School of Forestry and Environmental Studies Yale University

Carroll Brock M. G. Brock & Sons

Merle Conkin National Forest Products Association* M. Rupert Cutler The Audubon Society Peter Kirby The Wilderness Society Dudley Kircher Mead Corp. Bruce Lippke Weyerhaeuser Corp.

Norma Pace American Paper Institute

Carl Reidel Center for Environmental Studies Ormond Danford University of Vermont Tree Farmer of the Year, 1980 John Ward Robert D. Dav National Forest Products Association Renewable Natural Resources Foundation Henry Webster Kirk Ewart Michigan Department of Natural Resources Boise Cascade Corp. lohn Zivnuska Rodney Foil Department of Forestry and Resource Mississippi Agricultural and Forestry Management Experiment Station University of California at Berkeley

*John Ward replaced Merle Conkin on the ()’I’A Advisory Panel in October 1982.



### Acknowledgments

Volume II was prepared by the Office of Technology Assessment Industry, Technology, and Employment Program staff. OTA wishes to acknowledge the assistance and cooperation of D. A. Tillman, A, J.Rossi, and S. O. Simmons of Envirosphere Co., Bellevue, Wash., who contributed significantly to the assessment as contractors. The staff also wishes to acknowledge the special contributions made by the following individuals: Jay Johnson Weyerhaeuser Corp.

Jerome Saeman Energy Research Center University of Wisconsin

iv

### OTA Wood Use: U.S. Competitiveness and Technology Project Staff

Lionel S. Johns, Assistant Director, OTA Energy, Materials, and International Security Division

Audrey Buyrn, Industry, Technology, and Employment Program Manager

James W, Curlin, Project Director
Julie Fox Gorte, Assistant Project Director

W. Wendell Fletcher Kathryn Hutcherson Robie

Nicholas A. Sundt* William F. Davidson*

Carol A. Drohan, Administrative Assistant
Patricia A. Canavan, Secretary
Kathleen D. Frakes, Research Assistant Kathryn M. White, Editor

“(3TA c.ontractor

### Wood Science and Technology Working Group

R. Rodney Foil Mississippi Agricultural and Forestry Experiment Station Dean Einspahr Institute of Paper Chemistry John Haygreen Department of Forest Products University of Minnesota Jay Johnson Weyerhaeuser Corp.

T. Kent Kirk Forest Products Laboratory USDA Forest Service John Koning Forest Products Laboratory USDA Forest Service

Alfred H. Nissan Consultant Necmi Sanyer Forest Products Laboratory USDA Forest Service

Vance Setterholm Forest Products Laboratory USDA Forest Service Kenneth Skog Forest Products Laboratory USDA Forest Service

Robert N. Stone Forest Products Laboratory USDA Forest Service

Bruce Thoman International Paper Co.

John White Cooperative Forestry Staff USDA Forest Service

Jerome Saeman Energy Research Center University of Wisconsin



## Abstract

The role of technology in achieving self-sufficiency–and perhaps in expanding export capacity-in wood products has received little attention. Although the United States has immense timber resources, it has been a net importer of wood products for a number of years, and Government projections of future wood supplies and demands indicate rising timber prices and increased dependence on foreign supplies.Several ways exist to avoid wood shortfalls. They include increasing timber production through intensified timber management, better utilization of wood residues, more efficient harvesting, and use of currently underutilized species. Technology can help expand the resource base by enabling effective utilization of a wider range of wood species and sizes and by increasing the yield of products manufactured from a given amount of wood raw material through improved design and conservation. The Office of Technology Assessment has assessed U.S. wood use and production at the request of Congress. This volume reviews wood manufacturing technologies that might be used to extend the timber resource through improved utilization and explores the prospects for changes in the way wood products are manufactured and used.

# Contents

Chapter Page

I.

II.

III. Findings and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Characteristics of Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,,. 10 Microstructure of Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Chemical Characteristics of Wood....,,....,.. . . . . . . . . . . . . . . . . . . . . . . . 11 Physical Characteristics of Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Energy Consumption in Wood Products Manufacture . . . . . . . . . . . . . . . . . . . 13 Present and Prospective Uses of Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Wood as a Fuel. .,... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Industrial Wood-Fuel Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Residential and Commercial Fuelwood Use,,..,,., . . . . . . . . . . . . . . . . . . . . 19 Secondary Fuels and Chemicals From Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Wood Technology and the Resource Base... . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Research and Development on the Use of Wood . . . . . . . . . . . . . . . . . . . . . ..,, 23 Federal Government R&D Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 R&D in Academic Institutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Industrial R&D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Solid Wood and Panel Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Profile of the Lumber and Panel Products Industry . . . . . . . . . . . . . . . . . . . . . . . 34 Raw Materials...,.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Product Demand ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,,. 35 Industry Size and Distribution of Production . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Use of Solid Wood and Panel Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Industry Trends and Potentials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Product Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Forest Resource Use., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Efficient End Use of Wood Products, , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Lumber Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Lumber Manufacture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Potential Improvements in Milling Efficiencies and Lumber Manufacture . . 42 Consumption and Use of Lumber Products in the United States . . . . . . . . . . 48 Plywood and Panel Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Plywood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Particleboard ,.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Structural Composite Panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Fiberboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 Present and Future Use and Consumption of Panel Products. . . . . . . . . . . . . 58 Wood Use in Light Frame Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Wood Conservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 New Uses for Solid Wood Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 Composites of Wood and Other Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Pulp, Paper, and Fiber Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 Profile of the Pulp and Paper Industry ,.... . .,...,.,,,,...,,,,, ,,.,. 68 Uses of Pulp, Paper, and Paperboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Advanced Paper Materials . . . . . . . . . . . . . . . . . . . . . . . ...,.,..,.,,,,,,,,, 71 Role of Paper and Cellulosic Materials in the U.S. Material Mix . . . . . . . . . . . 72 Competition From Plastics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Competition From Electronic Technologies, .....,,, . . . . . . . . . . . . . . . . . . . 76

vii

# Contents–continued

Page Pulp, Paper, and Cellulose Fiber Manufacturing . . . . . . . . . . . . . . . . . . . . . . . . . 79 Mechanical Pulping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Chemical Pulping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Dissolving Pulp Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

List of Tables

Table No. Page 1. 2. 3. 4. 5. 6. 7. 8.

9.

10.

11. 12. 13.

14. 15. 16. 17. 18.

19.

20.

21. 22,

23. 24,

25.

26.

27. 28, 29. 30, Taxonomy of Major Forest Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Physical Properties of Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Structural Properties of Some Wood, Metals, and Masonries . . . . . . . . . . . . . . . 13 Energy Requirements for Primary Commodities . . . . . . . . . . . . . . . . . . . . . . . . 14 OTA Calculations of Wood-Fuel Removals, 1980 . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Estimated Wood Stove Shipments and Inventory . . . . . . . . . . . . . . . . . . . . . . . . . 19 Status of Selected Technological Developments in Wood Utilization . . . . . . . . . 24 Funding and Man-Year Commitments by Activities at the U.S. Forest Service, Forest Products Laboratory, Madison, Wis.: Fiscal Year 1981 ,,...., 26 1981 Funding and Scientist-Years by Activities at the U.S. Forest Service Experiment Stations, 1981 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Funding of Wood Utilization R&D Performed by U.S. Academic Institutions in Fiscal Year 1980 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Domestic Consumption of Lumber and Panel Products, 1976 . . . . . . . . . . . . . . . 37 Selected Statistics on the Lumber and Panel Products Industry, 1981 . . . . . . . . 38 Number of Primary Timber-Processing Establishments in the United States, by Industry and Type of Organization, 1972 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Lumber Production by Mill Size, 1979 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Large Mills and Production by Region and Size , . . . . . . . . . . . . . . . . 38 Types of Softwood Sawmills and Their Primary Product. . . . . . . . . . . . . . . . . . . 41 Summary of Major Technologies for Improved Lumber Manufacture . . . . . . . . 44 Plywood and Panel Products Consumed in New Residential Construction in the United States 1962-80 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Plywood End Uses and Their Susceptibility to Penetration by “New’’Panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 Summary of Major Technologies for Plywood and Panel Product Manufacture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .,,. 60 Benefits of Truss Framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., 63 Estimated North American Capacity by Grade of Top 20 Pulp, Paper, and Paperboard Producers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 U.S. Production of Paper and Paperboard in 1981 and Projected for 1984.... 71 Uses, Grades, Production, and Consumptionof Paper Products in the United States in 1979 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 New Information Technologies and Their Potential Impact on Paper Construction.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 Major Commercial Wood-Pulping Methods, Grades of Pulp, and End-Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 Summary of Process Variables for Mechanical Pulping . . . . . . . . . . . . . . . . . . . . 83 Energy Demand Per Ton of Kraft Paper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Energy Consequences of Pyrolytic Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Strength Properties of Press-Dried Hardwood Paper and Conventional Softwood Paper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

. Vlll

# Contents–continued

List of Figures

Figure No.. Page

I

. Three Characteristic Directions of Wood That Are Influenced by Wood Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2. U.S. Wood Energy Consumption, 1850-1980. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3. Estimated Wood-Fuel Consumption, 1961-81 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4. Timber Supply to and Product Output From Primary Processing Plants, 1976 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5. Chemicals From Wood. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 6. Historical Research and Development Expenditures . . . . . . . . . . . . . . . . . . . . . . . 29 7. U.S. Trade in Lumber and Panel Products, 1976. . . . . . . . . . . . . . . . . . . . . . . . . . 35 8. Flow Diagram of a Typical State-of-the-Art Small-Log Sawmill, Indicating Process Waste Streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 9. Present and Predicted Materials Balance for Softwood Lumber Based on Ovendry Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 10. The Maximum Yield of Lumber From Conventional and Innovative Processes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 11. Per Capita Consumption of I.umber 1950-79 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 12. The Truss Frame System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 13. Flow Diagram of a Small-Log Plywood Mill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 14. Material Balance for Softwood Plywood Based on Ovendry Weight . . . . . . . . . 52 15. Materials Balance for the Manufacture of Underpayment Particleboard Based on Ovendry Weight. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 16. Materials Balance for the Manufacture of Structural Particleboard Based on Ovendry Weight of Chipping and Flaking of Sound Wood . . . . . . . . . . . . . . 55 17. Idealized Typical Waferboard Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 18. Idealized Typical Oriented Strand Board Process . . . . . . . . . . . . . . . . . . . . . . . . 57 19. Historical Production of Major Panel Products, 1970-79 . . . . . . . . . . . . . . . . . . . 59 20. Offcenter, In-line Joint Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 21. Wooden I-Beam Construction, Cross-Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 22. Proportions of Woodpulp Produced by Commercial Pulping Processes . . . . . . . 80 23. Schematic Flow Diagram of Alternative Mechanical Pulping Processes . . . . . . 81 24. Wood and Energy Flows in Mechanical Pulping Mills in Conjunction With Recycling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 25. Material and Energy Flow into a Kraft Pulpmill . . . . . . . . . . . . . . . . . . . . . . . . . . 86 26. Overall View of Papermaking From Chemical Pulp by the Kraft Pulping Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

ix

# Findings and Conclusions

# Findings and Conclusions

1. Technologies for wood use could affect future U.S. timberrequirements in two ways: 1 ) by extending the wood resource through improved product recovery and 2) by substituting wood for nonrenewable materials. The United States currently has abundant productive timber resources compared to thoseof most other industrialized countries. However, the U.S. Department of Agriculture’s(USDA) Forest Service forecasts possible shortfalls in the year 2030 of domestic timber speciesand sizes currently used for structural materials, pulp, and paper. At the same time, the U.S. forest products industry sees a potential for increased export of wood products and a more active U.S. role in world wood trade,Technology will play a major role in both extending timber resources and developing new and improved ways to use wood,

Il. Existing and emerging manufacturing technologies couldincrease wood product yield significantly and may result in increased utilization of forest residues for industrial energy production. Because nearly half of all industrial forestproducts are lumber and structural panels, increased yield of these products alone couldhave a major impact on domestic timber demand. However, increased yield of solid wood products also could reduce the amount of waste wood available for energy generation in lumbermills and pulpmills, a situation that could stimulate greater use of forest residues and other biomass in the forest products industry, Lumber products, generally used for structural support, are long, thin, rectangular pieces of solid wood. Panel products often are used for structural sheathing and generally are manufactured in 4-by 8-ft sheets usually less than 1 inch thick. Pulp products include paper and paperboard, films, and fabrics,
The amount of roundwood required for lumber production could be reduced 20 to 40 percent by using currently available technologies such as Best Opening Face (BOF), saw-dry-rip (SDR), or edge-glue and rip (EGAR), although it will take several years to achieve even a 20-percent reduction. Such savings would be significant, since lumber consumption of over 50 million tons in 1979 accounted for about half of all wood products consumed.
Composites— such as parallel-laminated veneer (PLV) and corn-ply-are probably the most material-efficient lumber products. They are manufactured by gluing veneers or particles together and sawing the resulting boards into a variety of products. Use of these processes can increase lumber recoveries 40to 90 percent or more. However, this technology is not yet used on a large commercial scale (probably less than 1 percent of all lumber products are composites]; such technology would require new facilities entirely different from those in conventional lumber mills. Eventhough composite lumber products offer increased lumber recovery and use of lower quality wood, they are unlikely to replace conventional sawn lumber to any great extent duringthe next two decades because of the large capital investment requirements, high variable costs (e. g., glue costs), and possible problems resulting from formaldehyde emissions from adhesives. Adoption of several new technologies could increase lumber recovery of existing mills up to 30 percent without major plant alterations. Among these are the BOF program and the EGAR process. BOF is a computer-assisted method for increasing lumber volume and grade by optimizing sawlines. Laboratory tests and some inservice tests indicate that BOF could increase lumber yields by more than 20percent. EGAR is an innovative sawing-andgluing technique that reduces loss of wood inthe sawing process, can increase lumber recovery 10 to 13 percent, and permits the use of lower quality raw material.Product yields in the manufacture of composite wood panels are 75 to 80 percent by weight, compared with the average current plywood recovery of about 50 percent. Composite wood-panel products (particleboard) are manufactured from woodchips, flakes, wafers,or strands that are glued and formed into plywood-like sheets. Composite panels with the strength of plywood are now being produced

34 ● Wood Use: U.S. Competitiveness and Technology

and eventually will substitute for plywood in many structural uses.

Substitution of composite wood panels for plywood already has begun, and substantial additions to waferboard and oriented strandboard (OSB) production capacity has been completed, Composite panels will begin to replace significant amounts of plywood in structural use by the middle of the decade, Within 10 to20 years, it is likely that these products will replace most construction plywood, Limits on production of composite panels probably willhave more to do with access to investment capital in processing facilities than with institutional or technological constraints.
Increased use of improved mechanically produced pulps can increase fiber yields fromabout 50 percent to almost 95 percent, reducing wood requirements to 1.05 tons per ton of paper. Over 75 percent of current U.S. pulp and paper production is from the relatively low-yielding kraft chemical pulping process. Since about one-third of industrial roundwoodin the United States is used for pulp and paper (53.5 million tons in 1979), a significant improvement in overall fiber recovery would result if highly efficient mechanical pulpingreplaced chemical pulping. For example, thermomechanical pulping (TMP)—an improved mechanical pulping process that produces higher quality paper than other mechanical processes—could displace about 300 pounds of the kraft paper currently used in each ton ofnewsprint. Opportunities also may exist for reducing the amount of kraft pulp used in other printing papers. There probably are practicallimits, however, on the extent to which mechanical pulps can substitute for chemical pulps, because high-strength and permanently bright papers cannot yet be manufactured from mechanically produced pulps.

Opportunities for improved mechanical pulpsto make significant contributions to pulp consumption over the next two decades are reasonably good. Production of improved mechanical pulps already has begun and is expected to expand. Ill. Technology could expand the use of currently abundant hardwood species, enabling use of wood material now underutilized.

Over one-third of the total volume of existing U.S. timber is hardwood. Hardwood inventories are increasing at a rate over six times that of softwoods, which have been more heavily utilized because of their superior properties for the manufacture of many conventional woodproducts. In the Eastern United States, hardwoods comprise over 62 percent of the standing timber, yet account for only 44 percent of the harvest. Thus, in the East, and particularly in the South, hardwoods are a significant and underutilized wood resource. Because of theirwood qualities, softwoods currently are preferred for manufacture of lumber, plywood, and some types of paper, However, existing and emerging technologies may be capable of using hardwoods to make many products that are now produced mostly from softwoods.
Composite lumber and particleboard, which can be manufactured from hardwoods,could substitute for softwood lumber and plywood. In addition, SDR technology could enable the manufacture of high-quality sawnlumber from underutilized and abundant hardwood species, SDR is a modification of the normal sequence of lumber processing that may reduce defects and waste in hardwood lumber manufacture. The SDR process maybe adopted without major equipment changes or additions to existing mills.
Increased use of hardwoods for pulp and paper may be possible with the adoption of mechanical and chemimechanical pulping technologies. Hardwood species are used extensively for the production of newsprint andfine printing papers. However, papers manufactured from hardwoods are weaker than those made from softwoods, which have longfibers; thus, their end use is limited to applications where paper strength is not of prime importance. Chemimechanical pulping (CMP), which involves chemical treatment of wood prior to grinding, may be able to produce strong hardwood papers that could displace or supplement the use of some softwood papers,Findings and Conclusions ● 5

Press-dry papermaking technology offers perhaps the greatest opportunity to expand future hardwood utilization. Press drying, which produces paper from hardwood pulpusing high pressure and high temperatures during part of the papermaking process, could produce heavy-duty linerboard with strengthproperties generally superior to those of conventional kraft linerboard. Linerboard currently uses about one-fourth of the wood pulp produced in the United States (approximately 13 million tons/y r), and prospects are good for increasing linerboard exports. Response to themarkets and a combination of press-dry technology and hardwood CMP in the production of linerboard, could expand significantly theuse of several currently underutilized hardwood species. Softwood pulps also can be processed by press drying, but the principal advantage of the technology is that it enables manufacture of high-strength papers fromhardwoods. The press-dry process was developed by the U.S. Forest Products Laboratory (FPL) and requires further modification and testing before it can be commercialized.

IV. Conservation of solid wood materials through increasedrecycling of waste paper and improved structural design could reduce demands for wood. Approximately one-fourth of the total paper pulp produced in the United States annually comes from recycled paper. Recycling presents some opportunities for energy conservation. The use of 14 percent recycled fiber for the manufacture of newsprint, for example, couldreduce electricity consumption in paper making by 7 to 10 percent. Two major barriers to increasing recycling remain, however, in theUnited States: 1) used paper usually is contaminated with glue, ink, and other materials that are expensive and difficult to remove; and 2) the economics of waste-paper collection andtransportation make recycling generally unprofitable, except in metropolitan areas. Only a few paper mills operate with recycled paper alone; most often, they blend it with virginpulp, which lends strength to the weaker, recycled fibers. The practical upper limit for using recycled fiber in furnished paper is about 40 percent. Some construction techniques and designscan reduce structural wood products requirements in residential construction by nearly one-third. Since over 50 percent of the lumber and panel products consumed in the UnitedStates are used for residential and nonresidential construction or structural maintenance, significant savings in total wood consumption could be realized from a modest reduction in construction wood use. Designs that rely on the interaction of individual building components for structural strength–e.g., truss framing, wall and floor assemblies, and sandwich panels that replace framing and sheathing—also conserve wood. Penetration of these innovations intoconstruction markets is likely to be slow, however, due to the conservatism of building codes, the construction industry, and home buyers. Also, some current trends, such as the use of wider framing lumber for increased energy efficiency, may result in increased structural requirements.

V. New pulping technologies could reduce energy requirements for pulp and paper making and even produce additional energy for outside sale.An estimated one-half of the wood (both industrial roundwood and other wood) removed from U.S. forests, over 120 million ovendriedtons, eventually is consumed for energy production. Almost two-thirds of the wood fuel burned in 1981 was consumed by the wood products industry. The pulp and paper sector alone accounted for about 3 percent of total U.S. energy consumption. As a result of thislarge energy usage, pulp and paper manufacturers have become industrial leaders in energy conservation and electric cogeneration.

Innovations could boost waste heat recovery in mechanical pulping for use in paper drying, space heating, and water treatment. In addition, use of pulping technologies such as pressurized groundwood (PGW] pulping, CMP, and chemithermomechanical pulping(CTMP), would result in lower energy requirements than those of TMP and chemical pulping technologies. Process improvements in chemical pulping may allow mills to approach energy self-suf-6 ● Wood Use: U.S. Competitiveness and Technology

ficiency. Among the strategies available to reduce energy consumption are: 1) increasing the use of wood waste in cogeneration, 2) using spent pulping liquor more efficiently for fuel,and 3) recovering low-quality energy more efficiently through heat pumps and heat exchangers.

Improvements in drying technology offer the greatest opportunities for reducing energyconsumption in lumber and panel manufacturing because about 70 percent of the average energy consumption is used in kiln operations and panel drying. Solar kilns, vacuumkilns, and microwave drying are current options for reducing energy consumption. Improved operation of conventional steam-heatedkilns through use of sensors and computer controls also provide opportunities for reducing energy consumption.

Improvements in residential stove and furnace design and in technologies for producing industrial wood energy could probablyraise the efficiency of direct wood-fuel combustion to 80 percent of the heat-producing potential of the wood. Conversion from open fireplaces to efficient wood stoves could change wood fuel-use efficiency from negative values(heat loss) to as high as 50 percent. Use of selfstoking furnaces, heat storage devices, and circulating systems could raise residential wooduse efficiencies to 80 percent of the fuel’s heat potential. In larger commercial and industrial applications, fluidized-bed burners can achieve efficiencies of up to 80 percent, though current efficiency averages 70 percent. Gas turbinetechnologies coupled with fluidized-bed burners could efficiently cogenerate electricity if technologies were developed to cleanse the combustion gases.It is feasible (but uneconomical using existing chemical technologies) to convert forestbiomass to chemical feedstocks and intermediate products that are currently extracted from petroleum. These may be transformed into nearly all the major industrial organic chemicals. Optimistic projections indicate that liquefaction, gasification, pyrolysis, and hydrolysis of less than 60 million tons of wood and wood residues theoretically could supply a significant proportion of the synthetic polymerscurrently consumed in the United States. However, the complex processes required for theirmanufacture are uneconomic at this time. Production of ethanol and methanol from woodand the oxygen gasification of wood could result in production of liquid fuels and syngas for energy conversion.

VI. New wood products may serve as substitutes or complements for materials derived from nonrenewable

resources. For example, composite materials made of wood and fiberglass, plastics, or metal have demonstrated superior performance in someapplications, although these composites currently account for only a small proportion of the total wood materials used. Experiments atFPL have demonstrated the technical feasibility of producing very stiff, high-strength paper, which, with further development, may some day be used for wall sheathing or modular structural panels. Tests of paper constructionmaterials have yielded mixed results, and a significant amount of additional work is probably needed before paperboard could become a major structural material.

# CHAPTER 

# Introduction

### CHAPTER 1 

# Introduction

—

Few materials are as widely used or as versatile as wood. For millenia, wood’s extensivenatural occurrence and its adaptability, renewability, and workability have combined to makeit a material of choice in a wide range of applications. When abundant, wood has helpedbuild and fuel many great civilizations. Scarcity of wood has sometimes contributed to a civilization’s decline.For many purposes, wood has required comparatively little alteration from its natural state, More recently, technology has helped transform wood into an expanding variety of products bearing little resemblance to wood as it appears in trees or is used in conventional lumber (table 1). In addition to lumber and firewood, products that can be made from wood now include chemical feedstocks and plastics, reconstituted wood-building materials, liquid and gaseous fuels, food supplements, and 14,000 kinds of paper,

Table 1 .—Taxonomy of Major Forest Products

Status of

Product Description Major end use
Lumber type products Board s a - - Dimension a lumber

Timbers

Parallel laminated veneer (PLV)

Utility poles

Panel type products Plywood

Hardwood

Particleboard

Medium-density fiberboard Semirigid insulation board

Rigid insulation board Waferboard

Oriented strand board (OSB)

Corn-Ply 1“ thick, 4“ to 16’, > 1“ wide 2“ to < 5“ thick, > 2" wide, usually 4’ to 16’ long solid wood, sometimes edge glued 5 + thick, > 4“ wide, various lengths; solid or laminated wood Usually same dimensions as lumber and timbers, made from wood veneers laminated with parallel grains 9“ to 14” diameter, 50’ to 80’

Flat panels, usually 4’ x 8’, less than 1.5” thick, made from wood veneers laminated with grains of adjacent veneers perpendicular, Usually 3 to 5 plies (veneers) Flat panels made of individual wood fibers, usually glued together

Flat panels, less than 1.5” thick, cut to size of 4’ x 8’, composed of very small wood particles glued together Same as hardboard, with extremely flat, smooth surface and edges Flat panels made of individual wood fibers, usually loosely matted, fibers bonded by interfelting Same as semirigid insulation board

Flat plywood-like panels made with flat, nonalined wafers or large chips of wood glued and pressed together Flat plywood-like panels made with aligned strands or ribbon-shaped pieces of wood, Sometimes crossbanded (strands in different layers oriented perpendicular to adjacent layers), sometimes veneered Flat plywood-like panels or lumber-like pieces, with particleboard cores and wood veneer faces M M

M

G

M

M

M

M

M

D

D

G

G General purpose Structural framing

Structural framing beams, and large supports Structural framing and supports, Can be used in millwork and molding

Transmission lines also

Structural sheathing, flooring, and a variety of semistructural uses

Floor underpayment, facing for architectural concrete, wall linings, door inserts, stereo, radio and TV cabinetry, and furniture Underlay merit, furniture core

Furniture, wall siding

Insulation, cushioning

Interior walls and ceilings, exterior sheathing

Paneling, substitute for plywood in structural use, wallboard

Same as plywood

B Same as lumber and plywood

910 ● Wood Use: U.S. Competitiveness and Technology

Table I.–Taxonomy of Major Forest Products (continued)

Product Description

— Paper products Unbleached kraft paper

Bleached kraft paper

Newsprint and groundwood printing papers

Corrugating medium

Linerboard

Paperboard

Coated paper

Specialty papers

Tissue paper
Other products Rayon

Acetate

Cellulosic films Brown, somewhat coarse, stiff paper manufactured primarily by the kraft sulfate process from hardwoods and softwoods White fine textured paper manufactured by either the kraft sulfite process or the kraft sulfate process from either softwoods or hardwoods. The better papers are provided from softwoods Coarse textured paper of low strength and limited durability, which tends to yellow with age. It is manufactured from mechanical and semimechanical (particularly chemically treated) pulp, which uses either hardwoods or softwoods Coarse, low-strength paper produced primarily from sulfite pulping of hardwoods Stiff, durable, thick paper made primarily from unbleached kraft paper made by the sulfate process Stiff paper of moderate thickness made primarily from bleached sulfate kraft pulp Printing papers that have been coated with materials that improve printability and photo reproduction Diverse group of products ranging from thin filter papers to stiff card stock

Thin, soft, absorbent papers manufactured primarily from chemical groundwood pulps

Synthetic fiber produced by the viscose process using pure cellulose produced by the dissolving pulp process. Rayon has properties similar to cotton Synthetic fibers produced from dissolving pulp-like rayon, but further chemical treatment make them water resistant with properties more like nylon or orlon Film made from dissolving pulp by the rayon and acetate processes, but extruded as sheets of various thicknesses Status of lifecycle

M

M

M

M

M

M

M

M

M

M

M

D Major end use

.

Heavy packaging, bags, and sacks

Fine writing and printing papers and paperboard for packaging

Printing of newspaper and for other printing uses not requiring durability

Corrugated boxes as dividers and stiffeners between the paperboard liners Heavy duty shipping containers and corrugated boxes

Milk cartons, folding boxes, and individual packaging Magazines, annual reports, and books

Cigarettes, filter papers, bonded papers (with cotton fibers) index cards, tags, file folders, and postcards Toweling, tissues, and hygenic products

Woven cloth as a cotton substitute

Woven cloth as a substitute for nylon and other petroleum-derived synthetic fibers

Packaging (cellophane) protective coverings, photographic applications, transparent drafting and graphic materials NOTE: B

SOURCE Office of Technology Assessment



# Characteristics of Wood

Wood is grouped into hardwoods and soft- characteristics are significant between and woods. Hardwoods generally are broad-leaved within species and even between pieces of deciduous trees, while softwoods are conifers, wood from different parts of a single tree. with needles or scalelike leaves that generallyare evergreen. Although there are broad differences in the characteristics of wood from Microstructure of Wood

hardwoods and softwoods, variations in micro- Differences in microstructure between softstructural, physical, chemical, and mechanical woods and hardwoods give the wood fromCh. 1—Introduction ● 1 1

these species different properties, Softwoods have fewer cell types, generally longer fibers, thinner cell walls, and more uniform cellular arrangements than do hardwoods. Because of their strength, softwoods often are preferred in structural applications. Hardwoods vary considerably in their machining and drying characteristics, which makes the commercial use of hardwoods more complex, However, grain patterns and color make them attractive for furniture and cabinetry.

There also can be microstructural differences within species of wood. Leaning trees contain compression wood (softwoods) or tension wood (hardwoods), apparently a result of thetree’s microstructure changing to accommodate the uneven load distribution as it grows. Fertilization, pruning, and other silvicultural* practices also change the microstructure ofwood. These changes, currently under investigation by wood technologists, may have someeffect on the utilization of wood grown in controlled environments (the so-called plantation wood).

Chemical Characteristics of Wood
The major chemical constituents of wood include: 1) cellulose, 2) lignin, 3) hemicellulose, and 4) extractives. Cellulose, which comprises approximately 50 percent of wood by weight (ovendry), is the primary structural component. The exceptionall

y strong chemical bonds within cellulose molecules give wood great strength relative to its weight, Cellulose fibers are the major component of paper and can be alteredchemically to produce a wide range of products such as chemicals, plastics, synthetic fibers, and films, Lignin, which cements the fiber together, is a complex organic chemical the structure and properties of which are not fully understood. Theoretically, lignin could beconverted into a number of chemicals. Currently, however, it is burned to produce energyas a waste product from pulp and paper manufacturing, Hemicellulose is similar to cellulose in composition and function. It plays animportant role in fiber-to-fiber bonding in papermaking. Finally, several extractives are contained in wood but do not contribute to its strength properties,

Physical Characteristics of Wood
Physical properties of wood vary considerably, both between and within species. Some of the more important physical properties ofwood are: 1) density (or specific gravity); 2) mechanical properties (strength and stiffness are most important); 3) shrinking and swelling due to changes in moisture content; 4) thermal properties; 5) electrical properties; 6) machining or working qualities; 7) susceptibility to decay; 8) degree of resistance to chemicals;9) combustibility; 10) weathering; and 11) appearance, such as grain, texture, and sheen,The range of values for some of these properties and their importance is shown in table 2. Density (mass per unit volume] is generally a good indicator for other properties (including mechanical, thermal, and electrical). Specific gravity varies with different locations in the tree and is influenced by silvicultural practices; hence, it influences a tree’s other properties, Manipulation of growth factors is one of the few controls available to “manufacture” the wood substance to desired properties. This contrasts with other materials, in which manyvariables can be manipulated to achieve desired properties,
Wood moisture content (the ratio of the amount of water in the wood to its dry weight) is another important variable. This moisture,bound in the cell walls, influences wood properties. Stiffness and strength decrease, and thermal and electrical conductivity increase, as moisture content increases, The moisture content of living trees usually is above 50 percent but varies considerably by species, time of year, and associated weather conditions. Once felled, however, the wood dries and tends toward an equilibrium moisture content (EMC) corresponding to prevailing relative humidityand temperature conditions. Air or kiln drying is used to reduce the moisture content of12 ● Wood Use: U.S. Competitiveness and Technology

Table 2.— Physical Properties of Wood

Property Range or average Importance Density (specific gravity) 20-45 lb/ft 3 (0.3 to 0.7)

Shrinkage and swelling Hardwood: 10-19 percent by volume Softwood: 7-14 percent

by volume

Thermal properties

Electrical properties

Decay and chemical resistance

Combustibility

Working qualities

Weathering

Appearance Resistance: R= 1.25 [ft 2 h“ F/Btu/in] Diffusivity: D=O.25 x 10 -3 (in 2 /s)

Dielectric constant: 2-5 Resistivity: 10 10 to 10 13 ohm-m (10 3 to 10 4 when saturated)

— Density can affect the ability of wood to hold coatings such as paint, stain, and adhesives. It affects the machinability and other working qualities and the weight and ease of handling the products. Shrinkage upon drying can result in warping, crooking, and bowing in lumber. Some woods have a greater tendency toward internal stresses caused by shrinkage, which may make them less suitable for lumber or may require special treatment to avoid deformities. Shrinkage along the grain is only 10 percent of shrinkage across the grain. Wood is a good thermal and electrical insulator. Because its thermal conductivity is a fraction of that of most metals, wood tends to gain heat slowly from its surroundings.

Wood is a poor electrical conductor, though its conductivity increases with increasing moisture content.

Different species vary in resistance to decay and chemicals. Wood deteriorates more rapidly in warm humid environments than in other conditions. It is often used in chemical processing operations where exposure to mild acids and acidic salt solutions would corrode ordinary steel or cast iron. Two important aspects of wood combustibility are flame spread and char development. Rate of charring into large wood members is very slow; hence, strength is retained for a long time in a fire situation. Working qualities refers to the ease and quality of planing, shaping, turning, mortising, sanding, steam bending, and nail and screw splitting. They affect appearance, useful life, and range of use of wood products. Weathering causes boards to warp, pull out fasteners, check or split, and turn gray. Sometimes weathered appearance is desirable for decorative use. Color, grain, texture, sheen, and surface roughness affect the appearance of wood. Fine furniture woods require special characteristics, as do woods used for paneling and cabinetry. The appearance of structural material is less important. SOURCE Adapted from U S Department of Agriculture, Forest Service, Forest Products Laboratory, Wood Handbook Wood as an Engineering Material (Washington, D C U S Government Printing Off Ice, 1974)

green lumber to approach the EMC to meet the end-use requirement.

In contrast to most other structural materials such as ceramics, concrete, and metals, which have the same properties in all directions, wood is naturally anisotropic, having different mechanical and physical properties along itsthree dimensions. The three mutually perpendicular, characteristic dimensions of wood are called: longitudinal (along the grain), radial(across the grain, out from the center), and tangential (across the grain, tangent to the annual rings) (fig. 1). Stiffness and strength, as well as other properties, vary considerably in the three directions.

Strength, particularly along the grain, is one of the most important mechanical properties of wood. Wood’s strength is compared on a strength-to-weight basis with other materials in table 3.

During use, wood is subjected to a number of different loading modes including bending, compression, shear, and tension. Most impor-Ch. I—Introduction ● 1 3

Figure 1 .—Three Characteristic Directions of Wood That Are Influenced by Wood Properties

tantly, wood is a very efficient material forbending applications, and designers can compensate for its relatively low shear strength parallel to the grain by making long, slender structural members that stand up well to bending. * In addition, because its compression strength is relatively high, wood is an excellent material for columns. Its inherent strength is less important in the design of columnar supports than its geometry and stiffness. Clear wood also has high tensile strength. As a result, higher grade (clear] material is used in tension members of trusses or in the outer layers of laminated beams.

Energy Consumption in
Wood Products Manufacture
The amount of energy required to produce construction materials and paper from woodgenerally is less than that required for producing products from metals, plastics, or masonry on a weight basis (table 4). Production of paper, for example, uses less than half the energy per ton than does the production of plastics andless than 10 percent as much as the production of aluminum foil for packaging. Thus,wood, being a renewable resource, could substitute for other materials that require large amounts of energy for their manufacture.

Table 3.—Structural Properties of Some Wood, Metals, and Masonries14 . Wood Use: U.S. Competitiveness and Technology

Table 4.—Energy Requirements for Primary Commodities (million Btu (oil-equivalent)/ton))

Available residue Commodity Extraction Processing Transport energy N e t a total

Softwood lumber . . . . . . . . . . . . . . . . . 0.943 4.846 1.966 8.313 2.909 Softwood sheathing plywood . . . . . . 0.747 6.871 2.081 3.697 6.002 Structural flakeboard . . . . . . . . . . . . . 0.956 7.511 1.314 8.616 2,270 Underpayment particleboard. . . . . . . . 4.6172 b 8.101 1.198 1.529 12.387 Concrete . . . . . . . . . . . . . . . . . . . . . . . . 0.52 7.60 0.40

— 8.52 Concrete block . . . . . . . . . . . . . . . . . . 0.52 7.60 0.65

— 8.77 Clay brick . . . . . . . . . . . . . . . . . . . . . . . 0.57 7.73 0.76

— 9,06 Steel studs . . . . . . . . . . . . . . . . . . . . . . 2.45 46.20 1.67

— 50.32 Steel joists . . . . . . . . . . . . . . . . . . . . . . 2.45 46.20 1.67

— 50.32 Aluminum siding . . . . . . . . . . . . . ....26.80 172.00 1.67

— 200.47



# Present and Prospective Uses of Wood

Domestic production of wood has increased by about one-third since 1950. Much of thegrowth in demand for wood has been in highvalue wood products such as lumber, plywood and veneer, and pulp, while the declines have been in lower value products, such as railroadties and mine timbers. Wood is used for a variety of purposes, including shelter and otherconstruction, communication, packaging, information storage, energy, textiles, and chemicals.
The chemical constituents of wood, primarily carbon and hydrogen, may be converted to forms that can be used to manufacture a widerange of products currently derived from petroleum—although few now are so used, Chemicals recovered from wood through pulping are used in turpentine, rosins, pine oils, furfural, and other commonly used chemical products. Lignin, although currently burned as a waste product to produce energy within pulpmills, shows promise as an adhesive, dispersing agent, binder, and source of vanillin and dimethyl sulfoxide (DMSO). Rayon, cellulose acetate, and cellulose esters, manufacturedfrom woodpulp, maybe used for cloth, packaging films, and explosives. Sawdust and wood flour are used as cattle feed and as bulking agents in human food.As an energy source, wood’s historical importance is difficult to overstate. Until 1870, wood was the primary fuel for both industrial and residential heating in the United States. i Even in 1940, when coal had long supplantedwood as a residential heating fuel, more households were heated with wood than with gas,electricity, and oil combined. The recent resurgence of wood in home heating—brought about by the rising costs and potential shortages in other energy sources—has both stimulated and been stimulated by technological innovations in wood-burning stoves and other devices adapted to home heating.The forest products industry itself has become an industrial leader in the use of wood as an alternative energy source. Roughly halfof the energy needs of the industry are produced from wood residues and byproducts. In some cases, mills have become virtually energy self-sufficient. In addition, a few wood-fueled central electric-generating stations of modestsize have been constructed by utility companies. Gasification technologies offer potential for converting wood into energy products that are easily transported and may be used in conventional gas combustion equipment. Wood may also be converted to liquid fuels, such as ethanol and methanol. In the event of

I U. S. Department of Commerce, Bureau of the Census, Historical Statistics of the United States: Colonial Times to 1970 (Washington, D. C.: U.S. Government Printing Office, 1975), pp. 587-588.an oil supply interruption or larger increases

in the price of petroleum, wood could back up domestic supplies of coal and other fossil fuels.
Wood has been the paper industry’s major source of raw material for well over a century.Paper may also be manufactured from a variety of natural cellulose materials, including cotton, bagasse, and other agricultural crops, and from recycled waste paper, By removing lignin and other extractives and separating the strong individual wood fibers through chemical or mechanical processes, paper may be formed into a variety of products, ranging from tissues and newsprint to construction board. Some of the oldest and still major uses of wood are framing, sheathing, cabinetry, anda variety of semistructural and decorative purposes in construction. The most notable newdevelopments in wood utilization involve reducing wood to smaller integral components, such as chips, strands, flakes, wafers, or fibersand reconstituting them into products with performance characteristics different and frequently superior to those made from solid natural wood. Recent developments include waferboard and oriented-strand board (OSB) made from a variety of species into composites that can substitute for conventional plywood.

Modern materials science also has made it possible to combine different materials in a way that can produce composite products with performance characteristics superior to those of either of the parent materials, Wood and metal have been laminated to provide not only a more durable finished furniture panel, butalso one that resists cigarette burns by dispersing heat through metal foils. Composite panelsfaced with plastics are widely used for countertops, desktops, and tabletops. Plastic-impregnated papers are used for various types of packages that must resist or contain liquids.

In the future, wood maybe combined in verydifferent ways at the fiber level to produce entirely new materials. For example, wood materials could be extruded, molded, and formed into complex shapes by combining wood fibers with binders, adhesives, and resins. Wood also may be combined with other fibrous materials such as fiberglass or graphite to produce newhigh-strength, lightweight materials with special properties.



# Wood as a Fuel

This section updates information on wood energy use and summarizes several important aspects of wood energy explored in detail in a 1980 OTA report, Energy From Biological
Processes. 2 The rapid growth in coal and petroleum as energy sources since 1870 resulted in a rapid decline of wood’s contribution to total energy use. Since the 1973 oil embargo, wood energy use has grown rapidly, so that it again is the largest use for wood by volume (fig. 2).

(government Printing office, 1980). Ch. 1—Introduction ● 1 5

Figure 2.– U.S. Wood Energy Consumption, 1850-1980

3.0

2.5

2,0

1.5

1.0

Year

SOURCE Charles E Hewett, et al “Wood Energy in the Untted States, ” Annual Rewew of

Energy, Jack M Hollander (ed ) (Palo Alto, Cal if Annual Reviews, tnc ), 198176 ● Wood Use: U.S. Competitiveness and Technology

Wood-fuel consumption totaled 2,2 quadrillion Btu (2.2 Quads) in 19803—about 3 percent of U.S. energy use (74 Quads). 4 The forest products industry accounted for 63 percent of 1980 wood energy use. 5 Nearly all the remaining wood energy consumption was for residential home heating (fig. 3).
OTA estimates that energy accounted for about 55 percent of the wood removed fromU.S. lands in 1980, the first year for which comprehensive survey data is available (table 5). A

1981, op. cit. partial explanation for the high proportion of fuelwood compared with other wood used in 1980 is that demand for other forest products was low due to recession. However, use of wood as a fuel has increased rapidly since the 1%0’s, even during periods when demand for forest products was high. The potential exists for significantly greater wood energy production. OTA’s Energy From Biological processes assessment concludedthat wood has the greatest potential to contribute to the Nation’s energy supply among alternative biomass energy sources. The study found that 4 Quads/yr of wood energy couldbe produced from wood by the year 2000 without significant Government action. With incentives and improved forest management, as much as 10 Quads/yr could be produced. Much

Figure 3.— Estimated Wood-Fuel Consumption, 1961-81

11Ch.1—Introduction ● 17

of this amount could be produced from byproducts of wood processing, logging residues, and woody biomass removed during thinning of timber stands, stand conversions, and other managerncnt activities. 6

Industrial Wood-Fuel Use
The forest products industry consumed 81 mill ion ovendry tons (81 million cords) of wood in 1981. Industrial wood energy consumption totaled 1.4 Quads of wood fuel, of which about

1 .0 Quad was consumed by the energy-intensive pulp and paper industry and the remainder by the solid-wood-products sector. The pulp and paper industry now derives about half of its energy needs from wood fuels and lignin byproducts produced during pulping, 7 An estimated 73 percent of the solid-wood-products industry energy needs were supplied from wood in 1981, up from 69 percent in 1978. 8
Most wood fuels used by the industry come from wood residues and processing wastes, rather than from trees specifically harvestedfor energy use, However, some firms now harvest wood for energy use, and some residuesare traded among businesses within the industry as a marketable commodity.
Continued increases in wood-fuel use by the forest products industry are probable but will grow more slowly in the future. The industrynow uses over 96 percent of the woody raw materials that enter mills for either products or energy (fig. 4). Opportunities to increase woodenergy further may depend on: 1) increased recovery of woody materials at harvest, and 2) capital investment in more energy-efficient manufacturing processes.18 ● Wood Use: U.S. Competitiveness and Technology

Figure 4.—Timber Supply to and Product Output From Primary Processing Plants, 1976 (million cubic feet)

Supply to primary processing plants

Domestic roundwood 12.815 hardwoods 3,297 ● softwoods 9,518

Imported roundwood

+ 100 and chips

SOURCE: T. Ellis and C. D Risbrudt. Unpublished manuscriptCh. 1—/ntroduction ● 1 9

Over the long term, as new facilities and technologies designed for energy conservation gradually are introduced, it is possible that some forest product firms will produce more energy than they consume, thus becoming netenergy producers. The pulp and paper industry already is a leader in cogeneration—the simultaneous generation of useful heat andelectricity. The industry has the largest number of cogeneration facilities among U.S. industries and currently accounts for 29 percentof the U.S. cogeneration capacity, ranking second to the primary-metals industry in cogenerated electrical power, g At one Maine pulpand paper mill, total self-sufficiency in electricity reportedly has been achieved through a newly constructed biomass powerplant andcompany-operated hydroelectric stations. Surplus power is sold to a local utility. 10

Residential and Commercial Fuelwood Use
The U.S. Department of Energy (DOE) estimates that about 48,2 million ovendry tons (48.2 million cords) of wood was consumed in residential heating in 1981. 11 Residential fuelwood consumption has at least doubled since the 1973 oil embargo, according to the DOE survey. Other indications, such as a fourfold increase in the use of wood stoves (from 2.6 million in 1973 to nearly 11 million in 1981),also suggest rapid growth in residential fuelwood use 12 (table 6).
Home fuelwood use may continue to increase, although probably not as rapidly as inthe 1970’s. Factors that will affect home fuelwood use include: 1) price and availability of wood relative to alternative fuels, 2) proximityof fuelwood users to wood supplies, 3) homeowner willingness to cut and transport fuelwood and maintain wood-burning stoves and furnaces, and 4] introduction of technologically superior wood-burning stoves and furnaces Table 6.—Estimated Wood Stove Shipments and Inventory (thousands)

Wood stove Year shipments

1970 ... . . . . 224 1971 . . . . . . . 220 1972 ... 225 1973 ... . 235 1974 ... . 474 1975 ... . . 853 1976 . . 835 1977 . . . . . . 1,302 1978 . . . 1,681 1979 ... . . 2,116 1980 . . . 2,116 Wood stove imports

NA NA 20 20 80 280 200 240 380 437 437 Wood stove

inventory
3,079 2,866 2,751 2,630 2,744 3,295 3,850 4,807 6,088 7,868 9,531 1981 . 2,116 437 10,960

SOURCE U S Department of Energy Estfrnafes of U S Wood Energy Consurnpt(on From 1949 to 1981 (Washington, D C Department of Energy 1982)

that burn wood more efficiently or conveniently.Commercial sector (nonforest products businesses) wood-fuel use also is increasing, although currently it comprises less than 1 percent of total wood-fuel consumption. In many areas, market prices for wood fuel currentlyare competitive with fuel prices for oil, natural gas, and coal. Commercial wood-fuel use may continue to grow, especially in areas likethe South, which have abundant wood supplies. Some States actively encourage commercial use of wood fuels. The Georgia Forestry Commission, for example, finances wood-fuel demonstration projects in hospitals, schools, and other public institutions. 13
In a few instances, public utilities have established wood-fueled central electric-generating stations, as in Burlington, Vt., and Eugene,Oreg. Limitations on wood-fuel generating stations include large capital costs and difficulties in assuring wood supplies from timbersheds at economic transportation distances from plants.

Secondary Fuels and Chemicals From Wood
Almost all wood fuels are directly burned. A variety of long-established and emerging20 . Wood Use: U.S. Competitiveness and Technology

technologies can process wood and woodbased residues into “secondary fuels” (gas, liquid, and solid). Similar technologies and processes can be used to produce chemical feedstocks for the manufacture of a high proportion of chemicals, plastics, and other products now produced from petroleum (fig. 5).Bioconversion processes such as saccharification, fermentation, and gasification wereused to produce fuels and/or chemicals commercially on a minor scale during both World War I and World War II, but they were not ableto compete with petroleum fuels and petrochemicals in peacetime, 14 Recent developments have focused renewed attention on production of secondary fuels and chemicals from wood. The technologies for conversion of wood andother forms of biomass to energy and chemicals are discussed fully in OTA’s Energy From Biological Processes report. 15
The potential for wood to be used as an alcohol fuel is discussed in DOE’s Alcohol Fuels Policy Review. 18 If used on a widespread basis, methanol and ethanol could offset somewhat U.S. gasoline consumption (about 101 billion

— ... - Iq’rhe history of wood chemical and secondary fuel use through World War II is discussed in Egon Glesinger, The Corning Age of Wood (New York: Simon & S[;huster, 1949). Another book by Glesinger, Nazis in the Woodpile: Hit~er’s Plot fi)r Essential Ra~%’ Material (Indianapolis; New York: Bobbs-Merril, 1942) discusses the military and strategic importance of wood as a fuel and chemical to the Third Reich, IsEnergy From Biological Processes, vol. II: Technical and Environmental Analyses (Washington, D. C.: office of Technology Assessment, 1980), ISU,S, Department of Energy, Report of the Alcohol Fue/s polic~ Review (Washington, D. C.: U.S. Government Printing Office, 1979]. gal in 1981). 17 However, there are economic difficulties in commercializing processes to convert woody biomass to alcohol.
Wood currently is used to produce silvichemicals valued at over $5 OO million per year. Silvichemicals include naval stores (oleoresins, tall oil, turpentine, rosins, and the like) and chemicals derived from pulping byproducts, such as lignin products, vanillin, DMSO, and a variety of other useful substances,
Use of wood as a substitute for petroleumfeedstocks is technically possible but will depend on the price of petroleum and coal (which can also be used as a petrochemical substitute)and capital expenditures for new plant construction. Coal is widely viewed by the chemical industry as a more likely short-term substitute for petroleum feedstocks than wood. Nonetheless, evolutionary growth in wood chemical use is probable—especially when wood can be used in less highly processed forms or to produce chemicals not readily derived from coal or petroleum.Lignin chemistry is one promising area of research. 18 Lignin has a complex structure that makes it difficult to process, but, left intact, it can be used in plastics, adhesives, and various other compounds, About 3 percent of the ligninbyproducts produced during pulping are recovered for production of chemicals; the rest is burned for energy.

17Figure derived from Monthly Energy Review: November 1982, op. cit., p. 36. ‘BHenry J. Bungay, “Biomass Refining, ” Science, vol. 218, Nov. 12, 1982, p. 643.



# Wood Technology and the

While an extraordinary range of wood prod- of the 

# Resource Base

national materials mix, economics and ucts exists, they must compete with other ma- market forces generally determine which materials for their share of an often highly spe- terial is predominantly used for any specific cialized market. Just as wood can be substituted purpose, But other factors, including existing for many other materials, those materials can plant equipment and capital investment, substitute for wood in some applications, with energy consumption, raw material availability little change in product performance. In terms and security of supply, and institutionalCh. /—lntroduct/on ● 21

1 Separation via I

Wood

- 1 t Organic compounds

- Methan e22 . Wood Use: U.S. Competitiveness and Technology

considerations—government policies, industry structure, and societal customs, practices, and preferences—also play a role.Recently, the forest products industry has experienced changes in portions of its traditionalmarket shares. In the highly competitive market for residential building materials, which constitutes the largest single market for forest products, wood has retained its dominance but lost portions of its markets in several areas such as flooring, siding, and furniture, At the same time, a variety of new building materials made from wood are available that could help retain current markets or expand into other areas in time, Even within the family of wood products, substitution takes place: plywood has replaced lumber for many uses, and now particleboard challenges plywood in the market for structural panels. In some cases, composite materialshave enhanced wood’s competitiveness by permitting it to enter new markets and helping to retain portions of markets that otherwise might be lost. A salient example of the former is theplastic-coated boxboard that has virtually replaced half-gallon milk containers made of glass.
At one time, other biomass materials (primarily cotton) provided nearly all feedstocks for plastics manufacture. By 1960, fossil fuels accounted for 90 percent of plastic feedstocks,even though the volume of wood feedstocks remained about the same. Uncertainties about petroleum prices and supplies have led to somerecent, though modest, increases in woodderived feedstocks. In addition, petroleumderived plastics have competed successfully for many specialized markets formerly dominated by paper. Although wood is a renewable resource, in contrast to metals or fossil fuels for which a fixed amount is available, the possibility of a timber famine in the United States as a result of the scarcity of softwood sawtimber has beenraised repeatedly for more than a century. Softwoods have been used more heavily than hardwoods because of their wood properties and the fact that they tend to have most of the usable wood in a well-formed trunk. As a result, softwoods are growing scarcer relative tomany hardwoods, which remain largely underutilized. Moreover, over the past century, the real (deflated) price of softwood sawtimber has increased steadily.
The United States has a large inventory of both softwood and hardwood species, Growth,on a nationwide basis, still is greater than annual harvest for both types of wood, although the margin of annual growth over harvest is much narrower for softwoods. Capacity of the Nation’s forests to provide increasing amountsof wood maybe limited, however, and technologies for improving the efficiency of wood utilization could help extend the timber resource by offsetting increases in demand. Technology could increase utilization by: 1) increasing theproportion of products recovered from roundwood, or wood raw material, in primary processing; 2) expanding the ability to utilize hardwood species and defective material; and 3) increasing the efficient use of manufactured wood products,
The United States has harvested approximately 12 billion cubic feet (ft 3 ) of roundwoodannually for decades, In recent years, the proportion of this harvest that has been wasted hasdropped dramatically, In 1976, less than 4 percent of the roundwood entering primary processing was wasted, although that portion stillrepresented 10 million tons. Because many residues from one phase of the manufacturing process may be used as raw material for other uses (fig. 4), an increase in the product recovery at one point in the manufacturing process mayreduce the amount of residue available to produce other products or energy. While there are significant opportunities for technology tochange the products manufactured from a specific quantity of wood, there appears to be little chance to increase the efficiency of wood utilization in primary processing as a whole—with the exception of some pulping technologies that provide higher fiber recovery.
On the other hand, technology has already significantly affected the ability to use a wider variety of wood species and materials formerlyCh. 1—Introduction ● 2 3

considered worthless. The introduction of panel products and hardboard opened avenues for wood from limbs, branches, treetops, roots, hardwoods, and even dead or defective woodand bark. New technologies for paper manufacture offer enormous potential for usinghardwoods to produce strong papers for packaging and communication, Even in lumber and plywood manufacture, which still depend on wood cut from the trunk of the tree, the abilityto utilize smaller logs has expanded significantly. Possibilities also exist for increased useof hardwoods. Regardless of future levels of demand, wood-utilization technology has the potential to ease pressures on the timber resource base (table 7).
Significant efficient end

The future efficiency in on research opportunities also exist for more

use, particularly in construction. It maybe possible to reduce the amount of lumber and panel products used (through improved integrated structural design) without adversely affecting the quality and strength of the structure. Present commercial techniques could reduce wood consumption in framing by nearly one-third, for example.
Recycling technologies also may extend the timber resource base. Recycled wastepaper canreduce not only the amount of virgin wood fiber needed for pulp and paper manufacturing, but also the amount of energy consumed in the pulping process. Little solid wood is reused currently, but with appropriate designs and new methods of fastening, it also might be recycled.



# Research and Development on the Use of Wood

uses of wood and the degree of wood utilization largely depend and development (R&D). Three major institutional groups in the United States are involved in R&D on the use of wood: 1) the Federal Government, which funds as well as performs R&D; 2) the forest industry, which isinstrumental in developing products and improving manufacturing processes; and 3) academic institutions that conduct training and basic research. Each plays an important rolein the activities that lead to the invention, development, and eventual commercialization of wood products and processes.The relative proportions of industry and Government funding for all R&D in the United States have shifted in the past 30 years. In the 1950’s and 1960’s, the Federal Government was the major funding source for R&D, but the gapbetween industrial contributions and Government funding began to narrow in the early 1970’s, Industry outspent the Government for the first time in 1980. The National ScienceFoundation (NSF) estimates that over $69 billion was expended for all R&D in the UnitedStates in 1981. Forty-nine percent of the expenditures were made by industry, while 47percent came from Federal agencies. The remaining 4 percent originated from foundations and other private sources. Current trends suggest that industry funding as a percentage of total funding will continueto advance, while the Federal sector’s contribution will decline. 19 The funding structure for research alone (excluding the development function) is the reverse, however. In 1981, over 53 percent of the expenditures for basic andapplied research were derived from the Federal Government, while industry contributed approximately 37 percent. z” The private sectoractually performed more of the total R&D undertaken in the United States than it funded,because some private research was Government supported. In 1981, 71.2 percent of theR&D (measured by dollars expended) was performed by industry. The Federal Government

19J. Eluga, Probable l.eLels of R&D Expenditures in 1982: Forecast and Anal~’sis (Columbus, Ohio: 13attelle Columbus Laboratories, 1981), p. 2. ZONationa] Sclerlce Board, Science indicators 1980 (Washington, D. C.: .National Science Foundation, 1981), p, 253,

, ~~• 1 - rTable 7.—Status of Selected Technological Developments in Wood Utilization

. . Pulp and paper industry: Pressurized groundwood pulping (PGW)

Chemithermomechanical pulping (CTMP)

Hardwood chemimechanical pulping (CMP)

Press drying paper

Pyrolytic recovery

Organosolv pulping

Oxygen pulping

Solid wood products: Best opening face

Saw-dry-rip

Edge glue and rip

Parallel laminated veneer Rationale for or advantage of technology ——. End-use product Status of commercialization Wood type

Reduced energy requirements and higher quality paper in comparison with traditional groundwood pulping processes; less kraft pulp needed for mixing

Reduced energy requirements; higher quality paper than in traditional mechanical pulping technologies because long fibers are left relatively intact; less kraft pulp needed for mixing Permits utilization of low-value hardwoods such as red oak and poplar; reduced energy consumption in comparison with other mechanical techniques; less kraft pulp needed for mixingPermits utilization of hardwoods in production of linerboard that is superior in quality to conventionally dried softwood kraft paper,except in tear strength; reduced energy requirements and chemical processing needs Reduced energy requirements in recovering puIping chemicals Reduced energy requirements; expanded hardwood utilization Oxidation of pulping liquors reduces need for bleaching chemicals and facilities; mayreduce need-for water polIution control expenditures due to less chlorine in bleaching

Higher lumber recovery factor; permits product yield improvements of 4 to 21 0 / 0

Higher lumber recovery reduces defects in product by 19 to 87°/0 Higher recovery of product, higher lumber quality Permits higher recovery of lumber from logs, improves lumber quality; faster processing at the mill Newsprint, printing
papers

News print
pages

Newsprint
papers

Linerboard , printing

printing

Process efficiency

Process efficiency

Process efficiency

Lumber uses

Lumber uses

Lumber uses

Lumber and timber

uses Five mills worldwide as of 1980; Softwoods 15 mills ordered (4 in U.S.); rapid growth expected

Installed at some thermomechanical pulpmills

Two small mills in U. S.; rapid expansion possible

Feasible, but commercial-scale facility has yet to be developed

Demonstrated

Yet to be demonstrated; possible in next two decades Yet to be demonstrated; possible in next two decades

Mill-tested but not widely used

Used by some mills, but not widely accepted None

Some manufacturing currently in production Softwoods

Hardwoods

Hardwoods

Any

Hardwoods or softwood

Primarily softwoods

Hardwoods and softwoods Hardwoods and softwoods Hardwoods and softwoods. Ch. 1 —Introduction ● 25

I In

(u **E o-1** 

**Q**

I

c o

0

c

u o 0 3

.26 ● Wood Use: U.S. Competitiveness and Technology

conducted 13 percent; universities and colleges, 12 percent; and the balance was performed by miscellaneous nonprofit organizations.Within the forest products sector, the structure of R&D funding is obscured by the lack of reliable and sufficiently detailed informationon Government and industry outlays for woodutilization R&D. NSF reports an estimated aggregate expenditure in 1979 of $148 million forlumber and wood products R&D and $454 million for pulp and paper products R&D, but doesnot provide a breakdown of funding by contributor. 21 Funding levels for R&D within the forest products sector remained about the samefor 1977 through 1979, when measured in constant dollars. Between 1970 and 1980, R&D expenditures for lumber and wood products grew approximately 62 percent, and pulp and paper R&D increased 70 percent, when measured in actual dollars. occurred in the tion during the

211t)id., p. 279. However, little real growth

R&D budget because of inflapast decade. Federal Government R&D Activities
Wood-utilization research conducted by theFederal Government is concentrated in the Forest Service of the U.S. Department of Agriculture (USDA), In fiscal year 1981, the Forest Service funded over $16.8 million of in-house wood science and utilization research, about

72 percent of which was performed at the Forest Products Laboratory (FPL) in Madison, Wis.The balance was conducted at the regional Forest Experiment Stations and at various research centers throughout the United States,(University research funded by the Forest Service is discussed in a following section,) The Forest Service tends to concentrate its in-housewood science and utilization research on projects that generally are regarded as beneficial to the United States—i.e., that are long-term,high-risk, and therefore unlikely to be undertaken by the private sector,
FPL’s fiscal year 1981 R&D program included 18 activities involving approximately 97scientist-years of effort, funded for $12,1 million (table 8). Its fiscal year 1982 budget was targeted at $13.7 million to support an effort of 104 scientist-years. The laboratory’s research efforts are centered on the protection of wood

Table 8.—Funding and Man-Year Commitments by Activities at the U.S. Forest Service,

Forest Products Laboratory, Madison, Wis.: Fiscal Year 1981

Funds ScientistActivity (thousand dollars) Percent years

— Protection of wood in adverse environments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $ 1,178.5 Engineered wood structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,149.1 Wood fiber products and processing development . . . . . . . . . . . . . . . . . . . . . . . . . . . 942.9 Engineering properties of wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 888.3 Improved chemical utilization of wood ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 869.1 Structural composite products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 840.5 National timber and wood products requirements and utilization economics . . . 822.7 Improved adhesive systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 791.0 High-yield, nonpolluting pulping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 758.0 Quality and yield improvement in wood processing . . . . . . . . . . . . . . . . . . . . . . 690.0 Criteria for fiber-product design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., . . . . . . . 641.0 Microbial technology in wood utilization. ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525.0 Improvements in drying technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 503.7 Fire-design engineering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371.0 Engineering design criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370.0 Corrugated-package engineering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341.5 Center for anatomy research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293.0 Pioneering research unit in descriptive wood anatomy . . . . . . . . . . . . . . . . . . . . . . 141.0 Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $12,116.3 SOURCE Cooperative Research Information Service (CRIS), U S Department of Agriculture — 9.8 9.5 7.8 7,3 7,2 6.9 6.8 6.5 6.2 5.7 5.3 4.3 4.2 3.1 3.0 2.8 2.4 1.2

100.0 8

6 5 7 7 7 8 6 6 6 5 4 5 4 4 4 4 1

97Ch. 1—Introduction ● 2 7

from decay and insects and on the engineering of structural wood products, wood fiberproducts, and manufacturing processes. Approximately 35 percent of FPL’s budget is used for fundamental research—e.g., properties and anatomy of wood—and 65 percent is used for applied research. The level of research effort has been approximately the same since 1978, based on constant dollars expended. From 5 to 10 percent of the laboratory’s annual budgetis devoted to cooperative research with academic institutions.

In addition to research centered at FPL, the Forest Service supported an R&D program of $4.7 million and 40 scientist-years in fiscal year1981 at the research centers of the regional forest range and experiment stations (table 9).Most of this research centered on the utilization of hardwood species and on the economics of improving the performance of the regional wood products industries,R&D on wood energy and wood as a substitute for petroleum products is conducted by DOE at its national laboratories, although funding for these activities was reduced in the fiscal year 1982 and 1983 budgets. At its peak in fiscalyear 1981, DOE spent $11 million on R&D related to wood combustion, gasification, and liquefaction. This work is funded in fiscal year 1983 at $2.2 million. Other research related to wood science and utilization, such as researchon toxic preservatives and adhesives, may occur incidentally to the missions of other R&Dagencies, but its size in relation to the total Government effort is small.

R&D in Academic Institutions
Academic research plays a unique role in complementing the research in wood science and utilization undertaken by industrial andGovernment laboratories. Funding for academic research in fiscal year 1981 was approximately $9.5 million (table 10). Less than onethird of the academic research budgets in 1981 came from the Federal Government; State andindustrial contributions accounted for 71,6 perTable 9.— 1981 Funding and Scientist-Years by Activities at the U.S. Forest Service Experiment Stations

Actlvity
Improving wood-resource harvesting and
utilization . . . . . . . . .

New and improved systems, methods, and techniques for processing hardwoods ... . Regional economics of forest resources ... Low-grade hardwood utilization . . . . . . . . . . . . . Timber quality and product-yield potential of Western softwood resources ., ... ... .

Developing more productive markets and uses for forest resources of the Central and Southern Rocky Mountains ... . . . . .

Utilization of Southern timber. ... . ..

.

Wood products research . . . . . . . . ...

Processing Southern woods . ... . ...

. Total ., . ... . ... . . . . . . . Funds Location (thousand dollars) Percent Man-years

—

Forest Sciences Laboratory Missoula, Mont. $ 447,0 9.5 4.0

Carbondale, Ill, 361.0 7.7 3.0

Duluth, Minn. 512.0 10.9 4.1
Princeton, W.Va. 418.5 8.9 2.1

Pacific Northwest Range Exp. Sta. Portland, Oreg. 573.3 12.2 5.0

Ft. Collins, Colo. 286.8 6.1 4,0

Southern Forest Exp. Sta. Athens, Ga. 594.2 12.7 6,0
Southern Forest Exp. Sta. Athens, Ga. 500.3 10.7 6.0

Alexandria, La, 998.9 21.3 6.0 $4.692.0 100.0 ‘40.2

SOURCE Cooperatlve Research Information System (CR IS) U S Department of AgrlcuIture ‘ - -28 . Wood Use: U.S. Competitiveness and Technology

Table 10.— Funding of Wood Utilization R&D Performed by U.S. Academic Institutions in Fiscal Year 1980

Source (thousand dollars)MclntyreActivity Stennis Structural panels (including plywood and composites) . . . . . . . . . . . . . . . . . . $ 278.1 Economic analysis and data/information . . . . . . 76.2 Properties and performance of wood and wood products . . . . . . . . . . . . . . . . . . . . . 376.0 Energy and chemical production from wood. 181.3 Protection, preservatives, and coatings . . 78.8 Pulp and paper technology. . . . . . . . . . . . . . . . . . 125.6 General and miscellaneous wood utilization . . 42.6 Adhesives and bonding . . . . . . . . . . . . . . . . . . . . . 109.0 Structural design and fasteners. . . . . . . . . . . . . . 78,1 Drying and moisture characteristics ... . . . . . 119,1 Composite and laminated beams/lumber. . . . . . 54.8 Sawmill design and process technology . . . . . . 22.7 Wood anatomy and fiber quality . . . . . . . . . . . . . 40.7 Sawing and machining . . . . . . . . . . 3.2 Whole-tree chipping and chip processing . . . . 14.8 Species utilization . . . . . . . . . . . . . . . . . . . . . . 22.0 Total ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $1,623.0 Percent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.0 Other Federal Non-Federal

$ 103.7 $1,505.1 165,5 1,076.8
80,7 257,4 94.5 68.0 47,2 38.8 52.0 46.9 5.9 23.4 0 16.7
61.2 18.6 610.4

458.4 523.5 394.8 399.2 338,1 335,9 292,0 233,6 164.0 158.5 163.0 106,1 38,4 Total Percent

$1,886.9 1,318.5

1,067.1 897.1 696.8 588.4 489.0 485.9 466.0 458,0 294,3 210.1 199.2 182.9 182.1 79.0 19.9

13,9

11,2 9.4 7,3 6.2 5.2 5.1 4.9 4.8 3.1 2.2 2.1 1,9 1.9 0.9 $1,080.4 11.4 $6,797.8

71.6 $9,492.3

100.0 100,0

cent of the total. Major emphasis was placed on R&D related to composite structural panels (19.9 percent), economic analysis and wood products data (13.9 percent), and properties and performance of wood and wood products (11.2 percent). Within the federally funded portion of the academic research budget, 17 percent of thefunds originate from McIntyre-Stennis Act programs (76 Stat. 806), which are administered by the USDA’s Cooperative State Research Service. The Forest Service, NSF, DOE, and other agencies provided 11 percent of the total academic budget devoted to wood science and utilization research in 1981. The remaining 72 percent came from State and industry sources.While the proportions of R&D funds contributed by industry and the States are not identified by USDA in its Cooperative Research Information System (CRIS) (table 10), a recent survey of forest-products research in the Southsuggests that industry contributed approximately 15 percent of the academic researchfunds in that region, with the States accountSOURCE Cooperative Research Information System (CRIS), U S Department of Agriculture

ing for 47 percent of the funds expended, 22 The remaining 38 percent was funded by various Federal agencies. The Southern colleges and universities included in the survey received half (48.8 percent) of the total wood science andutilization R&D funds provided to all U.S. academic institutions in 1981. To the extent that the South reflects the national situation, the States appear to be the major funding sourcefor wood-utilization R&D at colleges and universities.

Industrial R&D
Because of the proprietary nature of much of the forest products industry’s R&D and the reluctance of the private sector to disclose R&D budgets, a detailed assessment of industrial R&D is not possible, although the information available suggests that major emphasis within the industry is aimed at process improvement rather than basic research.

ZZK. Thompson, status

of Forest products Research at public

Institutions in the South (Mississippi State, Miss.; Mississippi Forest Products Laboratory, 1982), p. 12.Ch. 1 —Introduction ● 29

In terms of both dollars and scientist manyears allocated, the forest products industry isthe largest supporter of wood science and utilization R&D in the United States. NSF estimates that in 1979 the industry spent a total of $148 million on lumber, wood products, and furniture R&D, and $454 million on paper and allied products R&D, Of the funds expended by the pulp and paper industry, 4 percent werefor basic research, 25 percent for applied research, and 71 percent for product and process development. According to NSF, the solidwood-products manufacturers spent 68 percentof their R&D budgets on development, 28 percent on applied research, and 4 percent on basic research. ’s A recent McGraw-Hill survey estimated thepulp and paper industry’s 1980 R&D expenditures at $508 million and its 1981 expenditures at $584 million,24 An estimated 40 percent ofthe R&D funds were spent for improving existing products, 27 percent for developing new products, and 31 percent for developing newmanufacturing processes, Industry analysts expect greater emphasis on new processes in the future and a slight increase in emphasis on new products by the pulp and paper industry through 1985, While actual-dollar R&D expenditures by theforest products industry increased at a significant rate between 1969 and 1979 (fig. 6), funding remained nearly level, measured in constant dollars. Between 1977 and 1981, R&D expenditures by the pulp and paper industry(fig. 6) increased approximately 10 percent annually in actual dollars, compared with anaverage annual increase of 15 percent in all industries. 25

Z~I n~ust r} Stllr] ie$ Groul), Science Resources Studies Hi.gh - iight.s: Reaj Growth in Industrial R&D Performance Continues
in 1979 (Washington, D. C.: National Science Foundation, 1981), NSF 81-313, p. 2, Zq~C[)nomiCs D~partm~nt, ,?Yth Annual McGra w’-Hill .!urtreJr
of flusine.s.s Plans for Research and Development Expenditures (New York: hlc~raw-}lil] Publications Co., 1982], p. 8.

25 ” A Research Spending Surge Defies Recession, ” Business I%reek, July 5, 1982, p. 68. Historical Research and Development Expenditures

160

150 “ R&D expenditures by the 140 “ lumber and furniture industry 130

— /

(1972)

40 “

30 20 10 I I I I I I I 1 I I

SOURCE Economics Department, 27fh ,4rmua/ McGrawWI// Survey of Bus/ness

Hans for Rese@rch

and Development Expenditures (New York McGraw
HIII Publlcatlon Co , 1982)

The manner in which the forest products industry reports R&D activities may mask thenature of industrial R&D programs, For example, many of the large pulp and paper producers and integrated forest products firms have extensive forest management research programs in addition to wood-utilization R&D. NSF, the Federal Trade Commission, and the Securities and Exchange Commission report aggregate R&D funding and do not report theproportion of corporate funds devoted to forest management versus that spent on woodutilization R&D. For this reason, the R&D funding statistics quoted in this report include forest management research; therefore, the actualamount spent on wood utilization R&D probably is less than reported.
Other industrial sectors also perform R&D that is used by the forest products industry; likewise, some forest products industry R&D affects other industries. The major R&D effort related to wood utilization is funded directly by the forest products industry. A relatively small proportion of the total wood-utilization R&D effort appears to come from machinerysuppliers, coating (paints) and resin manufacturers (chemicals), and users of wood products. It appears that most R&D performed by lumber firms is specifically used by the lumber indus-30 . Wood Use: U.S. Competitiveness and Technology

try, while less than 50 percent of the R&D performed by pulp and paper firms is used primarily by the industry itself. 26
Compared to other manufacturing industries, the pulp and paper sector is well below the mean in its funding of R&D as a percentage of sales and capital expenditures. In 1981, R&D expenditures by the pulp and paper industrywere less than 1 percent of its sales—significantly less than the 2.5-percent average for all manufacturing industries. 27 Electrical communications, aerospace, and the scientific instrument industries led all other manufacturing industries in 1981, Aerospace led all other manufacturing industries, devoting over 16.2 percent of its capital expenditures to R&D, which was 24 times more than that devoted by the pulp and paper industry. 28
The relatively low premium put on R&D by the forest products industry may be due to a combination of factors: 1) the industry is mature in the sense that wood products arewell developed and have been used in essentially the same form for a long time; 2) woodproducts are not high technology and, therefore, are not likely to be subject to revolutionarytechnological breakthroughs in their manufacture and use; 3) the industry is resourceoriented in that it focuses on the conversion of timber to useful products, rather than on the manufacture of a specific commodity that could be made from a range of materials; and4) forest industry management generally is promoted from within; thus, the industry’s R&D direction generally is less exploratory and is focused on product improvement or process efficiency rather than on new products.

. 28 E(:onomics Department, Op. Cit., pp. 11-12.

# Chapter II



# Solid Wood and Panel Products

### Chapter II 

# Solid Wood and Panel Products

—

Summary and Conclusions

3334 ● Wood Use: U.S. Competitiveness and Technology



# Introduction

Panels have been replacing lumber in construction for the past three decades. Plywood has been produced commercially in the UnitedStates since the turn of the century, but plywood manufacture, like lumber manufacture, relies on large-diameter, high-quality softwood timber, which is becoming increasingly scarce. As a result, technologies for panel manufacture have concentrated on expanding the resource base, Newer panels, made from wood wafersor strands, can be made from small logs, residues, and hardwoods and can substitute for plywood in construction applications, Two new panel products, waferboard and oriented strand board (OSB), already have captured some plywood markets and are expected to continue expanding. Most new, planned panel manufacturing capacity in the United Statesis in OSB or waferboard. Because these products can be made from hardwoods and from lower quality softwoods than can plywood, production facilities are located in the GreatLakes States and Northeast, closer to construction markets and suitable wood supplies. Advances in plywood manufacture also haveexpanded small log utilization through improvements in log peeling technology. Otherchanges in plywood production include increasing automation and improving dryingprocesses to reduce energy use, accelerate drying, and produce more stable panels. These improvements in primary manufacturing have been aimed principally at expandingthe usable resource base: increasing the ability t o use hardwoods and a greater proportion of the tree. Increasing the efficiency of wood use in construction also has potential to reducethe pressure on domestic timber resources, particularly the softwoods. Engineering analyses have shown that many houses are overbuilt, or capable of withstanding far greater stresses than required by housing codes. More careful matching of construction members—framingand sheathing—to the engineering requirements of the structure could help reduce the amount of wood required to build a home.
New construction technologies also haveshown some promise in reducing wood requirements. In particular, the use of factorymade wood trusses for floor, wall, ceiling, and roof framing reduces lumber requirementsand, at the same time, speeds up housing construction and reduces labor costs. Factorymade housing components, such as wall panels that combine framing and sheathing, also canreduce wood waste and construction labor requirements. Construction technologies, however, are slow to change, and the impact ofthese technologies on wood utilization is unlikely to be significant in the short run,



# Profile of the Lumber and Panel Products Industry

As the world’s largest consumer of industrial wood l (including pulp), the United States uses over one-fourth of the world’s timber products, more than half of which is lumber, plywood,and veneer, In 1979, the United States consumed approximately 50 million air-dry tons of lumber, 12 million tons of plywood, and 10 million tons of panel products, accounting for nearly half the U.S. consumption of industrial

1 Industrial wood includes all commer(; ial roundwood products eY(:ept fuelwood” roundwood. 2 In addition, the United States produces over 20 percent of the world’s softwood lumber, 15 percent of its hardwood lumber, nearly 45 percent of its plywood, 1.5 percent of its particle board, and 40 percent of its fiberboard,’

— — — 2 U S DA Forest Service, U.S. Timber Production, Trade, Consumption, and Price Statistics, 1950-1980, Miscellaneous Publication No, 1408, 1981. 3Roger A. Sed jo and Samuel J. Radcliffe, Postwar 7“rends in 1 l,s, Forest products Trade: A Global, National, and Regional l’iettr, Research Paper R-22 (Washington, E).(; ,: Resources For the Future, 1980).Ch. II—So/id Wood and Panel Products • 35

Despite its role as a major producer, the United States is a net importer of lumber andpanel products, except particleboard, It imports nearly 35 percent of the world’s total softwood lumber imports, over 5 percent of world hardwood lumber imports, 30 percent of worldplywood and veneer imports, and over 10 percent of world fiberboard imports (fig. 7). The U.S. trade pattern is dominated by imports of softwood lumber and plywood from Canada, imports of hardwood veneer and plywood from Asia, exports of softwood products (including logs) from Alaska and the Pacific Northwest to Japan, and some export of panel products from the west coast and the South to Japan, Europe, and Central and South America.

Raw Materials

In addition to the various timber used as rawmaterials, plywood and panel products manufacture is a major consumer of adhesives. Thelargest single adhesives market today is in plywood manufacture. 4 Production of composite panel products consumes significant amounts of phenol and urea formaldehyde resins. Other chemicals used by the industry include fireretardants and wood preservatives. Preservatives may become even more important in the future if wood use for foundations in housing construction continues to expand. All of these chemicals—adhesives, preservatives, and fireretardants—are largely derived from petroleum.

Product Demand
Because demand for lumber and panel products is linked closely to the homebuilding in4 Peter Gwynne, “Adhesives: Bound for Boundless Growth, ” Technolog~, January/February 1982, p. 43.

Figure 7.—

U S production (percent of world production) \

U.S. exports (percent of world exports)

U S imports (percent of world imports)

SOURCE Roger A Sedjo and Samuel J Radcllffe, Postwar Trends In U S forest Producfs Trade: A G/oba/ Natmna! and Reg/ona/ View, Resources for the Future, Research

Paper R.22, 198036
● Wood Use: U.S. Competitiveness and Technology

dustry, production of lumber and panel products follows the general pattern of housingstarts. In 1976, construction-related activity accounted for three-fifths of the lumber and twothirds of the plywood consumed in the United States. 5 New home construction is the majormarket for lumber and plywood, although residential upkeep and improvement and nonresidential construction also consume significant amounts. Periodic depressions in the housing industry create soft markets that greatly affect lumber, plywood, and panel demand, resultingin mill closures and curtailments in production. Other major uses of wood—manufacturing and shipping—account for 18 percent of thelumber and 10 percent of the plywood consumed in the United States. Furniture makingaccounts for the bulk of the wood used in manufacturing, and pallet manufacturing is the major market for wood in shipping. A summary of lumber and panel products use is shown in table 11.

Industry Size and Distribution of Production
The lumber and forest products industry consists of 35,000 establishments and employs nearly 700,000 workers, or nearly 4 percent of those employed in U.S. manufacturing. 6 Major wood products manufacturing sectors ofthe lumber and wood products group employed 219,000 people in 1981 (table 12). Although the industry is dominated by a few large firms, some segments are made up of small, competitive firms (table 13). The lumber industry is the most competitive component of the lumber and wood products sector. Of its 8,184 establishments, 80 percent employ fewer than 21 people, ’ Over 50 percent of the U.S. lumber output is produced by 10 percent of the mills (table 14).

5 USDA E’orest Service, An Analysis of the 7’in]ber Situation
in the United States 1952-2030, review draft, 1980.
‘U.S. Department of Commerce, Bureau of Industrial Economics, 1982 U.S. Industrial Outlook for 200 Industries With Projections for 1986 (Washington, D. C.: U.S. Government Printing C)ffi[;e, January 1982]. Lumber production is concentrated in theSouth and the West, where most of the softwood, sawtimber growing stock is located. While the South contains more sawmills than the West, its mills generally are much smaller.The West produces over two-thirds of the lumber output (table 15). Mills in the North andEast produce only 6 percent of the annual lumber output. The plywood and panel products industriesare more concentrated than the lumber industry and have fewer mills. Their 232 softwoodveneer and plywood mills, 366 hardwood veneer and plywood mills, and 68 particleboard mills employ about 77, OOO people, Because construction, like lumber, depends on high-value, large softwood logs, the Southand West are major plywood-producing regions. In 1979, the South and West produced 42 percent and nearly 47 percent, respectively, of [J. S. plywood manufactured; the remainder was produced in the northern Rocky Mountain States. Plywood production has been shifting to the South since the early 1960’s, primarily because of its lower wood prices.In 1979,96 percent of the panel manufacturing capacity was in plywood. A few plywood plants also produced corn-ply, a structural panel with veneer faces and a particle core. Only two waferboard plants existed in the United States in 1980, although there were plans to add several more plants between 1981 and 1983 in the Great Lakes States or Maine. 8 Unlike the plywood and lumber industries,which require sawtimber-quality trees, composite structural panels use hardwoods; small, lower quality trees; and, occasionally, millwaste. The nonplywood panel products industry, therefore, probably will continue to be concentrated in the East, particularly in the Great Lakes States, and the Northeast, where major construction markets are located,

—.—

7 See note 6. ‘Kidder, Peabody and Co., 1 nc., “Corn-ply, Waferboard, Or]- ented Strand Board: Revolution in the Structural Panel Market?”, I)e(; 24, 1980Ch. II—SolId Wood and Pane/ Products ● 37

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u-l38 . Wood Use: U.S. Competitiveness and Technology

Table 12.—Selected Statistics on the Lumber and Panel Products Industry, 1981

Value of product Value added

- Number of shipments (millions Number of employees Establishment (millions of dollars) of dollars) establishments (thousand) Sawmills and planing mills (SIC 2421) . . . . . $11,765.7 $5,552.2 7,544 151.0 Softwood veneer and plywood (SIC 2436) . 3,270 1,460 256 40.8 Hardwood veneer and plywood (SIC 2435) 1,200 430 321 21,3 Particleboard ., ... ... . . . . . . ... . . . . . 545 225 63 6.2

Table 13.—Number of Primary Timber-Processing Establishments in the United States, by Industry and Type of Organization, 1972

Single-unit Multi unit companies companics Total Industry Number Percent Number Percent Number Percent

– Lumber manufacturing. . . . . . . . . . . . . . . . . . . . . . 21,554 95 1,132 5 22,686 100 Plywood and veneer manufacturing . . . . . 332 54 276 46 598 100 Woodpulp manufacturing . . . . . . . . . . . . . . . . . . . . 82 25 249 75 331 100 Other primary timber manufacturing . . . . . . . . 4,081 86 679 14 4,760 100
Total establishments . . . . . . . . . . . . . . . . . . . . . . . . . 26,039 92 2,336 8 28,375 100

a s
, n g l

e . uni t cornpaflles operate at only one IOcatlon bForest Sew Ice estimate based on Bureau of the Census data

SOURCE U S Department of Commerce, Bureau of the Census, Census of Manufactures, 1972 Volume/ Subject and Spec/a/ Sfatfst/cs (Washington, D C U S Govern.

ment Pnnttng Office, 1976)

Table 14.— Lumber Production by Mill Size, 1979

Mill size Production (Million board feet) Number of mills percent (million board feet) Percent
Over 50 . . . . . . . . . . . . . . . . . . . 151 10 17,920 55 25-50, . . . . . . . . . . . . . . . 189 13 6,691 21 10 - 25 ......., . . . . . . . . . . . . . 288 20 4,588 14 5 - 10 ........,

. . . . . . . . . . . . 272 18 1,908 6 3- 5 . . . . . . . . . . . . . . . . . . . . . 233 911 3
Other. ... . . . . . . . . . . . . . . . . 334 23 478 1

Total . . . . . . ... ... . . . . . 1,467 100 32,496 100

SOURCE 1981 Directory of Forest Products Industry

Table 15.— Large Mills and Production by Region and Size

Production range Number of mills (million board ft) West South North and East

Over 50. . . . . . . . . . .“. . . . . . 115 32 4 25-50 . . . . . . . . . . . . . . . . . . 118 66 5 10-25 . . . . . . . . . . . . . . . . . . . . 114 136 38 5-10

. . . . . . . . . . . . . . . . . . . . . . 42 158 72 3- 5 . . . . . . . . . . . . . . . . . . . 27 112 94 Other . . . . . . . . 57 100 177

Total . . . . . . 473 604 390 Total production . . . . . . . . . . . . 22,131 8,287 2,078 Percent of total output . . . . . . . 68 26 6 SOURCE 1981 Directory of the Forest Products Industry.

Ch. //—Solid Wood and Panel Products ● 3 9



# Use of Solid 

# Wood and Panel Products

Three sectors of the lumber and wood products industry group are among the 45 rapidgrowth industries whose compound annualgrowth rates ranged from 6 to 20 percent between 1972 and 1978: 1) wood pallets and skids; 2) wood kitchen cabinets; and 3) structuralwood members, such as laminated or fabricated trusses, arches, and other structural members of lumber (not including standardsoftwood or hardwood dimension lumber). Although three-fourths of the rapid-growth industries attributed their success to new productdevelopment, of the three rapid-growth, woodusing industries, only “structural wood members” listed new products as a key growth factor. 9 Two of these new products, laminatedbeams and roof trusses, actually were introduced into the market during the 1 950’s. Two new developments, however, are trusses that can be used to frame entire houses and techniques for producing laminated beams, joists, and girders of many sizes and shapes.Such large, laminated beams and arches, frequently bent into specified shapes, have penetrated new markets, including the constructionof large indoor sports arenas, convention centers, and domes. Trusses, on the other hand, have not opened many new markets for wood products but have replaced larger dimension lumber in light frame construction.Other new products recently introduced include various types of fiberboard and particleboard. A medium-density fiberboard (MDF), first produced in the mid-1970’s, has rapidly expanded into furniture corestock marketsformerly held by particleboard and other panels. New types of particleboard include panels

fI [ I,s, [)~;~):l rl **mf!n t**  of (;0 m m Crc e, op. [: it. made from strands (thin shavings or slivers ofwood), flakes, or wafers, sometimes with veneer faces. These panels, first introduced inCanada and the United States in the mid1970’s, now strongly compete with softwood plywood for structural use.

The amount of lumber used in homes has remained fairly constant for several decades, while the amount of plywood and structural panels has increased. Panels for sheathing (walls) have replaced sheathing lumber. Now, however, plastic-foam sheathing is replacing wood-based sheathing in some markets owing to its superior insulation properties. New pane] products are expected to replace plywood for sheathing and underpayment (floors). The sametrend seems to have occurred in furniture manufacturing, where plywood and particleboard have replaced lumber as furniture corestock and have themselves been replaced by MDF. Shipping pallets have been replacing wood boxes and containers for materials handling.New types of pallets, made with plywood decking, particleboard, or MDF, are expected to replace some of the existing hardwood lumber pallets in the future. In general, new products introduced by the lumber and panel industries replace otherwood products already in use, rather than compete with other materials. If the forest industry hopes to expand the uses of wood, it probably will have to develop new products that can compete with steel, aluminum, plastics, and other structural materials, rather than products that simply replace other wood products. This probably will require greater interaction of other professions involved in the constructionindustry: building code offices and testing organizations, architects, and building contractors.40 . Wood Use: U.S. Competitiveness and Technology



# Industry Trends and Potentials

Most of the wood (over 96 percent in 1976) entering mills for primary processing is used as products or as an energy source. Wastes from lumber and veneer or plywood mills areused for fuel or for manufacturing particleboard, composite panels, pulp, or paper. 10 While the wood products industry as a wholeis quite resource-efficient, opportunities for increasing efficiency still exist in three areas:1) increasing the recovery of high-value primary products (lumber, plywood, particleboard); 2) expanding the use of underutilized species, wood residues, and defective materialsnow left in the woods after harvest; and 3) increasing the efficiency of the end use of wood products.

Product Recovery
The efficiency of product recovery in lumbermills, described as the “lumber recovery factor” (LRF), is measured by the number of board feet (12 inches by 12 inches by 1 inch) of lumber recovered from a cubic foot of log. Because the nominal dimensions of finished lumber are larger than the actual dimensions (a standardfinished 2- by 4-inch stud, for instance, measures approximately 11⁄2 by 31⁄2 inches), there are actually 16, rather than 12, board feet of lumber in a cubic foot of solid wood,
Lumber recovery efficiencies in the United States currently average about 41 percent (LRF of 6.5). With new technologies and processes, the product recovery in lumber mills could reach 60 to 88 percent (LRF of 10.0 to 13.0) for medium-sized logs. 11 The product recovery in plywood mills averages around 50 percent. New processes may improve efficiency slightly by enabling the use of materials which at one time were rejected as veneer stock. Finally,

wood for structural panel manufacture, Engineered panel products require roundwood to produce high-qua] ity flakes of specified dimensions.
“Jerome Saeman, “Solving Resource and Environment Problems by the More Efficient Utilization of Timber, ” Report of the President’s AdL’isorJ’ Panel on ‘rimber and the L’n L’irunrnent, April 1973. product recovery in particleboard, compositepanel, and fiberboard mills approaches 75 percent on a weight basis. 12 Improvements are aimed at reducing processing time, improving panel quality, and increasing automation.Since 53 percent of the wood entering sawmills is used to manufacture particleboard, fiberboard, paper, or energy, any increase in lumber output for one use tends to reduce the amount of wood available for other uses. These tradeoffs can be important in balancing lumberrecovery efficiency with other production processes, including the need for energy.

Forest Resource Use
The forest products industry continually seeks ways to use a larger proportion of thewoody biomass left in the forest after the marketable material is removed, Softwoods, which are intensively utilized, could provide even more wood material if the tops, limbs, branches, and dead, dying, or defective timberwere used. The volume of dead and dying timber in 1977 was estimated to be 21 ft 3 —almost double the amount harvested—and the volume of residues left from logging came to 8 billion ft 3 in 1976. New products and technologies, particularly in composite panel manufacture, could use these materials, although the amountthat would be economically recoverable is unknown. As second-growth timber replaced old growth and utilization standards changed, the lumber and panel industries adjusted theirprocesses to use smaller logs. This trend probably will continue, Moreover, as the price ofhigh-quality softwood stumpage increases, advances in lumber processing and the development of composite panel products have increased the industry’s ability to use the vast and largely untapped U.S. hardwood species.

IZ1~f;rsonal (communication w ith John Haygreen and Ja}’ Jo bn - son with OTA staff member Julie K, Gorte.Ch. I/—So/id Wood and Pane/ Products ● 4 1

Efficient End Use of Wood Products

The greatest opportunity to increase the efficiency of wood use may be in construction. Current techniques could reduce substantiallythe amount of wood used for home construction—particularly in single-family detached dwellings–without reducing the quality of the structure. Two developments are particularly noteworthy: 1) truss framing and 2) engineered panel assemblies, which combine sheathing and framing. Increased use of single trusses to frame floors, walls, ceilings, and roofs togethercould yield greater wood savings. Some analysts estimate that truss framing could achieve as much as 30 percent reduction in lumber use over conventional construction practices.Engineered assemblies or stressed-skin panels used for floors, walls, or ceilings, which combine sheathing and framing in sandwich panels or with adhesives, also may increase efficiency of wood use. Such assemblies are factory-built, as are trusses, and their use could reduce the wood wastes on construction sites from cutting and custom fitting, resulting in less wood use while providing structural strength and stiffness.Improvements in wood use in manufacturing and shipping are more limited. Major improvements probably exist in the manufacture of particleboard pallets or of pallets with plywood or composite-panel decking. Although construction techniques now being used may produce a more durable and versatile pallet,they probably will not replace traditional pallets to any significant extent. Conventional pallet manufacture requires lower capital investment than particleboard facilities.



# Lumber Products

Lumber products are of three basic types: 1] Softwood dimension lumber, 2) boards and finish lumber, the lumber dimension lumber, the mainstay of industrv, is manufactured in five and 3) timbers. Boards* and finish lumber are less than 2 inches thick and 1 inch or more in width. Dimension lumber is between 2 and 5 inches thick and at least 2 inches wide. Lumber that is 5 inches or more is classified as a timber.

* For purposes of this report, the term “hoard” is used only in reference to panel productt, one-in(:h lumber will be referred

to ;is “f]nish lumber. ” types of sawmills: 1)small-log mill; 2) stud mill; 3) large, common-log mill; 4) large, grade-logmill; and 5) high-deduct, 1arge-log mill. Distinguishing factors among these sawmill types are log diameter and type of lumber product (table 16). The most common mill is the small-log mill, which produces dimension lumber for light frame construction.

Table 16.—Types of Softwood Sawmills and Their Primary Products

Sawmill type “ - ‘ -- ‘

- Typical log diameter Primary products produced Small-log dimension mill ., .. .5” to 16” Random length dimension

- lumber Stud mills, ... ... ... , ... ,4” to 9” Studs 2” x 4” X 8‘ nominal Large, common-log mill ... , 16” to 30” Random length dimension lumber Large, grade-log mill ., ... . . 15” and larger Common, shop, and clear lumber High-deduct, large-log mill . . Large logs with greater than Clears and high-grade 30 percent deduct a commons
Adapted from Wllllston 1-9;; – “ aDeduct[on In recoverable lumber volume due to defects (n the logs

SOURCE Envlrosphere Co Wood /ts Present and Poten(/a/ Uses contractor report to OTA 198242 . W OO d Use: U.S. Competitiveness and Technology

Lumber Manufacture
The basic processing steps for lumber manufacturing are shown in figure 8. Materials and energy flows of a typical sawmill are shown in figure 9. The efficiency of lumber recovery tends to vary with mill size, with larger mills achieving higher recoveries.

Potential Improvements in Milling Efficiencies

and Lumber Manufacture
In 1979, lumber constituted almost 70 percent of the weight of all lumber and panel products produced in the United States and 53 percent of all wood products, except pulp and paper, consumed in that year. 13 Thus, even small improvements in milling efficiency can result in significant savings of the Nation’stimber resources, particularly softwood. Several such improvements can be made in lumber manufacture by: 1) improving lumber recoveryor wood-use efficiency in sawmilling, 2) decreasing energy requirements, and 3) improving grading procedures.

Improving Lumber Recovery and Wood Use The following existing technologies probablyhave the potential to more than double the efficiency of converting roundwood into lumber products (table 17). By installing or adopting technologies such as BOF, PLV, and SDR, theefficiencies of sawmills probably could be increased substantially, The potential increase in lumber recovery efficiency for PLV, EGAR,and BOF is shown in figure 10. In addition, several new technologies, such as SDR, corn-ply, and composite lumber, probably can reduce

Figure 8.— Flow Diagram of a Typical State-of-the-Art Small-Log Sawmill, Indicating Process Waste Streams

r F Log * > 1 e Stabber * Twin

- Trl- 1 band mill

Bucking Chips Sawdust Chips Sawdust Sawdust

Wood J

Chips

Product
sorter

NOTE” A log profile is shown at each machine (top) The shaded areas Indicate material which is chipped away, while verticle I!nes in other cross-sections indicate saw Ilnes

SOURCE” E M Williston, Lumber Manufacfurlng The Design and Operation of Sawmi//s arrd Paper Mi//s (San Francisco. M!ller Freeman Publications, 1976).Ch. II-Solid Wood and Panel Products . 43

——. —.

Figure 9.— Present and Predicted Materials Balance for Softwood Lumber Based on Ovendry Weight (OD wt.) (sawlog weight includes bark)

Sawdust

the lumber industry’s dependence on high-value softwood timber, whose scarcity (deflatedprice] has increased at the rate of about 2 percent per year (compounded) over the last century. The SDR process and the manufacture ofcomposite lumber and timbers allow manufacturers to utilize hardwoods, defective timber,and wood residues formerly considered unmerchantable,
Expanding the resource base by using largerproportions of the wood produced in the forest is one of two major opportunities that exist to improve total utilization efficiency ofwood in the United States. The other is increasing the efficiency in the way lumber is used(conservation). However, increasing the efficiency of mills may not significantly reduce thedemand on the forest resource, unless increasing amounts of forest residues can be harvestedeconomically and transported to mills. For example, the efficiency of lumber recovery mayreduce the amount of residue available to produce energy, and pulp, paper, particleboard, and other fiber-based panels. Nationwide, the unused wood from primary processing consistsof 52 percent softwoods and 48 percent hardwoods and represents 7.1 million tons of material, A significant portion of this material probably comes from lumber manufacturing, although the exact quantity is unknown.

Improving Yields in Traditional Sawmills There is a practical limit to the amount of lumber that can be recovered from any log, However, some new processes can increase thelumber-recovery efficiency of dimension lumber without major sawmill modifications; e.g.: 1) the BOF program, which can produce higher grades and increase recovery of lumber; 2) the SDR process, which enables the use of hard-Table 17.—Summary of Major Technologies for Improved Lumber Manufacture

—

Technology Stage of development

BOF

- Commercially available

EGAR Process IS developed; no significant commercial use. SDR Process is developed; no significant commercial use.

MSR Commercially available.

PLV Lumber -

Commercial availability limited — to a few specialty products. Effect on resource base Effect on recovery

None Theoretical increase of 20°/0
over conventional sawmilling. Possible increased small log Increases recovery 10-130/0 utiIization,
Increased hardwood utilization. Reduces defects in hardwood lumber; increases lumber
value.
None Reduces variability within lumber grades, allowing
more efficient use of lumber
in construction. Theoretical yield of 70-90°/0

Corn-Ply Lumber Not commercially available

Improved Drying (solar No significant commercial kilns, high temperature development. drying, vapor recompression, dehumidification)
SOURCE: Office of Technology Assessment Allows use of hardwoods, Theoretical %O/. recovery, wood residue, defective
wood.

— Lower energy requirements;
reduction in defects. Barriers to implementation

Field results have shown average 40/0 Increase over conventional sawmilling. More costly to manufacture;
more labor-intensive. Higher drying costs; requires high-temperature kilns.

Modification of codes to allow most efficient use of MSR
lumber.

Development of continuous laminating presses; lack of accepted method for assigning product strength values; requires new milling
facilities. Requires new milling facilities

or combination of veneer and particleboard facilities, Usually higher capital investment and/or longer drying time. Estimated time scale to significant contribution

—. o

15-20

10-20

0-5

15-20

15-20

15-25Ch. II—So/id Wood and Panel Products . 45

Figure 10.— The Maximum Yield of Lumber From Conventional and Innovative Processes 

# I

5 6 7 8 ‘j 10 11 12 13 14 15 16 17 lb 19 20

Log diameter

woods, previously limited by their tendency to warp; and 3) the EGAR process, which reduces waste and can produce higher quality lumber,

Best Opening Face.—The initial sawline, or the opening face cut, sets the position of all other sawlines and therefore has a significant effect on lumber recovery efficiencies and grades. Deciding how to make the initial cut often is left to the judgment of the head saw operator.While a skillful operator can achieve high efficiencies, a computer can simulate various sawing patterns and more quickly choose the optimal opening face. The BOF, a computerprogram for selecting the best first cut, was developed by FPL nearly 10 years ago. In 1973,the Forest Service initiated a sawmill improvement program to demonstrate the BOF concept. Under laboratory conditions, BOF yields 6 to 90 percent more lumber from 5- to 20-inchlogs and averages 21 percent more lumber recovery than does conventional sawing. Saw-Dry -Rip .—The SDR process can increasethe amount of sound, defect-free lumber recovered from hardwood timber by modifying slightly the conventional milling practices of sawing, ripping into lumber, and then drying,With SDR, crooks, bows, and twists in hardwood lumber may be reduced by first sawing,then high-temperature drying, and finally ripping” into lumber. Drying larger pieces at high temperatures by SDR minimizes the effect of the stresses that develop within wood as it grows, SDR may result in a lower LRF of green (undried) lumber than conventional milling, but this is generally more than compensated for by the reduction in warp.

Edge-Glue and Rip.—With EGAR, logs are sawn into flitches* * and lightly edged prior to drying.

* Kipplng is sawing lengthwlsr or [)a ra 1 lel to gra 1 n, a 10 I)g the l[)ngitudina] axis of the lumber,
* * A flitch is a crosswise slice from a log, with two sawn faces
and two ro’u nded, or u nsaw n edges.46 . Wood Use: U.S. Competitiveness and Technology

They are then glued edgewise into panels, and the panels are ripped into lumber. This reducesthe amount of wood lost in edging, which usually sacrifices some sound wood from lumber edges in order to produce solid lumber of standard widths. Ripping can be done to yield the highest grade and strongest lumber by avoiding knots near the edges of the lumber. The EGAR process theoretically can increase lumber recovery from 35 to 77 percent from logs of 5 to 20 inches in diameter. 14 It is estimated that EGAR can increase the output of finished dimension lumber by 10 to 13 percent by eliminating edging loss. 15 Moreover, EGAR lumber has greater strength and less warp than standard lumber. However, the process itselfis more labor-intensive than conventional lumber manufacture and requires additional drying, which may increase manufacturing costs. Several new lumber-drying processes that could reduce energy consumption may come into wide use in the future, Because the lumber industry is a small energy consumer, savingsin energy use by the lumber manufacturing industry probably will not contribute significantly to national energy conservation; they could, however, become more important to lumber manufacturers as energy prices increase. (The lumber industry, however, is a minor energy purchaser and is capable of producing much of its own energy through the use of mill wastes. )

Producing Composite Lumber and Timber Products
BOF, SDR, and EGAR are marginal modifications to conventional sawmilling. Lumber, or lumberlike products, also can be made from wood particles or veneer, as well as from solid wood or edge-glued pieces, Manufacturingsuch composite lumber can dramatically increase lumber recovery efficiency and extend the timber resource base through use of wood waste material and hardwoods, It is unlikely, however, that composite lumber products will replace conventional 2 by 4 framing lumber.

‘V-hernan, op. cit. Is(j[:orge B. Harpo]e, Ed Williston, and Hiram H. Hallock, “E(lAK Process hlakes Wide-Dimension Lumher From Small ],ogs, ” ,$c)uthern I,umberman, Dec. 15, 1977. Most opportunities for using composite lumber are in larger applications—for girders andbeams-or for specialty applications. Two major processes have been developed to manufacture composite lumber and timber products: PLV and corn-ply.

Parallel Laminated Veneer.—Also known as press-lam and laminated veneer lumber (LVL), the PLV process consists of laminating (gluing) veneers with all plies parallel (as contrasted to plywood, where the veneers are laminated withgrains perpendicular) to make dimension lumber or timbers. Like plywood veneers, the veneer sheets are press-dried, coated with adhesives, laminated in overlapping fashion, pressed, and ripped to desired dimensions. PLV has a number of advantages:

● it produces high-quality products from low-quality raw material or hardwoods;. lumber or timber dimensions are not limited by log size; and

● it can convert logs into ready-to-use products in 1 hour.In general, PLV produces higher grade lumber than does conventional lumber manufacturing. Moreover, PLV specialty products andlarge structural timbers from PLV might be attractive commercially; at least one firm now markets a joist, called Micro-Lam, * made from PLV. PLV also can be used to manufacture nonstructural wood products like millwork and cabinetry. Lumber recovery efficiency from PLV can be increased from an efficiency of 53to 91 percent for 9- to 20-inch logs, an efficiency significantly greater than that theoretically attainable from any other lumbermaking
process. Despite its advantages, PLV may not makesignificant penetration into conventional dimension lumber markets in the near future.PLV manufacture requires equipment that cannot readily be adapted to conventional sawmills; thus, shifting to PLV probably will require entirely new mills with high capital costs.As existing sawmills are depreciated, PLV facilities may be built as replacements, particu-

*Trademark of the Trus-Joist (lot-p,Ch. II-Solid Wood and Panel Products . 47

larly if real stumpage values increase and if building codes are modified to recognize fullythe superior properties of PLV lumber. However, it may be possible to modify plywood or panel mills to produce composite lumber and products such as composite timbers (beams,joists, arches, girders, and the like), The substitution of composites for dimension lumbermay occur slowly unless the price of high-quality softwood logs significantly increases. PLV can be used for large structural elements, such as beams or timbers, that vary in cross sectionacross their length to meet strength requirements. Com-ply.—Com-ply consists of a structural composite core, like particleboard, with veneerfaces. It can be made into studs, larger dimension lumber, or panels. Corn-ply studs are strong enough to substitute for standard studson a one-for-one basis in exterior house framing. The particleboard core constitutes 70 to 80 percent of the product and can be made from hardwoods. Because a corn-ply mill can use nearly all of its residues to produce the core material, it can operate with only 5 percentwaste, a lumber-recovery efficiency of 95 percent. Economic analysis of corn-ply lumber production shows, however, that it is unlikely that corn-ply lumber will be very competitive with either conventional or PLV lumber,

Decreasing Energy Requirements Up to 90 percent of the heat energy required in lumber processing is consumed in dryinglumber to a moisture content of 13 to 16 percent. Lumber normally is dried in a steam kiln (although air drying is used sometimes) in which heated air is circulated. Kilns may be heated by natural gas or propane directly or,more commonly, by steam coils. Softwood lumber requires from 2 million to 4 million Btu/ thousand board feet while hardwoods requireup to 6.5 million Btu. Several new drying technologies have been developed, including: 1)high-temperature kiln drying, 2) continuousfeed drying, 3) dehumidification, 4) predrying,5) pressure drying, 6) solar drying, 7) solar dehumidification, 8) vacuum, 9) vacuum-radiofrequency, and 10) vapor recompression drying, Of these, continuous-feed, dehumidification, pressure, solar dehumidification, vacuum, and vapor recompression drying may gain some commercial acceptance by 2000, although none seems likely to replace conventional steam kilns.

Improving Grading and Quality Dimension lumber is graded according to strength and stiffness, Grades determine what end uses may be made of construction lumber, Improved grading systems are being developed to better determine the end-use properties and characteristics of lumber and thereby avoid overbuilding with lumber products or using high-quality material where lower grades are suitable. Because different defects such astwist, bow, crook, rot, or knots affect mechanical properties differently, current practices of visual grading often result in a wide variabilityin lumber properties within each grade. Builders often use lumber of better quality than isneeded for construction to account for this variability in meeting building codes and avoiding liability. Improved ability to determine the strength and stiffness of lumber, together with building code acceptance of better design practices based on more precise grading, could result in significant resource savings. Since lumber strength is related to the presence of knots, a system that can determine precisely the effectof each knot on each board would be quite valuable. As yet, it is unavailable, Another development that could aid in making more efficientuse of framing lumber is a more precise understanding of the strength required in end-use applications, so that lumber strength can be matched to design specifications. Two major efforts are under way to improve grading inthe United States: 1) MSR, an alternative grading technology; and 2) ingrade testing, a research program,
Machine Stress Rating is a mechanical grading system that measures lumber stiffness in a nondestructive, stress-rating machine. It doesnot eliminate the use of visual grading but instead gauges the stiffness before visual graders determine the grade based on defects.48 ● Wood Use: U.S. Competitiveness and Technology

MSR lumber, with a narrower range of variability than visually graded lumber, reduces the amount of high-quality lumber needed to meet particular design specifications. The primarymarket for MS R-graded lumber is in truss fabrication, where lumber is used for roof, floor, and wall framing. The amount of lumber that could be saved using MSR varies and depends on the design of the truss.

The In-Grade Testing Program was initiated in l977 by FPL to develop more precise data on mechanical properties of various grades and species of lumber and to assess the importanceof these properties on the design and engineering of structures. Tests of walls, floors, and fullscale indicate that houses generally are overdesigned. Information from the In-Grade Testing Program may be used in conjunction with engineering structural analysis to improve theefficiency of lumber use in light frame construction.

Consumption and Use of Lumber Products

in the United States
Lumber consumption in the United States has been relatively stable for several decades, increasing from just over 5 billion ft 3 in 19.50 to almost 6 billion ft 3 in 1979. 16 At the sametime, per capita consumption of lumber has declined by over 20 percent over the past three decades (fig. 11).Construction (including new residential construction, upkeep, improvement, and nonresidential construction) uses about 60 percent of all lumber consumed in the United States. Theremaining 40 percent is used in shipping, manufacturing, and other uses, with shipping accounting for 43 percent of lumber used for nonconstruction purposes. New residential construction alone accounts for 40 percent of all lumber consumption.

New Residential Construction
Historically, the housing industry has experienced wide swings in residential construction activity, and there are indications that that

I%ee note 2. Figure 11 .—Per Capita Consumption of Lumber 1950-79

activity may continue to be erratic and uncertain. An upturn in homebuilding could drivesoftwood log prices up, increasing the incentives for lumber manufacturers to streamlineoperations and to increase product yields to remain competitive. Low rates of residential construction could force many small lumber mills out of business, concentrating the industry inthe larger mills, which tend to be more efficient. Other developments in the homebuilding industry also affect the lumber industry, suchas trends toward smaller houses and multifamily dwellings,
The amount of lumber used per unit depends largely on the type of dwelling constructed and, to a lesser extent, on building techniques and design. Single-family detached dwellings use approximately twice the amount of lumber used in multifamily dwellings and 4.5 times theamount used in mobile homes. Most singlefamily dwellings and small clustered units (e.g.,duplexes) are built onsite. Preassembled lumber products, such as trusses, have successfully penetrated the market for roofs in light frame construction and now account for the majority of roof framing. Floor trusses have been lesssuccessful, although they are gaining in acceptance in some areas. Trusses used to frame whole houses (fig. 12) recently have been de-Figure 12.— The Truss Frame System

Th IS truss framed system combl nes floor, wal Is, and roof

I nto a u r] !t Ized f ramp for st r uct L ra I cent I n u It y from the fou n d a t I o n u p t o the r I (j q e S(JU RCE USDA Forest SFrV Ice Forosl Products Laboratory

veloped by the FPL and are in limited use today.

Residential Upkeep and Improvement Home upkeep and improvement accounted for 14 percent of the lumber consumed in the United States in 1976 17 and almost 8 billion board feet of softwood lumber in 1980 18 compared with 4.7 billion in 197o. Indications are that such use may increase. The use of lumberper thousand dollars of expenditures on upkeep and improvement may have declinedslightly, however, primarily because of substitution of panel products for lumber.

New Nonresidential Construction

New nonresidential construction accountedfor just under 10 percent of the lumber consumed in the United States in 1976 for a range

IB( ;h 1 rl(; (It t I

I , u m her a n{i PI }IW ood F’ore\t I)rodu[,ts I ndustrj’ and the A[:apulco, Llcxlco; Apr. 3-4, 1982.

Panel products are used Forecasting, Inc., “The 80’s. Think Tank #l ,“



# Plywood and

for many things, mainly in construction, Single-family housing construction uses 43 percent of the plywood and 25 percent of the particleboard and other Ch. II—Solid Wood and Panel Products ● 49

of public, private, and commercial projects. Building construction, including commercialand other buildings, accounted for about twothirds of the lumber used in new nonresidential construction in the early 1970’s.* Totallumber use for new nonresidential construction, which normally responds to general economic activity, is expected to double in the next 50 years, primarily because of economic growth. 19

ManufacturingManufacturing, primarily of furniture, accounted for 11 percent of the lumber consumed in 1976. Much of the lumber once used forcorestock has been displaced—first by particleboard, then, more recently, by medium-density fiberboard.

Shipping Shipping accounted for 17 percent of the lumber consumed in 1976. Two-thirds of the lumber in shipping was used for pallets, with the remainder used for dunnage, blocking, bracing, and wooden boxes. These latter uses have been declining for two decades and are expected to continue declining.Most pallets are made of low-grade hardwood lumber, usually rough (unsurfaced) lumber. Pallet markets, which consume the majority of the hardwood lumber produced in the United States, expanded rapidly during the1970’s for materials handling, and some further expansion is expected. The rate of increase in industrial pallet use, however, is expected to decline as the market becomes saturated.

* Utilities, water and sewer systems, high ~tays, and other nont)uilrling construction accounted for the remaining one-third.
‘@.See note 5.



# Panel Products

structural panels produced in the United States (table 18), Panel products also are popular in residential upkeep and repair, accounting for 23 percent of the plywood and approximately50 ● Wood Use: U.S. Competitiveness and Technology

Table 18.—Plywood and Panel Products Consumed in New Residential Construction in the United States, 1962-80

Type of home (ft 2 , 3/8” basis)

Year Single family Multifamily Mobile
1962 . . . . 3,010 1,800 “ 1,840 1970 . . . . . . . . 5,385 1,910 1,300 1976 ., . . . . . . . 5,815 3,255 1,610 1978. , ... . . . 5,600 a 2,650 550 1980 . . . . . . . . 5,640 3,105 555

.- aF[gUT~~ for I ip 76 Include only Plywood
SOURCES USDA Forest Service, An Ar?a/ys/s of the T(rnber S(tuatlon In the Un/fed States, 1952-2030, Review draft, 1980 (Includes ftgures from 1962, 1970, and 1976) Thomas P Clephane, Out/ook for T/mber Supp/y/Dernarrd Through 1990, Morgan Stanely Investment Research, 1982 (Includes figures from 1978 and 1980)

40 percent of the structural panel market in 1976. The remainder is used in manufacturing, shipping, and other uses. There are three types of plywood and panel products:

●

●

●

● Plywood—a flat panel made of laminated, crossbanded wood veneers, where each layer is arranged with the grain at right angles to its adjoining layers. Structural composite panel—a panel madeof wood particles—e. g., chips, flakes, wafers, and strands—pressed into a flat paneland simultaneously bonded with a thermosetting adhesive. Particleboard—a nonstructural panel made from small wood particles bonded into a flat panel with adhesives under heat
pressure. Fiberboard—a flat panel made of individual woodpulp fiber (like paper) bonded together. Insulation board and hardboards are special kinds of fiberboards.

Plywood

Current Plywood-Manufacturing ProcessesPlywood manufacture consists of two processes: veneer production, and layup and gluing of the veneers into plywood (figs, 13 and14). The five methods for manufacturing veneers for plywood include: 1) rotary cut, 2) staylog cutting, 3) cone cutting, 4) sliced veneers, and 5) sawn veneers. Over 90 percent of the veneer produced is rotary cut, i.e., peeled ona lathe. Other methods produce specialty hardwood veneers used in furniture and cabinetry. To produce plywood, the veneer logs first are steamed and then are sent to a lathe that peelsoff a thin, continuous ribbon of veneer. The remaining core of about 4 to 5 inches subsequently is used for dimension lumber or is chipped to produce pulp and paper, particleboard, or fuel. The veneer sheet itself is cut into sheetsby a clipper, which also removes knots and defects. After drying, the veneer is placed on anassembly line, where adhesives (usually phenol formaldehyde) are applied, and the veneers are stacked to form plywood. A typical five-ply plywood layup line can produce 6 to 8 five-ply panels or 12 to 16 three-ply panels per minute.Following layup, a panel is cold-pressed to consolidate it before loading the press, It is then hot-pressed under pressures of about 15o pounds per square inch (psi) at temperatures ranging from 2400 to 3000 F. After the panels cool, they are trimmed and squared, sometimes sanded, and then graded and prepared for shipment,

Potential Improvements in Plywood Manufacture Current plywood recovery rates run between47 and 53 percent and probably average 50 percent. 20 Less than 1 percent of all roundwood used in plywood manufacture ends up as waste. Residues from plywood mills are usedto produce lumber, particleboard, pulp and paper, fiberboard, or energy. Because plywood mills now are capable of using smaller logs than in the past, increased efforts are being made to use hardwood for structural plywood, Technical developments in plywood manufacture are aimed primarily at: 1] expanding the number of species and quality of the timber that can be used forplywood; 2) increasing automation; 3) reducing energy requirements; and 4) increasing the degree of computer-assisted process control, particularly in peeling and clipping.

20 See note 8.Ch. II—Solid Wood and Panel Products ● 51

Figure 13.— Flow Diagram of a Small-Log Plywood Mill

Bucking Lathe Peeling

~ Clipping

Sawdust

Debarking Chips 

# I

Lumber Chips Chips

— Drying

Log yard

Expanding the Range of Usable Material.–The plywood industry historically has depended on aplentiful supply of large-diameter, straight, rotfree softwood timber. However, over the years, large softwood logs have become very costly, and future supplies are uncertain. As a result, in the early 1960’s, the plywood industry began to move to the South, attracted by inventories of largely unutilized Southern pine. By 1980,the South was producing nearly as much plywood as the West, generally using smaller logs. Technology still is being sought to handle and process small logs and expand the range of logs that can be peeled. Currently, 25 percent of the veneer logs are considered unpeelable. 21 Some mills lose 40 percent of their logs from splintering, crack- ‘4] }J1.,l [~h J I;rfJr]\/,CiA, “ I)r(’i f’nt in~ [’(III(;(JI Holt S1] inollt, ’” .llo(i- (‘[ /1 1’/\ LI ( )(){1 /“(’( h/) /(/ L]( ‘5

, ~) 1’( )( ,(’( ‘( I I 1) g> ( ) t t hll ,s(JI”[~l) t 11 1’1 \“ \i”[ )()(i (:1 1[}1(

. I’ortlrll)(l. ( )1’(’

. hldrl t) 1 (17’) ing, and breakage on the lathe caused by toosmall logs or internal defects. Because of the high value of veneer logs, increasing theamount of peelable material can greatly improve the productivity and profitability of the mill. Some techniques used to prevent wood losses include: 1) better chuck design to hold and rotate the logs against the knife; 2) new pressure-bar designs to position the knife on the log; 3) heating the log, which some believe can reduce the torque needed to peel the log; and 4) using backup torque rollers to increase deliverable torque at the lathe. New types of pressure bars mounted on the lathe to control veneer thickness and peeling performance show some promise, Roller bars produce lower forces needed for peeling than do conventional, fixed bars, but initially cost more and have higher maintenance costs. The recently developed steam-heated, contoured52 ● Wood Use: U.S. Competitiveness and Technology

Figure 14.—Material Balance for Softwood Plywood Based on Ovendry Weight (OD wt.) (veneer log weight includes bark)

Phenol-formaldehyde resin

0.01 \

1.0 ton

o

0 0 0

Panel trim and reject

0.07

Shavings and end trim

0.01

Chips

0.04 Sheathing plywood

0.45

Particleboard furnish

0.08

Studs
0.06

0.30

Total 1,01

SOURCE C W Boyd, et al Wood and F/t,er Ml ) 1 72 1976

fixed bar, however, may be as effective as the roller bars without the high cost.Increasing the chuck* diameter could increase the amount of peelable roundwood, but larger chucks increase minimum core size as well. Further chuck modification is unlikely toproduce significant increases in veneer recovery, and the backup roller was developed as ameans of providing this auxiliary torque. Research on the optimum design and location of the backup roller is under way.Finally, some efforts are being made to explore the potential of hardwoods in structural plywood production. Results of several studiesindicate that construction-grade hardwood plywood made from a mixture of high- and lowdensity species could be competitive economically with softwood construction plywood. 22Ch. II-Sol/d Wood and Panel Products ● 53

.54 ● Wood Use: U.S. Competitiveness and Technology

Particleboard

Current Particleboard Manufacturing Processes Other than plywood, most structural panels currently manufactured in the United States are particleboard made from a variety of wood particle types. The basic steps involved in standard particleboard manufacture (called dry-forming), are shown in figures 15 and 16, During the process, wood first is reduced tothe desired particle geometry by flaking, disking, hogging, or hammermilling. The particlesare dried using rotary-drum dryers or horizontal fixed dryers and classified according to size, They are blended then with adhesives and waxes and formed into a mat, sometimes with coarse particles at the core and finer particles at the surface. 27 The mat then usually is hotpressed to the desired thickness and density, allowing the adhesive to cure. Panels then are cooled, trimmed, sanded, and graded.
A small proportion of the particleboard produced is wet formed, or extruded, wherein adhesive-coated particles are forced through a hot die. The extrusion process produces a particle-
‘-~[!rlt; ~1’[;[l~~rt ;]lIc1 ~“r[;ci IdInh, “Arl ()~wrview’ of (:omposite 1100 [’(1s, “ F’urniturc l~c.sign ,~nd .lfanufa[:turing 54(3), Marc h 1982,

Figure 15.— Materials Balance for Particleboard Based on board that is weak in bending and stiffness and low in dimensional stability and generally is used for specialty purposes. To overcome strength problems, extruded particleboard often are honeycomb-shaped or fluted,

Potential Improvements in Particleboard ManufactureMany particleboard markets have been declining due to competition from new structuralpanel products in construction and from medium-density fiberboard in furniture corestock. Some particleboard probably will continue to be employed in nonloadbearing structural use and in a variety of home and miscellaneous uses, but only if it is cost-competitive with other products. Particleboard manufacturers havebeen facing increased competition for raw materials—largely planer shavings and other sawmill residues—from pulpmills, As a result, theparticleboard industry may focus on improving the utilization of forest residues and on developing economical harvesting and transportation methods.28

the Manufacture of Underpayment Ovendry Weight(OD wt.)

Urea-formaldehyde resin Wax

0.08 0.007

1.0 ton planer shavings, sawdust plywood and lumber trim

(OD wt.) Particleboard (5/8 in. thick)
0.979

Sander dust 0.094

Kerf from panel saws 0.014

v x } J

Total Fuel
0.108

1.087

NOTE Total IS more than 10 because of resin and waxes percentages may vary

SOURCE C W Boyd, et al , “Wood for Structural and Architectural Purposes, ” Wood and F/ber 6(1)’ 1-72, 1976Ch II. -Solid Wood and Panel Products ● 5 5

Figure 16.—Materials Balance for the Manufacture of Structural Particleboard Based (OD wt.) of Chipping and Flaking of Sound Wood on Ovendry Weight

NOTE Va\ues !n parentheses are those associated with chlpplng and flak!ng cull logs or other forms of residue with some rot Total IS more than 10 because of the
addltlon of resin and waxes Percentages may vary

SOURCE C W Boyd, et al “Wood for Structural and Architectural Purposes, ” Wood and Ftber 6(1) 1.72 1976

Structural Composite Panels
Structural Composite-Panel Manufacturing Processes Structural composite panels were developedin an effort to get more out of the wood resource, a focus still primary in the industry. Nearly all the new panel products developedin the last two or three decades can use hardwoods and some defective wood material as well, although high-quality structural panels usually require roundwood for raw material. In the 1980’s, R&D efforts likely will be aimed at improving the efficiency and engineering of particleboard-panel products made from flakes,chips, particles, and strands to meet design requirements. There are three general types of new panel products, the first two of which are expected to provide competition to plywood in structural use: 1) waferboard; 2) OSB; and 3) veneer-faced, composite-core panels.

Waferboard, or flakeboard, originally introduced in Canada, is a panel made of wood wafers or large, flat flakes. High-quality flakeboard can be made using as much as 8 percent bark (although too much bark can cause problems) and 12 percent decayed wood. It also can bemade from all hardwood and thus offers opportunities to extend the resource base and produce sheathing-quality panels at lower cost than possible with softwood plywood. The alignment of particles has proved difficult inwaferboard, however, and the nonaligned particles produce a product with much lower strength and stiffness than plywood. However, waferboard is strong enough to substitute forplywood in many sheathing applications. Waferboard has been accepted widely in Canada,and there are several waferboard plants operating in the United States. A basic manufacturing flow diagram is shown in figure 17.

Oriented strand board is made from strands or ribbon-like pieces that can be laid down in layers to produce a three- or five-layer boardwith crossbanded construction much like plywood (fig. 18). The structure of OSB may overcome the strength problems of waferboard,56 ● Wood Use: U.S. Competitiveness and Technology

Figure 17.— Idealized Typical Waferboard Process

Raw material

Press

Institute of Technology, June 1982

OSB, unlike waferboard, uses liquid resins,which could reduce adhesive costs. These resins also may provide flexibility in the type ofresins used, which may be useful if the industry moves to isocyanate (similar to Crazy Glue) binders in the future. 29Veneer-faced composite-core panels (comply) use particleboard cores with veneer faces,like plywood. These products have engineering properties similar to those of plywood, but sometimes are stronger and stiffer. However, their dimensional stability is somewhat less than that of plywood, and they are more dense, Corn-ply may be manufactured to a limited ex-

. — 29 Se~ note 8. tent in existing plywood or veneer facilities; however, it probably will not compete with waferboard and OSB.

Potential Improvements in Structural Composite Panel Manufacture In addition to extending the resource base, primary emphasis in R&D on structural panel products is in improving product performance, improving processing, and conserving energy.

Improving Product Performance.—Plywood retains much of the natural strength and physical characteristics of the original wood. Particleboard cannot match the performance of plywood in many high-stress, structural appli-Ch. Ii—Solid Wood and Panel Products • 57

Figure 18.—ldealized Typical Oriented Strand Board Process

Raw material

Flake

1 resin

Form and align 4 surface

J 

# {

SOURCE Henry M Montrey Ill Current Status and Future of Structura/ Pane/s In the Wood Products /ndustry, M S the.ws, Massachusetts

Institute of Technology, June 1982

cations and therefore has been used mainly forfloor underpayment and furniture corestock rather than sheathing, Research in producingstructural panels that can substitute for plywood in sheathing and other structural applications has been a major R&D focus. Efforts have centered on controlling particle geometry and alignment during mat formation.

Improving Processes .—Developments in processes for aligning particles and pressing panelsshow future promise. Particle alignment [orienting wood particles with parallel grain) within a composite structural panel helps retain more of the desirable mechanical properties of solid wood, but allows the use of a variety of wood raw materials. This is a major factor in producing composite panel products suitable for high-stress, structural applications.

Both mechanical and electrostatic processes are used to align the particles, Mechanicalalignment is used to produce OSB. Electrostatic alignment polarizes wood fibers or particles that become aligned with the electrical lines of force. These technologies are not developedfully; however, work on fiber alignment is continuing. Wafers historically have proven difficult to align. Equipment that could produce aligned waferboard may provide additional stimulus to this growing industry,

Developments in pressing panels have not been dramatic, but there is an ongoing inter-58 ● Wood Use: U.S. Competitiveness and Technology

est in continuous presses to speed processing and reduce bottlenecks associated with conventional presses. Although continuous presses are available for producing thin boards and medium-density boards, those that can be used to produce a wider variety of structural panel products have yet to be developed, Another trend in board-pressing is toward the use of closed-liquid heating systems rather thanthe conventional, steam-heating systems. Liquid heating systems provide higher temperatures, have less temperature variability, are less likely to have “cold spots, ” and save at least 20 percent of the energy required to operate a comparable steam-heated system.

Conserving Energy .—Particle drying is a major energy consumer in the manufacture of panel products. Innovations in drying have been modest.

Fiberboard

Current Fiberboard Manufacturing Processes
Fiberboard, insulation board, and hardboardare manufactured from individual fibers or fiber bundles, rather than from wood particles.The wet process, which can be used to manufacture any of these products, was first developed in 1924 by W. H. Mason and is known as the Masonite process. The prepared wood is heated by steam in a pressure vessel called a “gun.” The pressure in the gun is raised from 600 to 1,000 psi and then suddenly is reduced, causing the chips to explode into a coarse mass of fiber which is reduced further by milling.The fibers are formed into a mat, much like paper, and finally pressed in a hot press. Hardboard also can be manufactured usinga dry process in which the chips are presteamed and ground in a mill. Most fiberboard currently is produced using mechanical diskrefiners and thermomechanical pulping. Usually, resin and wax are applied to the fibers prior to milling, and the fibers are formed into a mat and hot-pressed like particleboard. Thedry process uses resin to bond the fibers together, while the wet process relies on the combination of natural bonding action of the lignin in the fibers and the contact of the fibers to produce a cohesive panel and a synthetic resin bond.
Fiberboards are not used generally in loadbearing applications because of their tendency to creep under load. Also, they tend to be less stiff than other wood panels of similar density.

Potential Improvements in Fiberboard ManufactureThere have not been many recent developments in the fiberboard field in the UnitedStates, with the exception of MDF, Some efforts have focused on using lower grade raw materials and hardwoods, but since fiberboardis not a major consumer of wood raw materials, gains in this area would affect only modestly overall demands on the resource base. In addition, many fiberboard products have been replaced partially by vinyl, plastics, aluminum, and other types of insulation.
MDF was developed in the United States around 1970, and growth of its manufacturing capacity and markets has been significant, By1981, the United States was capable of producing 668 million ft 2 of corestock MDF. 30 MD Fcan be produced using either wet or dry processes, and high-quality MDF corestock for furniture can be made from hardwoods. MDFprobably will be used more for interior paneling and nonstructural uses, such as trim, door jambs, furniture, and casegoods. However, when produced with an exterior resin it can be used for exterior siding on houses,

Present and Future Use and Consumption

of Panel Products
During the last 30 years, the decline in percapita consumption of wood products (including pulp) was offset partially by the increasingper capita consumption of plywood and veneer. Per capita use of plywood and veneer rose from 2.3 ft 3 in 1950 to 7.0 ft 3 in 1979, Overall consumption rose from 2,2 million tons (airsONatiOna] partic]~oard Association, “1 ndustry Board cawClty by State and Product, ” Furniture Design and Manufacturing 54(3), Mar. 11, 1982.Ch. II--Solid Wood and Panel Products ● 5 9

dried) to 11.8 million tons. During the same period, use of panel products (including fiberboard) rose from 1.3 million air-dry tons to 10.1 million. Statistics on per capita consumptionof structural panel products, exclusive of hardboard and fiberboard, are not available. Although conventional plywood probably will continue for another 10 to 20 years to be the major structural panel product used in the United States, the greatest growth in panel products markets in the past few years has been in particleboard and MDF (fig. 19). 31 In 1979, unveneered structural panel products(waferboard, OSB) accounted for only 1.5 percent of the demand for structural panels. The American Plywood Association estimates that this demand will grow to 6.1 percent by 1984,and other sources forecast even higher demands, perhaps up to 20 percent. Because of

.——.—— —. ‘ 1 S(!(! **[lOt(: 8**  the slow housing market since 1978, the apparent consumption of panel products (and most other wood products used primarily in light frame construction) dropped. Any resurgence in the housing market is expected to provide ample opportunities for growth of structural panel markets. Moreover, structural panels are expected to compete strongly with softwood plywood for most end uses (table 19).The striking feature of panel products markets has been the displacement of lumber andplywood by composite panels. Structural panels probably will continue to increase market shares relative to plywood and may begin to compete with nonwood materials such as steel, aluminum, and plastics for some structural products. A summary of major technical improvementsis shown in table 20. Improvements in processing efficiency have reduced labor requireFigure 19.— Historical Production of Major Panel Products, 1970-79

25,00(

20,000

15,000

c o

—

o

10,000

5,000

0 Softwood

Particleboard (million square

Insulating \ board (thousand tons) \ (thousand tons) Hardwood plywood (million square feet,

\ Med. density surface measure) fiberboard

\ (million square

feet. 3/4 a basis)



### I I I 

### 1

..-. * U ● I 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979
Year60 ● Wood Use: U.S. Competitiveness and Technology

ments, increased productivity, improved qual- already are using almost all the wood wastes ity control, and helped reduce energy for electricity and heating requirements, a requirements. Larger panel products mills trend expected to continue.

Table 19.— Plywood End Uses and Their Susceptibility to Penetration by “New” Panels

1976 End-market plywood susceptibility

Millions of Percent of square feet

New residential construction: Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Floors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Siding and trim. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wall sheathing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,091 2,660 960 505

Total new residential construction . . . . . . . . . . . . . . . . Repair and remodeling: Structural additions, alterations, and repairs . . . . . . . . . Shelving and furniture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Small building and construction . . . . . . . . . . . . . . . . . . . . Total repair and remodeling . . . . . . . . . . . . . . . . . . . . . .

Industrial markets: Products made for sale . . . . . . . . . . . . . . . . . . . . . . . . . . . Materials handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Plant repair and maintenance . . . . . . . . . . . . . . . . . . . . . . Repair and wholesale trade . . . . . . . . . . . . . . . . . . . . . . . .

Total industrial markets . . . . . . . . . . . . . . . . . . . . . . . . .

Nonresidential construction: Nonresidential building . . . . . . . . . . . . . . . . . . . . . . . . . . . Auxiliary uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Concrete forming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Farm building . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total nonresidential construction . . . . . . . . . . . . . . . . .

Other uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7,712

2,333 768 322
3,780

1,688 440 421 381
2,970

1,338 280 807 360
2,785
1,153
18,400 to penetration by “new” panels

-

— total High Medium Low

—

16.8 % x 14.5 x 5.2 2.7 x
x

41 .9 ”/0

12.7 4,2 1.7

20.50/o

9.2 2.4 2.3 2.1

16.20/, x

x
x

x

x

x x
x

7.3 x 1.5 x 4.4 x 1.9 x
15.1 %

6.30/o x
100.0% 48.20/ o 42.00/

, 9.80/o

-. — — Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 20.—Summary of Major Technologies for Plywood and Panel Product Manufacture

Estimated time scale to Barriers to significant contribution implementation (years)

— —

. Stage of Effect on Technology development resource base

———.——. New pressure nosebar Commercially available Increases ability to peel High capital costs o-1o design small logs; reduces number of unpeelable logs

— Backup torque roller In development Same as above None o-5

Waferboard Commercially available Allows hardwood and None o-5

residue use
Veneer-faced composite — Commercially available on Allows hardwood and ——— .— Requires integration of 10-20- - - core panels small scale residue use veneer and particleboard facility

Oriented strand board — Commercially available — Allows use of residue None o-1o

— — — SOURCE Off Ice of Technology AssessmentCh. II-Solid Wood and Panel Products ● 6 1



# Wood Use in Light Frame Construction

Wood Conservation
In general, houses probably are overdesigned, even considering the severe and unusual stresses to which they may be subjected. Failures are unusual in the wood members, but do occur at joints and edges. More sparing use of materials that are designed to providestrength and stiffness, based on new engineering designs, could improve the efficiency of wood use. Three areas where conservation of wood materials is possible are in conventionalconstruction, framing and attaching assemblies, and substitutions for individual framing members,

Conventional ConstructionConventional construction techniques commonly waste 3 to 7 percent of the lumber and plywood used in a home. This waste could be reduced through new design, and the value of the waste material could be reduced throughselection of lowest quality and smallest size material required. Door and window framing innonloadbearing walls possibly could be eliminated. Proper positioning of framing members, such as joists, studs, and windows and door framing, could further reduce the 1umberrequired. Off-center, in-line joist splicing (replacing overlapping joists over the center beam or support) could minimize the size and grade of joist required (fig. 20). Framing and Attaching Assemblies

Panel assemblies consist of framing and sheathing nailed or glued together, often incombination with insulation, siding, and finishing materials. The strength and stiffness of a panel assembly is greater than the framingor sheathing alone; assemblies can be engineered so that each component enhances the strength of the others. Additional development is probably needed to develop this concept fully.
Factor construction of engineered panel assemblies has two advantages: 1) it allows theuse of rigid adhesives, which increase the ability of individual pieces to share loads to agreater extent than occurs with mechanical fasteners or adhesives applied onsite; and 2) it reduces the scrap and shortens construction time. Factory-made assemblies are of two types: stressed-skin panels and sandwich panels.
Stressed-skin panels are made of framing fastened (usually with rigid adhesive) to a skin, or sheath. In Germany, stressed-skin panelsusing particleboard for skins are used in constructing one- and two-family homes. Stressedskin panels can be made with stringers of 2- inch dimension lumber with plywood or other panels bonded to either or both sides to act asa series of I-beams, Factory-fabricated stressedskin floor panels have been in use since 1965

Figure 20.—Offcenter, In-Line Joint Spacing

w

- ,.”

End joints properly located62 ● Wood Use: U.S. Competitiveness and Technology

and have performed satisfactorily. They haveyielded savings in floor material of 20 to 30 percent compared with conventional methods. Even greater efficiencies may be possible using sandwich panels constructed to bear theloads required on walls, floors, and roofs, Sandwich panels can use plywood or other panel product facings, and their cores can be madeof a variety of materials, such as foamed plastic, honeycomb paper, or bark. These panelsuse about 40 percent less wood than conventional construction,

Substitutions for Individual Framing MembersSome wood products can substitute for individual framing members. Two types of products that use less wood and provide needed structural strength are engineered wood beams and trusses.

At least one firm manufactures a wooden Ibeam, which is made with solid softwood flanges and a plywood web and can be usedas a grider, joist, or center beam (fig. 21). Similar products composed of particleboard or hardboard webs have been used in Europe for many years for structural framing of walls, roofs, ceilings, and floors. These do not use as

Figure 21 .—Wooden l-Beam Construction,

Cross-Section
Flange 4 (solid wood)

—

,

Web (ply

SOURCE Off Ice of Technology Assessment much wood as a solid wooden beam does and can be used in place of steel I-beams in light frame construction,

Trusses, or pieces of lumber joined together to form framing members, were developed in Germany as early as 1830. The widespread useof trusses for roof framing is at least three decades old, Floor trusses, although slower thanroof trusses to gain wide acceptance, now account for a minor portion of floor construction,Use of trusses to frame whole houses—consisting of floor, wall, roof, and ceiling members,all joined by truss plates—is a recent development. Truss framing designs could further reduce the amount of wood required for construction and may provide other benefits as well (table21), Trusses—which are joined with conventional truss plates, plywood gusset plates, or metal fasteners to distribute forces among members-increase the structure’s rigidity andreduce the risk of failure. Truss frames eliminate the need for immediate supports and require 30 percent less structural framing lumber than conventional construction. A truss frame system, for example, could consist of an open web floor system, trussed rafters, and wall studs tied together into a unitized frame.
Although the use of trusses and panel assemblies or sandwich panels offers many opportunities to increase the efficiency of wood use in housing, the housing industry is interested in cost savings, not in materials savings per se. The truss frame system and panel assemblies often are simpler and faster to erect on site and may save labor, 32 which can account for over30 percent of construction costs. Wood materials, on the other hand, account for a much smaller proportion of construction cost, and wood products designed to make light frame construction less costly therefore are morelikely to be accepted if they also are laborsaving. The housing industry historically hasbeen fairly conservative in adopting new building technologies. Part of this reluctance can beattributed to the need for building-code recogFramed System, ” no date,Ch. II—Solid Wood and Panel Products Ž 63

Table 21 .— Benefits of Truss Framing

Economic benefits

●

●

●

●

●

●

● Labor savlngs Material savings Qutck assembly Faster buyer occupancy Weather protection of equipment and materials. good working environment, and security Adaptable to high-volume processes and inventories of standard size lumber Many energy-savings features Fabrication and erection flexibility: • Uses existing truss-manufacturing technology

● Can use a variety of truss-fabrication methods and equipment

● Time flexibility in completing finished buiIdings • Flexibility in subcontractor scheduling

● Potential for relocatable structures Design flexibility.

● Engineering design services readily available

● Flexible space utilization from clearspan construct ion

● Variety and flexibility in housing design Safety and quality: Increased quality without added cost Strength through controlled assembly Strong connections between floors, walls, and roof Reduced opportunity for human error in constructionOvercomes major weakness of conventional construction (malted Joints) Meets or exceeds current structural, architectural, and safety provisions I n model codes

T rar> sfer PI an

nition of new construction products and techniques, but buyer acceptance and resistance ofbuilding labor trades to adoption of new systems probably are also significant factors.

New Uses for Solid Wood Material
Two new wood products could replace concrete, stone, or cinderblock in new home construction: 1 ) the all-weather wood foundation a n d 2 ] the underfloor plenum system.The all-weather wood foundation is a plywood-sheathed, stud wall made of preservativet mated plywood and lumber that is at least partially below grade. Watertightness is provided by a sump in the gravel pad beneath the wood footing, polyethylene film covering the exteriorof the foundation, and caulking between plywood panel joints. The National Association of Homebuilders Research Foundation, whichhelped develop the all-weather wood foundation, estimates that the system uses 33 percentmore wood than does a typical two-story dwelling built on a cinderblock foundations.

. The underfloor plenum system, designed to replace the concrete slab now used extensively in the south, provides a n underfloor areathrough which warm or cool air can be distributed throughout the house for heating or air conditioning, eliminating ductwork, Properlyconstructed, the plenum has shown no tendency to rot from excessive moisture or to present insect problems. Because it can be buried, it does not detract from the appearance of the home. It is cost competitive with concrete

structures.

The all-weather wood foundation has been accepted by building-code authorities, and there is no specific code prohibition against the underfloor wood plenum. Though both are cost competitive with conventional foundation building practices, they have not significant} penetrated the market. Again, the reason for this probably has to do with the conservatism of the building construction industry and buyer acceptance.

Composites of Wood and Other Materials
In general, the wood industry has not invested much time or resources in developingproducts that combine wood with other materials. Since the 1960’s, however, composites of metal or plastic skins laminated to a wood core have met a number of industrial uses becausethey are strong, durable, and corrosion-resistant, The metal-skinned wood panel has been used in the past in aircraft, housings, partitions, truck and trailer doors, train interiors, cabinets and cases, pallets, and escalator balustrades. Wood composites also may be combined withfoal insulation for cold-storage facilities. Although composite dimension lumber madefrom wood particles that incorporate continuous strands of high tensile-strength glass fibers have been developed, they have not per-64
● Wood Use: U.S. Competitiveness and Technology

formed satisfactorily to date because of tech- of wood and mineral-based products, such as nical problems that arise when materials with cement boards made from excelsior and a great deal of difference in stiffness are “mar- cement. ried. ” Some composite panels are composed

# CHAPTER II



# Pulp, Paper, and Fiber Products

### CHAPTER Ill 

# Pulp, Paper, and Fiber Products

Summary and Conclusions

Pulp and paper manufacturing is moving toward the production of higher quality pulps that require less wood input per ton of pulp andpaper produced. Increased energy costs, increasing raw material costs (for both roundwood and sawmill residues), a market that now emphasizes printability and other nonstrength factors, and the availability of immense amounts of less expensive hardwood timberhave prompted the U.S. pulp and paper industry to consider more energy-efficient and materials-efficient manufacturing technologies.The adoption of mechanical pulping technologies could reduce the amount of fiber required to produce a ton of paper from about 2.5 tonsof wood, for the kraft chemical pulping process, to about 1.05 tons for thermomechanical pulping. With this reduction, it is estimatedthat each future increase of 2 percent in pulping capacity would necessitate an increase of only 1.7 percent in wood fiber feedstocks. 1 These potential increases in pulping efficiencyand fiber yield can effectively extend the Nation’s usable wood supply, reducing the likelihood of raw materials shortages and relaxing the pressures on the shrinking U.S. timberland base. Expanded use of hardwood species that are presently underutilized may further extend the domestic timber supply. Pulping technologies like organosolv hold prospects for the industry to become a net energy producer. The organosolv process mayalso permit utilizing hardwood species and obtaining high fiber yields with little sacrifice in product strength. Such processes are still in the developmental stages but may be commercially available in 25 years. Meanwhile, the pulp and paper industry could reduce the amount of en-

‘G. Styan, “Impa{.t of North American Tlrnber Supply on Innovat ions i n Paper Ttx:hnology, “ pa~}er Tra~~ Journal, VC)I. 164, May 30, 1980, ergy required by increasing the use of mechanical pulping and expanding the use of recycled paper. In addition, the efficiency of chemical pulping may be increased by adopting pyrolytic technologies for the recovery of spent pulping liquor, autocaustisizing to reduce the energyrequired in the lime-kiln process, and using anthraquinone as a catalyst for chemical kraft pulping to increase fiber yields.Press-drying technology, while still in developmental stages, shows promise for both reducing the amount of energy required in the papermaking process and enabling the use of hardwood species not currently used in large quantities. In some respects, the quality of the paper produced by this method exceeds thatof unbleached kraft paper produced by conventional processes. It may also afford an opportunity for the U.S. pulp and paper industry tocapitalize on a growing export market in linerboard and other heavy-duty packaging materials. Advanced research and development (R&D)on improving the strength and stiffness of paper could lead to development of structural fiber products able to compete with a number of metallic, ceramic, and plastic materials. In addition, paper may be combined with othermaterials such as plastics, coatings, and synthetic fibers to produce composite materials with superior qualities.
Although plastics have made significant inroads in certain types of packaging, and havesignificantly displaced paper sacks for lightduty uses, paper still commands a major proportion of this market and will probably continue to do so. Moreover, increases in energycosts could improve paper’s competitive position relative to petroleum-based plastics, which require larger energy inputs in production. The paper industry could further strengthen its

6768
● Wood Use: U.S. Competitiveness and Technology

competitive position if it continued to adopt existing energy-efficient technologies. Electronic telecommunications technology,on the other hand, could have significant impacts on demand for printing and writing paper in the future. While the magnitude of itseffect on paper is yet uncertain, the introduction of advanced electronic devices such as electronic filing (the “paperless” office), video magazines, electronic newspapers, and video catalogs and directories may increasingly affect the use of paper now and during the nexttwo decades. Recently, the use of word processors and office copying equipment has increased the demand for paper products, a trend that may decline as electronic communications gain increased acceptance in offices. In thefinal analysis, the long-term effects of telecommunications technologies on paper requirements are unknown,



# Introduction

Profile of the Pulp and Paper Industry
The United States has the largest per capita paper and paperboard consumption in theworld, averaging more than 600 pounds annually. It is also the world’s largest producer ofpaper and paper products, accounting for approximately 35 percent of the world’s total output. The U.S. pulp and paper industry is ninthin size of tons produced and 11th in gross assets among the domestic manufacturing industries. In 1981, U.S. production of pulp, paper,and paper products was estimated at $82.1 billion (current dollars).’

Raw MaterialsIn 1978 the pulp and paper industry used approximately 77 million tons of pulpwood (oven dried). Forty-four percent of this came from chips and sawmill residues, which are wood wastes from the manufacture of lumber and other solid wood products. About 26 percent of the pulpwood used in 1978 was hardwood. (Trends in wood use in the past 40 years havebeen toward increased use of hardwood species and increased reliance on chips and sawmill residues.) In addition, the U.S. pulp and paper industry used approximately 15 milliontons of recycled wastepaper for pulp and paper production in 1978. 3

‘IJ. S. Department of (lommerCe, 1982 ]n~~st~ja] uut]~~k (Washington, D. C.: U.S. Government Printing Office, 1982), p. 39. ‘Joan E. H uher, The A’line Guide to the Paper Industr}r (Fairfie]d, NJ.: (Jharlcs H. Kline & (j{),, 1980), pp. (j6-67, The pulp and paper industry also uses about one-quarter ton of chemicals for each ton of paper or paperboard produced, ranking sixthamong all industries in dollar value of chemical products purchased. It is also the largestuser of water for processing among all manufacturing industries. Finally, the industry is one of the leading industrial consumers of energy, using roughly 7,2 percent of the Nation’s industrial energy requirements and 2,8 percent of the total energy used in the United States. Approximately half of the energy used by theindustry is produced internally from wood residues and other waste products. Because of the large energy requirements and the sensitivity of production costs to energy prices, the pulp and paper industry has become an industrialleader in energy conservation and cogeneration (internal generation of electricity from steam heat),

Product Demand Demand for paper and paper products is closely tied to economic growth and disposableincome levels. Although year-to-year fluctuations occur, correlating with economic trends, the industry is relatively free from the cyclicalvariations experienced by other primary industries such as mining, metals, and solid wood products.

Capital The pulp and paper industry ally high capital requirements has exceptionfor plant andCh. Ill—Pulp, Paper, and Fiber Products • 69

equipment, Capital investment currently ranges from $350,000 to $1 million per installedton of daily capacity, depending on a mill’s design and whether the investment is an addition to the existing mill or a new facility. 4 The paper industry invested $6.8 billion in capital expenditures in 1980; however, $369 million, or 5 percent, was spent on pollution controlequipment that did not increase production capacity.’

Industry Size and Production

With over 4,000 firms employing abou t 626,000 workers, the pulp and paper products industry is an important component of the U. S.economy. It produces over 14,000 different paper products, and its potential for developing new and even better paper and fiber products in the future is high. At the same t i me, moreefficient manufacturing processes could reduce energy use and lead to increased use ofpresently underutilized, but prevalent, hardwood species.
It is estimated that paper products account for almost three-fourths of the wood-based sales of the top 40 firms in the forest products industry. 6 While the pulp and paper sector consists of a large number of competing firms, the 10 largest firms manufacture over half of thepulp, paper, and paperboard products produced in North America. In addition, a number of the major pulp and paper manufacturersproduce a variety of secondary products, including solid wood items, containers, writing papers, and sanitary paper products (table 22). Fifteen companies that produce both paper and sol id wood products are prominent among thewood-based industries, but together they accounted for only 24 percent of all wood-based sales in the United States in 1978.7 In 1976, the South produced 67 percent of the Nation’s wood pulp. Southern forests are particularly attractive to the industry becauseof the abundance of both softwoods and hardwoods, The pulp and paper industry has expanded its capacity in the South in recentyears; while the South’s share of total pulp production was only 48 percent in 1947, it is now over two-thirds, The West produced 17 percent of the Nation’s wood pulp in 1976. The remaining 14 percent was produced i n the East and in the North Central States. B
While pulpmills are located near raw materials, the manufacturing sector of the industry,which makes containers, bags, sanitary products, and stationery, is concentrated near themarkets. Thus, the New England Middle Atlantic, and North Central States produce 62 percent of all paper products. Much of the timber resource in these regions is hardwood, which has not been used extensively for paper production in the past. Wood pulp production in these regions currently constitutes only 16 percent of total U.S. wood pulp production.

Uses of Pulp, Paper, and Paperboard
Total U.S. pulp production has been projected to increase from 53.2 million short tons in 1981 to 54.8 million short tons in 1982. How ever, the actual volume may be lower as a result of the 1981-82 recession. g In addition to thedomestic products used, approximately 4.3 million short tons of pulp were imported in 1981, primarily from Canada. Pulp exports totaled 3,7 million tons, most of which was shipped to Europe, Mexico, Japan, and Korea. The total53.8 million short tons of pulp used were converted into over 66 million tons of paper andpaperboard. Imports of primary paper and paperboard products were about 8 million tonsin 1981, while exports slightly exceeded 4 million tons,
Wood pulp is converted into a variety of paper products (table 23). The major uses of paper, which accounts for 49 percent of the wood70 . Wood Use: U.S. Competitiveness and Technology

-“ I

v **K**

ICh. Ill—Pulp, Paper, and Fiber Products ● 7 1

Table 23.—U.S. Production of Paper and Paperboard in 1981 and Projected for 1984 (thousand tons)

1981- 1984aPaperboard ... ... ..-.. ., . : 14,558 15,360 Kraft fiberboard ... ... . . 1,067 1,140 Other kraft paperboard ., ... 4,71 7 5,070 Bleached paperboard ., ... ... . 3,926 4,100 Recycled paperboard . 7,070 7,150 Total paperboard ., ... ... 31,33 8 33,020 Paper: Uncoated free sheet . . . . . . . . . . . . . 7,882 8,720 Coated free sheet and groundwood . 4,951 5,340 Uncoated groundwood ... 1,440 1,540 Bristols and other ... ... ... . 1,530 1,580 Total printing and writing . . 15,803 17,180 Newsprint ... ... . . ... . . . . 5,238 5,730
Unbleached kraft ., . ... ... ... . 3,891 3,760 Bleached regular and industrial . . 1,603 1,670
Tissue ., . . ... ... . . . . ... 4,485 4,730 Total paper ., . . ... ... ... . . . 31,020 33,070 Total paperboard and paper ... 62,358 66,090

a Morgan Stanley estimates —

SOURCE Thomas P Clephane and Jeanne Carroll Linerboard Industry Outlook

(New York Morgan Stanley & Co 1982) p 25
pulp produced, are for printing and writing papers [50.9 percent), newsprint (16.9 percent),tissue (14.5 percent), and packaging (17.7 percent). Over 51 percent of U.S. wood pulp production is converted to paperboard (a stiff,heavy paper). Linerboard, which is kraft paperboard used for boxes, shipping containers, and packaging, accounted for 46.4 percent of thepaperboard produced in 1981. Overall, packaging materials (both paper and paperboard)made up 59 percent of all paper and paperboard produced in the United States, and was one of the most rapidly expanding pulp uses. Since the price elasticity of demand (the change in demand resulting from a change in price) for paper products is generally small, the recent decline of relative prices has probably had only a small positive impact on apparent paper consumption. 10 The U.S. Department ofCommerce projects shipments of primary paper and paperboard products to rise at the rateof 3 percent annually for the next 5 years. Market projections through 1986 suggest a steady increase in domestic and worldwide demand

1 **O(;**

**a ]**  **~u la**  **t j(j**  **ns 1)F.**  **the K**  **ldd~r, Peilhodj’**  **Economics** G r~up illd ic. ate that the relative price elastic it~’ of demand for paper is approxi miitely 0.5 percent. for paper products in general. Demand for primary paper and board products is expected tobe exceptionally strong. Economic factors affecting demands for communications, packaging and shipping papers, and boards, however, will ultimately determine actual demand levels.The most promising markets during the ensuing 5 years are expected to be for linerboard and high-quality printing papers. An increase of 6 percent in the trend line of 1982 linerboard exports is forecast by some analysts, ll and thedemand for high-grade printing and publishing papers is projected to increase at an annual rate of about 7 percent. 12 Demand for both printing paper and linerboard is expected to expand at rates twice that for products of thepaper industry overall. While domestic consumption will probably increase gradually in response to a stronger economy, the demand for exports is expected to increase even more,in response to expansion of the industrial economies of the People’s Republic of China, Japan, Malaysia, Indonesia, the Philippines, Taiwan, and Korea.

Advanced Paper Materials
The development of stiff, durable paper, with strength characteristics currently achievable only at the experimental level, offers future prospects for new structural building products,Paperboard has been tested for use as sheathing and wall modules in buildings with mixed results. 13 The effects of moisture on the dimensional stability and stiffness of the paperboardis a major factor limiting the usefulness of paper as a structural material. New high-strength papers with protective coatings, coupled with innovative designs for paper-based structural materials, are a possibility, But considerableR&D remains to be done prior to commercialization.

I] Thomas p, C]epha ne and Jeanne Ca rrol ], Linerboard Indus’-

try Outlook (New York: Morgan Stanley & Co,, 1982], p. I Z

. IZCorp~rate Strategies, “A Narrowed Boise Cascade F’ocuscs on Paper, ” l?usiness il’eek, Apr. 26, 1982, p. 81. 13’’ Emergency Housing for $2,500, ” Technology Re\Fie~t”, Ma\’/ June 1982, p. 86. “Paperboard Houses Now Approved for all Exposures by FHA, ” Paper Trade Journal (Aug. 23, 1971], p. 53; “Paper Houses Buyers, ” Chemica) Engineering, Sept. 8, 1969, RP 76-71.72 . Wood Use: U.S. Competitiveness and Technology

Wood pulp may be converted into paperproducts ranging in character from superabsorbent fluffy tissue to extremely hard, boardlike materials. Wood pulp’s versatility results from the ability to vary paper’s stiffness overa wide range. Wood fibers are extremely flexible, strong, and durable. When brought into close contact, they form a durable fiber web as a result of hydrogen bonds, strong bondswhich provide the strength and stability of paper. Hemicellulose acts as an adhesive between the fibers and adds strength.
Stiffness is the major quality that makes papers so suitable for boxes, shipping containers,and, possibly, structural building materials. Although strength is also important, it is more frequently lack of stiffness that limits the choice of materials for these products. Becausecellulose fibers attract water, moisture can affect paper’s structural integrity by softening the fibers and reducing their stiffness, Tests inmodifying paper to enhance stiffness and moisture resistance, performed at the U.S. Forest Service Forest Products Laboratory (FPL), have demonstrated that super-strength paper may, on a weight basis, be capable of matching the performance of other solid materials like solid wood, aluminum, and steel. 14
The major factors affecting stiffness that are subject to control by the papermaker are fiber orientation, density and fiber bonding, and

IAv. setterho]m, ‘ ‘Factors That Affect the Stiffness of Paper, The Fundamental Properties of Paper Related to Its Uses, vol.

1
, F. Bolam (cd.) (London, England: The British Paper and Paperboard Industry Federation, 1976), pp. 253-266. shrinkage control during the drying cycle. *s The prospects for improving paper stiffness through the use of synthetic resin additives arenot considered as promising as improved bonding and fiber orientation in the papermaking
process. Researchers at FPL hypothesize that an elastic modulus of approximately 1.5 million pounds per square inch (psi), with a specific gravity of 0.4, could be achieved in paper in which the fibers are parallel and shrinkage is carefully controlled during drying. This level of stiffness is approximately equivalent to thatof wood parallel to the grain at the same specific gravity. Laboratory tests have produced paper sheets of specific gravity of 0.75, with a tensile strength of 38,000 psi and an elastic modulus of 3.8 million psi. 16 These values substantially exceed the specific strength and stiffness-to-weight ratios of all common structural materials, including solid wood. Only certain graphite and boron fiber composites surpassthe strength of this “super paper” at the specific gravity tested. Laboratory researchers conclude that paper can be produced that is stiffer and stronger than the wood from whichit is made, If high-strength papers can be developed that are capable of maintaining stiffness and dimensional stability in high humidity, they may be used for a range of structuralapplications now being served by wood, plastics, or metals—e.g., housing, furniture, and containers,

. IsIbid., p, 266. lelbid., p. 260.



# Role of Paper and Cellulosic Materials in the U.S. Material Mix

Competition with traditional paper commodities for U.S. markets comes primarily fromtwo areas: plastics and electronic communications. Competition from plastics is often in the form of substitution of plastic products for paper products and, occasionally, compositeproducts made from paper and plastics, Electronic communications, on the other hand, have the potential for displacing a share of the paper market by reducing the need for writing, copying, printing, and business forms. So far,however, electronic communications has probably resulted in greater consumption of paper, owing to increased use of word processors,high-speed computing systems, and inexpensive office copiers.Ch. Ill—Pulp, Paper, and Fiber Products ● 7 3

The impact of competition from plastics and products, in contrast to linerboard and paperthe electronics media on paper materials will boards used in shipping containers, will be serivary among paper products. Newsprint, writ- ously affected by competition from plastic ing and printing papers, business forms, paper products and the electronic media. The printbags, and wrapping papers constituted 47 per- ing and writing paper sector, which constitutes cent of paper consumption in the United States one-third of U.S. paper consumption, will likely in 1979 (table 24). Some anticipate that these experience the greatest impact from the expanTable 24.—Uses, Grades, Production, and Consumption of Paper Products in the United States in 1979

Apparent Product ion consumption Market Grade (thousand tons) Percent (thousand tons) Percent Newspapers . . ... . . . ... , . ... . ... Magazines, directories, catalogs . . . . . . . . . . . Newsprint Uncoated groundwood Coated papers Uncoated book 4,062

1,530 4,526

7,868 376 125

1,114

3,934

1,791

4,525
29,851

14,076

1,127

4,721

4,023

4,883 31,631

3,466

— 6

2 7

12 <1 <1

2

6

3 11,215

2,254 4,640 16

3 7

11 <1 <1

2

6

2

6

54

18

1

7

5

11 42

5

— 100 Magazines, annual reports, other periodicals . . Books . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . Commercial printing, envelopes, business forms, Iables, duplicator covers, and text . . Writing and related Thin paper Cotton fiber 7,913 391 126

1,116 Cigarettes, carbonizing condensers . . . . . . . Bond, writing, other business, and technical ., Tabulating index, tag and file folder, post card ... ... . . . . . . . . . . . . . . . Wrapping, bag, sack, shipping sack . . . . . . Bleached bristols Unbleached kraft packaging and individual converting 3,937 Bleached bags, wrapping glassine, greaseproof ., . . . . . ... , . . . . . . . . . . . . . . Other packaging and industrial converting
paper Special industrial
paper 1.729 Industrial converting . ... . . . . . . . . . . . . . .

Sanitary tissue papers, waxing, and wrapping tissues . . . . . . . . . . . . . . . . Total paper ... . . . . . . . . . . . . . ... . Facing for corrugated or solid fiber boxes . . . . 7

46 Tissues 4,514
37,835

12,611 Unbleached kraft Iinerboard 22 Tube, can, drum, file folder, shipping containers . . . . . . . . . . Other unbleached kraft fiberboard 2 1,050 Recycled corrugating medium, chip and filler board boxes, partitions and dividers . . . . . Semichemical paperboard 7 4,737 Folding cartons, milk cartons, paper plates, cups, posters . . . . . . . . . . . . . . . . Solid bleached paperboard 6 3,310 Folding cartons, setup boxes, gypsum wallboard facing . . . . . . . . . . . Recycled paperboard 12 49 7,533

29,241 Total paperboard ., . . . . . . . . ... . . . . .
Construction products, insulating board, binder, and shoe board . . . . . . . . . . . . . . . . . . Building and wet machine board 5

—
100 3,763

(462) Other . . . . . . . . . . . . . . . . . . . . . . . . . . Total paper ., ... . . . ... , ... ... , . . . . . . .

— 64,947 70.340

SOURCE Adapted from G Boyd Ill and H Dudley, Paper Industry Outlook for 1980 Through 1982, Part // (New York K!dder , Peabody & Co 1980) p 1074 ● Wood Use: U.S. Competitiveness and Technology

sion of electronic communication if telecommunications technology is accepted by the business community and home use expands significantly in the future. Plastic substitutesfor paper bags, wrapping papers, and miscellaneous office supplies could displace 10 percent of the paper consumed in the United States annually,

Competition From Plastics
The use of low-density polyethylene film (LDPE) for packaging, wrapping, and sacking, and high-density polyethylene film (HDPE) forprinting and wrapping paper, is a comparatively recent trend that began during the past decade and continues to expand at a steady rate. Plastics claimed only a l-percent share of thegrocery sack market (small sacks used for individual items) in 1979, but within 2 years expanded to 5 percent of the market. The plastics industry projects that plastics could capture asmuch as 25 percent of the grocery sack market by 1985,’ 7 but, according to some analysts, the penetration of plastics into the traditional kraft paper markets will probably be selective, For example, the grocery bag market (larger,multiwalled, heavy-duty bags) may be less vulnerable to inroads by plastics, at least during the intermediate term (10 to 15 years). l8

Several factors will determine the futurecompetitiveness of plastics in relation to paper products: 1) relative production costs, including raw material (resin for plastics andwood, and chemicals for paper), labor (in general, the paper industry is more labor-intensive), and energy consumption; 2) rate of technical innovation; and 3) consumer acceptance.

Sack/Bag MarketPlastics’ share of the merchandise bag market was estimated to be 35 percent in 1981, an increase of 10 percent over the previous year, Investment analysts at Morgan Stanley & Co.estimate that plastic bags will control 60 percent of the merchandise bag market by 1985. 19

“Clephane, p. 18. InIbid., p. 17. lgIbid., p. 16. Production of 275,000 tons of finished bags annually account for only 5 percent of the total production of unbleached kraft paper. Morgan Stanley estimates that by 1985, merchandise bags will require no more than 3 percent of thetotal production of unbleached kraft paper production. Large grocery bags consumed 12 percent (467,000 tons) of the unbleached kraft paperproduced in 1981, Small grocery sacks accounted for 95 percent of the 1.3-million-tontotal grocery sack market in 1981 and used approximately 34 percent of the unbleached kraftpaper produced during that year. Until recently, plastics were not considered to be serious competitors of kraft paper for the grocery bag/sack market; however, some analysts now predict that plastics may be able to capture rapidlyan increasing and significant share of the market, The paper industry confirms that plastics now compete at prices ranging from $0,029 to $0.031 per sack and sell for 10 to 15 percent less than unbleached kraft sacks. The majorplastic sack producers include several oil companies and chemical companies: Mobil, Exxon, and Union Carbide,
One reason for plastics’ current success in competing with kraft paper in the bag and sack market is the availability of low-cost resins.Another is technological developments in polyethylene that permit substantial reduction inplastic thickness and volumes without sacrificing strength. For example, development of the Unipol process for making linear, low-density,polyethylene resin in 1979 constituted a major breakthrough for the plastics industry because it required considerably lower capital investment and consumed less energy per unit of resin produced. Paper currently possesses properties that are superior to plastics as a material for bags and sacks. The rigidity of paper sacks enable them to stand freely for filling in grocery and retailstores. To compensate for lack of sidewall rigidity, plastic sacks must be mounted in racks for ease of filling. Although such technologydoes not yet exist, it might eventually be possible to develop a rigid-wall plastic sack capable of competing economically with paperCh. Ill—Pulp, Paper, and Fiber Products ● 7 5

sacks. The conversion from LDPE to newer low-density polyethylene film could provide even greater price advantages for plastic sacking.

Multiwall SacksOne major segment of the paper sack market that has not yet been seriously challenged by plastics is the multiwall, bulk shipping sack. Plastics have not made significant inroads inthis sector because the strength properties required put plastics at a cost disadvantage relative to kraft paper. Plastics currently occupy 10 percent of the multiwall sack market, andsome industry analysts assume that this market penetration will remain stable over the longterm unless unforeseen technological developments occur. Product developments in the pulp and paper industry may reinforce paper’s share of the multiwall sack market. For example, St. Regis Paper Co. recently introduced Stress Kraft, a superior-strength paper permitting a20-percent reduction in the weight of the paper used for multiwall sack construction. 20 Multiwalled sacks consumed approximately 26percent of the unbleached kraft paper produced in 1981.

Liquid Containers and Packaging

Plastic containers for liquid nificant gains in competition have made sigwith glass and coated-paper containers. Plastic l-gallon milk containers now dominate the market, althoughmost smaller l-quart and l-pint containers continue to be coated paper. Technological innovation accounts for the current inroads of plastics in the packaging sector, yet plastics have stillcaptured only a small proportion of the packaging and container market. Because plastics arepetroleum derivatives that are not biodegradable, and in some cases may produce toxicfumes if incinerated, plastic packaging products have met opposition from environmentalists. 21 The market for tissue wrapping papers and glassine and parchment papers has not been significantly penetrated by plastics, although plastic bakery bags and cereal box liners are in wide use, The major limitations to the use of plastics in these areas are primarily linkedto the difficulty of adapting automatic packaging machines for the new materials. HDPFs have properties similar to the cellulose filmsand may some day challenge conventional paper materials in this area.
While plastic and aluminum foil trays have significantly challenged paperboard fiber trays for packaging meats, fish, and prepared and frozen vegetables, recent trends in microwavecooking (which cannot use aluminum foil containers and requires heat-resistant receptacles)have resulted in a new generation of oven-resistant packaging. Polyester coatings have beenjoined with molded paper trays to create a composite product suited for microwave cooking conditions. 22
A number of composites, which combine paper with plastics and metals, provide a product superior to those made with one material. Among these are collapsible plastic bags inside paperboard cartons equipped with a spout fordispensing liquids, thermoplastic-coated paperboards for water-resistant food containers,paper meat trays coated with plastics, paperboards treated with clay-adhesive mixtures and bonded with metal foils, and paper cartons laminated with plastic foams.

Printing and Writing Papers Plastic films have not significantly displacedprinting and writing papers, except for specialized uses. The properties of paper (printability, flexibility, wearability, and price) are well suited for printing, recordkeeping, business forms, magazines, and books. The durabilityof plastics (e. g., in Mylar and waterproof papers) makes them useful for transparent reproducible graphics, children’s books, and outdoor use, However, the cost of printable plastic films is approximately twice that of the highest

‘z~lr, l,onl~ i re, 4’ I’al)crboar(l Packages fOr ot’ens,’” Fm[i Ellgl
neering, ]an~]ary I $)78, [). 62

,76 ● Wood Use: U.S. Competitiveness and Technology

grades of paper. 23 Paper industry analysts believe the probability is low that plastics will be able to displace paper in general business andcommercial use, except for the highly specialized applications named above.

Synthetic Fibers The major petroleum-based synthetic fibers that compete with rayon and acetate are the polyesters, nylons, acrylics, and olefins. In1968, the worldwide volume of cellulosic manmade fiber produced was about the same asthat of noncellulosic manmade fibers (3.9 million tons). 24 Since that time, the noncellulosicfibers have dominated the artificial fiber market. This trend may continue, although the market shares for rayon and acetates appear tohave stabilized. Some predict that a slight resurgence in the use of rayon may occur if petroleum prices increase significantly. Improvements in the viscose rayon process or the development of new processes that could reduce the cost of rayon manufacture may alsoreinforce the market position of cellulosic products. Some claim that the rayon industry has suffered from a reduction in R&D in the 1950’s and 1960’s, the period when petroleum-derived synthetics displaced rayon as the predominant manmade fibers. The rayon and acetate industries, however, consider their major competitor not to be the petroleum synthetics but natural cotton fibers, Cotton and rayon have similar properties with regard to moisture absorption and other wear characteristics, making possible development of improved, cottonlike rayon fibers that aredirectly substitutable for cotton. The rayon industry sees an opportunity to expand its market without meeting competition from petroleum synthetics, based on the forecast that worldwide demand for cotton will increase at

———-— — “’(Where Plastic Papers Stand in Printing, Bags and Tissues, ” Modern Plastics, March 1973, p. 55. Z4Committee on Renewab]e Resources for Industrial Materials (CORRI M), Fibers as Renewable Resources for Industrial Materiais [Washington, D. C.: National Academy of Sciences, 1976],

p. 234. a rate exceeding the capacity of the agricultural industry to meet the requirements. ’s

Competition From Electronic Technologies
Recent developments in large-scale, integrated circuitry are revolutionizing the communications and information fields by reducing the size of computers and microprocessors,expanding their capacities and flexibilities, reducing costs, and increasing availability to a wider range of potential users. 26 Through the use of satellite communications, microwave,and interfacing devices on home television receivers, electronic communications may belinked with large centralized information systems that are capable of providing a wide rangeof user services. Further developments in optical digital-disk technology (a specially coated plastic disk on which information is encoded by a high-powered laser beam) may enable thepermanent storage and relatively cheap retrieval of immense amounts of information. 27 Fundamental research on new concepts of data storage and retrieval may pave the way in thefuture for even greater expansion of information technology.

Achievements in telecommunications technology during the past two decades offer a number of opportunities for improving thespeed and flexibility of communications, Electronic mail is being considered by the U.S. Postal Service and private firms as a way to speed textual communications and eliminatethe need for handling and physically transporting mail. 28 Some foresee electronic filing leading to the paperless office. 29 Video magazines, which may be transmitted directly into the

**Z5c;**

**.** DaU], op. Cit., P, 84’ z6LJ.S. congress, office of Technology Assessment, COmputerBased National Information Systems: Technology and Public Policy’ Issues, OTA-CIT-146 (Washington, D. C.: U.S. Government Printing Office, September 1981), pp. 3-12.
“C. Goldstein, “Optical Disk Technology and Information, ” Science, vol. 215, Feb. 12, 1982, p. 862. “J, Free, “Electronic Mail: Good-bye to Paper?” Popular Science, September 1980, pp. 78-141.

‘ e ’’ Electronic Filing to Threaten Cut Size Paper Markets, ” Fiber Market News, No. 72, Dec. 14, 1981, p. 1,Ch. Ill—Pulp, Paper, and Fiber Products ● 7 7

home via satellite and conventional televisionreceiver, are in the early stages of development. 30
Television-adapted versions of the phone directory, retail catalogs, and other merchandising devices, which can be viewed on home televisions, are currently being evaluated for public use. 31 Also, a number of major newspaper publishers are interested in producing electronic newspapers; in the United Kingdom atleast three such teletexts are already operating. 32 Futurists consider as long-range prospects the use of vast central information systems—’’hypertex capableable of retrieving, displaying, and manipulating information from “grand libraries” through personal consoles. 33
Such broad-scale application of electronic communications could affect dramatically theuse and demand for paper in the future. Although telecommunications has experiencedrapid growth during the past decade, its application for office and home use is still in its infancy, Thus, uncertainties regarding the rate of commercialization and public acceptance and forecasts of its impacts on paper must be considered speculative. While there is little disagreement among analysts that electronic communications may ultimately displace the need for some writing and printing papers, the timing and extent of the impacts are subjects of debate. Euro-Data Analysts, a British-based market consulting group specializing in the paper,board, and packaging industry, forecasts a major shift from the use of paper toward increased reliance on electronic media. 34 Over the longterm, Euro-Data considers it likely that the developed countries will achieve a nearly paper30’’Tips on Tiipe: (;assette Magazines Arrive, ” Time, June 14, 1982, p. 78.

314 ’ Paper Chases the EIectroni{; Age, ” Bosjness Week, Apr. 5, 1982, pp. 112-115,
32K. Edwards, “The Ele(;tmnic Newspaper, ” Communications Tomorrow

(Bethesda, ~ld,: World Future Society, 1981), pp. 54-59. “H. Freedman, “Paper’s Role in an E]ec,tronic World, ” Communications Tomorrow’ (Bethesda, Md,: World Future Society, 1981), pp. 60-65.

**34Eu rO-Data**  **Analyst S** 

**,** The Impact

of Communications Technologies on llemand for Printing and Writing Papers (Ashtead, Surrey, U. K.: Euro-Data Analysts, 1980), less society as the rate of commercializationof electronic communications accelerates. Euro-Data forecasts that during the current decade, paper will lose a share of the market to the electronic media through video telephone directories, office communications, telex, videobooks, video newspapers, consumer magazines, and electronic funds transfers.The American Paper Institute (API) sees immediate competition with the electronic mediain electronic fund transfers, office reproductions that require less paper, electronic mail,and electronic storage and microforms .35 Beyond 1985, API anticipates competition developing in direct-mail advertising; voice message systems that would reduce the requirements for envelopes and business forms; expanded use of home video catalogs and directories; video publication of periodicals; interactivevideotext, which might reduce book publishing; and video systems displaying time-critical news, which could displace some newsprint.By 1995 and beyond, portable handheld video displays could displace printed magazines, books, and newspapers (table 25). API notes that the electronic media accounted for over60 percent of the total communications expenditures during the 1970’s. If the trend continues, its share could exceed 70 percent by the year 2000, while the paper-based media’s share may drop to less than 30 percent. 36
Other analysts agree that electronics technology will probably reduce the demand for printing and writing papers during the next decade, International Resource Development, Inc. (IRD), a technology consulting firm, sees homevideo as potentially flattening the growth in demand for paper directories and catalogs within 6 years. 37 IRD projects that by 1991, electronic filing could reduce demand for office paper by300,000 tons per year (5 percent of current office consumption). Data Resources Inc. (DRI) estimates that home video systems could start affecting newsprint demand by 1985. 38 If elecssAmerican Paper ] n st itute, Information Technolog~’ and paper Demand (New York: API, 1981], p. 52. j~Ibid “’’Paper Chases in the Electronic Age, ” op. cit., p. 112. ‘eIbid.78 ● Wood Use: U.S. Competitiveness and Technology

Table 25.—New Information Technologies and Their Potential Impact on Paper Construction

Paper end-use categories/relevant information techniques Paper end-use categories/relevant information techniques

Commercial business and printing papers: . Printing papers.” —Advertising: direct mail— Home video information (videotex and teletext) may open new avenues for advertising and could thereby adversely impact print-based advertising, including direct mail. Timeframe: beyond 1985. —Printing: financial and legal— Expanded use of word processors and intelligent printer/copiers will encourage more in-house production of forms. Electronic funds transfers will continue to grow, subtracting from the use of printed forms in financial transactions.

● Office graphic reproduction —Growth i n the use of intel - Iigent copier/printers will encourage more in-house offsetprinting. Timeframe: currently taking place; trend is expected to continue.Duplexing and reduction capabilities, both of which operate to conserve paper, will become common features of office copiers, including those positioned at the low end of the price scale. Timeframe: currently taking place; trend is expected to continue. Converting papers:

●

●

●

✎ Envelopes- Expanded use of electronic mail and voicemessage systems may hold down the number of envelopesused by businesses and individuals. (Voice-message systems are not expected to come into widespread use before 1985.) Business forms—An increased proportion of businessforms will be produced in-house using intelligent copierprinters. Electronic storage and microforms will continue to displace paper forms in selected applications. Stationery and tab/et—A modest, negative impact fromelectronic mail, electronic pads, and voice-message systems appears possible. Timeframe: beyond 1985. Magazine publishing: Modest, negative impact possible fromhome video information. The future development of a fullpage portable display for reading electronically stored information could also impact paper consumption by magazines. (The advent of portable displays is not anticipated until the 1985-95 timeframe, or beyond.) Other periodical publishing: Home video information mayhold down paper consumption for catalogs and directories. The future use of videodiscs as a storage medium for reference materials may have a negative influence onpaper consumption for catalogs and directories. Timeframe: beyond 1985. Book publishing: Possible use of home and office videodiscsto store large quantities of infrequently examined information could limit future demand for reference books such as encyclopedias. Interactive videotex may Iikewise have a negative influence on the demand for reference books. Timeframe: beyond 1985.As noted above, next to magazines, the advent of a portable, full-page display possessing adequate image quality for prolonged periods of reading may lead to reductionsi n the demand for paper-based, printed materials, including books. Timeframe: 1985-95, or beyond. Computerized printers reduce the need for special labels in certain applications. Newspaper publishing: Home video information may draw classified advertising and financial listings away from newspapers. It may also compete with newspapers bybecoming an efficient transmitter of time-critical news information. Timeframe: beyond 1985.Advent of compact display could also have repercussions on newsprint consumption. Timeframe: 1985-95, or beyond.

SOURCE American Paper Institute, Information Technology and Paper Demand (New York, API, 1981), pp 10-11

tronic media affect newspaper advertising as television has, by 1995 they could displace800,000 metric tons (tonnes) of newsprint annually (15 percent of current U.S. production),
In the short term, demand for writing and printing paper seems to have increased with the proliferation of word processors and office copiers, which enable fast and inexpensivecopies of texts and graphics to be made, Although this phenomenon is considered by some industry analysts to be temporary, others forecast that paper will continue to dominateoffice communications, magazines, and newspapers. 39 However, both International Business Machines (IBM) and American Telephone and Telegraph (AT&T) have stepped up activitiesin the field of information storage and transmitSQFree~ rn~ n, op. (: it., P. Go. tal, and some analysts consider their entry into the market as the harbinger of rapid progress and expansion in electronic communications. M

With 30 percent of U.S. paper production being used for storage and transmission of information, the short-term trend in increased paper usage as a result of electronic officeequipment is expected by some industry analysts to give way to sharp decreases in paper use during the next 20 years .*1
The future impact of electronic media on paper demand may depend on its effects on theattitudes of a generation of children accus40(;. 11 rown, “Tomorrow in the Pulp and Paper Industry: An Outsider’s v’iew, ” speech to 1982 Annual Employee Regulations Conferen(;e of the American Paper Institute and Fiber Box Association, St. Louis, Me., ]an. 27, 1982 (New York: Kidder Peabody’ and Co., Inc., 1982), p. 4. 41 ibid.Ch. Ill—Pulp, Paper, and Fiber Products . 79

tomed to the partial substitution of electronicsfor paper. While many older people, not so accustomed, find acceptance of nonprinted media difficult, the present school-age generation,who use nonprinted communications throughout their educational careers, will accept electronic communications for business and home use more readily. In addition, although current technology limits the use of electronic communication to desktop consoles and large computer and wordprocessing installations, the development of handheld portable devices withreadable screens—and microelectronic processors capable of storing entire books and magazines—could have a significant impact on the substitution of electronic media for print.



# Pulp, Paper, and Cellulose Fiber Manufacturing

Paper was supposedly invented in 105 A.D. by Ts’ai Lun, a member of the Chinese imperial

court. 42 Ts’ai Lun’s method for papermaking involved soaking tree bark, hemp, rags and other cellulosic materials in water to soften them and then beating the softened materialuntil the fibers separated and swelled. He dispersed the fibers in a wet suspension and formed a thin sheet that was transferred to a felt cloth and pressed. The resulting web was dried in the sun. Paper is still made by essentially the same process: 1) pulping, to separate and clean thefibers; 2) beating and refining the fibers; 3) diluting, to form a thin fiber slurry, suspended in solution; 4) forming a web of fibers on a thinscreen; 5) pressing the web to increase the density of the material and remove excess liquid; 6) drying to remove remaining moisture; and 7) finishing, to provide a suitable surface for the end use. The three methods for pulping wood and other cellulose materials include chemical pulping, mechanical pulping, and semichemical or chemimechanical pulping—a combination of the first two methods.In mechanical pulping, wood chips from debarked logs are ground, or are passed through a mill, and in some versions of the process aretreated with high-pressure steam (thermomechanical) to separate the individual fibers,which can then be formed into sheets of paper. Mechanically separated fibers contain lig**4zF, F,**  **Wa ngaa**  **rd, WOOd:**  **lfs** Structure and properties ((] nl ~’ersity Park, Pa.: Pennsylvania State Uni\’ersity, 1 981), p. 335, nin, which makes them remain stiff, bond poorly, and yellow with age.
Chemical pulping is done by cooking wood chips in acid, alkaline, or neutral salt solutions under pressure and high temperatures, which breaks down the wood structure and dissolves some or most of the lignin and hemicellulose contents. Delignification by chemicals causesthe individual fibers to become flexible and increases contact and binding among the fibers forming the paper mat, thus increasing thestrength of the paper. Semichemical and chemimechanical pulping first breaks down the wood chemically, then by grinding. The range of commercial pulping processes currently used by the pulp and paper industry is shown in table 26. Nearly three-fourths ofthe wood pulp is produced by the kraft process (fig. 22).

Mechanical Pulping

Commercial Mechanical Pulping Technologies There are four basic mechanical pulpingprocesses: 1) stone groundwood pulping, 2) refiner mechanical pulping, 3) thermomechanical pulping, and 4) the recycling of paper. Flowdiagrams of the three mechanical pulping processes are shown in figure 23. Mechanical pulping is generally used with softwoods becauseof the added strength imparted by the long fiber length of softwood species. Mechanical pulps are used principally to manufacture newsprint, printing papers, and tissues that do not require high-strength paper. Secondary80 • Wood Use: U.S. Competitiveness and Technology

Table 26.—Major Commercial Wood-Pulping Methods, Grades of Pulp, and End-Products

Pulp grades Chemical pulps: Sulfite pulp . . . .

Kraft sulfate pulp

Dissolving pulp Percent yield per Wood type dry weight of wood End-products, utilizing grade

. . . . . . . . . . . . . . Softwoods and hardwoods 53-56 b I c 45-50 a ’ d

. . . . . . . . . . . . . Softwoods and hardwoods 40-50 a 52-53 b

. . . . . . . . . . . . Softwood 33-35

Semichemical pulps: Cold-caustic process . . . . . . . . . . . Hardwoods and softwoods 80-95

Neutral sulfite process . . . . . . . . Hardwoods 70-80

Mechanical pulps: Stone groundwood e . . . . . . . . . . . . Softwoods 95 Refiner mechanical (RMP) e . . . . . . Softwoods 95

Thermomechanical (TMP) e . . . . . .Softwoods 95 Fine and printing papers

Bleached—printing and writing papers, paperboard. Unbleached— heavy packaging papers, paperboard Viscose rayon, cellophane, acetate fibers, and film

Newsprint and groundwood printing
papers Newsprint and groundwood printing
papers

Corrugating medium Newsprint and groundwood printing
papers Newsprint and groundwood printing
papers

— aBleached pulps made from softwoods bun bleached pulps made from softwoods.

cUnbleached pulps made from hardwoods dBleached pUIpS made from hardwoods ‘For paper and board
SOURCE George H Boyd Ill and Chad E Brown, Paper /r?dusfry. Ouf/ook for Market Pu/p (New York Kidder, Peabody & Co , 1981), p 5

Figure 22.— Proportions of Woodpulp Produced by Commercial Pulping Processes

Unbleached kraft 380/o

Sulfite 4 0 /
0 \-- ’

Ground wood
9 0 /

0

uses include wallpaper and paperboard. Recycled pulp is used mainly for the manufactureof folding boxboard (grayboard), tissue, corrugated board, and newsprint.In the stone groundwood (SG) process, debarked short logs (roundwood) are fed whole into grinders. The abrasion of the grinding wheel against the wood physically separates the wood fibers. The grinding process usuallyis automatic and continuous, although sometimes it is semicontinuous, Refiner mechanical pulping (RMP) uses chips in lieu of roundwood and produces paper with higher strength than conventional groundwood because of less damage to the fibers in the pulping process, A wider range of species, including hardwoods, can be processed by the refiner pulping
process.
The most advanced commercial mechanicalpulping system is the thermomechanical process (TMP), which was developed as a modification of the RMP process. In TMP, wood chipsare steamed for several minutes under pressures ranging from 4 to 45 psi and subsequently refined in one or two stages.
Recycled pulp is manufactured from wastepaper, which is processed into paper stock forfurther use in making paper. A small proportion of the paper stock (5 to 10 percent) is deinked, usually with caustic, soda-based chemicals. Most recycled paper, however, is pulped without de-inking. Pulping is accomplished through violent agitation and shearing action82
● Wood Use: U.S. Competitiveness and Technology

Figure 24.—Wood and Energy Flows in Mechanical Pulping Mills in Conjunction With Recycling

t
waste paper I I

I

I 400 Ibs , ~

310 Ibs wastepaper I 

### I

I

of kraft pulp to improve its wet strength and processing on the paper machine. While paper using TMP consumes 11 to 13 percent lesschemical pulp than ordinary newsprint, improved materials efficiency is gained at the expense of higher energy consumption. When the cost of energy is considered as well as the cost of wood, TMP is actually more costly than SG. Pulp yields from all the mechanical pulping processes typically are near 95 percent recovery, which is a higher yield per unit of wood than with the chemical pulping methods. The principal variables that influence the choice of mechanical pulping methods are: 1) furnish (raw material) requirements or wood species,2) pulp strength, 3) expected gross energy consumption, and 4) expected net energy consumption.Ch. III—Pulp, Paper, and Fiber Products ● 8 3

The process variables that affect the quality of mechanically produced pulp are listed in table 27. Increases in paper strength are gainedby increases in energy consumption, but brightness and opacity, qualities that affect the use of paper for printing, are largely independentof the pulping process. Recycling can effectively reduce the consumption of both wood raw material and energy when used in conjunction with other mechanical pulping processes.However, it does so at the sacrifice of some paper strength.

Improvements in Mechanical PulpingTechnical improvements in mechanical pulping have largely been directed at reducing energy consumption and improving the quality of mechanical pulps. Pulp yield is approaching the practical upper limit, since all of the lignin and most of the hemicelluloses remain in thefiber, and fiber recovery from mechanical pulping is frequently twice as high as that from competitive chemical pulping. By reducing energy costs, mechanical pulping has remained cost competitive, and improvements in paperquality have enabled mechanical pulps to displace some of the more costly, higher quality pulps produced by chemical processes. As noted in table 27, although improvements inquality result in some increases in the consumption of energy, the higher quality pulp produced more than offsets the higher costs of energy. Three major developments in mechanicalpulping technologies show promise for improving pulp quality and/or reducing energy consumption: 1) pressurized groundwood (PGW) pulping, 2) chemithermomechanical pulping (CTMP), and 3) hardwood chemimechanical pulping (CMP). Each of these new processes has reached some stage of commercialization.A fourth major development is waste-heat recovery.

PRESSURIZED GROUNDWOOD PULPING In PGW pulping, debarked logs are fed to the grinding wheel through a heated, pressurized chamber. The heat and pressure help separate the fibers, breaking down fewer fibers in the grinding process and improving pulp quality. The longer fibers give the end product a higher tear index than paper made from SG, but it isslightly inferior to that of TMP. The tear resistance for PGW pulp is 5.6, compared with 3.9 for SG and 7.1 for TMP (table 27), The tensile index for PGW pulp (35) also lies between that for SG pulp (32) and TMP (37). In addition toimproved strength, PGW promises some reduction in energy consumption. It is estimated that the energy requirement may be reduced by 40percent from that required for the thermomechanical process, or from 1,833 to 2,417 kWh/ ton of pulp to approximately 1,100 to 1,450 kWh/ton. 43

43 C;, \V. E\ans, “Pressured Process for Grounciwoo[] Pr{jdl]( - tion Making Health~’ Progress, “ })ujp a~]d }~a[}(~r, [’()] 54. 1980,

pp. 76-78.

Table 27.—Summary of Process Variables for Mechanical Pulping (based on the production of 1 ton of ovendry pulp)

Process

Ground wood Refiner mechanical Thermomechanical Variable pulping pulping pulping Recycle
Furnish type .

, Debarked logs Residual chips, Residual chips, Waste paper sawdust sawdust Furnish requirements . . . . . 2,100 lb 2,100 lb 2,100 lb 2,200 lb Energy requirements (kWh/ton) . 1,340-1,790 1,800-2,400 1,800-2,000 360 Strength: Burst . . . . . . . . . . . . . . . 1.4 1.8 2,0 Tear . . . . . . . . . . . . . . . . . . . . 3.9 5,7 7.1 Tensile, . . . . . . . 32.0 35.0 37.0

Other: Brightness . 60.0 57.0 57.0 Opacity . ., . 95.0 95.0 94.084 ● Wood Use: U.S. Competitiveness and Technology

By 1980, five mills worldwide had installed PGW systems. Fifteen more plants have been ordered, including four to be located in the United States. Some industry analysts consider PGW technology to have significant potentialfor reducing mechanical pulping energy requirements and for displacing some high-quality chemical pulps in the manufacture of newsprint and other printing papers.

CHEMITHERMOMECHANlCAL PULPING CTMP involves treating softwood chips with mild sulfite solutions prior to pulping. This “sulfonation” treatment results in paper with higher tear indices than do TMP, RMP, or SG pulping processes. 44 Energy consumption for CTMP may range from 1,360 kWh/ton to 2,000 kWh/ton, depending on the strength of the sulfite solution. Thus, energy consumption of CTMP lies within the range of SG pulping, is less than that required for RMP or TMP, and results in a higher quality paper. Pulp yields decrease slightly to between 85 and 95 percentwith CTMP, but these yields are still large compared to chemical pulping and to mechanical chemical pulp blends. Some TMP pulpmills have begun to add sulfite chemicals in their operations to improve pulp quality and reduce energy consumption.

HARDWOOD CHEMIMECHANICAL PULPING Mechanical methods for producing pulp from underutilized hardwood species involve pretreating hardwood chips with hydrogen peroxide or sodium hydroxide and processing them like RMP. Both poplar [softwood) and red oak (hardwood) have been pulped successfully by these techniques. However, fiber recoveriesare lower for hardwood CMP than for softwood CMP. Pulp recoveries of 80 to 85 percent have been reported for poplar, 90 to 95 percent for red oak. Energy consumption for CMP ranges from500 to 1,500 kWh/ton using hydrogen peroxide for chemical pretreatment and 700 to 1,100

.44~ Atack, et ~]., “Sulphite Chemimechanical Refiner PulpAnother Option for Newsprint, ” Pulp and Paper, vol. 54, 1980, Pp. 70-72. kWh/ton using sodium hydroxide. 45 Hardwood CMP consumes significantly less energy thando either SG or other chemimechanical hardwood pulping technologies.Pulp and paper technologists expect hardwood CMP to expand significantly during the next 10 to 25 years because of the large volumesof inexpensive hardwood available, a phenomenon that could have a profound impact on the utilization of presently underutilized speciessuch as poplars, red alder, and American sycamore that are abundant throughout the Eastern United States. Pulp produced by hardwood CMP can be used to produce newsprint and printing papers. Two small U.S. mills, which range in capacity from 200 to 250 tons of pulp per day, have already installed CMP systems to process hardwood species.

WASTE HEAT RECOVERY SYSTEMS Mechanical pulping systems create a large amount of frictional heat during the grinding and refining processes. Heat recovery systemsthat enable use of waste heat (for drying paper, space heating, and water treating) are important to the reduction of energy costs in the pulping process. Such systems are particularlyimportant in TMP, which requires large quantities of mechanical energy and produces highquality heat (i.e., high heat under temperature and adequate pressure) .46 Because of the highertemperature of waste heat from TMP processes, a higher percentage of usable waste heatcan be recovered from TMP than from conventional groundwood pulping,Heat recovery technologies currently recapture 3 million to 5 million Btu/ton of pulp produced.” For mills consuming 1,800 to 2,400 kWh/ton, 95 percent efficiency in heat recoverywould represent a total of 5.8 million to 7.8 mil45J, D. Sinkey, ‘lCMP and C’I’MP-A Review,” paper presented at Forest Products Resear[;h Society Conference, St. Paul, Minn., 1981. 4EP, J. Walker and E, J. 13atsis, “Heat Recovery From TMP Operations Results in linergy Consert’ation, Pulp and Paper, vol. 52, 1978, pp. 146-148. ‘T’rhe Fossj) ~’nerg~, ~’onser~,atjon Potential Associated W’iih Producing Wood Pr’oducts From Managed Stands (Bellekwe, Wash.: Envirosphere Co., 1981).Ch. Ill—Pulp. Paper, and Fiber Products . 85

lion Btu. 48 With current technology, the industry captures 50 to 65 percent of the theoretically recoverable waste heat, Widespread adoption of these efficient systems has not yetoccurred because of the problems of retrofitting and high capital costs.

Future Prospects for Mechanical PulpingThe three major new mechanical pulping technologies—PGW pulping, CTMP, and CMP—have improved pulp quality and reduced energy consumption compared with conventional groundwood processes. The resulting higher quality mechanical pulps will displace the kraftpulps that are currently mixed with mechanical pulps to improve paper strength. For example, the shift from SG pulping to TMP displaced 300 pounds of kraft pulp per ton of newsprint. Use of the new technologies willfurther reduce the amount of kraft pulp required in newsprint and printing papers, reducing the demand for softwood timber because the pulp yield from these processes is nearly twice that of kraft processes. The configuration of mechanical pulpmills for newsprint manufacturing will likely change significantly during the next 10 to 20 years. By employing CMP and CTMP technologies, using a higher percentage of hardwood as raw material, and installing highly efficient heatrecovery systems (85 percent recovery), the mechanical pulpmill of the future could reduce its heat requirements by 1.0 million Btu [300 kWh/ton of heat) and reduce electrical energy consumption by 97o kWh/ton of newsprint from that currently required by TMP mills.Savings of this magnitude of purchased electric power is equivalent to a savings of 11 million Btu of heat input at the powerplant. In addition, 3.5 million Btu of usable heat could be recovered, offsetting over 50 percent of thatcurrently required in the pulp and papermaking process. Further improvements in energy efficiency and wood utilization could result if a recycle pulpmill were integrated with either SG or TMP pulpmills (fig. 25). The practical upper limit of recycled fiber in the pulp mix is estimated to be about 40 percent. A small proportion of kraft pulp is required in the mix to strengthen the newsprint if larger proportions of recycled pulp are used. 49 The major gainsin energy efficiency between a wholly roundwood C M P or CT M P mill and one integratedwith a recycle pulpmill are in reduced electrical-energy consumption. Reductions in energy consumption of between 179 and 358 kWh/tonof pulp may be achieved by recycling, so Process heat requirements remain approximately the same when recycling is used, but the amount of recoverable waste heat is decreased from 3.5 million to 2,2 million Btu.
Substantial technical improvements are possible in mechanical pulping processes within the next 20 years, providing that economic incentives exist and capital formation is possible.

Chemical Pulping

Commercial Chemical Pulping Technologies Chemical pulping processes involve treatingwood chips with chemicals to remove the lignin and hemicellulose, thus separating and delignifying the fibers, Delignification gives thefibers greater flexibility, resulting in a substantially stronger sheet of paper—because of greater contact between the fibers in the finished sheet—than can be manufactured from fibers with lignin produced by mechanical pulping. Two major chemical pulping technologies are currently in use: 1) kraft (sulfate) pulpingand 2) sulfite pulping. The kraft process dominates the pulp and paper industry, accounting for over 75 percent of all pulp produced for paper and paperboard in 1979. 51 Otherchemical pulping processes, such as acid sulfite pulping, bisulfite pulping, and neutral sulfite semichemical pulping account for approximately 3 percent (the remainder was produced by mechanical pulping), Paper made from pulp86 ● Wood Use: U.S. Competitiveness and Technology

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ICh. Ill—Pulp, Paper, and Fiber Products ● 8 7

produced by the kraft process accounts for most of the bleached boxboard and linerboardused by the packaging industry (which consumes 58 percent of the paper in the United States). In addition, bleached softwood kraft pulps often are mixed with mechanical pulps to add strength to newsprint and printing papers. Bleached hardwood kraft pulps are added to bleached softwood pulp to improve printability for specialty paper products like magazine stock and coated papers.

KRAFT (SULFATE) PULPING The kraft process involves treating wood chips and sawdust with a sodium sulfide and sodium hydroxide solution. The highly alkaline chemical mixture is cooked in a digester for 1 to 3 hours at temperatures ranging from 320° to 350

0 F (fig. 25). The complete pulp and paper making process is shown in figure 26.Fiber recovery from the kraft pulping process is largely a function of the wood species used, the amount of chemicals used, the time and temperature of cooking, the degree of bleaching, and the paper strength required.Generally, kraft pulp recoveries from softwoods are approximately 47 percent for unbleached pulp and 44 percent for bleached. s’ Hardwood recoveries range from 50 to 52 percent for unbleached kraft pulp and 45 to 50 percent for bleached. Energy is used in a mill in different forms(as chemical heat of reaction, as thermal energy, and as electrical energy), and these typicallyare expressed in different units (Btu for thermal and for heat of reaction in fuel combustion, and kWh for electricity). While the units may be converted simply (i.e., 1 kwh = 3,412 Btu), the actual forms of energy may not be converted without loss of energy available for doing useful work. Thus, in a typical powerplant, it takes 10,000 Btu of heat input to produce 1kWh of electricity (in contrast to the unit conversion above), and two-thirds of the input is

szp, J Hu~~ey, Comparison of Mills Energy Balance: Effects of Conventional Hydropyrolysis and Dry Pyrolysis Recovery Systems (Appleton, Wis.: Institute of Paper Chemistry, 1978). lost as exhaust. There are, then, two ways to compare a mill’s energy uses: 1) simple unit conversions, representing all uses in a common unit; or 2) representing all uses in terms of theheat values of their original forms, while recognizing energy conversion losses. The different conclusions reached by these approaches is illustrated by the following: the first method gives rise to the conclusion that self-generation in today’s typical kraft paper mill provides about 50 percent of the mill’s energy needs, while the second method (table 28) shows that 82 percent of the primary fuel supplying the total energy needs of a typical kraft mill is self-generated. The first method relates better to concerns for fossil-fuel avoidance, while the second helps relate the fuel value of wood-process residuals to other potential uses. Of the two approaches, the latter is the more useful for assessing process efficiency. Energy consumption is a major cost in themanufacture of kraft pulp and paper. The combined process requires approximately 30 million Btu of primary fuel per ton of bleachedkraft paper (table 29). This energy value includes fossil fuel burned at an outside powerplant to provide purchased electricity as well as the thermal energy derived from the woodresource. Approximately 78 percent of the energy demand is for thermal energy used in the plant, the major portion of which is used for paper making and self-generation of electricity rather than in the pulping process. While thecombined kraft pulp and paper making process requires approximately 1,050 kWh/ton of electricity, mostly for drive motors, all but 101 kWh generally is produced internally through cogeneration (table 29). Burning waste liquorsand bark provides 82 percent of a mill’s primary energy needs. The kraft process is suitable for pulping bothsoftwoods and hardwoods. Wood chips, sawdust, and wood residues from sawmills and veneer mills can be used as furnish, Over 35 percent of the total wood supplied for kraft paper are wood residues. In the Pacific Northwest, nearly 90 percent of the wood originates from sawmill or veneer mill residues. Whole tree chips, including bark and branches, currentlyare used in limited quantities, although their

proportion of the total furnish is increasing. Because of the density, extractive content, and chemical nature of these materials, increases in their use may cause the pulping liquors (chemicals) to react more slowly, resulting ina need for longer digestion periods and increased energy expenditures.

SULFITE PULPINGThe four fundamental sulfite pulping processes currently in commercial use are: 1) acidsulfite, 2) bisulfite, 3) neutral sulfite, and 4) alkaline sulfite. The major differences between the sulfite processes are the levels of acidity and alkalinity of the sulfite chemical solutions used to break down the wood and remove the lignins. The cooking liquor consists of a salt base—generally calcium, magnesium, sodium or ammonium—and sulfuric acid. Sulfite processes are suitable only for species with low extractive contents, i.e., those low in tannins, polyphenols, pigments, resins, fats, and thelike, because of the interference of these substances with the sulfur pulping process. Although calcium is the cheapest base available, it forms insoluble compounds that cannot be reclaimed economically or disposed of easily. Thus, calcium-based pulping is seldom used.Because magnesium- and sodium-based chemicals are recoverable, and ammonium-basedchemicals can be burned without harmful environmental effects, they are the most frequently used. Sodium-based sulfite pulping can consist of multistage cooking, successive stages of which differ in acidity. Because one stage optimizes chemical liquor penetration and the other theCh. Ill—Pulp, Paper, and Fiber Products ● 8 9

Table 28.—Energy Demand Per Ton of Kraft Paper

Thermal: Process: Digester. ... . Bleach plant . Paper machine Evaporation. ., Liquid heating Other . . . . . . . .

Subtotal ... . . Lime kiln . . Total . ... . .

Electric: Self -generated: Energy demands

Million Btu

. . . . . . . . . . . . . 3.8

. . . . . . . . . . . . . . 2.4

. . . . . . . . . . 6.8

. . . . . . . . . . . . . 3.0

. . . . 2.9

. . . . . . . . . . . . 2,5

. . . . . . . . . . . . 21,4

. . . . . . . . . . . . . . 2,0

. . . 23.4

. . . . Fuel-value material recovered in plant and burned for electricity 5.7 b Purchased from outside: ... ..

. Fuel used by outside powerplant to produce electricity . . . . . . . . 1 .0 c

Totals: Total electricity . ... . ... Total fossil fuel consumed . . . . . . 30.1

— aHurley, P J kWh

949 a

101 a

1,050

blncremental heat ra[e tO generate electricity In plant 6000 BtulkWh

cAssumes out SI de electrlc PI ant IS fess! l-fueled at 10,000 BtulkWh

SOURCES J J Watkins and W S Adams, “The St Regls Hydrolysis Process

as an Approach to Energy Conservation In the Pu 1P & Paper Industry, ” Proceed~ngs of TAPP/ ’78 Engfr?eenrrg Corrference Book /// P J Hurley, Corrrpar/son of Mi//s Energy Rdar?ce Effects of Conven f/ona/ Hydropyro/ys/s and Dry Pyrolysls Recovery Sys(erns (Appleton, WIS Institute of Paper Chemistry, 1978)
removal of lignin, more lignin may be removed with less fiber degradation, so that fiber yields are higher, fibers are stronger, and a wider range of wood species may be used. Neutral sulfite pulping, using sodium and ammonium bases, recovers the largest proportion of fiber (75 to 90 percent) of all the sulfite pulping methods.

Improvements in Chemical Pulping Two kinds of improvements have been made in chemical pulping technologies: 1) better efficiency of current processes and 2) development of new pulping technologies that depart from the conventional commercial processes. The greatest potential for dramatically improvingpulp and paper manufacturing lies in new technologies. Such innovations could enable theuse of large quantities of currently underutilized hardwood species and may even have prospects for developing superior new papers for future specialized uses. At the same time, new concepts in energy use and cogeneration could achieve new levels of energy efficiencies. Among the most promising new pulping andpapermaking processes are: 1) press-dried paper, 2) green liquor pulping, 3] autocausticizing, and 4) pyrolytic recovery of chemicals inspent pulping liquor. These developing technologies are not yet commercially available.

PROCESS IMPROVEMENTS Major efforts in process improvements, ormeans in which the efficiency of existing commercial processes is improved, have centeredon increasing fiber recovery and energy efficiency. Most such efforts have focused on the kraft process, which produces 90 percent of allchemical pulps manufactured. Greatest emphasis has been placed on reducing energy consumption because it is the largest cost factor. Anthraquinone (AQ) recently has been tested as a catalyst in kraft pulping. When added in small quantities to the cooking liquor, AQ speeds up the pulping process and can improve fiber recovery by as much as 2 to 4 percent. Although the percentage increase in yield may seem small, the increases in absolute yield are considered substantial because of the verylarge volumes involved. AQ pulping was developed by Canadian Industries, Inc., and is

Table 29.—Energy Consequences of Pyrolytic Recovery (basis: 1 ton pulp)

Recovery method Energy required Conventional hydropyrolysis Dry pyrolysis Process yield (percent ovendried) . . . . . . . . . . . . 47.5 48.75 47.5 Electricity (kWh): Internally generated . . . . . . . . . . . . . . . . . . . . . . . . . 949 850 812 Purchased . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 256 258 Inplant fossil fuel (thousand Btu) ... . . . . . . . . . . . . . . . 10,411 5,458 6,296 Inplant fossil-fuel savings (percent). . . . . . . . . . . . . . . . . . . . 48 0/0 40 ”/0

Paper Chemistry 1978)90 ● Wood Use: U.S. Competitiveness and Technology

used commercially in both Japan and theUnited States. Its potential broad-scale application in the United States, however, maybe limited by its cost and the lack of technology to recover the used AQ. 53 The U.S. Food and Drug Administration (FDA) recently has approvedAQ for use in paper packing for food, opening new market potentials for AQ pulp. The industry’s goal is for the kraft pulping process to become as energy self-sufficient as possible. Substantial gains in energy efficiency are expected within the next 20 years, but it is not known whether total self-sufficiency isattainable. Kraft mills may approach self-sufficiency if some modifications are made; for example: 1) the temperatures in boilers that burn wood residues and black (lignin) liquorcan be reduced (primarily by adding more efficient heat exchangers for heat recovery, and 2) lime kilns maybe fueled with dried sawdust without seriously contaminating the calcined lime used for making the pulping liquor. The latter has been demonstrated successfully in Sweden. 54 These system modifications are expensive and may increase the operating costs of a plant. Their adoption will depend on the future costs of energy and the availability of capital.

GREEN LIQUOR PULPING AND AUTOCAUSTICIZATIONEconomy in chemical pulping depends on effective recovery of chemicals from the used cooking liquor. Upon interaction with wood in the cooking process, the “white liquor, ” thatis, the original sodium sulfide and sodium hydroxide solution, becomes “black liquor,” rich in lignin salts and other organics removed fromthe wood in the pulping process. The black liquor is pumped to evaporators that remove the water and concentrate the remaining salts and organic solids. The resulting viscous solution is burned in a recovery furnace to remove the organic residues (fig. 26).The remaining salts—mostly sulfides and carbonates of soda—form a molten stream referred to as “smelt” and are recombined withwater to form “green liquor. ” The sodium carbonates in the green liquor normally are converted into hydroxides for reuse by the addition of calcium hydroxide in a process referred to as “causticizing.” Pulping of hardwoods and softwoods usinggreen liquor, which eliminates the causticizing process, is now an accepted commercial technology for producing semichemical pulps. In this process, disodium borate is used insteadof sodium hydroxide in the original white liquor, and the liquor produced by dissolving the smelt can be reused directly in the digester. Inthis way, the entire regeneration loop, including the lime kiln, is removed. As much as 18percent of the fossil energy required for pulping can be eliminated by autocausticization. Elimination of the lime kiln not only reduces energy consumption, but reduces capital costs by $35/annual ton of capacity and operating costs by $3/ton. 55 Industry experts give autocausticizing a high probability of commercial acceptance.

PYROLYTIC RECOVERY Technology for pyrolytic recovery of black liquor has been developed in two processes: 1) a hydropyrolysis method developed by the St. Regis Paper Co., and 2) a dry pyrolysis methoddeveloped by Weyerhauser Corp. Pyrolytic recovery consists of applying heat in the absenceof oxygen (anaerobic combustion) to decompose the organic compounds in the black liquor. These new spent-liquor recovery techniques, designed to extract energy from the spent liquor while retaining the chemicals forreuse, are more energy efficient than are current processes. They are important because regeneration of the pulping chemicals requires a large share of the energy used in the pulping
process.Hydropyrolysis technology currently is being evaluated on a pilot basis in St, Regis’ Pensacola, Fla., mill. The process shows potential

53Hub~r, op. cit., P. 85.
WK. Lappe, “Advanced Drying Process is Key to Burning Peat, Wood Byproducts, ” Energy Systems Guidebook (New York: McGraw-Hill, 1980). ‘5]. Jansen, “Pulping Processes Based on Autocausticizable Borate, ” The Delignification Methods of the Future (Helsinki, Finland: Europa Symposium, 1980).Ch. Ill—Pulp, Paper, and Fiber Products ● 9 1

for reducing the energy requirements for evaporating weak black liquor, i.e., that recovered in the initial washing stage, and for aiding in the energy recovery process. It is estimated that fossil-fuel energy required for generation of process heat may be reduced by 50 percentwith the application of hydropyrolysis technolog y. 56
St. Regis’ experience with its pilot plant indicates that application of hydropyrolysis technology results in a tradeoff between purchased fossil fuel and purchased electricity. Lowered heat requirements for liquor recovery result inless process steam; thus, the potential for cogenerating electricity along with the steamneeded is limited. The results of these tradeoffs are shown in table 29, where the data suggest that an in-mill fossil fuel savings of up to48 percent can be achieved with hydropyrolysis and approximately 40 percent with dry pyrolysis. However, considering the fossil fuel used to generate the purchased electricity, the net fossil fuel savings are 28 percent and 20 percent, respectively.

OTHER CHEMICAL PULPING TECHNOLOGIES

Attempts to develop alternative pulping technologies that increase yields, energy efficiency, and pulp quality of the kraft process have led to two new chemical pulping concepts that show some promise: 1) organosolv (alcoholysis) pulping and 2) oxygen pulping. Since both still are under development, and neither has reached the demonstration stage, they must be considered long-range (25 + years) prospects for commercial application,

Organosolv Pulping.-Organosolv pulping is atwo-stage process involving hydrolysis (decomposition of the wood by dilute acids or enzymes) and the removal of lignin with an organic solvent, usually a mixture of alcohol and water. The still-experimental process is suitablefor both hardwoods and softwoods. Pulp recovery from organosolv pulping ranges between 50 and 60 percent for hardwoods, and 40 and45 percent for softwoods. Typical hardwoodfiber recoveries compare favorably with those from kraft pulping: approximately 50 percentfor red alder, sweetgum, and American sycamore, and 60 percent for cottonwood and trembling aspen. Fibers produced by the organosolv process are weaker than those recovered by the kraft process, Thus, the papers produced from organosolv pulp are suitable for uses where strength is not the most important property, such as for printing papers, fluff pulps, and dissolving pulp, Reaction temperatures are low—between 320° and 370° F for hardwoods and 360° to 390 0 F for softwoods if acid catalysts are used. Little waste is produced by the process, andlow alcohols are recovered easily by distillation, thus requiring relatively low capital investment .57
Oxygen Pulping.—An extension of existing oxygen bleaching technologies, oxygen pulping may reduce or eliminate the need for bleachingplants in the paper mill. Oxygen pulping involves the introduction of gaseous oxygen intothe pulping liquor to stimulate oxidative fracture of the cellulose-lignin bonds. This process could save capital and operating costs because equipment costs are lowered, less bleaching chemicals are used, and pollution control expense is cut by eliminating chlorine from the bleaching process.
The cost of oxygen pulping is largely a function of the cost of oxygen. Oxygen production requires approximately 400 lbs of oxygen and 54 kWh/ton of pulp produced (based on 1.2 kWh/hundred cubic feet(H3),or0.135 kWh/lb.Several manufacturers currently are developing plant equipment capable of applying oxygen pulping commercially.

PRESS DRYING PAPER Press drying technology developed at FPL shows promise for both reducing the amountof energy required in the paper-making process and enabling the use of underutilized hard**57N Sa**  **~, b.er,**  **.$ta tcls**  of N~t%F Pulping Processes; Problems (i tl[] pe~s~ectjl,es (~fa~ison, Wis,: U.S. Forest Product I.aborat(}r}, 1982], p. 10,92 ● Wood Use: U.S. Competitiveness and Technology

wood species. Press drying uses high-yield hardwood or softwood kraft pulp to produce linerboard with strength superior to that ofconventional softwood kraft paper in every respect except tear strength (table 30). At the same time, press drying can reduce the amountof energy used in the drying process by applying pressure to the fiber (pulp) mat as it is dried. With conventional drying technology, pressure and heat are applied separately. The superior strength of press-dried paper comes from the combined effects of heat andpressure, which force the fibers into closer contact and cause stronger bonds to be formed between them. The heat and pressure also cause natural polymer flow and cross-linkages amongthe fibers as a result of the hemicellulose contained in the pulp. Paper produced from pressdrying kraft red oak pulp has been shown tohave burst strength and tensile strength approximately 13 percent higher, and compression strength 50 percent better, than that of conventionally dried pine kraft paper. The lower tear strength of press-dried hardwood paper may limit its use for wrapping or sack paper; however, its higher burst strength and tensile strength make it suitable for linerboard.
Estimates of the potential net energy savings from using press-drying technology are about 19 percent for the papermaking process, 58 Although a commercial-scale, press-dried papermaking machine has not been built yet, pressdrying may actually reduce equipment requirements and capital investment in both the drying section and the pulping process because it can use unrefined pulp. 59 The major limitation to press drying paper, which must be overcome before the technology can be appliedcommercially, is the low speed of the papermaking machine and the resulting slow production rate of the pilot-scale equipment used at the FPL.

Dissolving Pulp Technologies
Dissolving pulp technologies are not pulping technologies as such, but secondary processesthat produce nearly pure cellulose (alpha-cellulose) for conversion to rayon, plastics, and other chemicals. Pulps made by either the kraftor sulfite process are purified further chemically to remove all hemicellulose and leave only pure cellulose, which then can be transformed into products like viscose rayon, cellophane, and acetate fibers and film. The largest single use for dissolving pulp is in the viscose rayon process, which accounts for over 99 percent of the world’s rayon production. A variety of hardwood and softwood species is suitable for the production of dissolving pulp, including pine, hemlock, spruce, oak, birch, and gum. Highly resinous wood, such as Southern yellow pine, normally is not used for dissolving pulp because of the difficulty ofremoving extractives in the purification process. The highest grades of dissolving pulp are called cord, acetate, and nitrate pulps, which approach 98 percent pure cellulose; normal grades of viscose rayon pulp contain some hemicellulose and maybe only 93 percent pure. Because of the need for nearly pure cellulose,

“v. Setterholm and Peter Ince, “The Press Drying Concept for Papermaking, ” Southern Lumberman, Dec. 15, 1980. 59P. J. Ince, “FPL Press Drying Process: Wood Savings in Linerboard Manufacture,” TAPPI, vol. 64, 1981, p, 109,

Table 30.—Strength Properties of Press-Dried Hardwood Paper and Conventional Softwood Paper

Anticipated Present Conventional strength strength strength with oak with oak with pine Burst strength (lb/in w) a . . . . . . . . . . . . . . . . 155 145 97 Tensile strength (lb/in w) . . . . . . . . . . . . . . . 100 68 54 Compression (lb/in w) . . . . . . . . . . . . . . . . . . 45 30 20 aPounds per inch of width SOURCE U S. Forest Products Laboratory, 1981Ch. lIl—Pulp, Paper, and Fiber Products ● 9 3

pulping yields for the kraft and sulfite processes are reduced to approximately 28 to 38 percent, depending on the pulp purity desired. The low yield of high-quality, alpha-cellulosepulps makes them expensive to produce—energy and pulpwood costs account for 50 to 60 percent of the manufacturing costs. 60
Total U.S. production of dissolving wood pulp was approximately 1.5 million short tons in 1979 (23 percent of world production). Approximately 61 percent of the dissolving pulpproduced was used for textile fibers; the remainder was used for the manufacture (in descending order) of chemicals and plastics, cellophane, cellulose nitrate (for propellants), andspecialty papers for use in industrial and automotive filters. In addition to the viscose rayon process for the production of fibers and cellophane (whichis made by the same viscose process but is extruded through a slot to form film rather than through holes to form threads), cellulose may be converted into acetate forms (acetyl esters)that can be manufactured into cellulose acetate, cellulose diacetate, and cellulose triacetate for conversion into fibers. Cellulose nitratecontinues to be produced in significant quantities as an explosive and a propellant. Other products manufactured from dissolving pulpinclude ice cream thickeners, detergents, carbon fibers of high strength and stiffness, and gels used in hand lotions and food products.

Rayon Manufacture Rayon, first made in 1881, is the oldest manmade synthetic fiber. The success of rayon in the

●

● market is due to several factors:
Cellulose continues to be the cheapest polymer for fabrics. Rayon’s moisture absorption, capacity for absorbing dyes, and ability to swell makes it suitable for clothing. Rayon also can be blended with other synthetic fibers, like nylon, to improve their moisture-absorbing qualities.

OOC, B. Metz, “Dissolving Pulps-The Future Economic Situation, ” Proceedings of the 5th International Dis.~ol~in,g Pulp.s Conference **(~’ienna, Austria:**  **Oct.** 8-10, 1980). ● properties of the dissolving pulp can be varied to produce pulps suited for specific end uses. For example, ITT Rayonier, a leading U.S. producer of dissolving pulps, offers 16 grades of pulp matched to the properties of the rayon to be produced.Rayon is made by dissolving cellulose xanthate in alkali and spinning the fiber through small pinhole jets into a sulfuric acid bath, which coagulates the fiber into final form. If the same xanthate-viscose solution is forced through a narrow slit, a cellophane film is formed.
Major developments in rayon technology have been aimed at:improving the efficiency of rayon production; reducing energy requirements; controlling or eliminating environmental pollutants generated by the viscose rayon
process;developing more cottonlike rayons to supplement cotton production; and developing a completely new system for converting chemical cellulose to fiber by a nonviscose, environmentally sound, more efficient process using recoverable cellulose solvents. 6l
Major emphasis has been placed on developing a rayon with a high wet-strength to remedy the shortcomings of conventional rayon and to compete with cotton more effectively.A number of new fibers outperform conventional rayon; they include Courtauld’s “Corval, ” a cross-linked fiber; American Viscose’s “Avril”; and Enka’s “Fiber 700. ”Process developments within the rayon industry seem to be moving toward automation and computer control. Experts foresee new, versatile rayons made by solvent-extrusionprocesses similar to those used for making nylon and polyester. These may lead to a future one-step process from pulp to viscose solution; however, many of the current developments i n this area are treated as proprietary and are no t open to inspection

.

“G, Daul, “Rayon Revisited, ” Chemtech, Februarj 1981, p. 84.94 ● Wood Use: U.S. Competitiveness and Technology

The viscose process is one of the most versatile for manufacturing textile fibers. Modification of the viscose manufacturing processeasily can accommodate stretching and orienting the fiber and building certain desired properties into it. For example, it is known that the addition of metallic salts, such as zinc and other modifiers, will delay the reformation torayon to allow time for spinning and manipulating the fiber. Formaldehyde also has beenfound to be an effective modifier for the production of super-strong fibers; however, environmental problems associated with it must still be overcome. 62
Research to improve the strength and performance of rayon materials continues. These efforts include the search for new solvents for use in the spinning (forming) process. One suchprocess that shows promise uses a special solvent (methyl-morpholine-N-oxide, MMNO) to orient the molecules in solution to form rayon with high-strength cellulose fibers. Success ofthe MMNO process may depend on development of a solvent recovery system needed to make the manufacturing process economically competitive. 63 Some experts see the testing ofother new solvents leading to a major new system for manufacturing rayon. 64

Other Cellulosic Products

A number of other from dissolving pulp.
‘Z1bid., l]. M. products can be made

For example, cellulose

**L33R, N.**  **Armstrong,** C. C. McCorsky, and J. K. Varoa, ‘‘Spinnable Solutions of Cellulose Dissolved in Amine Oxides, ” f%octxxiings of

the 5th International llissol~’ing PUII>S Conference [Vienna, Austria: oct. 8-10, 1980).

**~411, I,.**  **Hergert,** R. B. Hammer, and A. F. Turbak, ‘‘New Methods for Preparing Rayon, ’ Proceedings of the 4th International Dissol~ing Pulps Conference (Chicago, 111.: Sept. 28-30, 1977), acetate is produced by steeping dissolving pulp or cotton liners in acetic acid to prepare fibers for conversion to acetate, This same process may be used to produce cellulose butyrate and cellulose propionate for the production of plastics. An acetate of slightly different chemical form, cellulose triacetate, also can be madefrom dissolving pulp. Unlike rayon, it is waterrepellent like nylon, orlon, and terylene. Its water repellency is attributable to the degreeof acetylation of the fibers. It has good thermal properties and wear characteristics, and frequently is used in fabric blends with nylon, wool, and rayon in women’s clothing.Cellulose esters—acetate ester, acetate butyrate, and acetate propionate—are a family of plastic materials derived from dissolving pulp that can be formed, molded, and extruded by a variety of thermoplastic processes. Higher forms of these materials also maybe prepared; however, their high production costs restrict them to highly specialized applications such as cellulose acetate phthalate, which is used as a coating on pharmaceuticals. Cellulose esterpowders are used in fluidized-bed and electrostatic coating processes, as well as in rotationalmolding processes. Modified cellulosic polymers are used in preparation of films, coatings, fibers, lacquers, and adhesives, Finally, dissolving pulps also may be used toproduce a variety of chemical products, including methyl- and carboxymethyl-cellulose, that are used as thickeners in latex paints and ice cream; ethylcellulose, used as a thermoplastic molding compound; and nitrocellulose, used as a propellant/explosive.