Utilization of Douglas-Fir Bark

FOREST :; LABORATORY LIBRARY I urig - ZAT ;DOUGLAS ,f. r, by J. ALFRED HALL ) ,C7 NORTHWEST FOREST AND RANGE EXPERIMENT STATION l' FOREST SERVICE, U.S. DEPARTMENT OF : -- , PORTLAND, OREGON 1971 CONTENTS Chapter Page I. SUMMARY AND CONCLUSIONS 1 Uses of Whole Bark 1 Physical Fractionation 2 Whole -Bark Extracts 2 General Chemistry of Douglas -fir Bark 3 Wax 3 Cork 3 Alkali Extracts 3 Fiber 4 Tannin 4 Dihydroquercetin and Quercetin 4 "Phenolic Acids" 5 Adhesive Compositions 5 I I . INTRODUCTION 6 III. ANATOMY 6 IV. USES OF WHOLE BARK 9 Fuel 9 Domestic Fuel 11 Pyrolysis 15 Producer Gas 16 Board and Tile Manufacture 20 Agricultural Use of Douglas -fir Bark 24 Toxicity 25 Grinding and Screening 25 Use as Mulch 26 Soil Conditioning 26 Ammoniation and Composting 26 Ornamental 27 Discussion 27 Related Patents 28 V. PHYSICAL FRACTIONATION 29 Uses of Physical Fractions . 33 Silvacons -- General 33 Drilling Muds 34 Cork in Boards and Floor Tile 35 Cork in Shell Wads 35 Cork in Patching Veneer 36 Fiber Fraction 36 Powder Fraction 37 Whole -Bark Extracts 37 VI. GENERAL CHEMISTRY OF DOUGLAS-FIR BARK 39 Chapter Page VII . WAX 43 VIII. CORK 47 IX. ALKALI EXTRACTS 48 X. FIBER 53 XI. TANNIN 58 XII. DIHYDROQUERCETIN AND QUERCETIN 68 XIII. "PHENOLIC ACIDS" 72 XIV. ADHESIVE COMPOSITIONS 84 XV. LITERATURE CITED 86 XVI. PATENTS CITED 95 XVII. APPENDIX 97 Photomicrographs of Douglas -fir cork 97 Letter from Sandy Hill Corporation 99 Letter from Government Forest Experiment Station, Meguro, Tokyo, Japan 101 Weyerhaeuser's Bulletin 10 -A 105 "A Review of the Chemistry of Quercetin" by A. S. Ryan (Weyerhaeuser Timber Co.) 109 Partial Bibliography on Quercetin in Pharmaceutical Use (Weyerhaeuser Co.) 135 Pharmaceutical and Medical References for Quercetin (Weyerhaeuser Co.) 136 CHAPTER I SUMMARY AND CONCLUSIONS The Douglas -fir region produces annually about 1.5 million tons of bark that must be disposed of some way. Existing outlets are taking substantial quantities of bark, but cannot effect much reduction in the pile of waste bark. Increasing public demand for abatement of air pollution, e.g., from "wigwam burners," makes imperative exploration of all possibilities of commercial use of Douglas - fir bark. The physical and chemical makeup of old- growth Douglas-fir bark is unique and lends encouragement to increased attempts to find uses for it. USES OF WHOLE BARK Power fuel. --There are indications of expanding use of bark for generation of power, especially for the forest products industries and metropolitan or smaller municipal areas. Domestic fuel.-- As for domestic fuel, it appears that existing equipment is cap- able of making satisfactory briquets of Douglas -fir bark, similar in usefulness to the well known "Presto-Log." Increasing use of planer shavings for other purposes than compressed fuel may encourage use of bark for domestic fuel in the form of pressed logs. Pyrolysis and charcoal manufacture. -- Charcoal can be made from Douglas -fir bark by conventional methods of dry distillation, and some production of charcoal briquets from bark has begun rather recently, but with no recovery of the products of distillation. The yield of charcoal from Douglas -fir bark is considerably higher than from wood. Considering the chemical composition of Douglas -fir bark, I suggest that research be conducted on pyrolysis under reducing conditions, at relatively low temperatures and under high vacuum in order to recover possibly valuable products. Such recovery might make pyrolysis of bark quite profitable. Board and tile manufacture. -- Much work has been done on the use of barks for board and tile manufacture, or in molding compounds for various uses. Most of this work has been done in Europe where appreciable quantities of board are made from various barks. As for Douglas -fir bark, work has been done mostly in taking advantage of the plastic and thermosetting properties of the raw material without additives. Some commercial production of boards containing large proportions of bark has been carried out, and some continues. Suggestions are made for further research in the field of use of Douglas -fir involving use of the basic, known, chemical features plus additives, in attempts to improve the usefulness of the bark or its physical fractions. As old- growth fir is exhausted, the use of second- growth bark, with lower content of cork, will bring about changes in technique. Agricultural use. --Dr. W. B. Bollen of the Pacific Northwest Forest and Range Experiment Station estimates that about 100,000 tons of bark per year are used for agricultural purposes in the Pacific States. Dr. Bollen's extensive work in the field gives the basis for proper use of bark as mulch or soil improver and amendment, with much fine data on proper use of nitrogen with bark. Present unsystematic marketing of raw, ground bark is expected to develop into better organized production and specific uses on specific soils. Various additives and methods of improvement are cited and discussed. Suggestions are offered for treatment of dry bark with anhydrous ammonia and subsequent heat treatment with formaldehyde to produce a product with bound nitrogen in slowly available form. A review of the considerable amount of related literature dealing with other barks is presented. PHYSICAL FRACTIONATION An historical survey is given of the many efforts to develop and market products based on physical separation of the bark into its principal fractions: cork, fiber, fines. The surviving industry producing these fractions is at Longview, Wash. (Weyerhaeuser Co.). The patents involved are listed and discussed, along with the multitude of uses suggested. Twenty years' experience by Weyerhaeuser Co. in producing and marketing the physical fractions have resulted in a continuing business of modest size. One of the best markets has been for fines in drilling muds. Considerable success has also been obtained in fields of use for the cork fraction. The fiber fraction has been found quite satisfactory for wide use in reinforcing certain plastics, especially when further refined by chemical means. A major difficulty in the field of marketing physical fractions has been uneven demand. Physical fractionation as the basis for a multiproduct business might give greater flexi- bility. WHOLE -BARK EXTRACTS More work has been reported on extracts from whole hemlock bark than for Douglas - fir. A large amount of effort is reported on combinations of "polyphenolic extracts, " with formulations for use in resins. Water extracts and various alkali extracts, along with various condensing agents, are described. Also, uses of extracts for drilling muds, tanning agents, etc., are listed. Some of this work has led to successful businesses, mostly applied currently to hemlock but with appreciable inroads being made by Douglas -fir. The usefulness of crude aqueous or alkaline extracts of whole bark might be expanded by better knowledge of their actual chemical composition. 2 GENERAL CHEMISTRY OF DOUGLAS-FIR BARK In spite of the expenditure of much manpower and money, the general chemistry of Douglas -fir bark remains unsatisfactory from the point of view of a basis for successful diversified chemical industry. The raw material is highly variable, according to age of tree, height in the trunk, and probably site. Good information is available on the nature of the wax and cork fractions, although the nature of the "phenolic acid" component of the latter is still open to much questioning. This class of materials, the phenolic acids, comprises most of the fines fraction and is a component of the fiber fraction, both products of physical separation. Dihydroquercetin is the only specific pure chemical thus far obtained in quantity, and its markets are limited. WAX Wax is obtained by solvent extraction of whole bark and from the cork fraction after treatment with alkali. During the 1950's, considerable interest was shown in Douglas -fir bark wax for commercial development. Decreasing use of the natural waxes, along with economic problems of a single product industry based on bark, have caused failure of any commercial production. Earlier indications of combined production of wax, tannin, and dihydroquercetin were not realized. The composition of the wax is reasonably well known, not offering any physical superiorities over other better known natural waxes. In the future, if demands for natural waxes increase, or costs of production of Douglas -fir bark wax decrease by virtue of a multiproduct industry based on bark, wax by direct extraction and by hydrolysis of cork might become important. CORK The physical cork fraction has been rather well characterized, except for the phenolic acid content. It contains dihydroquercetin in considerable percentage (mostly over 15 percent). Wax content varies from 5 -10 percent. The hydrolyzed wax (alkali) yields an array of hydroxy acids and unsaturated fatty acids, along with around 40 percent of phenolic acids. Much more work should be executed to determine: (a) The nature of the phenolic acids from cork. (b) The mode of combination of these with the wax acids. ALKALI EXTRACTS The voluminous work on various alkali extracts and their proposed uses is reviewed. Much of the work, especially by Weyerhaeuser Co., led to a pilot scale operation and some attempts to market various fractions for various purposes. The concept of solvent 3 extraction of wax components from the alkaline extract was developed. But, with the exception of limited success in invading the drilling mud field, little of lasting value seems to have been accomplished. Again, it seems clear that much more intensive work in the basic chemistry of Douglas -fir bark must be done before accurate guides can be developed for commercializa- tion. FIBER The crude fiber fraction of the bark, physically separated, averages around 40 percent. The older trees have bark of lower fiber content, the younger ones, higher. In future processing of young-growth bark, the recovery of values from the fiber should be increasingly important.

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