Chemicals from Douglas-Fir Bark

Douglas-fir sawlog bark was found to contain 25 percent to greater than 50 percent cork, 30 to 42 percent bast fibers, and 20 to 35 percent amorphous powder. These factions contained 40, 20, and 34 percent, respectively, of extractives, with sound, whole bark containing 25 to 30 percent extractives. Destructive distillation of the bark yielded 45 percent charcoal, 10 percent tar, and 18 percent combustible gases. Commercially extractable quantities of tannin, wax, and flavanones were found. The bark yielded 7.5 to 18 percent hot-water-extractable tannin with the greatest quantities found in second-growth timber 57 to 70 years of age and the tops of older trees, and the least found in the butt logs of old-growth trees. Hand-peeling gave the greatest tannin yields, 200 pounds of tannin per ton of bark. Douglas-fir tannin was found comparable to quebracho tannin for all major industrial uses including leather tanning, petroleum industry uses, and concentration of low grade iron ores. A 7.5 percent yield of wax was obtained, 5 percent soluble in petroleum-type hydrocarbons and 2.5 percent soluble in aromatic or chlorinated hydrocarbon solvents. The components of the hexane-soluble waxes, such as ferulic acid, afford modification of wax properties and may be used for conversion into vanillin. Certain fiavonoids and their derivatives and related compounds were found in commercial quantities. Dihydroquercetin was found in yields up to 7 percent. This compound, along with quercetin and its glucoside, rutin, are valuable products in the pharmaceutical trade. The extracted bark residue was found useful for fuel, soil conditioners, and in destructive distillation or for mechanical separation of cork, bast fibers, and other bark products. A listing of extraction equipment is presented.

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