A Burning Question . . . Bark Utilization

The traditional conversion of wood through manufacture into lumber, plywood, veneer, and other commodities involves the generation of large volumes of residues. As timber costs have increased, more and more uses have been found for these wastes–Pres-to-Logs, pulp chips, and particleboard raw material, for example. Simultaneously, the volume of bark requiring disposal has increased, since virtually all logs are barked and the bark segregated. Bark disposal by burning, either as boiler fuel or in wigwam burners, has become more difficult as the proportion of bark to hogged wood increases and as air pollution becomes a greater concern. Estimates of bark volume available in Oregon range from 2 to 3 million tons annually of which about half is burned for fuel and most of the remainder in wigwam burners. Research on bark utilization has been going on for more than 20 years and has taken two major approaches: physical use and chemical use. Physical uses include the use of bark as a mulch and agricultural soil additive, as a decorative product in landscaping, and as a filler in plastic moldings. In regard to chemical uses, several potentially valuable bark constituents have been investigated by neutral or alkaline extraction. Some of them, for example dihydroquercetin, are chemicals of outstanding characteristics, but development will require market research, promotion and plant investment. One drawback to chemical utilization of bark is that even though extraction of a high value product may be economically feasible, some 90 percent of the original bark may remain and still require disposal. Large volume uses for bark must still be developed. A new major project is under way at Oregon State University’s Forest Research Laboratory on “Incineration or Alternate Use of Bark”. This project will involve research along six lines; 1) Study of burner modification and testing of promising leads, 2) Sanitary landfill, 3) National survey of bark markets, 4) Incineration, 5) Steam and electric power generation, and 6) Extractives from bark.

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