Expanding the Use of Wood Residues for Pulp Production

A continuing increase in per capita paper consumption will increase demand of raw material for pulp production. In Oregon, more pulp and paper expansion is based on utilizing the large volumes of mill residue available from sawmills and veneer operations. Usage of Oregon mill residue has increased from 1,360 tons in 1944 to 863,000 tons (0.D.) in 1955. Current supply of residue is in excess of 2,000 tons per day. Mills which have installed barkers and chippers have found residue recovery to be higher than expected 0.7 units compared to 0.5 units per 1000 board feet. Two specific problems that could limit expansion of the paper industry are assurance of long term wood supply and limitation in usability of Douglas-fir pulp. Long-term continuous expansion of the paper industry in the state is dependent also on research to: 1) Increase raw material available through closer utilization of all wood residues. 2) Increase yield of pulp per unit of wood. 3) Increase utility of pulps produced. Likelihood of using logging residues will be increased by developing: 1) Methods of removing bark in the woods. 2) Means of separating bark from chips. 3) Processes and products that will tolerate appreciable amounts of bark. Close utilization of wood residues should include use of hardwoods, sawdust and planer shavings. In Oregon, large stands of several hardwoods species are unexploited. Investigations of their pulping potentialities would be desirable. Sawdust is used for filler pulps and require special digesters. Shavings produce better pulps but present handling problems because of their low bulk density. Process developments, particularly in the production of high yield pulps, will result in maximum utilization of residues. Complete residue utilization in the Northwest depends on extending the usefulness of Douglas-fir pulps. Limitations of Douglas-fir as a pulp species stem from the tendency of its fibers to darken with exposure to heat, light, and chemical processing, its resistance to bleaching, and its fibers characteristics which are not well suited to use in sheets where softness, printability, and dimensional stability are important. It is desirable to devise methods of pulping Douglas fir or treating its pulp to enlarge the number of types of papers in which it can be used. The Oregon Forest Products Laboratory currently is working on two projects to extend use of Douglas-fir pulps. One project is concerned with manufacture of corrugating medium and the other with manufacture of newsprint.

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