246 Evaluation of beetle-killed white spruce for pulp and paper

RICHARD A. WERNER Institute of Northern Forestry, Pacific Northwest Forest and Range Experiment Station, United States Department of Agriculture Forest Service, Fairbanks, AK, U.S.A. 99701

E RWIN E. ELERT Forest Products Laboratory, United States Department of Agriculture Forest Service, Madison, WI, U.S.A. 53705

AND

EDWARD H. HOLSTEN Forest Pest Management, State and Private Forestry, United States Department of Agriculture Forest Service, Anchorage, AK, U.S. A. 99504 Received April 19, 1982 Accepted November 17, 1982

WERNER, R. A., E. E. ELERT, and E. H. HOLSTEN. 1983. Evaluation of beetle-killed white spruce for pulp and paper. Can. J. For. Res. 13: 246-250. A kraft pulping study on standing white spruce (Picea glauca (Moench) Voss) killed by spruce beetles (Dendroctonus rufipennis (Kirby)) in south central Alaska showed no difference in pulp yield between trees dead for 1 year and those dead for as long as 50 years. Strength properties of beetle-killed white spruce remained extremely high in all dead trees regardless of how long they had been dead, so they apparently could be used for producing high-quality kraft pulps. These are the first results reported in which standing trees dead for as long as 50 years produced high-quality bleached and unbleached pulps.

WERNER, R. A., E. E. ELERT et E. H. HOLSTEN, 1983. Evaluation of beetle-killed white spruce for pulp and paper. Can. J. For. Res. 13: 246-250. Une étude de fabrication de pâte kraft à partir d’épinettes blanches (Picea glauca (Moench) Voss) sur pied tuées par le dendroctone de l’épinette (Dendroctonus rufipennis (Kirby)) au centre sud de l’Alaska n’a révélé aucune différence dans le rendement en pâte entre des arbres morts depuis 1 an et ceux morts depuis aussi longtemps que 50 ans. Les propriétés mécaniques de l’épinette blanche tuée par le dendroctone se sont conservées extrêmement bien chez tous les arbres morts peu importe depuis combien de temps, de telle sorte que de toute évidence ils peuvent être utilisés pour la fabrication de pâte kraft de haute qualité. C’est la première fois qu’on rapporte que des arbres morts depuis aussi longtemps que 50 ans, encore sur pied, produisent des pâtes blanchies et non blanchies de haute qualité. [Traduit par le journal]

Introduction owing to depressed wood product markets. To establish During the past 10 years, outbreaks of the spruce the possibility of extending the harvest, we studied the beetle (Dendroctonus rufipennis (Kirby)) have infested relation of pulping characteristics of beetle-killed white about 920000 ha of white spruce (Picea glauca spruce to how long the trees had been dead. (Moench) Voss) in south central Alaska. Numerous Several similar studies on true firs (Dyer and Thaxter spruce beetle outbreaks have occurred throughout south 1957; Balch 1951; Shea et al. 1962), eastern hemlock central Alaska, dating back to the 1920’s. One such and balsam fir (Hiscock et al. 1978), and jack pine outbreak (1968-1973) in the Tyonek area (Fig. 1) in­ (Heinig and Martin 1949) indicated pulping qualities fested 49 000 ha of mature white spruce. Volume killed were poor in trees dead for 4 years or more. High yields amounted to 179 m 3 of pulpwood or 80% of the white of quality kraft pulp were produced from defoliated jack spruce volume in the infested area. pine trees that had been dead from 1 to 7 years (Hunt Properties of beetle-killed white spruce vary with the and Benoit 1979). Yield of kraft pulp was not affected length of time trees are dead, and whether stem decay in beetle-killed southern pine trees dead for 2 years. but was present at the time of tree mortality. Blue-stain paper quality was reduced as the wood deteriorated on fungi and checking occur in trees within 4-5 years after the stump beyond 2 years (Ifju et al 1979). the trees die but do not degrade the wood for pulp chip utilization. Harvesting of beetle-killed trees is usually Methods impossible because most of the infested areas in south Sample collection central and interior Alaska are inaccessible, lack paper- Five sites located on south aspects or flat areas and that mills, or foreign industry is not interested in raw pulp contained standing trees killed by spruce beetles were sam- WERNER ET AL 247

FIG. 1. Study area and sampling sites pled from 1975 to 1979. Four sites were in south central Alaska and one was at Haines Junction, Yukon Territory, at a latitude of ca. 61° N. These sites were selected because the length of time the trees had been dead was known through records of the beetle infestation. Selected trees were dead for 1, 6, 20, 30, and 50 years. Trees from each site had been dead for the same number of years. A 1-m-long log was cut from each of 10 dead trees and 10 live green trees per site midway from the base to a point where the stem was 10 cm in diameter. Logs were immediately wrapped in burlap and sent to the Forest Products Laboratory. Madison, Wisconsin, for physical and chemical analyses and pulping evaluation. Chipping and pulping Samples from each log were taken to determine physical and chemical characteristics (Table 1). Bark was mechani­ cally removed from green logs. whereas the loose bark on dead logs was removed by hand. Hatton (1978) showed that mechanical debarking of spruce and fir trees killed by spruce budworm removes much of the decayed sapwood and is the most economically critical step in the chipping process. The majority of beetle-killed trees dead for more than 20 years contained no bark. Chips 15.9 mm long were made in a conventional four-knife disk chipper: sawdust and oversized pieces were discarded. Chips retained on the 3-mm slotted screen were mixed together for the 10 dead log samples from each site. This was repeated for green logs prior to kraft digestion. Kraft pulping conditions were selected to give different yields from each site (Table 2). All digestions were made in a stationary, 22-L, stainless steel digester equipped with a heat exchanger and a liquor-circulating system using indirect steam heating throughout. At the end of each digestion. the liquor was blown from the digester, and chips were immedi­ ately washed in the digester with 90°C water. The digested chips for the bleachable pulps were transferred to a stainless steel tank with an electric agitator and disintegrated to pulp at 2% consistence using 90°C water. The resulting pulps were then screened through a flat screen with 0.305-mm slots, dewatered, and sampled for determining yield and Kappa number. The semichemical cooked chips were ground in a 248 CAN. J. FOR. RES. VOL. 13, 1983

20.3-cm attrition mill to pulps with Canadian Standard free- pled for yield, as before, without screening. Handsheets were nesses of about 700. The pulps were transferred to the tank tested for physical properties according to TAPPI standard and agitated at 2% consistence at 90°C. dewatered, and sam- methods.

TABLE 2. Conditions used in kraft pulping* of beetle-killed Alaska white spruce

Time Time at Active after maximum alkali Total† mortality temperature charged yield Kappa Source (years) (min) (%) (%) No. Tyonek 1 115 18.0 47.0 30.3 1 55 16.0 54.0 75.0 1 25 15.5 58.7 115.5 Tyonek 6 90 19.0 48.6 35.2 Palmer 20 100 18.0 45.4 34.6 20 40 16.0 51.8 85.5 Haines Junction 30 100 18.0 46.3 30.7 30 40 16.0 53.3 82.3 Chitina 50 100 18.0 46.2 30.2 50 30 16.0 54.3 97.0 50 20 15.5 59.I 112.0 Green wood Fresh 90 17.0 46.5 36.5 Fresh 120 19.0 45.4 23.4

*Constant cooking conditions used in all digestions: 25.0% sulfidity, liquor-to-wood ratio of 4 to 1, 90 min for temperature rise from 80°C to the maximum temperature of 170°C. Tests made according to TAPPI standard methods †Moisture-tree wood basis.

TABLE 3. Strength properties* of unbleached and bleached white spruce pulp

Beating time at Burst index at freeness, minutes freeness, KPa·m2/g Time after (Canadian standard) (Canadian standard) mortality Kappa Source (years) No. 600 mL 500 mL 300 mL 600 mL 500 mL 300 mL Unbleached Tyonek 1 30 21 38 62 10.3 11.2 11.7 1 75 49 69 96 10.8 11.6 12.0 1 115 79 101 129 10.7 11.0 11.0 Tyonek 6 35 19 34 57 10.6 11.5 11.7 Palmer 20 35 12 29 58 9.2 10.3 10.9 20 85 55 80 123 9.9 10.0 11.0 Haines Junction 30 31 13 29 57 9.3 10.3 10.9 30 82 60 82 118 9.8 10.4 10.9 Chitina 50 30 23 40 67 10.6 11.4 11.8 50 97 57 80 112 11.4 11.8 11.4 50 112 75 100 128 10.2 10.6 11.0 Green wood Fresh 36 25 43 68 12.0 12.8 12.9 Fresh 23 20 35 59 11.8 11.9 12.6 Bleached† Tyonek 1 30 12 24 45 9.7 11.2 12.7 Palmer 20 35 1 14 43 7.4 9.5 11.1 Haines Junction 30 31 5 17 50 7.8 9.7 11.2 Chitina 50 30 13 26 45 9.8 11.2 12.3 Green wood Fresh 36 10 15 40 9.6 10.9 11.9

*Tests made according to TAPPI standard methods †Five-stage CEDED bleaching process. WERNER ET AL 249

Statistical analysis unimportant and did not apparently result in serious loss The physical and chemical characteristics of individual of wood properties or pulp quality (Tables 1 and 3). The trees representing six different treatments were compared by content of alcohol-benzene and hot-water extractives a one-way analysis of variance. Duncan’s multiple range test of the aged dry wood was. as expected, less than green was used to compare individual means of the six treatments wood, except for wood aged for 20 years from the for significant differences. Palmer area. Noticeable differences were found between the wood Results and discussion samples in cooking time at maximum temperature to a Some differences in the physical and chemical prop­ given Kappa number (Table 2). but this had almost no erties of the dead wood samples may not be attributable adverse effect on the pulp strength. which was typical to beetle killing and subsequent seasoning of the wood. of white spruce (Table 3). The apparent increase in but to the ages and location of the trees (Table 1). There yields for the dead wood at a given Kappa number is was insignificant variability in the physical and chem­ probably because of differences in the loss of water- ical properties of green wood; therefore, data were soluble extractives (Table I) that occurred as the dead combined for all sampling sites. As expected, moisture wood lost its bark. content of the wood decreased with time since death; Comparison of strength properties of handsheets however, differences in percent moisture content be­ (Table 3) indicated only a slight loss of strength in the tween trees dead for l and 50 years were insignificant burst factors and breaking lengths of the beetle-killed compared with green, fresh-cut wood. pulp, but the tear factors remained equal to those of The blue stain in all dead logs was less than 20% of pulp made from green, fresh-cut spruce. Part of these the sapwood portions, and only the green wood samples small differences may reflect no more than the inherent were free of dark stains. The amount of decay in all variability of fresh wood from the five sites. dead logs was less than 10% and nonexistent in green Pulps were bleached without difficulty to high bright­ logs. There was less than 5% decay visible in the ness, using a conventional five-stage process, with screened chips. and this small amount of decay was nearly complete retention of tear and breaking length

TABLE 3. (Continued)

Tear index at Breaking M index at Density at freeness, freeness, mN · m2/g freeness, N · m/g kg/m3 (Canadian standard) (Canadian standard) (Canadian standard) Brightness, 600 mL 500 mL 300 mL 600 mL 500 mL 300 mL 600 mL 500 mL 300 mL Elrepho

Unbleached 10.6 9.8 9. 1 134 141 141 750 790 810 30.3 9.9 9.3 8.9 134 141 145 730 760 790 21.7 9.2 8.6 8. 1 132 134 136 720 750 770 19.8 11.6 10.0 9.4 129 137 143 720 760 780 31.6 10.8 9.6 9.2 116 129 138 730 770 810 27.5 9.2 9.2 7.8 120 128 132 690 730 770 22.3 10.2 9.0 8.1 116 129 138 740 780 830 28.3 8.3 7.8 7.6 119 130 I36 720 750 780 22.8 10.4 9.3 9.0 134 141 147 750 780 810 28.3 8.4 8.0 8.6 137 141 141 740 770 790 20.7 8.3 7.9 7.8 130 135 133 710 750 780 20.2 10.8 9.5 8.9 143 153 154 740 780 820 27.3 12.0 10.3 9.6 140 149 154 740 780 820 30.9 Bleached† 12.5 10.0 8.3 126 142 152 780 800 830 93.1 12.9 9.7 8.5 90 120 138 770 800 820 90.8 12.4 9.8 8.0 95 114 142 740 820 860 92.1 10.7 9.5 8.7 130 142 150 770 800 820 92.6 12.1 10.1 8.9 128 138 153 760 810 840 92.9 250 CAN J. FOR RES VOL 13. 1983 properties. Burst factors at the 600- and 500-mL free­ Acknowledgments ness levels of bleached beetle-killed and green, fresh- We thank P. Rush, R. Wolfe, and K. Zogas, United cut wood pulp were lower than unbleached green wood States Department of Agriculture Forest Service, and and beetle-killed wood pulps. J. S. Monts, K. Guttman, and D. Morgan, Yukon The strength properties of beetle-killed standing Forest Service, for their technical assistance. and spruce remained high in all dead trees regardless of how J. S. Hard, G. R. Sampson, N. Sanyer, D. Woodfin, long they were dead: therefore. sound and dried dead and K. Kilborn, United States Department of Agricul­ trees should be suitable for producing high-quality kraft ture Forest Service. for reviewing the manuscript. pulps. So far as we know. this is the first report of standing trees dead for as long as 50 years producing BALCH, R. E. 1951. Studies of the balsam woolly aphid, high-quality bleached and unbleached pulps. Adelges piceae (Ratz.), and its effect on balsam fir. Abies Sound and dried beetle-killed spruce are usually balsamea (L.) Mill. Can. Dep. Agric. Publ. No. 867. found on south aspects or flat areas of south central DYER, H. L., and R. T. THAXTER. 1957. Yield and quality of Alaska. The low winter temperatures and short growing pulp made from balsam fir wood (Abies balsamea) pos­ season coupled with low moisture content of the beetle- sessing abnormally high density caused by the balsam killed trees probably preclude rapid biodeterioration. woolly aphid (Adelges piceae). Tappi, 40: 64A-74A. Beetle-killed spruce that contain stem decay prior to HATTON, J. V. 1978. Debarking wood losses and chip quality beetle attack would probably be unsuitable for wood of spruce budworm-killed softwoods in New Brunswick. pulp. Trees of this category have been found in over- Tappi. 61: 43-46. HEINIG, M., and J. S. ARTIN mature spruce stands located on north aspects in south M . 1949. Sulphate pulping of dead, standing jack pine (Pinus banksiana), U.S. Dep. central Alaska. These northern aspects receive less di­ Agric. For. Serv., For. Prod. Lab.. Rep. R1746. rect solar radiation during both winter and summer HISCOCK, H. L., J. HUDAK, and J. P. MEADES. 1978. Effect months and are usually characterized by a somewhat of saprot on pulping properties of balsam fir killed by the higher relative humidity than flat or southern aspects. eastern hemlock looper in Newfoundland. Newfoundland For. Res. Cent., Inf. Rep. N-X-161. Conclusions HUNT, K., and P. BENOIT. 1979. Kraft pulping of jack pine Forest resource managers should have ample time to killed by the Swaine sawfly. Can. J. For. Res. 9: 149-153. IFJU, G., K. G. ODERWALD, P. C. FERGUSON, and H. J. salvage standing beetle-killed white spruce if the trees HEIKKENEN. 1979. Evaluation of beetle-killed southern are sound and free from decay. in the presently inacces­ pine as raw material for pulp and paper. Tappi, 62: 77-80. sible areas of south central Alaska. knowing the product SHEA, K. R., N. E. JOHNSON, and S. MCK EE, 1962.Deteri­ potential of the dead wood. Logging of these stands oration of Pacific silver fir by the balsam woolly aphid. J. would be feasible if paper mills are developed locally or For. 60: 104. if out-of-state markets are found. Reprinted from Reimpression du

Canadian Journal Journal of canadien Forest Research de la recherche forestière

Evaluation of beetle-killed white spruce for pulp and paper

R. A. WERNER, E. E. ELERT, AND E. H. HOLSTEN

Volume 13 • Number 2 • 1983

Pages 246-250

National Research Conseil national Council Canada de recherches Canada

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