Pulpability of 


Beetle-Killed Spruce

United States


Department of


Agriculture


Forest Service


Forest


Products


Laboratory


Research


Paper


FPL–RP–557 Gary M. Scott


David W. Bormett


Nancy Ross Sutherland


Said Abubakr


Eini Lowell
Abstract

Infestation of the Dendroctonus rufipennis beetle has resulted

in large stands of dead and dying timber on the Kenai Peninsula in Alaska. Tests were conducted to evaluate the value of

beetle-killed spruce as pulpwood. The results showed that

live and dead spruce wood can be pulped effectively. The two

least deteriorated classes and the most deteriorated class of

logs had similar characteristics when pulped; the remaining

class had somewhat poorer pulpability. The more deteriorated wood required the same or slightly less refining energy

to achieve a certain level of freeness. The presence of sap rot

decay was found to be an important indicator of pulping

efficiency and resultant pulp quality. Log deterioration had

mixed effects on paper properties.

Keywords: pulp, spruce, sap rot, Dendroctonus rufipennis

August 1996

Scott, Gary M.; Bormett, David W.; Sutherland, Nancy Ross;

Abubakr, Said; Lowell, Eini. 1996. Pulpability of beetle-killed spruce.

Res. Pap. FPL–RP–557. Madison, WI: U.S. Department of

Agriculture, Forest Service, Forest Products Laboratory. 8 p.

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Pulpability of Beetle-Killed Spruce

Gary M. Scott, Research Chemical Engineer

David W. Bormett, Chemical Engineer

Nancy Ross Sutherland, General Engineer

Said Abubakr, Supv. Chemical Engineer

Forest Products Laboratory, Madison, Wisconsin

Eini Lowell, Research Forest Products Technologist

Pacific Northwest Station, Portland Oregon

Introduction

Infestation of the Dendroctonus rufipennis beetle has resulted

in large stands of dead and dying timber on the Kenai Peninsula in Alaska. White spruce (Picea glauca (Moench) Voss)

is the major species affected along with the hybrid lutz spruce

(Picea lutzii Little). Once infested, the trees are attacked by

decay organisms such as fungi and other microorganisms.

Because post-infestation time may affect the pulpability of the

wood and resultant paper properties and because the beetle

has killed a large amount of timber, tests were conducted to

evaluate the value of the beetle-killed material as pulpwood.

This study is part of a larger project investigating the recovery of beetle-killed material for a variety of end uses (Lowel1

1993).

A primary effect of beetle infestation is the elimination of a

tree’s natural defenses against fungal decay. Hundreds of

species of fungi have been identified in wood. These have

been broadly categorized as brown rot, white rot, soft rot,

and sapstain or sap rot fungi (Parham 1983). Brown rot fungi

preferentially attack cellulose and hemicellulose

(carbohydrates), which leads to reduction in pulp quality and

yield. Soft rot fungi tend to attack both carbohydrates and

lignin, discoloring and softening the wood; pulp quality is

generally degraded. White rot fungi also tend to attack both

lignin and carbohydrate components, but some of these fungi

preferentially attack lignin. Thus, yield and quality may not

be as affected by the presence of these fungi. Sapstain fungi

are usually found in the sapwood of softwoods; these fungi

mainly attack stored carbohydrates, but they may also cause

some chemical degradation of the wood. The initial fungal

attack on the wood (“incipient decay”) is often invisible and

difficult to detect.

Several previous studies examined the pulpability of dead,

dying, and decayed trees. In a kraft pulping study of standing

white spruce killed by spruce beetles in south–central

Alaska, Werner and others (1983) found no difference in pulp

yield between live trees and trees that had been dead for as

long as 50 years. Paper strength properties also remained

nearly unaffected, being on par with those of pulp from

recently dead trees. The report provides several references on

the effect of decay on pulp qualities for true firs (Abies spp.),

hemlock (Tsuga spp.), balsam fir (Abies balsamea), and jack

(Pinus banksiana) and southern (Pinus spp.) pines (Werner

1983).

Lowery (1977) studied dead timber, both down and standing, in the Rocky Mountains. The species included Engelmann spruce (Picea engelmannii), Douglas-fir (Pseudotsuga

menziesii), western larch (Larix occidentalis), and lodgepole

pine (Pinus contorta). The results indicated that the lower

moisture content of the dead wood required the use of more

power for chipping and resulted in the production of more

fines. Kraft pulping of lodgepole pine yielded pulp suitable

for paper and board products.

The sulfite pulping process and its effect on wood infected

with various types of decay was studied by Björkman and

others (1964). The authors classified the decay as either firm

or soft rot, depending on the effects on the wood, and as light

or dark, depending on the discoloration of the wood. Firm

light rot is the same as white rot decay, whereas the other

categories represent various types of soft and brown rot decay. The authors found that firm light rot did not cause

significant deterioration of pulp quality. However, the other

types of decay (soft dark rot, soft light rot, and firm dark rot)

reduced pulp quality and yield. The discoloration caused by

decay increased the amount of pulping and bleaching chemicals compared to that required for sound wood.

Samples of green wood and dead wood from insect-killed

lodgepole pine in Montana were chemically (kraft and sulfite)

and mechanically pulped (McGovern 1951). For kraft pulping, the green wood and sound dead wood had very similar

pulping and papermaking characteristics. The decayed dead

wood pulped more quickly and had lower residual lignin

content, lower yield, and slightly lower strength. Chemical

analysis of the wood indicated lower holocellulose and α–

cellulose content. The pulpability of beetle-killed southern

pines (Pinus taeda L. and Pinus echinata Mill.) was evaluated for the kraft process (Ifju and others 1979). The logs

were evaluated for pulp Kappa number and yield, and paper
2

strength properties based on time since death of the tree.

Although no decline in yield was observed, there were slight

increases in Kappa number. Tear strength of pulp from recently dead wood was observed to decrease slightly whereas

tensile strength increased slightly. A loss of tensile strength

was observed after longer periods. The authors concluded

that the beetle-killed material was usable for kraft pulping up

to 2 years after the death of the tree.

Experimental Procedure

The trees were harvested from several locations on the Kenai

Peninsula in Alaska. Table 1 provides a detailed description

of the logs obtained for pulping. As the table indicates, the

samples represented six different locations.

The logs were obtained from trees that had been classified by

visual inspection into four deterioration classes, ranging from

live or recently dead trees (class 1) to trees exhibiting major

deterioration such as sloughed bark and large weather checks

(class 4) (Table 2). After the trees were felled, the log and

defect volumes were estimated using Scribner rules (Forest

Service 1985) and cubic rules (Forest Service 1991). Gross

volumes were estimated using Bruce’s formula for butt logs

and Smalian’s formula for all other logs. The percentage of

net cubic volume is reported in Table 1; when the net volume was less than 100 percent, the cause of the volume

reduction is noted.The presence of incipient decay was not

evaluated.

The logs were shipped to the Forest Products Laboratory in

Madison, Wisconsin, where they were debarked using draw

knives, chipped in a four-blade chipper, screened, bagged,

and stored at 5°C. During screening, the amount of oversized and undersized chips was not noted. The moisture

content (dry basis) was determined (Table 1). The chips were

pulped in a 23-L, stainless-steel digester with pumped liquor

circulation and indirect steam heating. The charge was

2.5 kg of ovendry chips with a 4:1 liquor-to-wood ratio. The

chemical charge was 18 percent active alkali on wood for the

low Kappa cooks and 16 percent active alkali on wood for

the high Kappa cooks; 25 percent sulfidity was used for both

cooks.

Each log was pulped to two Kappa levels: nominal 30 and

80 Kappa. For each cook, the temperature was ramped from

80°C to 170°C over a period of 90 to 100 min. For the low

Kappa level, the cook was held at constant temperature for

40 min. For the high Kappa level, the cook was held at

constant temperature for 90 to 100 min. The liquor was

drained, and the chips were washed in the digestor and then

fiberized in an atmospheric refiner. The pulp was screened in

0.3-mm slotted plates, dewatered, shredded, and stored for

papermaking and testing. Screened yield and Kappa number

were determined (Tappi test method T 236) (Tappi 1994–

1995).

Some samples from deterioration classes 1 and 4 were further

tested for papermaking properties because we expected that

these samples would show the greatest differences. Beater

curves were generated by refining the pulps to various Canadian standard freeness (CSF) values to determine papermaking properties. The pulps were refined in a PFI mill, a laboratory refining apparatus, according to Tappi test method

T 248. The following properties were measured: CSF (Tappi

test method T 227), Kajaani fiber length (T 271), thickness

(T 220), moisture content (T 412), burst strength (T 220),

tensile strength (T 220), and tear strength (T 220) (Tappi

1994–1995).

Table 1—Description of test logsa

Log

number

Deterioration

class Region

d.b.h.

(cm)

Height

(m)

Net cubic

volume (%)

Chip moisture

(%) Notes

132-2 1 Falls Creek 36.8 3.35 20.0 27.2 80% decay

715-1 1 Snug Harbor 50.0 2.90 50.1 58.0 Decay, break

722-1 1 Falls Creek 35.1 2.68 96.4 36.8 Decay

609-1 2 Falls Creek 31.2 2.62 58.4 19.7 Sap rot

242-1 2 Trail Lake Hatchery 53.6 3.05 93.8 32.8 Decay

831-1 2 Snug Harbor 41.9 2.84 100.0 20.9 No defect

308-2 3 Tern Lake 36.1 2.96 68.1 20.8 Sap rot

324-1 3 Juneau Road 30.4 2.65 72.8 17.0 Decay, sap rot

341-1 3 John’s Creek 48.5 6.77 85.9 15.7 Decay

422-1 4 Juneau Road 35.3 2.90 80.0 18.2 Decay

424-2 4 John’s Creek 45.2 3.75 81.2 16.8 Sap rot

407-1 4 Trail Lake Hatchery 25.4 2.77 100.0 17.2 No defects

a

Each log was 2.44 m long. Measurements: d.b.h. is diameter at breast height; height, point at which tree section

was taken for study; net cubic volume, amount of sound wood in log by volume. Chip moisture was measured after

chipping and screening and is reported on a dry basis.
3

Experimental Results

The overall results indicate that deterioration classification

alone did not have a great effect on pulpability of the wood.

However, we were able to make several general observations:

• The amount of decay in the logs was not necessarily a

function of the deterioration class: the amount of decay

varied widely in each deterioration class, ranging from

0 to at least 80 percent. The individual samples represented the variation observed throughout the entire sample, but did not reflect deterioration from beetle-kill alone.

While introduction of sap rot fungi can be attributed to

beetle activity, the amount of heart rot seen in those trees

indicated that it was present prior to attack by beetles.

• The deterioration class did not affect wood pulpability or

properties of the resultant paper to a great extent. Other

factors seemed to have a greater effect on pulp quality.

• The presence of sap rot tended to increase the Kappa

number of the resultant pulp while decreasing the yield.

Pulping Properties

Details on the high and low Kappa cooks are shown in

Tables 3 and 4, respectively. The H-factor is a measure of the

relative extent of cooking. It is calculated by integrating the

reaction rate, an exponential function of temperature, over the

time of the cook (Vroom 1957). In general, the higher the

H-factor, the lower the resultant pulp Kappa number. As the

tables indicate, the variation in ramp–cook time did not

cause any variation in the degree of cooking since most

pulping occurred during the constant temperature phase of

the cooking process.

Table 5 summarizes the pulp yield and Kappa results for the

high and low Kappa cooks. The high Kappa values represent

a linerboard grade of paper and the low Kappa cooks, a

bleachable grade of pulp (the low Kappa cooks were divided

into two subgroups based on H-factor). Note that for both

high and low Kappa cooks, the results for deterioration

classes 1, 2, and 4 were very similar on the basis of yield.

The high Kappa results (H-factor of 611) showed that the

least deteriorated class had a slightly lower Kappa number

than the other classes and that deterioration class 3 had the

highest Kappa number. For the low Kappa results (H-factors

of 1375 and 1528), a similar trend was apparent for deterioration class 3: lower yield and higher Kappa number in both

cases. Deterioration classes 1, 2, and 4 produced similar

results in these cooks. However, statistical analysis among

the groups revealed no significant differences.

A closer look at the class 3 samples indicates that log 308

had a much lower yield and higher Kappa number for both

the high and low Kappa cooks (Tables 3 and 4). This log

was only 68 percent sound; all the defect was a result of sap

rot, which can lead to inferior pulps. Logs 609-1, 324-1, and

424-2 of deterioration classes 2, 3, and 4, respectively, also

contained sap rot. Table 6 shows the effect of sap rot on pulp

yield and Kappa number for all deterioration classes. For the

high Kappa cooks, the Kappa number increased with the

presence of sap rot by 11 points; pulp yield decreased

slightly. For the low Kappa cooks, Kappa number rose

slightly, but there was a greater decrease in pulp yield. The

presence of sap rot also increased the variation between the

samples, as evidenced by the larger standard deviations.

The presence of decay in logs and chips can have several

deleterious effects on the chemical pulping of wood. Fungal

degradation itself can result in yield losses and changes in

Kappa number as a result of the relative amount of degradation of carbohydrates and lignin by the organisms. Additionally, if the carbohydrates are preferentially attacked, the

Kappa number will rise as the lignin to carbohydrate ratio

increases. Also, the presence of the fungus and its metabolites can neutralize the pulping chemicals, leading to less

availability of chemicals for pulping and resulting in higher

yields and Kappa numbers for the same cooking time. Additional effects, such as the opening of the cell wall structure by

fungal growth, can increase liquor penetration into the cell

wall. The relative extent to which these effects take place,

which depends on the type of fungus and the exposure conditions, affects the final pulping results.

Log 831-1 (class 2) showed no visible defects, but pulping

efficacy was decreased (Tables 3 and 4). Some unaccountable

environmental factor may have caused this decrease in pulpability. Incipient decay may have also caused the variation

in results.

The moisture content of the wood chips differed significantly

based on log deterioration (see Table 1). The average moisture content of deterioration class 1 was 40.7 percent; average

moisture content of classes 2, 3, and 4 was 24.5, 17.8, and

17.4 percent, respectively. Lower moisture content can affect

the chipping process through increased energy requirements

(Lowery 1977) as well as the pulping process through varied

liquor penetration. There was a good deal of variation in chip

moisture content within a deterioration class. This variation

was probably caused by environmental factors such as the

exposure of the tree, time of harvesting, and climatic conditions at the site.

Table 2—Deterioration classes of beetle-killed spruce

Deterioration

class Description

1 Trees green or infested; needles green,

but attacked by beetles

2 Trees recently dead; red–brown needles;

retention of fine branches and twigs; bark

still tight

3 No fine branches and twigs; gray crown;

tight bark or at least 90 percent of bark

remaining; small weather checks

4 Trees dead for a long time; some large

branches broken off; bark loosened and

more than 10 percent sloughed away;

large weather checks apparent in many

trees
4

Table 3—Pulp yield for high Kappa values

Log

number

Deterioration

class

Digestor

number

Timea

(min:min) H-factor

Yield

(percent)

Kappa

number

Fiber length

(mm)

132-2 1 208 100:40 611 53.80 74.36 2.72

722-1 1 211 100:40 611 53.97 69.50 2.72

609-1 2 217 90:40 611 54.12 71.21 2.72

242-1 2 209 90:40 611 56.76 67.55 2.72

831-1 2 225 98:40 611 50.95 86.38 2.72

308-2 3 228 95:40 611 48.97 100.93 2.72

324-1 3 310 98:40 611 52.97 83.76 2.72

324-1 3 317 100:40 611 53.76 82.76 2.84

341-2 3 223 100:40 611 51.87 77.03 2.84

422-1 4 307 99:40 611 54.36 69.61 2.56

424-2 4 304 102:40 611 54.02 85.41 2.41

407-1 4 321 102:40 611 55.62 72.42 2.41

a

Ramp–cook time.

Table 4—Pulp yield for low Kappa values

Log

number

Deterioration

class

Digestor

number

Timea

(min:min) H-factor

Yield

(percent)

Kappa

number

Fiber length

(mm)

132-2 1 329-1 95:90 1375 48.85 27.84 2.72

715-1 1 224 100:90 1375 47.78 26.15 2.72

722-1 1 330 95:90 1375 48.88 25.46 2.72

609-1 2 324-2 95:90 1375 48.04 25.92 2.72

242-2 2 324-1 95:90 1375 49.88 24.12 2.72

831-1 2 301 100:90 1375 44.96 26.39 2.72

308-2 3 228-2 102:90 1375 42.19 31.19 2.72

324-1 3 309 95:90 1375 45.84 29.31 2.72

341-2 3 329-2 95:90 1375 47.11 31.02 2.72

422-1 4 302 110:90 1375 46.85 24.87 2.49

424-2 4 303 93:90 1375 45.95 26.44 2.33

407-1 4 322 95:90 1375 48.55 25.26 2.33

132-2 1 214 100:100 1528 44.69 22.73 2.25

722-1 1 215 100:100 1528 50.03 22.88 2.25

609-1 2 216 100:100 1528 45.04 23.16 2.25

242-2 2 210 104:100 1528 48.74 21.51 2.25

341-2 3 222 95:100 1528 45.93 26.11 2.25

a

Ramp–cook time.

Table 5—Average pulp yielda

H-factor

Deterioration

class

Number of

samples

Net volume

(%)

Yield

(percent) Kappa number

611b 1 2 58.2 53.89 (0.12) 71.93 (3.44)

2 3 84.1 53.94 (2.91) 75.04 (9.98)

3 4 74.9 51.89 (2.10) 86.12 (10.31)

4 3 87.1 54.67 (0.84) 75.81 (8.43)

1375c 1 3 55.5 48.50 (0.63) 26.48 (1.22)

2 3 84.1 47.63 (2.49) 25.48 (1.20)

3 3 75.6 45.08 (2.57) 30.51 (1.04)

4 3 87.1 47.12 (1.32) 25.52 (0.82)

1528c 1 2 58.2 47.36 (3.78) 22.81 (0.11)

2 2 76.1 46.89 (2.62) 22.33 (1.17)

3 1 85.9 45.93 (NA) 26.11 (NA)

a

Numbers in parentheses indicate standard deviation.

b

High kappa number.

c

Low kappa number.
5

Refining and Papermaking Properties

Figure 1 shows the number of PFI mill revolutions compared to CSF values for the high Kappa number pulps. The

number of revolutions indicates the amount of refining energy

needed to reduce CSF, a measure of pulp drainability. Comparison of the curves shows a wide variation in the amount of

refining necessary to reach a certain freeness level. For example, to reach 500 CSF, the three logs from deterioration class

4 required approximately 6,000, 8,000, and 10,000 revolutions (average 8,000); deterioration class 1 logs required

8,000 and 12,000 revolutions (average 10,000). Log 132-2

(class 1) contained a large amount of decay (80 percent),

which probably contributed to the lower refining energy

caused by the degradation of the fibers. On average, less

refining energy was needed for the more highly deteriorated

class 4 logs than the class 1 logs. However, differences in

amount of refining energy seemed to be more dependent on

the logs themselves rather than the deterioration class. Variations within a deterioration class may have caused the type of

decay (e.g., sap as opposed to heart) found in each log, with

environmental factors presenting a secondary influence.

Figures 2 to 4 show the effect of the high Kappa cook on

strength properties. Only slight differences occurred between

deterioration classes. For the same CSF, burst and tensile

indices were in general slightly higher for class 4 than for

class 1, whereas tear index tended to be slightly lower.

These results may be due to the relative amount of decay

noted in each log; log 407-1 (class 4) showed the highest

burst and tensile indices at all CSF levels and no signs of

decay (see Table 1). The higher net volume for the class 4

logs compared to class 1 logs (87.1 versus 58.2 percent,

respectively) may have contributed to the higher strength

values. The tear results collaborate well with the measured

average fiber length shown in Table 3. The tear strength of

paper is strongly dependent on average fiber length. Logs

324-1 and 722-1 (all in class 1) had an average fiber length of

2.84 and 2.72 mm, respectively—11 percent higher than the

average fiber length of the class 4 logs.

The number of PFI revolutions as a function of CSF for the

low Kappa pulp is shown in Figure 5. Again, the differences

among classes seemed less significant than the variation

among logs. Log 132-2 required less energy for refining,

possibly as a result of the great extent of decay in the log.

Table 6—Effect of sap rot decay for all deterioration

classesa

Hfactor Condition

Number

of

samples

Yield

(percent)

Kappa

number

611b Logs with

 sap rot

 5 52.77

(2.17)

84.81

(10.61)

Logs without

 sap rot

 7 53.90

(2.00)

73.84

(6.40)

All logs 12 53.43

(2.06)

78.41

(9.76)

1375c Logs with

 sap rot

 4 45.51

(2.43)

28.21

(2.48)

Logs without

 sap rot

 8 47.86

(1.54)

26.39

(2.18)

All logs 12 47.07

(2.11)

27.00

(2.35)

1528c Logs with

 sap rot

 1 45.04

(NA)

23.16

(NA)

Logs without

 sap rot

 4 47.35

(2.46)

23.31

(1.97)

All logs 5 46.89

(2.37)

23.28

(1.70)

a

Numbers in parentheses indicate standard deviation.

b

High kappa number.

c

Low kappa number.

16

14

12

10

 8

 6

 4

 2

 0

PFI ( x 103 revolutions)

800 750 700 650 600 550 500 450 400 350 300 250

CSF (ml)

Log 132-2 (1)

Log 722-1 (1)

Log 407-1 (4)

Log 422-1 (4)

Log 424-2 (4)

+

x

x +

+

+

x

x

x

Figure 1—Revolutions of PFI mill as a function of

Canadian standard freeness (CSF) for high Kappa

value cook. Number of revolutions is a measure of

energy needed to refine fibers. Numbers in parentheses are deterioration classes.

10

 9

 8

 7

 6

 5

 4

 3

 2

 1

 0

Burst index (kPa-m2/g)

800 750 700 650 600 550 500 450 400 350 300 250

CSF (ml)

Log 132-2 (1)

Log 722-1 (1)

Log 407-1 (4)

Log 422-1 (4)

Log 424-2 (4)

+

x

x

+ +

+

x x x

+

Figure 2—Burst index of paper made from high

Kappa cook as a function of CSF.
6

Only strength properties showed a trend similar to that for

the high Kappa pulp. Both burst (Fig. 6) and tensile (Fig. 7)

strength indices were slightly higher for the more deteriorated

logs. However, as for the high Kappa pulps, these values

were strongly dependent on the amount of decay present.

Regardless of the deterioration class, the lower the net volume measured, the lower the burst and tensile indices. As for

the high Kappa pulp, the tear index showed strong dependence on fiber length (Fig. 8). Log 132-2 had an average fiber

length of 2.72 mm and exhibited the highest tear strength

values. Log 715-1 (class 1) and logs 422-1 and 424-2 (class

4) had fiber lengths from 2.25 to 2.49 mm and showed lower

tear strengths.

These results should be interpreted as indicative of expected

trends for pulping this kind of material. As mentioned earlier, the samples had different parameters that could not be

accounted for in the interpretation. For example, there were

significant variations in the breast height diameter of the

logs, height of the sample from the ground, and growth

location of the tree (Table 1). More significantly, the net

volume of sound wood in the logs varied between the

classes, which seemed to have a significant effect on paper

properties. The variation in location was especially important since exposure, soil conditions, and other environmental

factors may have contributed to wide variations in the quality

of the resultant fiber irrespective of the effect of deterioration.

In addition, the height at which the tree section was taken

may have significantly affected the amount of juvenile wood

in the sample. Juvenile wood is known to have a significant

effect on the kraft pulping process, typically resulting in a

decrease in yield and an increase in liquor consumption.

Conclusions

The results of this study indicate that beetle-killed spruce can

be pulped effectively. Our conclusions are as follows:

• Beetle-killed spruce can be pulped effectively with the

kraft pulping process. Pulp yield from deteriorated logs

was similar for high and low Kappa levels.

• Extent of log deterioration has little effect on pulping.

There was little apparent difference between deterioration

class 1 (control) and classes 2 and 4. Class 3 seemed to

have slightly less favorable pulping characteristics. However, the sample sizes and number of uncontrolled variables and environmental factors were such that no rigorous

statistical interpretation of these data was possible.

• Refining energy is the same or slightly less for pulp

produced from more deteriorated wood. This is to be expected since the cell wall structure would be weakened by

the action of fungi and other organisms. The refining energy was strongly dependent on the presence of decay—

logs with lower net volume required less refining energy.

• Log deterioration has mixed effects on paper properties. In

general, tear strength was slightly lower and tensile

strength slightly higher for the more deteriorated wood.

Burst and tensile strength were strongly dependent on the

amount of log decay, as measured by the net cubic volume of sound wood. Tear strength was strongly dependent on fiber length, which tended to be shorter in the more

severely deteriorated wood. However, strength properties

were still of an acceptable quality when compared to the

control.

• Chip moisture content is affected by several factors. Moisture content of the resultant chips varied from 17 to

58 percent. Although log deterioration was a factor in the

moisture content level, environmental factors (such as exposure, aspect, location) were probably significant as well.

Recommendations

This study should be used as a preliminary indication that

deteriorated wood is pulpable by the kraft process. However,

variations in parameters, especially the region from which the

logs are obtained and environmental factors, need to be

carefully taken into account to isolate the effect of log deterioration from other variables.

Two methods of obtaining statistically reliable data are

(1) to investigate a large number of samples such that the

effects of uncontrolled parameters can be taken into account

and the data subjected to statistical analysis, and (2) to

investigate selected samples from a restricted area such that

environmental factors are similar for all samples; the sample

logs should also be of similar sizes and cut from the same

distance above ground.

If a particular area or stand of trees is to be harvested for

pulping, we suggest that option 2 be utilized to evaluate the

trees for pulpability. This method would be the most costeffective in terms of amount of research needed to produce

high quality data. However, since the presence of decay

seems to be a key factor in the suitability for pulping, an

assessment of the harvested logs using the net cubic volume

as the parameter should also give a good indication of the

quality of the material for pulp and paper manufacture.

References

Björkman, Erik; Forssblad, Lars–Henrik; Malm, Erik

[and others]. 1964. The use of decayed wood from some

conifers and broadleaf trees for chemical pulping purposes.

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0.12

0.10

0.08

0.06

0.04

0.02

 0

Tensile index (kN-m/g)

800 750 700 650 600 550 500 450 400 350 300 250

CSF (ml)

Log 132-2 (1)

Log 722-1 (1)

Log 407-1 (4)

Log 422-1 (4)

Log 424-2 (4)

+

x

x

+ +

+

x x x

+

Figure 3—Tensile index of paper made from high

Kappa cook as a function of CSF.

7

6

5

4

3

2

1

0

Tear index (mN-m2/g)

800 750 700 650 600 550 500 450 400 350 300 250

CSF (ml)

Log 132-2 (1)

Log 722-1 (1)

Log 407-1 (4)

Log 422-1 (4)

Log 424-2 (4)

+

x

x

+ +

+ x x x

+

Figure 4—Tear index of paper made from high

Kappa cook as a function of CSF.

9

8

7

6

5

4

3

2

1

0

PFI (revolutions x 103)

750 700 650 600 550 500 450 400 350 300 250

CSF (ml)

Log 132-2 (1)

Log 715-7 (1)

Log 722-1 (1)

Log 407-1 (4)

Log 422-1 (4)

Log 424-2 (4)

+

x

x

+

+

x

x

x

+

Figure 5—Revolutions of PFI mill as a function of

CSF for low Kappa cook.

750 700 650 600 550 500 450 400 350 300 250

CSF (ml)

Log 132-2 (1)

Log 715-7 (1)

Log 722-1 (1)

Log 407-1 (4)

Log 422-1 (4)

Log 424-2 (4)

+

x

x

+ +

x

x

x +

10

 9

 8

 7

 6

 5

 4

 3

 2

 1

 0

Burst index (kPa-m2/g)

+

Figure 6—Burst index of paper made from low

Kappa cook as a function of CSF.
8

0.14

0.12

0.10

0.08

0.06

0.04

0.02

 0

Tensile index (kN-m/g)

CSF (ml)

x

+ +

+

x

x

x

+

750 700 650 600 550 500 450 400 350 300 250

+

x

Log 132-2 (1)

Log 715-7 (1)

Log 722-1 (1)

Log 407-1 (4)

Log 422-1 (4)

Log 424-2 (4)

Figure 7—Tensile index of paper made from high

Kappa cook as a function of CSF.

9

8

7

6

5

4

3

2

1

0

Tear index (mN-m2/g)

750 700 650 600 550 500 450 400 350 300 250

CSF (ml)

Log 132-2 (1)

Log 715-7 (1)

Log 722-1 (1)

Log 407-1 (4)

Log 422-1 (4)

Log 424-2 (4)

+

x

x

+

+

+

x

x

x

+

Figure 8—Tear index of paper made from high

Kappa cook as a function of CSF.