Experiences with the utilization of bark-beetle-killed ... · Götz Martin 1; Gero Becker ;...

Experiences with the utilization of bark-beetle-killed Norway spruce (Picea abies) pulp-

wood in mechanical pulping operations for supercalandered magazine paper

Götz Martin1; Gero Becker1; Siegfried Fink2 1Institute of Forest Utilization and Work Science, Albert-Ludwigs-University Freiburg, Germany 2Institute of Forest Botany and Tree Physiology, Albert-Ludwigs-University Freiburg, Germany

Abstract

Bark Beetles like Ips typographus or Pityogenes chalcographus are a big threat for European softwoods, espe-cially for Picea abies (Norway spruce), the most important European tree species utilized in mechanical pulping operations. In recent years the amount of bark-beetle-killed (BBK) Norway spruce rose dramatically. Since 2001 more than 7.8 million m³ (20 % of the total harvest) of BBK Norway spruce were harvested in south-west Ger-many. Seven mill-scale grinding and lab-scale bleaching trials were performed to investigate the influence of BBK spruce pulpwood on the pulp and paper quality. The results show that BBK Norway spruce can be used in me-chanical pulping operations but the achieved pulp and paper quality is somewhat inferior compared with fresh and sound Norway spruce. The initial brightness was determined to be 60.2 %. At a freeness level of 75 °SR, BBK spruce gave a tensile index of 38.3 Nm/g while fresh Norway spruce produced laboratory sheets with a ten-sile index of 39.2 Nm/g. It was found that mainly secondary infestations with blue stain and red streak fungi are responsible for the lower pulp and paper quality produced from BBK Norway spruce wood. A rapid and consequent harvesting and proc-essing of bark beetle infected forest stands could be a solution of this problem. Keywords: Picea abies; wood properties; mechanical pulping; pulp and paper properties; bleaching; wood sup-ply; spruce bark beetles; dead wood; fungal infestation; red streak; blue stain

Introduction

The European pulp and paper industry is currently facing a difficult time. Besides increasing costs for energy and overcapacities on the European paper market [1] major problems are shortages on the wood market and thereby rising costs for Norway spruce pulpwood, the most important raw material of wood-containing paper grades in Europe. The rising costs for spruce pulpwood and problems in availability are enhanced by the boom-ing sawmill industry, the utilization of small-diameter wood for energy recovery [2], and also due to new silvi-cultural management concepts which prefer mixed deciduous forests instead of pure softwood monocultures. A possible solution for overcoming these problems could be the utilization of raw material which is not used by the European pulp and paper industry so far, for example BBK Norway spruce pulpwood. Bark Beetles like Ips typographus or Pityogenes chalcographus are a big threat for European softwoods espe-cially for Norway spruce. In recent years the amount of BBK Norway spruce rose dramatically. This is mainly in succession of unfavourable weather conditions, e.g. the catastrophic windthrow "Lothar" in 1999 as well as hot and dry summers in 2003, 2004 and 2006. Since 2001 more than 7.8 million m³ (20 % of the total harvest) of BBK Norway spruce were harvested in south-west Germany. Bark beetles and their associated fungi kill Norway spruce trees due to the interruption of the trees sap flow [3; 4; 5]. The infected trees normally die in the second year of the infestation. In succession of the insect and fungal attack the moisture content of the infested trees decreases very rapidly [6]. The effect of pulpwood with a low moisture content on the quality of pulp and paper is well known from many studies [7; 8; 9; 10]. The authors of these studies state, that the quality of groundwood pulp made from pulpwood with a high moisture content is su-perior to the pulp quality made from dried out pulpwood. Furthermore negative impacts on the pulp and paper quality of BBK spruce pulpwood can be expected from the fungi associated with bark beetles in Europe. Baier [11] states, that among others, the blue-stain fungus Cerato-cystis polonica uses bark-beetles as a vector to penetrate into trees. C. polonica is well known for causing dis-colorations in the sapwood of infected trees due to melanin like pigments in their hyphen [12]. According to Kleist [13] also Stereum sanguinolentum, an agent of red streak, is associated with spruce bark beetles. Besides

the enzymatic discoloration, [13; 14] a loss of yield and decreasing strength properties are reported [15; 16] in conjunction with S. sanguinolentum. The aim of the present study was to examine if the utilization of BBK spruce pulpwood could be an alternative for the production of wood-containing printing papers, especially when shortages on the wood market occur and sound Norway spruce pulpwood is not available anymore for a reasonable price. Material and Methodology

The BBK spruce pulpwood used in this study comes from two different forest stands in the north-western part of Germany; both were traditional forest stands. The average altitude of the sites was around 300 m above sea level. Both forest stands were infested by bark-beetles in early spring of 2004 and died in the same year of the infesta-tion. The total wood volume (approx. 200 m³) was harvested and processed into logs of 2 m length in November 2004. The logs were transported to the participating paper mill (STORAENSO Reisholz Mill) five days after cut-ting and were stored for additional seven days (maximum) at the wood yard. Due to the very fast processing, an additional negative influence of log storage on the pulp and paper quality could be excluded. For the measurement of the wood properties 72 logs (out of 1500 logs in total) were randomly selected at the mill wood yard and two stem discs were cut out from the middle of each log. All wood measurements were done on these stem discs in the wood laboratory of the Institute of Forest Utilization and Work Science in Freiburg. The basic density (DIN 1306) was determined on a sub-set of six small wood samples taken from the North-South radius of each stem disc. Moisture content was measured according to DIN 52183. The growth ring width and the latewood content were determined on four radii at each stem disc using the computer based “WinDEN-DRO” program. According to the STFI standard procedure, the first 15 growth rings were defined as juvenile wood. All growth rings older than 30 years were defined as mature wood. For the determination of the compres-sion wood content a photo-optical method described by Wernsdörfer et al. [17] was applied. For the mycological analysis, performed at the Institute of Forest Botany in Freiburg, small discolored sapwood samples were taken from the stem discs and placed on a culture medium in plastic Petri dishes. All isolations were made on 2% malt extract agar and incubated at room temperature in the dark. Altogether, seven mill scale grinding trials were performed at STORAENSO Reisholz Mill with an atmospheric VOITH chain grinder (technical details in table I). Three grinding trials were made with pure BBK Norway spruce. For estimating the potential of BBK Norway spruce it was also important to know how this raw material is performing in mixtures with sound and fresh Norway spruce pulpwood. Therefore two grinding trials were performed with a mixture of 50 % BBK Norway spruce and 50 % sound Norway spruce and two more grinding trials with a BBK Norway spruce content of 25 %. Fresh and sound spruce wood from the same region studied in a previous project [18] was used as a reference. Table I: Technical details of the grinder

Parameters of the grinder Quantity

Stone diameter 140 cm

Peripheral stone speed 18 m/s

Stone pattern 10/40°

Feeding rate 1.8 m³/h

Pit temperature 75 °C - 78 °C

The logs which were used in the grinding trials were marked with red colour at the front and the back end of the logs. The logs were selected after passing the debarking drum (figure I) and fed by hand into the grinder. In total, a wood volume of 70 m³ was ground during these seven trials. Pulp samples were taken directly at the grinder's pit, to make sure that only the BBK Norway spruce was tested and evaluated.

Figure I: Selection of Norway spruce after passing the debarking drum The analysis of the pulp and paper properties was done at the laboratory of STORAENSO Reisholz Mill. In total, 32 pulp samples were taken during the seven grinding trials directly at the grinder’s pit. For measuring the paper properties 160 Rapid-Köthen sheets (DIN 54358) with a grammage of 80 g/m² were produced (see table II for more details). Table II: Pulp and paper testing methods

Property Fiber prop-erties

Freeness (SR°)

Tensile Index

Tear Index

Porosity (Bendtsen)

ISO-Brightness

Method Kajaani FS 200

DIN EN ISO 5267-1/2006

DIN 53112 DIN EN 21974-94

DIN 53120-T01-98

DIN 53145-T01-03

Fiber properties of the produced pulp were measured with the Kajaani FS 200 measuring device. For the analysis of the degree of fibrillation, the pulps from 100 % BBK pulpwood and from the reference pulpwood were stained with the Simons stain method [19]. Following the mill-scale grinding trials, lab-scale bleaching trials with sodium dithionite were performed in the laboratory of STORAENSO Reisholz Mill (table III). After adding the bleaching agents and the bleaching addi-tives, the pulp with a consistency of 4 % was stored for a 2 h period at a temperature of 70 °C in the water bath.

Table III: Concentration of the bleaching agent and the bleaching additives

Bleaching chemicals Quantity

Sodium Dithionite 1.0 %

Chelating agents 0.4 %

Results

Wood properties

An overview of the BBK spruce wood properties and the properties of the reference wood is given in table IV. Table IV: Wood properties of BBK spruce and reference pulpwood

Age (years)

Moisture content (%)

Diameter (cm)

Basic density (g/cm³)

Ring width (mm)

Latewood content (%)

Juvenile wood content (%)

Compression wood content (%)

Stand 1 (Essen)

51 27.6 20.5 0.48 1.96 20.0 21.1 5.1

Stand 2 (Lüdenscheid)

31 33.3 20.1 0.40 3.05 11.5 45.5 6.7

BBK spruce 45 29.3 20.4 0.46 2.29 17.3 28.5 5.7

Reference [18]

22.0 46.6 13.8 0.40 3.36 15.3 71.0 4.8

The results of table IV show, that the BBK spruce pulpwood used in the present study was very heterogeneous and that at least the pulpwood from the forest stand in Essen is not representing typical German spruce pulp-wood. Significant differences between the two bark-beetle infested stands and the reference were found in the age of the pulpwood logs. The pulpwood logs from the forest stand in Essen were on an average nearly fifteen years older than the logs from the forest stand in Lüdenscheid and more than thirty years older than the fresh and sound pulpwood which was used as a reference. In dependence of the high age of the BBK spruce pulpwood also the amount of juvenile wood was significantly lower than in the reference pulpwood logs. The BBK pulpwood's moisture content of 29.3 % was significantly lower than typical spruce pulpwood which has an average moisture content of 46.6 %. The lowest moisture content was found in the forest stand in Essen, namely 27.3 %. This is, according to Kärenlampi [10], lower than the fiber saturation point of spruce wood fi-bers. The average basic density of the BBK pulpwood logs was significantly higher than the basic density of the fresh and sound pulpwood logs used as a reference. This is mainly caused by the slow growth speed of the forest stand in Essen, with a yearly increment of 1.96 mm, and is also in coherence with the low juvenile wood content. The slow growth speed is not a result of the insect infestation but of a lack of silvicultural treatment which is obvious also from figure II.

Yearly increment of two BBK pulpwood logs from Essen

0,0

1,0

2,0

3,0

4,0

5,0

6,0

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51

gro

wth

rin

g w

idth

, m

m

Figure II: Yearly increment of two BBK pulpwood logs from the forest stand in Essen

What the compression wood content concerns, no significant differences were found between the BBK pulp-wood logs and the reference logs. In the mycological survey performed at the Institute of Forest Botany in Freiburg different fungi were identified. Besides some mould fungi, the well known blue-stain fungus C. polonica and also the brown rot fungus S. san-gunitolentum were detected. It is widely accepted that these species are responsible for sapwood discolorations of the infected trees. In the present study discolorations were found on nearly 80 % of the stem discs. In some cases around 50 % of the stem disc surface was discolored. An other interesting result of the mycological survey was that a huge amount (up to 0.5 %) of fungal chitin was found in the produced laboratory sheets. Pulp and Paper properties

In total, 32 pulp suspensions from BBK pulpwood logs and 160 laboratory sheets were investigated to determine the pulp and paper properties of the BBK pulpwood logs. For a better comparability with other studies all results presented are interpolated for a freeness of 75 °SR (equivalent to 74 CSF). An overview of the results of the pulp and paper properties is given in tables V to VII. Table V: Fiber properties at freeness 75° SR

Pulp property 100 % BBK pulpwood

50 % BBK pulp-wood

25 % BBK pulp-wood

Reference [18]

Longfiber content (%) 14.5 13.0 15.1 14.8

Weighted fiber length (mm) 0.72 0.70 0.73 0.72

Shives content (%) 2.5 3.1 1.8 1.8

Fiber properties

The results presented in table V show, that no clear tendencies about the impact of BBK spruce pulpwood was found regarding the fiber properties of the produced pulp. Especially the trials with 50 % BBK spruce pulpwood are not in accordance with the expectations. Comparing the fiber properties from the 100 % BBK spruce pulp-wood with the fresh and sound reference pulpwood, a significant lower shives content can be detected in the rev-erence pulpwood. Another finding came from the visual interpretation of microscope images which were made from Simons stained pulp fibers. It seems that the reference wood was stronger fibrillated than the 100 % BBK pulpwood (figure III).

Figure III: Simons stained pulp fibers from 100 % BBK (left) and reference pulpwood (right) Strength properties

In contrary to the findings concerning the fiber properties clear tendencies and significant differences between the different wood assortments were found regarding the strength properties of the produced laboratory sheets. The results are presented in table VI.

Table VI: Strength properties at freeness 75 °SR

Paper property 100 % BBK pulp-wood

50 % BBK pulp-wood

25 % BBK pulp-wood

Reference [18]

Raw density (g/cm³) 0.446 0.454 0.456 0.477

Tensile Index (N m/g) 37.9 38.5 39.5 39.3

Tear Index (mN m²/g) 9.2 8.6 9.3 8.9

Bendtsen Porosity (ml/min) 165 148 110 107

The results of table VI show that the raw density of the laboratory sheets decreases with an increasing content of BBK spruce pulpwood. At a freeness level of 75 °SR the laboratory sheets produced from 100 % BBK pulp-wood had a raw density of 0.446 g/cm³ while it was 0.477 g/cm³ with 100 % fresh and sound spruce pulpwood. This is a significant difference at the 95 % level. Similar results were found regarding the tensile index and the porosity of the laboratory sheets. The results show, that the tensile index of BBK pulpwood at a freeness of 75 °SR is 4 % lower than the tensile index of the reference pulpwood (figure IV). No different tensile indices could be found comparing the reference pulpwood with the 25 % BBK pulpwood trials.

Tensile Indices of 100 % BBK pulpwood and the reference pulpwood

25

30

35

40

45

50

55

60

60 65 70 75 80 85 90

Freeness [SR]

Tensile Index (m

Nm

²/g)

Reference 100% BBK pulpwood Linear (Reference) Linear (100% BBK pulpwood)

Figure IV: Tensile Indices of 100 % BBK pulpwood and the reference pulpwood The porosity shows clearly the influence of an increasing BBK pulpwood content. At the same freeness level the sheets from 100 % BBK pulpwood have the highest porosity with 165 ml/min while the reference has the lowest porosity with 107 ml/min. In contrary to the other strength properties presented no clear tendencies or significant differences could be found regarding the tear index of the tested raw material. Due to the fact that the tear index is strongly dependent on the fiber length of the pulp [20; 21], it could not be expected from the results of the fi-ber properties to find significant differences in this paper property. Brightness

From the optical properties only the initial ISO-Brightness was measured in the present study. The results in fig-ure V show, that the initial brightness was strongly influenced by an increasing content of BBK pulpwood in the tested wood assortments.

Initial ISO-Brightness of pulps with different amounts of BBK pulpwood

56

58

60

62

64

66

68

100 % BBK pulpwood 50 % BBK pulpwood 25 % BBK pulpwood Reference

ISO

-Bri

ghtn

ess [%

]

Figure V: Initial ISO-Brightness of pulps with different amounts of BBK pulpwood

The brightness decreased significantly with an increasing amount of BBK pulpwood. In the present study the brightness decreased roughly about 6 brightness points (10 %) when 100 % BBK pulpwood is compared with the fresh and sound reference pulpwood. The results of figure 4 also indicate that the influence of BBK pulp-wood on the paper brightness is stronger than its influence on the pulp suspension and the paper strength proper-ties. Even a small amount of BBK pulpwood (25 %) caused a significant drop in the initial ISO-Brightness. Energy consumption

Due to increasing production cost, energy consumption in mechanical pulping is a topic of growing interest. An overview of the energy consumption in the present study is given in table VIII. Since many mechanical pulp producing paper mills use the specific energy consumption (SEC) per volume (ster (0.7 m³) or m³) for steering the produced pulp quality, not only the SEC per ton are presented here. Table VIII: Specific energy consumption (SEC) for pulping BBK pulpwood

100 % BBK pulpwood

50 % BBK pulpwood

25 % BBK pulpwood

Reference [18]

SEC (kWh/t) 1259.5 1359.5 1345.2 1320.7

SEC (kWh/m³) 528.2 532.0 508.0 480.7

Regarding the SEC per ton no clear tendencies were found between the different wood assortments. This is mainly caused by the basic density of the different wood assortments. Due to the very high basic density of the BBK pulpwood (especially from the stand in Essen) the SEC per ton to reach a freeness of 75 °SR was the low-est for the 100 % BBK pulpwood. In contrast to that result, there seems to be the tendency that the high density 100 % BBK pulpwood needs more energy per volume to reach a freeness level of 75 °SR than the low density reference. Bleaching

The results in table IX show that bleaching with dithionite is loosing its efficiency when BBK pulpwood is in-volved. The largest brightness gain of 9.8 brightness points was achieved with fresh and sound spruce pulpwood of the reference. With an in creasing content of BBK pulpwood the brightness gain decreased from 9.4 bright-ness points (25 % BBK pulpwood) to 8.8 brightness points with 100% BBK pulpwood. Although the brightness gain was lowered with an increasing amount of BBK pulpwood a final paper brightness of 71.5 % could be achieved in the laboratory.

Table IX: Bleaching of BBK pulpwood with dithionite

100 % BBK pulpwood

50 % BBK pulp-wood

25 % BBK pulpwood

Reference [18]

Initial Brightness (%) 62.5 62.6 63.4 65.1

Final Brightness (%) 71.5 72.3 72.8 74.9

Brightness gain due to bleaching

8.8 9.7 9.4 9.8

Discussion

Stone groundwood pulping of wood is a very complex production method in which the pulp quality is influenced by different parameters. Besides some technological features like the specific energy consumption [22) or the grinding zone temperature [23], the wood properties of the utilized raw material have a strong influence on the final product quality. It is commonly accepted that slowly grown wood with a high latewood and mature wood content has longer and thicker fibers than fast grown wood with a high juvenile wood content [24, 25]. It is also widely accepted in the literature that, at least in the field of TMP production and chemical pulping, slow grown wood with long fibers tends to produce stronger pulps than fast grown wood with short fibers [20; 21; 26; 27]. The average BBK pulp-wood used in these trials was very slow grown material with a high latewood and mature wood content com-pared with the typical spruce pulpwood used in Germany [18] for the production of stone groundwood pulp. This is important for the further interpretation of the results, because it was expected from the analysis of the wood properties, that the BBK pulpwood would produce pulp and paper with good fiber and strength properties. The results of the present study are not in accordance with the expectations gained from the literature concerning the influence of wood properties on product quality. As shown in the previous chapter, the BBK pulpwood pro-duced pulps with lower strength properties and a lower brightness than fresh and sound Norway spruce pulp-wood. The deterioration of the pulp and paper quality from BBK pulpwood can be justified with its specific fea-tures of low moisture content [4; 28] and discoloration of the logs sapwood due to fungal attacks [5; 13; 29]. It seems that mainly the low moisture content of the pulpwood logs is responsible for the low strength properties of the produced pulp in the present study. These results are in good agreement with the results of other studies. Tuominen [30] for example is referring that pulping of dry wood leads to a pulp with a higher shive content and a reduced tensile index while the tear index is unaffected. Similar results were found in a previous study under-taken at STORAENSO Reisholz Mill [31] in which freshly cut logs where dried down in a vacuum dryer to a mois-ture content of 30 %. Also in this study an increased shive content (25 %) and a decreased tensile index (4.5 %) was detected, while tear index seemed to be unaffected by the low moisture content. Due to the short period of time since death of the BBK pulpwood in the present study, fungal infestations seem to have only a small influ-ence on the lower strength properties of produced paper. Authors [32; 33] of studies concerning the influence of fungal infestations on pulp and paper properties state, that significant effects in wood properties like basic den-sity occur in a time frame of one to three years after the first infestations. As mentioned earlier, the BBK pulp-wood used in this study was harvested in the same year of the first bark-beetle attack. In contrast to the strength properties, it seems that the initial brightness of the produced paper is strongly influ-enced by the fungal discoloration. In the already mentioned study of Martin [31] the initial brightness of dry pulpwood was reduced by only two brightness points compared with fresh and wet pulpwood. This is in good accordance with studies of Bauch [14], Behrendt [12] and Christiansen [3] where the influence of fungal infesta-tions on wood colour is described. This conclusion is also supported by the results of the trials with a BBK pulpwood content of 25 % where the brightness was still reduced significantly while the strength properties were not affected. Similar to the initial brightness also the bleachability of BBK pulp with dithionite is reduced compared with the bleachability of pulp produced from fresh and sound Norway spruce pulpwood. This is in good agreement with the results of another study [14] which shows that discoloration of blue-stain fungi can be bleached easily with hydrogen peroxide but not with dithionite.

The results of the present study show, that an increasing amount of BBK Norway spruce pulpwood has a nega-tive influence on pulp and paper quality. This result is supported by the results from other studies which exam-ined the suitability of different insect damaged tree species for the production of pulp and paper. Atack [32] is reporting a loss in brightness and a higher SEC when budworm killed Balsam fir (Abies balsamea) was ground. Ifju et al. [34] are referring in connection with bark-beetle killed Southern pine (Pinus teada) that tear strength was reduced in the pulps produced. Similar results were found by Scott et al. [35] for chemical pulp from BBK White spruce (Picea glauca) pulpwood. Conclusions

The results of the present study show that BBK Norway spruce pulpwood can be used as a raw material for the production of high quality supercalandered magazine papers but the achieved quality is somewhat inferior than using fresh and sound Norway spruce pulpwood. Especially the initial pulp brightness is already negatively in-fluenced when only small amounts of BBK pulpwood are mixed with fresh and sound pulpwood. The strength properties of the produced paper are also influenced by the amount of BBK pulpwood if the amount of BBK pulpwood exceeds 25 % of the whole wood input. The deterioration is less pronounced than that of the initial pulp brightness. If the amount of BBK pulpwood is lower than 25 % there could be even an economical benefit for the pulp and paper mill due to the lower wood price. The loss in quality of BBK pulpwood is mainly caused by the low wood moisture content and secondary infesta-tions by wood destroying fungi. Therefore, rapid harvesting activities and fast processing of the BBK pulpwood logs improves the BBK pulpwood quality. If a fast utilization is not possible, the best way to preserve wood quality is to debark the logs immediately after logging and to store the pulpwood logs in water or sprinkling them with a high water flow rate [9; 36] to prevent a further negative influence on the pulp and paper quality. On the woodyard the BBK pulpwood should be stored separately from the sound and fresh pulpwood logs. Thereby, it is possible for the pulp and paper mills to mix the BBK pulpwood in specified ratios with the fresh and sound pulpwood. Mixing BBK with sound pulpwood is essential for minimizing quality fluctuations.

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sam Fir; Journal of Pulp and Paper Science 11 (1), 1-7 33. Hatton, J. (1985) Kraft and bisulphite pulping of budworm-killed wood; Pulp and Paper Canada 86 (6),

103-111 34. Ifju, G; Oderwald, R.G; Ferguson, P.C. (1979) Evaluation of beetle-killed southern pine as a raw mate-

rial for pulp and paper; Tappi Journal 62 (2), 77-80 35. Scott, G; Bormett, D; Sutherland, N. (2000) Beetle-killed spruce utilization in the Kenai peninsula;

Tappi Journal 83 (6), 48 36. Persson, E; Filipsson, J; Elowson, T. (2002) Brightness, bleachibility and colour reversion of ground-

wood made of wet- and dry stored Norway spruce (Picea abies) pulpwood; Paperi ja Puu – Paper and Timber 3 (6) 411-415

1

Experiences with the utilization of bark-beetle-killed Norway spruce (Picea abies)

pulpwood in mechanical pulping operations for supercalandered magazine paper

Götz Martin, Institute of Forest Utilization and Work Science

Albert-Ludwigs-University Freiburg, Germany

The 2007 TAPPI International Mechanical

Pulping ConferenceMinneapolis, Minnesota, USA May 6-9, 2007

Experiences with the utilization of

bark-beetle-killed Norway spruce

(Picea abies) pulpwood in mechanical

pulping operations for

supercalandered magazine paper

Götz Martin, Gero Becker, Siegfried Fink

2





Content

• introduction

• state of knowledge

• material and methodology

• results and discussion

– wood properties

– fiber properties

– strength properties

– optical properties

– energy consumption

• conclusionsFig. 1: Bark beetles and larvae gallery

3





Introduction

• the European pulp and paper industry is

currently facing a difficult timePreisentwicklung Papierindustrie

0

20

40

60

80

100

120

140

160

180

2000 2001 2002 2003 2004 2005 2006 2007

Preisindex [%]

Erzeugerpreis Holzpreis Energiepreis

4





Introduction

• Norway spruce

pulpwood shortages

on the German wood

market

– booming lumber

industry

– bioenergy

– silvicultural

management concepts Fig. 2: Empty woodyard at Stora Enso Reisholz Mill

5





Introduction

• growing amount of

BBK spruce on the

wood market

– 20 % of the annual

harvest

– unfavorable weather

conditions

• windthrow

• snow breakage

• hot and dry summer

climate

Fig. 3: Bark Beetle infected forest stand

6





State of knowledge

• bark beetles and associated

fungi kill trees due to the

interruption of the tree

sapflow

– low moisture content

– discolorations of the trees

sapwood

– slightly higher resin content

Fig. 4: fungal discolorations

7





Research objectives

• to analyze the consequences and effects of BBK pulpwood on pulp and paper quality

• to estimate the potential of BBK pulpwood as a raw material resource in the pulp and paper industry

• to develop recommendations for the utilization of bark beetle damaged wood

8





Material and Methodology

• mill scale grinding trials

with an atmospheric

chain grinder

• laboratory scale

reductive bleaching

trials

• pulp and paper

analysis

• wood analysisFig. 5: BBK pulpwood at the forest road

9






logging

storage on

wood yard

cut to length/

debarking

marking

stem selection

grinding

pulp sampling

pulp and paper

analysisbleaching

stem

selection

wood

analysis

data analysis

Fig. 6: Trial layout

10





Results – wood properties

0.4013.846.622Reference

0.4620.429.345BBK

pulpwood

Density

(g/cm³)

Diameter

(cm)

Moisture

content (%)

Age

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Results – wood properties

15.315.33.36Reference

28.517.32.29BBK

pulpwood

Juvenile wood

content (%)

Latewood

content (%)

Ring width

(mm)

12





Results – mycological survey

• different fungi were detected

– red streak (Stereum

sangunitolentum)

– blue stain (Ceratocystis

polonica)

• 80 % of the stem discs

showed discolorations

• fungal chitin was detected in

the produced laboratory

sheetsFig. 7: fungal discolorations

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Results – pulp and paper propertiesLongfiber content

Longfiber content (>1,3 mm) at Freeness 75 SR

11,5

12

12,5

13

13,5

14

14,5

15

15,5

1

Longfiber content (%)

100 % BBK 50 % BBK 25 % BBK Reference

14





Results – pulp and paper propertiesTensile Index (Nm/g)

Tensile index at Freeness 75 SR

37

37,5

38

38,5

39

39,5

40

1

Tensile index (N m/g)


15





Results – pulp and paper propertiesTear Index (mNm²/g)

Tear index at Freeness 75 SR

8,2

8,4

8,6

8,8

9

9,2

9,4

1

Tear index (mN m²/g)


16





Results – pulp and paper propertiesBendtsen porosity (ml/min)

Porosity at Freeness 75 SR

0

20

40

60

80

100

120

140

160

180

1

Porosity (ml/min)


17





Results – pulp and paper propertiesISO-brightness (%)

Brightness at Freeness 75 SR

57

58

59

60

61

62

63

64

65

66

67

1

Brightness (%)


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Results – pulp and paper propertiesSpecific energy consumption

Specific energy consumption at Freeness 75 SR

1200

1220

1240

1260

1280

1300

1320

1340

1360

1380

1

SEC (kWh/t)


Specific energy consumption at Freeness 75 SR

450

460

470

480

490

500

510

520

530

540

1SEC (kWh/m³)


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Results – pulp and paper propertiesBleaching

Bleaching of 100 % BBK spruce (Dithionite 1 %)

62,5

71,5

8,8 9,8

64,0

73,8

0

10

20

30

40

50

60

70

80

1

ISO-Brightness (%)

100 % BBK spruce 100 % BBK bleached Reference

Reference bleached Delta_100 % BBK spruce Delta_Reference

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Conclusions

• decreasing strength properties and lower

brightness with BBK pulpwood

• BBK pulpwood shows a lower bleachability with

dithionite than fresh and sound pulpwood

• the low moisture content is responsible for the

low strength properties

• fungal infestations are responsible for the low

initial ISO-brightness

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Conclusions

• mixing BBK pulpwood with fresh and sound

pulpwood is beneficial for the pulp and paper

quality

– the amount of BBK pulpwood should not exceed 25

% for the production of high quality mechanical pulp

• rapid and consequent harvesting and

processing of BBK pulpwood will improve the

pulp and paper quality

• financial benefit for the pulp and paper mills

due to the lower purchasing price

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Acknowledgements

• thanks to:

– the employees of Stora Enso Reisholz Mill for their

support during the grinding trials and the analysis of

the pulp and paper properties

– Stora Enso Forest Central Europe for the provision

of the BBK pulpwood and the logistical support

– Stora Enso Publication Paper Division for their

financial support

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Thank you for your attention

Götz Martin

Institute of Forest Utilization and Work Science


Tel: 0049-761 - 203 9242

E-Mail: [email protected]

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Fig. 5: Marked (spruce)

pulpwood

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Fig. 8: Stem selection

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Fig. 10: Pulp sampling

Experiences with the utilization of bark-beetle-killed ... · Götz Martin 1; Gero Becker ;...

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