Original Research Journal of Bioresources and Bioproducts. 2019, 4(2): 73–79 DOI: 10.21967/jbb.v4i2.227
Pulpwood Quality of the Second Generation Acacia auriculiformis
Md. Moinul HAQUE1, 2, M Nashir UDDIN1, M A QUAIYYUM2, Jannatun NAYEEM1, M Zahangir ALAM2, M Sarwar JAHAN1* 1 Pulp and Paper Research Division, Bangladesh Council of Scientific & Industrial Research Laboratories, Dhaka 1205, Bangladesh 2 Department of Applied Chemistry and Chemical Engineering, University of Dhaka, Dhaka 1205, Bangladesh *Corresponding author: M Sarwar JAHAN, [email protected] Received 23 March 2019; Accepted 25 April 2019
Abstract: The physical, chemical and fibre characteristics of the 6, 8 and 10 years old akashmoni (Acacia auriculiformis) wood from the second generation seed and their suitability for pulping were assessed and compared with the wood of 10 years old from the first generation seed. The A. auriculiformis of 8 years old had the highest α-cellulose and lower lignin than those of 6 and 10 years old, which are similar to the first generation wood. This study also evaluated the effect of cooking time, temperature and active alkali on kraft pulping. The most important influence factors for pulp yield and kappa number were active alkali charge and time. The highest screened rejects were observed for young tree. Delignification degree of the 1st generation was faster than that of the 2nd generation A. auriculiformis. Keywords: second generation Acacia auriculiformis; α-cellulose; wood density; pulping; active alkali and cooking time
Citation: Md. Moinul Haque, M Nashir Uddin, M A Quaiyyum, et al., 2019. Pulpwood quality of the second generation Acacia auriculiformis. Journal of Bioresources and Bioproducts, 4(2): 73–79. DOI: 10.21967/jbb.v4i2.227
1 Introduction 50% total yield with kappa number of 20. The pulp could be bleached using conventional CEH bleaching sequence Akashmoni (Acacia auriculiformis), an exotic fast giving brightness higher than 75%. Miyanishi and growing tree species, was introduced to Bangladesh in Watanabe (2004) studied on A. mangium, which was used 1960s as the shade tree in tea estates. In 1983, the trial for the first time afforestation in 1991 at provinces of plantations of the Acacia were established and people South Sumatra, Indonesia. Prior to the construction of a found that the A. auriculiformis and A. mangium were new pulp mill, kraft pulping characteristics of plan- promising species in respect to survival and growth per- tation-grown A. mangium was investigated in laboratory. formance. The participatory plantations were raised by It was found that the pulp yield was very high and exotics fast growing species such as Acacias, Eucalyptus. comparable to E. globules. Khristova et al. (2004) studied In the social forestry programs, these exotics species on two A. seyal varieties (fistula and seyal) grown in provided return shortly. The A. auriculiformis are able to Sudan for pulping and papermaking with different create vegetation cover in degraded forest areas easily. alkaline methods. The alkaline sulfite anthraquinone and The Acacia also planted in agro-forestry. Bangladesh methanol (ASAM) pulping gave the best results in yield, Forest Department has 44 000 hm2 forestland for social degree of delignification and strength properties. In our forestry program. Produced wood can be utilized in pulp previous study, A. auriculiformis from the first generation mill as Bangladesh facing acute shortage of raw material. seed was investigated and obtained pulp yield of 43%– A lot of studies have been carried out on the pulping of 44% and kappa number of 22–24 at the conditions of Acacia species. Pulpwood samples from 8-year old A. 20% alkali and 2.5 h of cooking in soda, 16% alkali and mearnsii and Eucalyptus grandis plantations grown in 2.5 h of cooking in soda-AQ, and 18% alkali in 2 h of Zimbabwe were evaluated for kraft pulping, bleaching cooking in kraft process (Jahan et al., 2008). Rosli et al. and papermaking properties by Muneri (1997). At about (2009) studied on the influence of the pulping variables the same kappa number, the A. mearnsii pulp had lower (active alkali charge, sulfidity, temperature and pulping strength properties but higher opacity. Xue et al. (2001) time) on the pulp yield, kappa number and strength studied on three species of plantation fast-growing Acacia properties of A. mangium kraft pulp. When beaten to a woods of different ages, which were subjected to kraft freeness of 500 mL and 50% yield, the kraft pulp from A. cooking and bleaching by the use of CEH sequence. mangium evidenced excellent physical properties. Santos These three Acacias were easily pulped using the con- et al. (2012) investigated A. melanoxylon and its natural ventional kraft process with acceptable pulp yields, i.e., variability. Under the same experimental conditions of
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Journal of Bioresources and Bioproducts, 2019, 4(2): 73–79 kraft pulping, screened pulp yield ranged from 47.0% to generation seed. The chemical and morphological chara- 58.2%, kappa number of 10.9–18.4 with the variation of cteristics were also assessed. The effects of alkali concen- wood density from 449 kg/m3 to 649 kg/m3 were tration, duration and temperature on both pulp yield and obtained. Pulping properties and fibre characteristics of the kappa number were assessed by means of an incomplete, clones of A. mangium grown in Vietnamwere reported by centered, factorial design. The best operational conditions Griffin et al. (2014). Kraft pulp yield at kappa 20 was were chosen to evaluate the effects on pulp yield and similar for that of the diploid and tetraploids clones, kappa number. compared with the diploid clones (683 μm and 15.6 μm), tetraploid clones produced pulp with significantly longer 2 Materials and Methods (883 μm) and wider (20.0 μm) fibres. A lot of variations among different studies were found. 2.1 Materials The pulping wood quality of A. melanoxylon was The A. auriculiformis was collected from the Gazipur evaluated by Lourenço et al. (2008) in relation to the Forest Station at the age of 6, 8 and 10 years old from the presence of heartwood. Pulping heartwood differed from second generation seed and the 10 years old A. auri- sapwood in chemical and optical terms: lower values of culiformis was from the first generation seed. The 8 years pulp yield (53% VS. 56%, respectively), higher kappa old A. auriculiformis was not available in the same plan- number (11 VS. 7), and lower brightness (28% VS. 49%). tation site. It was collected near another plantation site. Khider et al. (2012) investigated A. mellifera stem for its Three trees were selected for this experiment. Left from suitability for pulping and paper production. The Soda- top and bottom and branches of these trees was discarded AQ, AS-AQ, ASAM and soda processes were evaluated, and the remained portion was debarked and chipped into and results found that the ASAM pulping shown the 0.5 cm×0.5 cm×2.0 cm size. The chips were ground in a excellent results in yield, degree of delignification, mech- Wiley mill and the 40–60 mesh size was used for che- anical and optical properties. Xiong et al., (2016) carried mical analysis. out the kraft cooking of acacia wood as well as the 2.2 Physical, morphological and chemical properties beating and paper-making experiments of the resultant pulp. The results showed that the acacia wood kraft pulp The basic wood density of A. auriculiformis was deter- with yield 52.25%, kappa number 17.9, viscosity 987.3 mined according to Pulp and Paper Technical Association mL/g, breaking length 9.32 km, tensile index 93.6 N·m/g, of Canada (PAPTAC) Standard A. 8P. For the meas- tearing index 10.0 mN·m2/g and bursting index 5.34 urements of fiber length, sample was macerated in a 2 kPa·m /g was obtained at the conditions of 15% alkali solution containing HNO3 and KClO3 (1꞉1). A drop of charge, 30% sulfidity, 1:4 liquor to wood ratio and 2 h macerated sample was taken in a slide. The fiber diameter cooking at the 165℃. Liew and Chong (2016) studied the and length was measured by image analyzer Euromex- organosolv pulping of acacia hybrid. Wood chips were Oxion using Image Focus Alpha software. digested at 185℃ for 3 h and pressure of 1.1–1.2 MPa. It The extractive (T204 om88), 1% alkali solubility was observed that increasing of ethanol concentration led (T212 om98), water solubility (T207 cm99), Klason to increment in pulp yield and delignification degree. At lignin (T211 om83) and ash content (T211 os76) were 90% ethanol concentration, pulp yield of 44.19% with determined in accordance with Tappi Test Methods. 5.24% reject and 15.32 kappa number was screened. Holocellulose was determined by treating extractive free From the above results on acacia pulping, there are a lot wood meal with NaClO2 solution. The pH of the solution of variations of the pulp yield and delignification degree. was maintained at 4 by adding CH3COOH-CH3COONa The A. auriculiformis is one of the most common buffer and -cellulose was determined by treating holo- exotic trees in Bangladesh and millions of scattered trees cellulose with 17.5% NaOH. are planted around farms, homesteads, roads and villages. 2.3 Pulping A tree improvement program for Acacias was started in 1981 by the Bangladesh Forest Department with the aim Pulping was carried out in a thermostatically controlled of improving the growth and stem of the species. App- electrically oil bath contained four bomb digesters. The arently, the growth of Acacias from the second generation capacity of the digester was 1.5 L. The normal charge was seed was hindered. 100 g of oven dried A. auriculiformis. Pulping conditions This work dealed with the optimization of the kraft of kraft are as follows: Active alkali was 14%, 16%, 18% pulping of A. auriculiformis grown from the second and 20% on oven-dry raw material as Na2O. Cooking generation seed in social forestry plantation program in time was 1.5 h, 2.0 h and 2.5 h at maximum temperature, Bangladesh at the age of 6, 8 and 10 years and compared and cooking temperature was 160℃, 165℃ and 170℃. with 10 years old A. auriculiformis grown from first Ratio of liquor to material was 4. Sulphidity 30% for kraft
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Md. Moinul HAQUE et al.: Pulpwood Quality of the Second Generation Acacia auriculiformis process. Table 1 Chemical, morphological and physical properties of After digestion, pulp was washed till free of residual 1st and 2nd generation A. auriculiformis chemicals, and screened by flat vibratory screener (Yasuda, 2nd 1st Japan). The screened pulp yield, total pulp yield and generation generation Parameter screened reject were determined gravimetrically as per- Age (a) centage of oven dried raw material. The kappa number 6 8 10 10 (T236 om99) of the resulting pulp was determined in acc- Extractive (%) 7.8 2.6 7.0 4.06 ordance with Tappi Test Methods. Three replicates of all 1% Alkali (NaOH) solubility 14.09 11.39 13.23 15.49 experiments were done and the average reading was taken. (%) Cold water solubility (%) 4.29 2.22 2.20 3.24 3 Results and Discussion Hot water solubility (%) 8.61 6.45 4.60 5.20 3.1 Chemical, morphological and physical properties Holocellulose (%) 60.1 66.8 60.9 65.0 α-cellulose (%) 41.2 43.4 42.3 43.0 The average chemical composition, morphological and Pentosan (%) 12.8 13.2 15.2 16.9 physical properties of A. auriculiformis obtained from the first and second generation seeds are shown in Table 1. It Klason lignin (%) 30.4 25.2 29.8 33.2 is seen that extractives soluble in acetone were higher than Ash content (%) 0.395 0.410 1.32 0.65 that of the other hardwood species (Jahan et al., 2010). Density (g/mL) 0.3126 0.3808 0.4231 0.5110 Extractives in A. auriculiformis from the first generation Fiber length (mm) 0.85 0.76 0.78 0.89 seed were 4.06%, while the same from the second gener- Fiber width (µm) 14.24 15.69 17.89 16.13 ation seed was above 7% except 8 years old. In another study on A. melanoxylon, extractives ranged from 5.3% to amount of energy and chemicals. Lower lignin content of 7.8% (Miyanishi and Watanabe, 2004). Acetone soluble pulpwood makes them suitable for delignification to extractives were much higher than the Eucalyptus species reach a desirable kappa number at milder pulping (1.3–2.2) (Ribeiro et al., 2018). Cold and hot water conditions (lower temperatures and chemical charges). solubilities decreased with tree age. Holocellulose and Unfortunately, the lignin content in A. auriculiformis was α-cellulose are the most important components of pul- higher than that of the other hardwoods in Bangladesh pwood, which affect pulp and papermaking properties. (Jahan et al., 2011; Mun et al., 2011), which was similar The highest holocellulose and α-cellulose value were to the lignin content obtained by Yamada et al. (1991) and determined as 66.6% and 43.4%, respectively, for 8 years higher than our previous study (Yamada et al., 1991). old A. auriculiformis from second generation seed, which As seen in Table 1, wood density increased from were similar to A. auriculiformis from the first generation 0.3126 g/cm3 at the age of 6 years old to 0.4231 g/cm3 at seed. The A. auriculiformis from 8 years old was coll- the age of 10 years old. The A. auriculiformis wood was ected from plantation site of Gazipur district. Nutritive denser from the first generation seed than the second value of the soil may affect the properties of wood. The generation (0.5110 g/cm3 VS. 0.4321 g/cm3). Similarly, α-cellulose content in A. auriculiformis was found to be Jusoh et al. (2013) found significantly lower wood 44.1% in our previous study (Jahan et al., 2008) and 35% density for the second generation A. mangium. As shown studied by Yamada et al. (1991). The α-cellulose content in Fig. 1 of cross section, growth of the second generation in A. auriculiformis in this study was much lower than of A. auriculiformis was slower than that of the first that of Eucalyptus species (Ribeiro et al., 2018). Pentosan generation. According to Zobel and Buijtenen’s study is the main hemicelluloses component in hardwood (1989), faster growth did not affect wood density. species, and it contributes fiber bonding in paper sheet The average fiber length of A. auriculiformis from and also increases pulp yield. As shown in Table 1, pen- different ages and the first and second generation were in tosan content increased with the tree age. The pentosan the range of tropical hardwoods (0.7–1.5 mm) considered content in A. auriculiformis at 10 years old was 15.2%, as short (Hale, 1959). No relation was found in the fibre which was 1.7% lower than that of the first generation length and tree age of A. auriculiformis. The average fibre seed. The pentosan content in A. auriculiformis was found length of A. auriculiformis from the second generation as 15.8% in other study (Yamada et al., 1991). The was 0.80 mm, which was lower than the fibre length of A. pentose sugars content in Eucalyptus species was very auriculiformis from the second generation (0.89 mm). close to the pentosan content in A. auriculiformis (Ribeiro Similarly, Jusoh et al. (2013) found slightly lower fibre et al., 2018). length of the second generation A. mangium. The fiber Lignin is the undesirable part pulpwood, which is width was medium-narrow and in the hardwood range removed during pulping process. It requires the high (l0–35 μm).
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Table 2 Effect of active alkali, cooking time and temperature on pulping of 6 years A. auriculiformis Active Pulp yield (%) Temperature Time Kappa alkali (℃) (h) number (%) Screened Reject Total 160 1.5 16 36.80 12.09 48.89 24.60 165 1.5 16 44.20 2.1 46.30 22.40 170 1.5 16 44.99 0.2 45.19 20.63 160 2.0 16 43.34 0.8 44.14 22.02 165 2.0 16 41.60 0 41.60 21.22 170 2.0 16 40.85 0 40.85 20.06 160 2.5 16 41.68 0 41.68 21.91 165 2.5 16 41.00 0 41.00 21.20 170 2.5 16 39.51 0 39.51 20.40 160 1.5 18 43.24 0.4 43.64 19.92 165 1.5 18 42.30 0.1 42.40 18.97
Fig. 1 Cross section 1st and 2nd generation A. auriculiformis 170 1.5 18 42.00 0.1 42.10 18.05 160 2.0 18 42.88 0.2 43.08 18.35 3.2 Pulp yield and kappa number 165 2.0 18 41.20 0 41.20 18.00 170 2.0 18 40.80 0 40.80 17.81 Experimental results of the kraft pulping of A. auriculi- formis of 6, 8 and 10 years old wood chips are shown in 160 2.5 18 40.95 0 40.95 18.00 Table 1. Effects of each independent experimental vary- 165 2.5 18 40.10 0 40.10 17.51 ing in time, temperature and active alkali charge on the 170 2.5 18 39.69 0 39.69 17.24 total pulp yield and kappa number were analyzed using 160 1.5 20 41.86 0.2 42.06 19.32 MATLAB software. Apparently, it is seen that pulp yield 165 1.5 20 41.27 0 41.27 18.24 from 8 years old A. auriculiformis was higher compared 170 1.5 20 39.43 0 39.43 17.37 with the 6 and 10 years old counterpart. The mean 160 2.0 20 41.04 0 41.04 18.47 screened pulp yield of 8 years old A. auriculiformis was 165 2.0 20 40.14 0 40.14 17.35 44% ranging from 41% to 46% with kappa number of 17–25, while those were 41% ranging from 36% to 45% 170 2.0 20 39.02 0 39.02 17.02 with kappa number of 17–24 and 42% ranging from 39% 160 2.5 20 39.05 0 39.05 17.92 to 45% with kappa number of 17–32 for 6 and 10 years 165 2.5 20 39.00 0 39.00 17.80 old A. auriculiformis, respectively. Oluwafemi (2007) 170 2.5 20 38.40 0 38.40 17.40 demonstrated that the oldest age class tree had the highest screen pulp yield. The uncooked material (rejects) for 8 Table 3 Effect of active alkali, cooking time and years old A. auriculiformis was very low (0.67%) when temperature on pulping of 8 years A. auriculiformis only cooking with 14% active alkali charge for 2 h Active Pulp yield (%) Temperature Time Kappa alkali cooking at 170℃ and it was zero in all other conditions. (℃) (h) number (%) Screened Reject Total But the reject was 12.1% for 6 years old A. auriculiformis at the conditions of 16% active alkali for 1.5 h cooking at 8 years 160℃. Similarly, results from Oluwafemi (2007) also 170 2.0 14 46.13 0.67 46.8 24.65 showed that the rejects in the older tree was lower 170 2.0 16 44.34 0 44.34 19.48 compared with the young tree. Screened reject decreased 170 2.0 18 44.16 0 44.16 17.25 from 12.1% to 0.2% with increasing temperature from 170 2.0 20 44.00 0 44.00 16.38 ℃ ℃ 160 to 170 (Table 2–4). The screen pulp yield range 170 1.5 16 44.64 0 44.64 20.94 in this study was close to the screen pulp yield from A. 170 2.0 16 44.34 0 44.34 19.48 mangium studied by Rosli et al. (2009) but much lower than eight-year-old clones of A. mangium grown in 170 2.5 14 45.21 0.20 45.41 23.22 Vietnam (Griffin et al., 2014). Another study showed that 170 2.5 16 43.32 0 43.32 18.18
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Md. Moinul HAQUE et al.: Pulpwood Quality of the Second Generation Acacia auriculiformis
Table 4 Effect of active alkali, cooking time and temperature linear dependence on both operational variables. on pulping of 10 years A. auriculiformis For total pulp yield: Active Pulp yield (%) Total pulp yield (10 years) = 82.05–0.151temp– Temperature Kappa Time (h) alkali (℃) number 1.56time–0.69AA (R2=0.89, adjusted R2=0.87) (1) (%) Screened Reject Total Total pulp yield (8 years) =55.482–2.993time– 170 2.5 16 42.86 0 42.86 18.15 0.31AA (R2=0.70, adjusted R2=0.59) (2) 170 3.0 16 40.94 0 40.94 17.17 Total pulp yield (6 years) =99.36–0.217temp– 160 1.5 16 44.91 0 44.91 32.12 3.544time–0.826AA 165 1.5 16 44.24 0 44.24 27.65 (R2=0.84, adjusted R2=0.81) (3) 170 1.5 16 43.34 0 43.34 24.89 Similarly, the most influential factors for kappa num- 160 2.0 16 43.94 0 43.94 23.67 bers were active alkali charge and cooking time, which 165 2.0 16 42.68 0 42.68 23.09 also showed an almost linear dependence on both oper- 170 2.0 16 42.43 0 42.43 22.05 ational variables (equations (4)–(6)). 160 2.5 16 43.12 0 43.12 23.56 For kappa number: 165 2.5 16 42.23 0 42.23 23.07 Kappa number (10 years) = 85.28–0.189temp– 170 2.5 16 41.11 0 41.11 21.70 2.547time–1.571AA (R2=0.736, adjusted R2=0.702) (4) 160 1.5 18 42.52 0 42.52 21.65 Kappa number (8 years) =46.051–2.936time– 165 1.5 18 41.62 0 41.62 20.13 1.25AA (R2=0.853, adjusted R2=0.795) (5) 170 1.5 18 41.30 0 41.30 18.53 Kappa number (6 years) =64.899–0.162temp– 160 2.0 18 42.43 0 42.43 19.44 1.124time–0.932AA 165 2.0 18 41.05 0 41.05 19.24 (R2=0.792, adjusted R2=0.765) (6) 170 2.0 18 40.16 0 40.16 19.05 In order to optimize the pulping conditions, three- 160 2.5 18 41.43 0 41.43 19.13 dimensional (3D) response surface plots were created by 165 2.5 18 39.79 0 39.79 18.90 plotting the response (total pulp yield and kappa number) 170 2.5 18 39.10 0 39.10 18.23 on the Z-axis versus the most influential two independent 160 1.5 20 41.24 0 41.24 19.06 variables time and alkali charge as shown in Fig. 2 and Fig. 3. Pulp yield decreased linearly as cooking time and 165 1.5 20 40.34 0 40.34 18.79 alkali charge increased. Pulp yield of 8 years old A. 170 1.5 20 40.07 0 40.07 18.6 auriculiformis was 44.34% at the conditions of 16% AA 160 2.0 20 41.10 0 41.10 18.52 and 2 h of cooking, while the same for 6 years old was 165 2.0 20 41.06 0 41.06 18.11 40.85% and 42.43% for 10 years old. Under the same 170 2.0 20 40.48 0 40.48 18.24 conditions, kappa numbers were 20.1, 19.5 and 22.1 for 6, 160 2.5 20 40.12 0 40.12 18.31 8 and 10 years old A. auriculiformis, respectively. 165 2.5 20 39.38 0 39.38 18.40 3.3 Comparison of pulping of wood between 1st and 170 2.5 20 39.22 0 39.22 17.20 2nd generation seed From the above discussion, it is clearly seen that 8 years 6 years old A. auriculiformis produced pulp yield of about old A. auriculiformis from the second generation seed 50% with kappa number of about 20 at the conditions of show better pulp yield and delignification. Therefore, the 60 min cooking at 170℃ (Xue et al., 2001). This var- pulp yield-kappa relationship of 8 years old A. auri- iation can be explained by variation of location. culiformis was compared with 10 years old A. auri- Effect of cooking time, temperature (temp) and active culiformis from the first generation. As shown in Fig. 4, alkali (AA) charge on total pulp yield as well as their the delignification degree of the first generation A. auri- statistical significance on the basis of F-test number are culiformis was faster than that of the second generation. presented in regression equations (1)–(3). As shown in Pulp yield of 44% was achieved for the 1st generation A. equations, cooking time at the maximum temperature had auriculiformis with kappa number of only 12, while to a pronounced effect on pulp yield followed by active obtain the same pulp yield, the kappa number reached 20 alkali charge. Effect of temperature on pulp yield was less for the 2nd generation. Although the lignin content in the in employed cooking conditions. 1st generation A. auriculiformis was higher, easier The most influential factor were active alkali charge delignification can be explained by higher syringyl to and cooking time and pulp yield, which showed an almost guaiacyl ratio of lignin (Fengel and Wegener, 1989).
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Fig. 3 Effect of active alkali and cooking Fig. 2 Effect of active alkali and cooking time on kappa number time on pulp yield
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