Forestry Studies | Metsanduslikud Uurimused, Vol. 66, Pages 27–32

Chemical composition and fi ber properties of fast-growing species in Latvia and its potential for forest bioindustry

Inese Sable1,*, Uldis Grinfelds1, Laura Vikele1, Linda Rozenberga1, Dagnija Lazdina2, Martins Zeps2 and Aris Jansons2

Sable, I., Grinfelds, U., Vikele, L., Rozenberga, L., Lazdina, D., Zeps, M., Jansons, A. 2017. Chemical composition and fi ber properties of fast-growing species in Latvia and its potential for forest bioindustry. – Forestry Studies | Metsanduslikud Uurimused 66, 27–32. ISSN 1406-9954. Journal homepage: http://mi.emu.ee/forestry.studies

Abstract. Bioenergy, including energy from wood, currently provides about 9–13% of the total global energy supply. Every fi bre of fast-growing wood has a value for its potential use as a material in both pulp and paper and wood chemical industries. The aim of this study was to assess the chemical composition and fi bre’s properties of fast- growing species in Latvia – , hybrid aspen, lodgepole pine, poplar and willow. Results showed a variation of cellulose, lignin, extractives and ash contents among the species. Kraft pulp yield and amount of residual lignin were measured and properties of pulp fi bres determined. Form factor and fi ne content in pulp were measured. Pop- lar and aspen wood had the highest content of cellulose, while lodgepole pine had the highest lignin content in wood and the longest kraft pulp fi bres. Willow had 20% of fi nes in pulp. Individual results suggest the most suitable application of each species.

Key words: fi ber properties, poplar, aspen, hybrid, lodgepole pine, kraft pulp.

Authors’ addresses: 1Latvian State Institute of Wood Chemistry, 27 Dzerbenes str., Riga, LV-1006, Latvia; 2Latvian State Forest Research Institute ‘Silava’, Rigas str. 111, Salaspils, LV-2169, Latvia; *e-mail: [email protected]

Introduction al., 2013). Within this bioenergy category, wood plays an important role worldwide In order to limit global warming through and also in Latvia (Neimane et al., 2011). the reduction of CO2 emissions, the EU tar- Measurements and calculations were get is to reduce the fossil fuel consumption done to estimate the energy potential of with a view to achieving a share of 20% geographically available abandoned agri- renewable energy in 2020. To reach this cultural lands for short rotation wood spe- target, national targets were set according cies production in Latvia to meet EU 2020 to the renewable energy potential of each renewable energy targets (Abolina et al., country (Vanneste et al., 2011). The use of 2015). In addition to scientifi c and practi- biomass for bioenergy signifi cantly reduc- cal projects, also forestlands’ owners are es greenhouse gas emissions. The carbon constantly informed about the opportuni- dioxide it gives off when it is burned is ties in short rotation forestry (Daugaviete counterbalanced by the amount absorbed & Lazdina, 2014). when the in question was grown. In Latvian conditions, most promising Bioenergy currently provides about 9–13% fast-growing wood species for bioenergy of the total global energy supply (Long et are willow, poplar, aspen, their hybrids

DOI: 10.1515/fsmu-2017-0004 © 2017 Estonian University of Life Sciences. All rights reserved 27

I. Sable et al. and lodgepole pine. Several plantations via. The planting design of this experiment were planted and short rotation experi- was: block plots for 25 (block size mental trials were accomplished in Latvia 5 × 5 ), planted by 3 × 3 m in 3 to in former farmlands to investigate the infl u- 5 replications. Seven aspen hybrid clones ence of fertilizing, cultivation, weather con- (Sable et al., 2013b) – eight sample trees for ditions, harvesting and other factors on bio- each clone – were selected for this study. mass yield and quality (Lazdina, 2009, 2010; Aspen and hybrid aspen were cut at the Bārdule et al., 2012; Lazdina et al., 2012). age of 19–20 years. Willow samples were Nevertheless, every fi bre of fast-grow- grown in sandy loam soil, in Olaine parish ing wood has a value for its potential use and were cut at the age of 8 years; diameter as a material in both pulp and paper and at breast height (DBH) of the selected sam- wood chemical industries. Poplar hybrids ples was 4.55 ± 0.08 cm, height – 9.5 ± wood was intended primarily for manu- 0.10 m. The material of poplar was collect- facture of pulp and paper products, but ed in 14 stands (at the age of 54–65 years), solid wood products have been recently located in the central and western part of considered as well (Pliura et al., 2007). In Latvia, which were established on fertile recent years, it has been investigated also drained mineral soil and mineral soil with from the chemical composition point of normal moisture regime (Jansons et al., view – as a source of different lignins and 2014). Lodgepole pine was represented by their derivatives (Kim et al., 2013); thermal 26 sample trees from 3 provenances from decomposition of poplar wood was stud- Canada; plant production in Latvia was ied with the aim to convert solid biomass carried out in 1985 on dry, sandy soil (Myr- mainly into a liquid product known as tillosa forest type) and trees were cut at the bio-oil (Dong et al., 2012). Aspen and hy- age of 24–25 years. brid aspen wood and fi bres were studied Wood chemical analyses and kraft as a source for the pulp and paper indus- cooking were made from the stem wood at try both in Latvia (Sable et al., 2012b, 2013a, the height of 1.0 to 1.3 m. 2013b; Treimanis et al., 2006; Zeps et al., The content of cellulose (as a weight 2008, 2012) and other countries (Francis et percent of holocellulose according to TAP- al., 2006; Tullus et al., 2011). PI 203cm-99), Klason lignin (according The aim of this study was to assess the to TAPPI 222om-98), extractives (accord- chemical composition and fi bre’s proper- ing to TAPPI T280pm-99) and ash were ties of fast-grow ing wood in Latvia – aspen determined in wood (according to TAP- ( tremula L.), hybrid aspen (Populus PI T211om-02). tremuloides Michx. × Populus tremula L.), Pulp fi bres were obtained by the kraft lodgepole pine (Pinus contorta Douglas ex cooking method (in a 2-l laboratory digest- Loudon), poplar (Populus balsamifera L. × er at 170°C, 57.4 g l–1 active alkali as NaOH, P. laurifolia Ledeb.) and willow (Salix vimi- sulphidity 29.8 %, and liquor to wood ratio nalis L.). 4.5 l kg–1). Fibre properties (length, width and form) were determined by a “Fiber Tester” (Lorentzen & Wettre, Sweden). Material and Methods Klason lignin in pulp was determined ac- cording to TAPPI 222om-98. All aspen sample trees were grown natu- The ANOVA procedure was used for rally in former agricultural and forest the determination of the factor (species) lands – in Aegopodiosa, Hylocomiosa and effect on the inspected properties. If the Mercurialiosa a total of 18 trees were cut. factor was signifi cant (p < 0.05), the Bonfer- Hybrid aspen trees were grown on former roni test was used (post hoc) to determine, agriculture lands in the central part of Lat- which species differed. The ANOVA pro-

28 Chemical composition and fi ber properties of fast-growing species in Latvia and its potential for forest bioindustry

Table 1. Chemical composition of wood of different species (means ± standard deviation). Species Cellulose (%) Klason Lignin (%) Extractives (%) Ash (%) Aspen 52.3 ± 1.7 18.0 ± 1.6 2.7 ± 1.0 0.4 ± 0.0 Aspen hybrid 51.8 ± 1.5 19.3 ± 1.2 2.0 ± 0.6 0.4 ± 0.0 Lodgepole pine 47.6 ± 1.7 28.6 ± 1.3 2.6 ± 0.5 0.293 Poplar 53.7 ± 2.6 23.0 ± 2.5 3.32 1.434 Willow 49.8 ± 2.0 26.8 ± 0.21 2.0 ± 0.2 0.32 21.35 1.55 1 Ai & Tschirner, 2010 2 Fengel & Weneger, 2003 3 Sable et al., 2012a 4 Sannigrahi et al., 2010 5 Caslin et al., 2012

cedure was not used for comparing data Measurements of residual Klason lignin in from other sources, which are marked and pulp showed 1.3% for aspen pulp, 1.5% for reference is given below (Table 1). AH pulp, 4.1% for LP pulp and 2.2% for poplar pulp, but the result of 3.6% for wil- low pulp was found in the literature (Ai et Results al., 2010), because of the lack of the current experiment in the case of this species. A Poplar had a signifi cantly (p < 0.05) higher statistical procedure indicated a signifi cant content of cellulose among the tested wood (p < 0.05) difference among the residual species. The content of cellulose of aspen lignin content in pulp of all tested species. was much higher than that of willow and Table 2 explores measurements of the lodgepole pine (LP), but the difference tested fi bre parameters. Considerable dif- between aspen and aspen hybrid (AH) as ferences among species (p < 0.05) appeared well as between willow and LP was not in fi bre length. Aspen and HA fi bres were signifi cant (p > 0.05). Differences of lignin equal, but shorter than pine, poplar and content in wood were signifi cant (p < 0.05) willow fi bres. LP fi bres were longer than among all tested species. those of other species, except willow. There The content of extractives in aspen was was no difference between the length of considerably higher (p < 0.05) than in as- willow and pine fi bres and also between pen hybrid and willow, but these two poplar and willow fi bres. did not differ (p > 0.05). The result of LP Fibres of LP were wider (p < 0.05) than showed a signifi cant (p < 0.05) difference those of other species; poplar fi bre was in HA. Original experimental data for ash wider (p < 0.05) than all others, except pine content were only for aspen and HA, and fi bre, and there were no differences among they did not differ. fi bres of aspen, HA and willow. Kraft pulp yield was measured after LP fi bres had a lower (p < 0.05) shape the pulping process, and results (Figure 1) factor than other species; a signifi cant were 51.7% for aspen, 50.6% for AH, 40.7 % (p < 0.05) difference was also between as- for LP, 53.9% for poplar and 44.6% for wil- pen and its hybrids. low. Signifi cant differences (p < 0.05) were Measurements of the fi ne content in among all species tested, except those be- pulp showed a signifi cant (p < 0.05) differ- tween aspen and its hybrid. ence among all tree species.

29 I. Sable et al.

80 10 Kraft pulp yield

Klason lignin in kraft pulp 8 60

6 40 4 Kraft pulp yield, % pulp yield, Kraft

20 pulp, % in kraft Lignin 2

0 0 pine pine Aspen Aspen Poplar Poplar hybrid Willow Lodgepole Lodgepole

Figure 1. Kraft pulp yield and residual Klason lignin content of wood, used for bioenergy.

Table 2. Dimensional parameters, form and fi ne content of kraft pulp fi bres of different species (± standard deviation). Fibre length Fibre width Fibre form factor Fines in pulp Species (mm) (μm) (%) (%) Aspen 0.8 ± 0.05 21.5 ± 0.7 94.9 ± 0.7 3.4 ± 1.0 Aspen hybrid 0.8 ± 0.08 21.3 ± 1.1 93.9 ± 1.0 4.1 ± 1.0 Lodgepole pine 1.4 ± 0.4 27.7 ± 2.6 91.2 ± 1.0 1.3 ± 0.2 Poplar 1.0 ± 0.07 24.9 ± 1.5 94.3 ± 0.7 5.2 ± 1.1 Willow 1.2 ± 0.08 21.6 ± 0.8 94.4 ± 0.8 20.2 ± 1.2

Discussion and Conclusions cals, displacing the materials currently pro- duced from crude oil and natural gas (Pye, The chemical composition of a tested wood 2006). Wood extractives consist of terpenes, species (Table 1) elucidates the possibilities resin acids, and fatty acids (Elder, 2004) – of its using. Each component separately and the source for natural chemicals. the composition as a whole provides an op- Figure 1 gives useful information about portunity to increase the marketing value of the yield of fi bres after kraft pulping, and wood. Cellulose is the source of fi bres for the results are in accordance with the the ; also, modifi ed chemical composition of wood. Poplar had fi bres can be used for textile. Micro- and the highest content of cellulose and also nano-scale cellulose products have a wide showed a high yield of kraft pulp. The val- range of applications for innovative com- ues for cellulose content in the current study posite materials, electronics, pharmaceuti- are in accordance with those in the previ- cals, etc. (Moon et al., 2011). Lignin and its ous investigation (Treimanis et al., 2006; Ai derivatives could be an excellent source of & Tschirner, 2010; Zeps et al., 2012) or are industrial specialty and commodity chemi- slightly higher. The differences from other

30 Chemical composition and fi ber properties of fast-growing species in Latvia and its potential for forest bioindustry works can be explained as the dependence current study, with a smaller average di- of pulp yield on the chosen pulping method ameter; therefore the highest result of the conditions. Another important factor that fi ne content was detected. The presence indicates the pulp quality is the content of and variations of fi nes can change the op- residual lignin. It can affect the production tical properties of paper products (Pauler, and utilisation of paper and paper prod- 2012), depending on the requirements for ucts, and can infl uence both mechanical their quality. Different types of wood had and optical properties. The highest number different response (degree of delignifi ca- in the case of LP is logically connected with tion) during the kraft cooking, thus the op- the results of the lignin content in wood, timization of cooking parameters is needed because softwood usually has more lignin for each type to obtained fi bers of similar/ than hardwood (Fengel & Wegener, 2003). best properties. The result of willow, in the case of the lignin content both in wood and in pulp, is closer Acknowledgements. This research was to softwood characteristics. Based on the conducted as a part of the European Re- quite different information (Ai & Tschirner, gional Development Fund’s Project “Fast- 2010; Caslin et al., 2012) about the properties growing tree plantations: development of of willow wood and fi bres, we can conclude methods of establishment and mana gement about the strong dependence of these prop- and assessment of suitability of wood for erties on external conditions. production of pellets” (No 2DP/2.1.1.1/13/ Fibres of softwood normally are longer APIA/VIAA/031). and wider than those of hardwood (Fen- gel & Wegener, 2003). Our study confi rms References (Table 2) this well-known fact with the ex- ception of the case of willow. The result of Abolina, E., Volk, T.A., Lazdina, D. 2015. GIS based 1.2 ± 0.08 disagrees with other studies (Ai agricultural land availability assessment for the & Tschirner, 2010), where 0.34 mm of the establishment of short rotation woody crops in Latvia. – Biomass and Bioenergy, 72, 263–272. willow fi bre length is given. Aspen, AH Ai, J., Tschirner, U. 2010. Fiber length and pulping and poplar fi bre length results are in accor- characteristics of switchgrass, alfalfa stems, hy- dance with the studies performed by Ai & brid poplar and willow biomasses. – Bioresource Tschirner (2010) and Zeps et al. (2012). The Technology, 101(1), 215–221. Bārdule, A., Lazdiņa, D., Bārdulis, A., Lazdiņš, A., claim of the dependence on growing condi- Vīksna A. 2012. Utilization of wood ash, sewage tions is testifi ed by Treimanis et al. (2006), sludge and digestate in short rotation bioenergy namely, if they are similar, fi bre properties plantation in Latvia. – Book of Abstracts of the th diversify insignifi cantly. Tree age is the 17 International Conference “EcoBalt 2012”, Lat- via, Riga, Oct. 18–19, 2012. 15 pp. main factor that infl uences fi bre length. It Caslin, B., Finnan, J., McCracken, A. 2012. Willow is known that the average fi bre length itself varietal identifi cation guide. Teagasc, Carlow, is not always a good predictor of the prod- Ireland. 64 pp. uct properties, and every parameter must Daugaviete, M., Lazdiņa, D. 2014. Sustainable man- agement of plantation forest. (Plantāciju meži be taken into account. The form factor of ilgtspējīgai saimniekošanai). – Agrotops, 2–4. (In fi bre provides information about its shape. Latvian). If it is 100%, the fi bre is completely straight. Dong, C., Zhang, Z., Lu, Q., Yang, Y. 2012. Charac- In the pulping process, all natural wood fi - teristics and mechanism study of analytical fast pyrolysis of poplar wood. – Energy Conversion bres are deformed and the measured num- and Management, 57, 49–59. bers are in the interval of 91–94%. Elder, T. 2004. Non-wood products: Chemicals from Obvious differences between the fi ne Wood. Encyclopedia of Forest Sciences. USDA – content in pulp were caused by the vari- LA, USA, Forest Service, Pineville, 607–612. Fengel, D., Wegener, G. 2003. Wood – chemistry, ul- ety of species, tree age and diameter. Wil- trastructure, reaction. Berlin, Walter de Gruyter. low trees were the youngest samples in the 613 pp.

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Received March 14, 2017, revised May 2, 2017, accepted June 12, 2017

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