- Email: [email protected]
Physico-chemical properties of wood pellets from coppice of short rotation tropical hardwoods
Fuel 160 (2015) 531–533
Contents lists available at ScienceDirect
Fuel journal homepage: www.elsevier.com/locate/fuel
Short communication
Physico-chemical properties of wood pellets from coppice of short rotation tropical hardwoods Menandro N. Acda ⇑ Department of Forest Products and Paper Science, University of the Philippines Los Banos, College, Laguna 4031, Philippines
h i g h l i g h t s Coppice from short rotation tropical hardwoods collected from industrial tree plantation in the Philippines. Coppice biomass were dried, grounded and pressed into fuel pellets. Proximate, ultimate and elemental analyses were performed to determine physical and chemical properties of the pellets. Properties of pellets were within recommended limits for class A2 pellets under EN 14961-2.
a r t i c l e
i n f o
Article history: Received 18 June 2015 Received in revised form 1 August 2015 Accepted 6 August 2015 Available online 14 August 2015 Keywords: Pellets Coppice Gmelina arborea Acacia mangium Paraserianthes falcataria
a b s t r a c t The study investigated the physical and chemical properties of wood pellets from coppice of intensively cultured tropical hardwoods viz., Gmelina arborea, Acacia mangium and Paraserianthes falcataria. Proximate, ultimate and elemental analyses were performed to assess fuel properties of pellets from coppice feedstock. In general, physical and chemical properties of pellets from coppice biomass were within recommended limits for class A2 pellets under EN 14961-2. Pellets from coppice of tree species used in this study showed good potential for compressed solid fuel for industrial and residential heating applications. Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction Short rotation tropical hardwood species intensively cultured in industrial tree plantations have known abilities to coppice. Wood production in fast growing tree species is routinely maximized by coppicing trees in the early stages of growth [1,2]. Coppicing is the process of repeatedly cutting a tree to ground level, resulting in vigorous regeneration of new shoots from the base. Coppiced trees have fully developed root system so regrowth is rapid and the wood from the new stems may be harvested in 5–7 years. Woody biomass from coppiced trees is a potential source of sustainable biomass for bioenergy production [3]. Recent studies have shown that short rotation coppice (SRC) can be converted to fuel pellets [4]. Pellets are compressed solid fuel of high density and high combustion efficiency [5]. Its geometry and cylindrical form facilitates transport over long distances, compact storage and ⇑ Tel.: +63 49 536 3432; fax: +63 49 536 3206. E-mail address: [email protected] http://dx.doi.org/10.1016/j.fuel.2015.08.018 0016-2361/Ó 2015 Elsevier Ltd. All rights reserved.
control feeding to burners and boilers [6]. These attractive properties have resulted in soaring demand for wood pellets in Europe and North America [7]. However, before woody biomass from coppice of tropical hardwoods can be used for pellet production, its fuel characteristic must first be evaluated. No or limited studies have been reported in the literature on the use of SRC trees from tropical hardwoods for compressed solid fuel. Coppiced trees contain large proportion of juvenile wood and their physical and chemical properties vary widely with that of the parent tree [8]. Consequently, an understanding of their variation is necessary in order to make quality pellets from this biomass material. The present paper reports on the physical and chemical properties of wood pellets produced from coppice of Gmelina arborea Roxb, Acacia mangium Willd and Paraserianthes falcataria (L) Nielsen. These short rotation tree species are widely cultivated in industrial tree plantation in the Philippines, Malaysia, Indonesia and other Southeast Asian countries and their coppice could offer an alternative source of woody biomass for bioenergy production.
532
M.N. Acda / Fuel 160 (2015) 531–533
2. Materials and methods 2.1. Coppice Four year old coppice of G. arborea, A. mangium and P. falcataria (8–12 cm diameter) were collected from tree plantation of the University of the Philippines Los Banos in Quezon province. G. arborea, A. mangium and P. falcataria are fast growing tree species intensively cultivated in industrial tree plantations and commonly used to produce wood for light construction, crafts and furniture, decorative veneers, pulp, fuel, and charcoal. The coppice were transported to the laboratory, debarked, chipped and hammermilled to about 4 mm particle size. The ground biomass was dried to about 18% moisture content using a rotary drier (80–110 °C) prior to the pelleting operation. 2.2. Pelleting process The dry woody biomass were pressed using a laboratory pelletizer at a uniform rate through a fix ring die and rotating roller cylinder (MZLP 200 Flat Die Pellet Press) to form pellets of uniform density and shape (8 mm diameter). Binders or lubricants were not used to consolidate or increase strength of pellets in this experiment. When the pelleting process reached a stable temperature (85 °C), sample pellets were randomly collected and cooled by ambient air then stored in plastic containers for physical and chemical testing. Three replicate batches were made for each species. 2.3. Physical and chemical analysis Pellets were randomly selected from each batch for measurement of physical and chemical properties. Dimensions were determined by measuring the length and diameter of 20 randomly selected individual pellets. Particle density for each species was calculated based on the average weight and average volume of 20 pellets. Bulk density was determined using the weight and volume (500 mL) of pellets measured using a 1000 mL graduated cylinder. Proximate, ultimate and elemental analyses were conducted using ten pellets randomly selected pellets from each batch. Proximate analysis consisted of determination of moisture, ash content, and volatile matter using thermogravimetric-differential thermal analysis (TG-DTA, STA 6000 Perkin Elmer). Gross calorific values (GCV) of each type of pellets were measured at constant volume in dry basis using an isoperibol bomb calorimeter (Parr Instrument Company, USA) [9]. Net calorific value (NCV) of pellets was estimated using the equation described by Kuokkanen et al. [10]. Three replicates were used for each calorific measurement. The mechanical durability of each batch of randomly selected pellet was determined using a four sided (12 cm 30 cm) rotating chamber (15 rpm) to induce particle collisions against one another and the walls of the chamber. Five replicate measurements per sample were performed. Ultimate analysis for the presence of C, H, N and S was performed using an automated organic elemental analyzer (Dumas combustion method) (Exeter Analytical) in an oxygen-enriched helium atmosphere attached to a stable isotope ratio mass spectrometer (Finnigan Delta Plus XP). The O content was obtained by difference from the sum of C, H, N and S contents. Elemental analysis for the presence of heavy metals such as Cd, Pb, Zn, Cr, Cu and other trace elements such as Mg, Ca, Fe, K, and P. were determined using inductively coupled plasma-mass spectroscopy (ICP-MS, Agilent 7500cx) and atomic absorption spectroscopy (Model AA420FS, Varian Instruments).
Table 1 Physical characteristics of wood pellets from coppice of G. arborea, A. mangium and P. falcataria. Properties
G. arborea
A. mangium
P. falcataria
Diameter, mm Length, mm Moisture (%) Particle density (g cm 3) Bulk density (kg m 3) Mechanical durability (wt.%)
8.24 20.68 4.10 1.24 621.24 98.14
8.41 18.56 3.78 1.29 732.45 98.48
8.13 26.45 4.35 1.22 687.23 98.29
Table 2 Proximate analyses of wood pellets from coppice of G. arborea, A. mangium and P. falcataria using thermogravimetric-differential thermal analysis. Property
G. arborea
A. mangium
P. falcataria
Moisture (%) Ash (%) Volatile matter (%) Fixed carbon (%) Gross calorific value (MJ kg 1) Net calorific value (MJ kg 1)
6.15 1.00 62.17 30.67 19.78 19.65
5.48 0.79 63.68 30.05 19.83 19.69
5.21 1.45 64.13 29.16 20.01 19.87
3. Results and discussion The diameter and length of pellets from coppice of G. arborea, A. mangium and P. falcataria showed that all samples were fairly uniform in diameter but with some variation in size (Table 1). Pellet temperature directly after pelleting was about 85 °C. Pellet particle and bulk densities for all species were >1.22 g cm 3 and 621–732 kg m 3, respectively. Mechanical durability of all coppice feedstock were >98 wt.% indicating low levels of potential breakage during pellet handling and storage. Proximate analyses showed that pellets from coppice of G. arborea, A. mangium and P. falcataria had moisture content less than 10% after the pelleting operation (Table 2). Pellets from coppice of P. falcataria showed slightly higher ash content (1.45%) compared with pellets from G. arborea and A. mangium (0.79–1.0%). However, the levels of ash reported in this study are within permissible limits (<1.5 wt.%) of class A2 pellet of EN 14961-2 [11]. Feedstock with high ash contents are generally problematic during thermal conversion due to problems associated with ash removal, slagging, corrosion of equipment and deposit formation in the furnace [12]. In addition, frequent equipment cleaning and maintenance may be an issue with pellets containing high ash content for household heating applications [13]. The quantities of volatile matter in all three species studied were relatively high (62–64%). Calorific measurements of coppice pellets from G. arborea, A. mangium and P. falcataria resulted in heating values of about 19–20 MJ kg 1. Similar ranges of heating values were reported for various wood species and energy crops in the literature [14,15]. Ultimate analysis showed that all samples contain high proportion of C, H and O indicating the high energy potential of coppice pellets (Table 3). The samples of G. arborea and A. mangium showed low levels of N (<0.5%) and S (<0.05%). These would indicate very low levels of emissions containing nitric oxides (NOx) and SO2 if pellets are used in thermal conversion processes. The low levels of N and S is considered one of the strength of biomass utilization for energy purposes in terms of contribution to environmental protection [16]. In this regard, the G. arborea and A. mangium show better performance than P. falcataria. Minor and trace elements of pellets from coppice of G. arborea, A. mangium and P. falcataria are shown in Table 4. Low levels of ash forming elements including Ca, Fe, K, Mg, Na and P were present in pellets from the coppice of all three species tested. However, the marginal amount of ash forming elements in all sample tested
M.N. Acda / Fuel 160 (2015) 531–533 Table 3 Ultimate analyses of wood pellets from coppice of G. arborea, A. mangium and P. falcataria. Element (wt.%, d.b.)
G. arborea
A. mangium
P. falcataria
C H O N S
47.62 5.51 47.51 0.35 0.03
46.50 5.65 47.43 0.39 0.03
47.20 5.41 44.90 2.41 0.08
Table 4 Elemental analyses of wood pellets from coppice of G. arborea, A. mangium and P. falcataria. Element
G. arborea mg kg (d.b.)
Na Mg P K Ca Mn Fe Cr Cu Zn Cd Pb
8.13 1.48 41 283 338 24.15 255.6 3.21 3.70 30.7 0.046 1.54
1
A. mangium mg kg (d.b.) 3.17 2.48 55 424 483 8.28 648.4 3.90 3.86 29 0.05 2.06
1
P. falcataria mg kg (d.b.)
533
properties of coppice compared with stem wood had no or limited detrimental impact on pellet properties. Acknowledgements The author wishes to thank the University of the Philippines through the OVPAA’s Enhanced Creative Work and Research Grant Program for providing funding support for this project; the UPLB Land Grant Office for providing the coppice; the Advanced Device and Materials Testing Laboratory (ADMATEL), DOST for assistance in TG-DTA; the National Institute of Geological Sciences (NIGS) and the Institute of Chemistry, UP Diliman for assisting in the ICP-MS and chemical analyses of the samples.
1
3.86 2.06 43 566 514 8.24 565 5.40 3.82 14.8 nd 0.75
nd – No detection.
indicate that pellets from these feedstock may be used for industrial heating requirements and problems associated with slagging, fouling and sintering formation should be manageable. Content of heavy metals such as Pb, Cd, Cu and Cr were very small (<0.10 mg kg 1) and within the guidelines of EN 14961-2 [10]. 4. Conclusions In general, pellets produced from coppice of G. arborea, A. mangium, and P. falcataria formed pellets that were homogenous with uniform size and shape. Moisture content, particle density and bulk density were all within recommended limits. Calorific values of pellets from all coppice species tested have thermal energy of about 19–20 MJ kg 1 suitable for industrial and residential heating applications. Proximate and ultimate analyses showed high levels of volatile matter and fixed carbon in all coppice pellets tested indicating their high energy potentials. Low levels N and S or ash forming elements such as Ca, Fe, K, Mg, Na and P suggest limited pollutant emission and deposit problems if pellets are used as fuel in combustion processes. Variation in physical and chemical
References [1] Goel VL, Behl HM. Growth, biomass estimations and fuel quality evaluation of coppice plants of Prosopis juliflora on sodic soil site. J Trop For Sci 2000;12:139–48. [2] Thakur PS, Seghal S. Growth, leaf gas exchange and production of biomass in coppiced and pollarded agroforestry tree species. J Trop For Sci 2003;2003 (15):432–40. [3] Hinchee M, Rottmann W, Mullinax L, Zhang C, Chang S, Cunningham M, et al. Short-rotation woody crops for bioenergy and biofuels applications. In Vitro Cell Dev Biol – Plant 2009;45:619–29. [4] Stolarski M, Szczukowski S, Tworkowski J, Klasa A. Pellets from biomass of short rotation willow coppice. In: The 8th Polish–Danish workshop on biomass for energy. Starbienino, Poland; 2003. p. 163–6. [5] Di Giacomo G, Taglieri L. Renewable energy benefits with conversion of woody residues to pellets. Energy 2009;34:724–31. [6] Hartmann H, Lenz V. Biomass energy heat provision in modern small-scale systems. In: Myers RA, editor. Encyclopedia of sustainability science and technology. New York: Springer; 2012. p. 1351–400. [7] Heinimo J, Junginger M. Production and trading of biomass for energy – an overview of the global status. Biomass Bioenergy 2009;33:1310–20. [8] Phelps JE, Isebrands JG, Jowett D. Raw material quality of short rotation, intensively cultured Populus clones. I. A comparison of stem and branch properties at three spacings. IAWA Bull 1982;3:193–200. [9] ASTM E711. Standard test method for gross calorific value of refuse-derived fuel by the bomb calorimeter. Philadelphia, PA, USA: American Society for Testing and Materials; 2004. [10] Kuokkanen M, Kuokkanen T, Stoor T, Niimaki J, Pohjonen V. Chemical methods in the development of eco-efficient wood-based pellet production and technology. Waste Manage Res 2009;27:561–71. [11] EN 14961–2. Solid biofuels – fuel specification and classes – Part 2: Wood pellets for non-industrial use. European Committee for Standardization; 2011. [12] Obernberger I, Brunner T, Barnthaler G. Chemical properties of solid fuelssignificance and impact. Biomass Bioenergy 2006;30:973–82. [13] Stahl M, Wikström F. Swedish perspective on wood fuel pellets for household heating: a modified standard for pellets could reduce end-user problems. Biomass Bioenergy 2009;33:803–9. [14] Telmo C, Lousada J. Heating values of wood pellets from different species. Biomass Bioenergy 2011;35:2634–9. [15] Carroll JP, Finnan J. Physical and chemical properties of pellets from energy crops and cereal straws. Biomass Bioenergy 2012;112:151–9. [16] Tillman TA, Rossi AJ, Kitto WD. Wood combustion: principle, processes and economics. Orlando, FL: Academic Press; 1981. p 43.
Contents lists available at ScienceDirect
Fuel journal homepage: www.elsevier.com/locate/fuel
Short communication
Physico-chemical properties of wood pellets from coppice of short rotation tropical hardwoods Menandro N. Acda ⇑ Department of Forest Products and Paper Science, University of the Philippines Los Banos, College, Laguna 4031, Philippines
h i g h l i g h t s Coppice from short rotation tropical hardwoods collected from industrial tree plantation in the Philippines. Coppice biomass were dried, grounded and pressed into fuel pellets. Proximate, ultimate and elemental analyses were performed to determine physical and chemical properties of the pellets. Properties of pellets were within recommended limits for class A2 pellets under EN 14961-2.
a r t i c l e
i n f o
Article history: Received 18 June 2015 Received in revised form 1 August 2015 Accepted 6 August 2015 Available online 14 August 2015 Keywords: Pellets Coppice Gmelina arborea Acacia mangium Paraserianthes falcataria
a b s t r a c t The study investigated the physical and chemical properties of wood pellets from coppice of intensively cultured tropical hardwoods viz., Gmelina arborea, Acacia mangium and Paraserianthes falcataria. Proximate, ultimate and elemental analyses were performed to assess fuel properties of pellets from coppice feedstock. In general, physical and chemical properties of pellets from coppice biomass were within recommended limits for class A2 pellets under EN 14961-2. Pellets from coppice of tree species used in this study showed good potential for compressed solid fuel for industrial and residential heating applications. Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction Short rotation tropical hardwood species intensively cultured in industrial tree plantations have known abilities to coppice. Wood production in fast growing tree species is routinely maximized by coppicing trees in the early stages of growth [1,2]. Coppicing is the process of repeatedly cutting a tree to ground level, resulting in vigorous regeneration of new shoots from the base. Coppiced trees have fully developed root system so regrowth is rapid and the wood from the new stems may be harvested in 5–7 years. Woody biomass from coppiced trees is a potential source of sustainable biomass for bioenergy production [3]. Recent studies have shown that short rotation coppice (SRC) can be converted to fuel pellets [4]. Pellets are compressed solid fuel of high density and high combustion efficiency [5]. Its geometry and cylindrical form facilitates transport over long distances, compact storage and ⇑ Tel.: +63 49 536 3432; fax: +63 49 536 3206. E-mail address: [email protected] http://dx.doi.org/10.1016/j.fuel.2015.08.018 0016-2361/Ó 2015 Elsevier Ltd. All rights reserved.
control feeding to burners and boilers [6]. These attractive properties have resulted in soaring demand for wood pellets in Europe and North America [7]. However, before woody biomass from coppice of tropical hardwoods can be used for pellet production, its fuel characteristic must first be evaluated. No or limited studies have been reported in the literature on the use of SRC trees from tropical hardwoods for compressed solid fuel. Coppiced trees contain large proportion of juvenile wood and their physical and chemical properties vary widely with that of the parent tree [8]. Consequently, an understanding of their variation is necessary in order to make quality pellets from this biomass material. The present paper reports on the physical and chemical properties of wood pellets produced from coppice of Gmelina arborea Roxb, Acacia mangium Willd and Paraserianthes falcataria (L) Nielsen. These short rotation tree species are widely cultivated in industrial tree plantation in the Philippines, Malaysia, Indonesia and other Southeast Asian countries and their coppice could offer an alternative source of woody biomass for bioenergy production.
532
M.N. Acda / Fuel 160 (2015) 531–533
2. Materials and methods 2.1. Coppice Four year old coppice of G. arborea, A. mangium and P. falcataria (8–12 cm diameter) were collected from tree plantation of the University of the Philippines Los Banos in Quezon province. G. arborea, A. mangium and P. falcataria are fast growing tree species intensively cultivated in industrial tree plantations and commonly used to produce wood for light construction, crafts and furniture, decorative veneers, pulp, fuel, and charcoal. The coppice were transported to the laboratory, debarked, chipped and hammermilled to about 4 mm particle size. The ground biomass was dried to about 18% moisture content using a rotary drier (80–110 °C) prior to the pelleting operation. 2.2. Pelleting process The dry woody biomass were pressed using a laboratory pelletizer at a uniform rate through a fix ring die and rotating roller cylinder (MZLP 200 Flat Die Pellet Press) to form pellets of uniform density and shape (8 mm diameter). Binders or lubricants were not used to consolidate or increase strength of pellets in this experiment. When the pelleting process reached a stable temperature (85 °C), sample pellets were randomly collected and cooled by ambient air then stored in plastic containers for physical and chemical testing. Three replicate batches were made for each species. 2.3. Physical and chemical analysis Pellets were randomly selected from each batch for measurement of physical and chemical properties. Dimensions were determined by measuring the length and diameter of 20 randomly selected individual pellets. Particle density for each species was calculated based on the average weight and average volume of 20 pellets. Bulk density was determined using the weight and volume (500 mL) of pellets measured using a 1000 mL graduated cylinder. Proximate, ultimate and elemental analyses were conducted using ten pellets randomly selected pellets from each batch. Proximate analysis consisted of determination of moisture, ash content, and volatile matter using thermogravimetric-differential thermal analysis (TG-DTA, STA 6000 Perkin Elmer). Gross calorific values (GCV) of each type of pellets were measured at constant volume in dry basis using an isoperibol bomb calorimeter (Parr Instrument Company, USA) [9]. Net calorific value (NCV) of pellets was estimated using the equation described by Kuokkanen et al. [10]. Three replicates were used for each calorific measurement. The mechanical durability of each batch of randomly selected pellet was determined using a four sided (12 cm 30 cm) rotating chamber (15 rpm) to induce particle collisions against one another and the walls of the chamber. Five replicate measurements per sample were performed. Ultimate analysis for the presence of C, H, N and S was performed using an automated organic elemental analyzer (Dumas combustion method) (Exeter Analytical) in an oxygen-enriched helium atmosphere attached to a stable isotope ratio mass spectrometer (Finnigan Delta Plus XP). The O content was obtained by difference from the sum of C, H, N and S contents. Elemental analysis for the presence of heavy metals such as Cd, Pb, Zn, Cr, Cu and other trace elements such as Mg, Ca, Fe, K, and P. were determined using inductively coupled plasma-mass spectroscopy (ICP-MS, Agilent 7500cx) and atomic absorption spectroscopy (Model AA420FS, Varian Instruments).
Table 1 Physical characteristics of wood pellets from coppice of G. arborea, A. mangium and P. falcataria. Properties
G. arborea
A. mangium
P. falcataria
Diameter, mm Length, mm Moisture (%) Particle density (g cm 3) Bulk density (kg m 3) Mechanical durability (wt.%)
8.24 20.68 4.10 1.24 621.24 98.14
8.41 18.56 3.78 1.29 732.45 98.48
8.13 26.45 4.35 1.22 687.23 98.29
Table 2 Proximate analyses of wood pellets from coppice of G. arborea, A. mangium and P. falcataria using thermogravimetric-differential thermal analysis. Property
G. arborea
A. mangium
P. falcataria
Moisture (%) Ash (%) Volatile matter (%) Fixed carbon (%) Gross calorific value (MJ kg 1) Net calorific value (MJ kg 1)
6.15 1.00 62.17 30.67 19.78 19.65
5.48 0.79 63.68 30.05 19.83 19.69
5.21 1.45 64.13 29.16 20.01 19.87
3. Results and discussion The diameter and length of pellets from coppice of G. arborea, A. mangium and P. falcataria showed that all samples were fairly uniform in diameter but with some variation in size (Table 1). Pellet temperature directly after pelleting was about 85 °C. Pellet particle and bulk densities for all species were >1.22 g cm 3 and 621–732 kg m 3, respectively. Mechanical durability of all coppice feedstock were >98 wt.% indicating low levels of potential breakage during pellet handling and storage. Proximate analyses showed that pellets from coppice of G. arborea, A. mangium and P. falcataria had moisture content less than 10% after the pelleting operation (Table 2). Pellets from coppice of P. falcataria showed slightly higher ash content (1.45%) compared with pellets from G. arborea and A. mangium (0.79–1.0%). However, the levels of ash reported in this study are within permissible limits (<1.5 wt.%) of class A2 pellet of EN 14961-2 [11]. Feedstock with high ash contents are generally problematic during thermal conversion due to problems associated with ash removal, slagging, corrosion of equipment and deposit formation in the furnace [12]. In addition, frequent equipment cleaning and maintenance may be an issue with pellets containing high ash content for household heating applications [13]. The quantities of volatile matter in all three species studied were relatively high (62–64%). Calorific measurements of coppice pellets from G. arborea, A. mangium and P. falcataria resulted in heating values of about 19–20 MJ kg 1. Similar ranges of heating values were reported for various wood species and energy crops in the literature [14,15]. Ultimate analysis showed that all samples contain high proportion of C, H and O indicating the high energy potential of coppice pellets (Table 3). The samples of G. arborea and A. mangium showed low levels of N (<0.5%) and S (<0.05%). These would indicate very low levels of emissions containing nitric oxides (NOx) and SO2 if pellets are used in thermal conversion processes. The low levels of N and S is considered one of the strength of biomass utilization for energy purposes in terms of contribution to environmental protection [16]. In this regard, the G. arborea and A. mangium show better performance than P. falcataria. Minor and trace elements of pellets from coppice of G. arborea, A. mangium and P. falcataria are shown in Table 4. Low levels of ash forming elements including Ca, Fe, K, Mg, Na and P were present in pellets from the coppice of all three species tested. However, the marginal amount of ash forming elements in all sample tested
M.N. Acda / Fuel 160 (2015) 531–533 Table 3 Ultimate analyses of wood pellets from coppice of G. arborea, A. mangium and P. falcataria. Element (wt.%, d.b.)
G. arborea
A. mangium
P. falcataria
C H O N S
47.62 5.51 47.51 0.35 0.03
46.50 5.65 47.43 0.39 0.03
47.20 5.41 44.90 2.41 0.08
Table 4 Elemental analyses of wood pellets from coppice of G. arborea, A. mangium and P. falcataria. Element
G. arborea mg kg (d.b.)
Na Mg P K Ca Mn Fe Cr Cu Zn Cd Pb
8.13 1.48 41 283 338 24.15 255.6 3.21 3.70 30.7 0.046 1.54
1
A. mangium mg kg (d.b.) 3.17 2.48 55 424 483 8.28 648.4 3.90 3.86 29 0.05 2.06
1
P. falcataria mg kg (d.b.)
533
properties of coppice compared with stem wood had no or limited detrimental impact on pellet properties. Acknowledgements The author wishes to thank the University of the Philippines through the OVPAA’s Enhanced Creative Work and Research Grant Program for providing funding support for this project; the UPLB Land Grant Office for providing the coppice; the Advanced Device and Materials Testing Laboratory (ADMATEL), DOST for assistance in TG-DTA; the National Institute of Geological Sciences (NIGS) and the Institute of Chemistry, UP Diliman for assisting in the ICP-MS and chemical analyses of the samples.
1
3.86 2.06 43 566 514 8.24 565 5.40 3.82 14.8 nd 0.75
nd – No detection.
indicate that pellets from these feedstock may be used for industrial heating requirements and problems associated with slagging, fouling and sintering formation should be manageable. Content of heavy metals such as Pb, Cd, Cu and Cr were very small (<0.10 mg kg 1) and within the guidelines of EN 14961-2 [10]. 4. Conclusions In general, pellets produced from coppice of G. arborea, A. mangium, and P. falcataria formed pellets that were homogenous with uniform size and shape. Moisture content, particle density and bulk density were all within recommended limits. Calorific values of pellets from all coppice species tested have thermal energy of about 19–20 MJ kg 1 suitable for industrial and residential heating applications. Proximate and ultimate analyses showed high levels of volatile matter and fixed carbon in all coppice pellets tested indicating their high energy potentials. Low levels N and S or ash forming elements such as Ca, Fe, K, Mg, Na and P suggest limited pollutant emission and deposit problems if pellets are used as fuel in combustion processes. Variation in physical and chemical
References [1] Goel VL, Behl HM. Growth, biomass estimations and fuel quality evaluation of coppice plants of Prosopis juliflora on sodic soil site. J Trop For Sci 2000;12:139–48. [2] Thakur PS, Seghal S. Growth, leaf gas exchange and production of biomass in coppiced and pollarded agroforestry tree species. J Trop For Sci 2003;2003 (15):432–40. [3] Hinchee M, Rottmann W, Mullinax L, Zhang C, Chang S, Cunningham M, et al. Short-rotation woody crops for bioenergy and biofuels applications. In Vitro Cell Dev Biol – Plant 2009;45:619–29. [4] Stolarski M, Szczukowski S, Tworkowski J, Klasa A. Pellets from biomass of short rotation willow coppice. In: The 8th Polish–Danish workshop on biomass for energy. Starbienino, Poland; 2003. p. 163–6. [5] Di Giacomo G, Taglieri L. Renewable energy benefits with conversion of woody residues to pellets. Energy 2009;34:724–31. [6] Hartmann H, Lenz V. Biomass energy heat provision in modern small-scale systems. In: Myers RA, editor. Encyclopedia of sustainability science and technology. New York: Springer; 2012. p. 1351–400. [7] Heinimo J, Junginger M. Production and trading of biomass for energy – an overview of the global status. Biomass Bioenergy 2009;33:1310–20. [8] Phelps JE, Isebrands JG, Jowett D. Raw material quality of short rotation, intensively cultured Populus clones. I. A comparison of stem and branch properties at three spacings. IAWA Bull 1982;3:193–200. [9] ASTM E711. Standard test method for gross calorific value of refuse-derived fuel by the bomb calorimeter. Philadelphia, PA, USA: American Society for Testing and Materials; 2004. [10] Kuokkanen M, Kuokkanen T, Stoor T, Niimaki J, Pohjonen V. Chemical methods in the development of eco-efficient wood-based pellet production and technology. Waste Manage Res 2009;27:561–71. [11] EN 14961–2. Solid biofuels – fuel specification and classes – Part 2: Wood pellets for non-industrial use. European Committee for Standardization; 2011. [12] Obernberger I, Brunner T, Barnthaler G. Chemical properties of solid fuelssignificance and impact. Biomass Bioenergy 2006;30:973–82. [13] Stahl M, Wikström F. Swedish perspective on wood fuel pellets for household heating: a modified standard for pellets could reduce end-user problems. Biomass Bioenergy 2009;33:803–9. [14] Telmo C, Lousada J. Heating values of wood pellets from different species. Biomass Bioenergy 2011;35:2634–9. [15] Carroll JP, Finnan J. Physical and chemical properties of pellets from energy crops and cereal straws. Biomass Bioenergy 2012;112:151–9. [16] Tillman TA, Rossi AJ, Kitto WD. Wood combustion: principle, processes and economics. Orlando, FL: Academic Press; 1981. p 43.