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  Review Proximate analysis, backwards stepwise regression between gross calorificvalue, ultimate and chemical analysis of wood C. Telmo a, * , J. Lousada b , N. Moreira b a University of Trás-os-Montes and Alto Douro (UTAD), Forestry Department, Quinta dos Prados Apartado, 1013-5001-801 Vila Real, Portugal b CITAB, Centre for the Research and Technology of Agro-Environment and Biological Sciences, UTAD, Quinta dos Prados Apartado, 1013-5001-801 Vila Real, Portugal a r t i c l e i n f o  Article history: Received 1 October 2009Received in revised form 4 January 2010Accepted 11 January 2010Available online 1 February 2010 Keywords: Heating valueProximate analysisUltimate analysisChemical analysisWood a b s t r a c t The gross calorific value (GCV), proximate, ultimate and chemical analysis of debark wood in Portugalwere studied, for future utilization in wood pellets industry and the results compared with CEN/TS14961. The relationship between GCV, ultimate and chemical analysis were determined by multipleregressionstepwisebackward.Thetreatmentbetweenhardwoods–softwoodsdidnotresultinsignificantstatistical differences for proximate, ultimate and chemical analysis. Significant statistical differenceswere found in carbon for National (hardwoods–softwoods) and (National-tropical) hardwoods in volatilematter, fixed carbon, carbon and oxygen and also for chemical analysis in National (hardwoods–soft-woods) for  F   and (National-tropical) hardwoods for Br. GCV was highly positively related to C (0.79***)andnegativelytoO(  0.71***). Thefinal independent variablesof themodel were(C, O, S, Zn,Ni, Br)with R 2 =0.86;  F   =27.68***. The hydrogen did not contribute statistically to the energy content.   2010 Elsevier Ltd. All rights reserved. 1. Introduction AccordingtotheNationalForestInventory2006,thePortugueseforest area is occupied mainly by  Quercus suber   736700ha,  Pinus pinaster   710600ha and  Eucalyptus globulus  646700ha. However,only the two last species have potential to be used for energy inlarge-scale because  Q. suber   it is only used in the cork industryand is a protect species. The  E.  globulus used primary for paperindustry is nowhaving a great competition fromthe pellets indus-try that uses this species in the sawdust mixtures. There are nostudies about proportion and potentially of these species and theothersreferredinthispaperinPortugalthatiswhytheimportanceof our study, to known these species better. However there is re-search studies in other countries to others softwoods and hard-woods with similar properties like (Baernthalera et al., 2006;Brunner et al., 1998; Brunner et al., 2002; Faaij et al., 1997; Lindet al., 1998; Nordin, 1994; Obernberger and Biedermann, 1998;Obernberger, 1999).An analysis programme of biomass fuels has been carried outwithinthe framework of CEBIO(Competence Networkfor Bioener-gy) and the University of Tras-Os-Montes and Alto Douro.The parameters tested within the framework of this analysisprogramme Tables 1 and 3, were gross calorific value, ash content,volatilematter, fixedcarbon, the contentsof C, H, O, NandS deter-mination of major elements (Na, K, Ca, Mg, Fe and P), minor ele-ments (Mn, Zn, Ni, Cr, Cd and Cu) andthree halogens (F, Cl andBr).Thewoodfuel propertiesgross calorificvalue(GCV), proximate,ultimate and chemical analysis determined according to the Euro-pean Committee for standardization (CEN/TS). The determinationof the GCV, vary within a species and between species, generallysoftwood species have higher carbon content and heating valuesthan hardwood species. According to (CEN/TS 14961, 2005) thetypical value of GCV for softwoods in dry basis is 20.5MJ/kg andforhardwoods20.2MJ/kg.Theproximateanalysisofwoodwithoutbark in dry basis is 0.3% to ash (CEN/TS 14961, 2005). The quantityof volatiles in biomass fuels is high and usually varies between 76and86wt.%drybasis(d.b.) inwoodybiomass(VanlooandKoppe- jan, 2002) and 15% to 25% fixed according to same literature, butnot defined in CEN/TS 14961 (2005). The ultimate analysis of soft-wood species is generally 51% carbon, 6.3% hydrogen, 42% oxygen,0.1% nitrogen, 0.02% sulfur and 0.01% on a dry ash free basis. Inhardwoods the C content is 49%, H 6.2%, O 44%, N 0.1%, S 0.02%and Cl 0.01%. The range of content for softwoods species in C is(47–54%), H (5.6–7.0%), O (40–44%), N (<0.1–0.5%), S (<0.01–0.05%) and Cl (<0.01–0.03%). The range of content for hardwoodsspecies in C is (48–52%), H (5.9–6.5%), O (41–45%), N (<0.1–0.5%),S (<0.01–0.05%) and Cl (<0.01–0.03%) (CEN/TS 14961, 2005).The chemical analysis which includes (major, minor and halo-gens elements in mg/kg in a dry basis), are as follow. The typicalvalues in softwoods for major elements contents in (mg/kg) areAl (100), Ca (900), Fe (25) K (400), Mg (150), Mn (147), Na (20)and P (60). The typical values in softwoods for minor elements 0960-8524/$ - see front matter    2010 Elsevier Ltd. All rights reserved.doi:10.1016/j.biortech.2010.01.021 *  Corresponding author. Tel.: +351 914 165 175; fax: +351 259 350 859. E-mail address:  telmimore@hotmail.com (C. Telmo).Bioresource Technology 101 (2010) 3808–3815 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech  contents in (mg/kg) are Cd (0.10), Cr (1.0), Cu (2.0), Ni (0.5) and Zn(10). The typical values for major elements contents in hardwoodsin (mg/kg) are Al (20), Ca (1200), Fe (25) K (800), Mg (200), Mn(83), Na (50) and P (100) (CEN/TS 14961, 2005).Thetypical values inhardwoodsforminorelementscontentsin(mg/kg) are Cd (0.10), Cr (1.0), Cu (2.0), Ni (0.5) and Zn (10). Thetypical variation on major elements contents in softwoods (mg/kg) is Al (30–400), Ca (500–1000), Fe (10–100) K (200–500), Mg(100–200), Mn (no value), Na (10–50) and P (50–100). The typicalvariation on major elements contents in hardwoods (mg/kg) is Al(10–50), Ca (800–20000), Fe (10–100) K (500–1500), Mg (100–400), Mn (no value), Na (10–200) and P (50–200) (CEN/TS 14961,2005).The minor elements had the same typical value and the sametypicalvariationinhardwoodsandsoftwoods, thetypicalvariationfor minor elements contents (mg/kg) is Cd (<0.05–0.50), Cr (0.2–10.0), Cu (0.5–10.0), Ni (<0.1–10.0), Zn (5–100) (CEN/TS 14961,2005).While major elements are of key relevance regarding ash melt-ing, deposit and slag formation as well as corrosion, minor ele-ments are of special importance for particulate emissions as isthe environmental assessment of the ashes produced and theirsubsequent utilization.The thermal utilization of solid biofuels is influenced by thekindof solidbiofuel used, itsphysical characteristics anditschem-ical composition (Directive 2000/76/EC, 2000).Thecalorificvalueofwoodcanberelatedtoitchemicalcompo-sition(Fengel andWegener, 1983). Major elements contributing tothe calorific value are carbon, hydrogen, nitrogen, oxygen and sul-fur. Elemental analysis can be used to describe biomass fuels,determine their calorific values (Friedl et al., 2005) and their ex-pectedimpactontheenvironment.AnexampleofthatistheScon-tent in woods whose importance does not result especially fromSO 2  and SO 3  emissions but from is role in the corrosion processes.AhigherconcentrationofScancausesulphationandleadstoClre-lease. It can cause corrosion by FeCl 2  and ZnCl 2  in the boilers. TheSO 2  emissions are not significant for wood combustion becausetheir low S content, but can be relevant for agricultural residues,grasses and straw.ThemethodusedisdescribedinSection2,intotal17samplesof debarked wood were obtained within the framework of the analy-sisprogramme. Theobjectivesoftheworkweretogetanoverviewabout the gross calorific value, proximate and ultimate analysisand the chemical composition of debark wood in Portugal, for fu-ture utilization in wood pellets industry. The variations of theseproperties among the species and between softwoods, Nationalhardwoods and tropical hardwoods, using Turkey–Kramer test, aswell as a comparison between the analyses results achieved andthe limiting values defined in the CEN Technical Standards andSpecifications for Solid biofuels. Finally, the determination of therelationship between gross calorific value, ultimate and chemicalanalysis by multiple regression stepwise backward. 2. Methods All measurements and analyses were performed by us in theChemicalDepartmentoftheUniversityofTras-Os-MontesandAlto  Table 1 Mean of gross calorific value (Mj/kg), proximate and ultimate analysis of wood (wt.% in dry basis). Species GCV ASH VM FC C H O N S Pinus pinaster   20.1 0.2 85.8 14.1 48.4 6.0 45.3 0.1 0.00 Pseudotsuga menziesii  19.7 0.4 83.9 15.7 47.6 5.9 45.8 0.2 0.01 Cedrus atlantica  20.3 0.4 82.9 16.7 50.3 5.6 43.6 0.2 0.00 Castanea sativa  18.7 0.1 79.6 20.3 47.1 4.9 47.7 0.2 0.02 Eucalyptus globulus  17.6 0.5 86.3 13.3 46.2 5.8 47.2 0.2 0.02 Fagus sylvatica  19.1 0.5 85.7 13.9 46.7 5.9 46.8 0.2 0.02 Quercus robur   18.7 0.3 81.7 18.0 47.2 5.5 46.8 0.2 0.01 Fraxinus angustifolia  19.2 0.4 84.9 14.7 47.7 6.1 45.6 0.2 0.04 Prunus avium  18.3 0.1 84.9 15.0 48.6 5.8 45.3 0.2 0.05 Salix babilonica  18.2 2.4 80.8 16.8 47.2 5.6 44.4 0.4 0.00 Populus euro-americana  18.8 0.5 87.1 12.4 47.8 6.0 45.4 0.2 0.03  Acer pseudoplatanus  18.6 1.0 85.1 13.9 46.8 5.8 46.1 0.2 0.06 Chlorophora excelsa  20.3 2.8 74.7 22.5 50.7 6.0 40.4 0.2 0.00 Entandrophragma cylindricum  19.0 1.0 81.7 17.3 47.8 5.8 45.1 0.3 0.01 Gossweilerodendron balsamiferum  20.4 0.4 83.8 15.8 50.4 6.2 42.5 0.5 0.01 Bowdichia nitida  20.7 0.1 81.8 18.2 52.3 6.1 41.3 0.2 0.03 Hymenaea courbaril  19.2 0.7 81.7 17.6 48.3 5.7 45.1 0.2 0.04  Table 2 Mean, SD in brackets, test comparison of means of proximate and ultimate analysis by type of wood (wt.% in d. basis). Note: mean values with the same letter are not significantlydifferent for p<0.05 by Tukey–Kramer test. Species (treatment) Ash VM FC C H O N SHardwoods (H) (1) 0.8 a 82.8 a 16.4 a 48.2 a 5.8 a 45.0 a 0.2 a 0.02 a(0.8) (3.2) (2.8) (1.8) (0.3) (2.2) (0.1) (0.02)Softwoods (S) 0.3 a 84.2 a 15.5 a 48.8 a 5.8 a 44.9 a 0.2 a 0.01 a(0.1) (1.3) (1.2) (1.4) (0.2) (1.2) (0.0) (0.01)H. National (HN) (2) 0.6 a 84.0 a 15.4 a 47.3 a 5.7 a 46.2 a 0.2 a 0.03 a(0.7) (2.6) (2.4) (0.7) (0.3) (1.0) (0.1) (0.02)S. National (SN) 0.3 a 84.2 a 15.5 a 48.8 b 5.8 a 44.9 a 0.2 a 0.01.a(0.1) (1.3) (1.2) (1.4) (0.2) (1.2) (0.0) (0.01)H. National (HN) (3) 0.6 a 84.0 a 15.4 a 47.3 a 5.7 a 46.2 a 0.2 a 0.03.a(0.7) (2.6) (2.4) (0.7) (0.3) (1.0) (0.1) (0.02)H. Tropical (HT) 1.0 a 80.7 b 18.3 b 49.9 b 5.9 a 42.9 b 0.3 a 0.02.a(1.0) (3.3) (2.4) (1.9) (0.2) (2.2) (0.1) (0.02) C. Telmo et al./Bioresource Technology 101 (2010) 3808–3815  3809  Douro. The gross calorific values were measured in the MechanicalDepartment. The contents of the elements (C, S and N) weredetermined in the fito-chemical and food composition labora-tory, in UTAD. The element (H) was done in Lisbon in a Lecolaboratory.  2.1. Determination of gross calorific value The gross calorific value at constant volume in dry basis wasdetermined according to (CEN/TS 14918, 2005). The samplesweightsrangingfrom0.5to0.6gtoavoidinvalidcombustion,theywere combusted in a Parr 6300 automated isoperibol calorimeter.There were three replications for each sample.  2.2. Determination of ash content  The ash content was determined by burning 1g of oven-driedsample in a platinum crucible in a muffle furnace model (LentonThermal Designs EF 11/8B) at 550±25  C. All analyses were donein duplicate and the results were expressed on a dry weight basisaccording to CEN/TS 14775 (2004).  2.3. Determination of volatile matter  The volatile matter was determined by burning 1g of oven-dried sample in a fused silica crucible with lid in a muffle furnacemodel (Lenton Thermal Designs EF 11/8B) at 900±10  C. All anal-yses were done in duplicate and the results were expressed on adry weight basis according to (CEN/TS 15148, 2005).  2.4. Fixed carbon The fixed carbon content was obtained by subtracting from100% the sum of volatile matter and ash contents in percentage.  2.5. Determination of Major elements (Na, K, Ca, Mg, Mn, Fe,Zn and P) Heat the sample (550  C) according to the procedure describedin CEN/TS 14775 (2004) to obtain ash.Digestion: Resistance heating 220  C, digestion with HNO3(65%), HF (40%), H3BO3 (4%), according to CEN/TS 15290 (2006).Detection: With flame atomic adsorption spectrometry (FAAS).  2.6. Determination of Minor elements (Ni, Cr, Cd and Cu) Digestion: Resistance heating 220  C, digestion with HNO 3 (65%), HF (40), H 3 BO 3  (4%), according to CEN/TS 15297 (2006).Detection: Graphite furnace atomic absorption spectroscopy (GF-AAS).  2.7. Determination of (F, Cl and Br) Digestion: Bomb combustion in oxygen; absorption in NaOH(0.05M).Detection: High-performance liquid chromatography (HPLC).Cl determined according to CEN/TS 15289 (2006).  2.8. Determination of total content of (C, S and N) TheSimultaneousdeterminationofSulfur/CarbonwasdoneinaLeco SC-144DR using direct combustion and infrared detection. Innitrogen determination the sample is dropped into a hot furnaceand flushed with pure oxygen for very rapid combustion, andformed By-products of combustion (CO 2 , H 2 O, NO  x  and N 2 ). Thenpassthroughthefurnacefilterandthermoelectriccoolerforsubse-quentcollectioninaballast apparatus. Thesecollectedgasesintheballast are mixed, and a small aliquot dose is then used for furtherconversion of the gases. The remaining aliquot that has been re-duced is measured by the thermal conductivity cell for Nitrogen,in a Leco FP-528. Two determinations per sample were performedaccording to CEN/TS 15104 (2005) to the (C, N) and according toCEN/TS 15289 (2006) to (S) determination.  2.9. Determination of total content of (H) The Leco TruSpec TRSCHNC was used to determine Hydrogen,however it can analyze carbon and nitrogen. The system is basedon the Dumas method of combustion, there are three phases dur-ing an analysis cycle: purge, burn, and analyze. In the sample-droppurge phase, the encapsulated sample is placed in the loadinghead, sealed, and purged of any atmospheric gases that have en-tered during sample loading. The ballast volume (zero volume atthis point) and gas lines are also purged. During the burn phase,the sample is dropped into the primary furnace (950  C) andflushed with pure oxygen for very rapid combustion. The productsof combustion are passed through the after-burner furnace, fur-nace filter, pre-cooler, and thermoelectric cooler before collectingin the ballast volume. In the analyze phase, the combustion gasesin the ballast become homogeneous by means of passive mixing.A series of infrared detectors then measure the evolved gases forcarbon and hydrogen. In addition, a 3cc aliquot is captured in aloop before the ballast piston is forced down to evacuate the bal-last. Anoptimizeddetector was usedfor Hydrogen. The final resultwas displayed as weight percentage, according to CEN/TS 15104(2005).  2.10. Determination of total content of (O) The oxygen content was obtained by subtracting from100% thesum of (C, H, N, S and ash) contents in percentage.Themean,standarddeviationandatestcomparisonmeans(Tu-key–Kramer) were done for proximate, ultimate and chemicalanalysis by type of wood in dry basis. The correlation coefficientmatrix was determined for the GCV, ultimate and chemical analy-sis. A backward stepwise multiple regression was employed be-tween the dependent variable (GCV) and the independentvariables (ultimate analysis and chemical analysis of wood in drybasis). 3. Results and discussion Table 1 shows the mean of gross calorific value, proximate andultimateanalysisofseventeenwoodspecies.Ashcontent(Ad),vol-atilematter(Vd)andfixedcarbon(FC)areconsideredasproximateanalysis and they were determined on weight percent in dry basis(wt.% in dry basis). Carbon (C), hydrogen (H), oxygen (O), nitrogen(N) and sulfur (S) contents are considered as ultimate analysis.They also were determined using weight percent in dry basis(wt.% in dry basis).The gross calorific valueranges from17.6MJ/kgin E. globulus  to20.7MJ/kg in  Bowdichia nitida . These ranging values of the GCV,were on the typical variation for softwoods, had a lower value inNational hardwoods, and were almost in the limits for tropicalhardwoods, according to CEN/TS 14961 (2005) typical variations.The data of this Technical Specificationwere obtained froma com-bination of research work mainly from Sweden, Finland, Denmarkand Germany. These values describe properties that can be ex-pected in Europe in general, however they were compared to trop-ical hardwoods values too. It can be seen that ash content rangedfrom 0.1% in ( Castanea sativa ,  Prunus avium ,  B. nitida ) to 2.8%weight in dry basis in  Chlorophora excelsa . The majority of the spe- 3810  C. Telmo et al./Bioresource Technology 101 (2010) 3808–3815  cies were in the typical variation for typical value of ash, usuallytropical species have much higher ash content comparing withtemperate forest species, but not always. Volatile matter is in therange of 74.7% in  C. excelsa  and 87.1% in  Populus euro-americana .Fixed carbon is in the range of 12.4%in  P. euro-americana  and22.5% in  C. excelsa . Ultimate analysis is very important in orderto determine the theoretical air–fuel ratio in thermo-conversionsystems, to calculate the heating values and also to have knowl-edge of the pollution potential. This study showed that the majorelemental constituents of biomass are carbon, oxygen, and hydro-gen. The elemental contents of (C, H, O, N and S) listed in Table 1show clearly that these biomass fuels contain higher proportionof carbon content compared with hydrogen and oxygen which in-creasedtheenergyvalue.Withtheexceptionof  C. sativa , E. globulus and  Fagus sylvatica  were the oxygen content is higher than carboncontent.Theweightfractionofcarbonrangedfrom46.2%in E. glob-ulus  to 52.3% in B. nitida , hydrogen from 4.9% in C. sativa  to 6.2% in Gossweilerodendron cylindrica , oxygen from 40.4% in  C. excelsa  to47.7% in  C. sativa . The measured values of these three componentsare in the range reported by CEN/TS 14961 (2005) for softwoods,tropical hardwoods and had a lower value in some National hard-woods.TheNitrogencontentrangedfrom0.1%in P. pinaster  to0.5%in Gossweilerodendron cylindrica , sulfurrangedfrom0.00%in P. pin-aster   to 0.06% in  Acer pseudoplatanus . A very low nitrogen and sul-fur content was reported in this study for the majority of thespecies with exception of the sulfur content in  A. pseudoplatanus higher than the typical variation (0.01–0.05%). Coniferous anddeciduous wood has the lowest N content according to CEN/TS335 (2003).Low chlorine content ranging from 0.00% in almost all the spe-cies to 0.01% in ( F. sylvatica ,  Quercus robur  ,  P. euro-americana ,  Gos-sweilerodendron balsamiferum ). The values of Cl are in the typicalvariation limits (<0.01–0.03%), (CEN/TS 14961). The lower contentof nitrogen and sulfur in biomass fuels is especially important forenvironmentprotection.TheconcentrationsofN,SandClindiffer-ent species are of major importance because they cause gaseousemissions (NO  x ,  SO 2 , HCl). Recent investigations have show thatone of the main environmental impacts of solid biofuels combus-tion is caused by NO  x  emissions (Nussbaumer, 2002). The NO  x emissions thus increase with increasing fuel N content (Obernber-ger et al., 1995; Leckner, 1993). The maineffect of Cl are the corro-sive effect of chloride salts and HCl on metal parts in the furnaceand boiler (Riedl and Obernberger, 1996; Salmenoja and Makela,2000) HCl and particulate (KCl, NaCl, ZnCl2 and PbCl2) emissions.According to (Obernberger, 2003), Cl induced corrosion and HClemissionproblems are to be expectedat fuel concentrations above0.1wt% (d.b.) and can therefore be of relevance for straw, cereals,grasses and fruit residues. The Cl content in wood is generally verylow.The S contained in solid biofuels forms gaseous SO 2 , sometimesSO 3 , alkali, alkali-sulphates. Theefficiencyof Sfixationinashesde-pends on the concentration of Ca in the fuel. According to (Obern-berger, 2003), emission problems are expected at S concentrationsabove 0.2wt%.Table2showsthemean,standarddeviation,Tukey–Kramertestfor ash content, volatile matter, fixed carbon (proximate analysis),carbon, hydrogen, oxygen, nitrogen, and sulfur content (Ultimateanalysis) of wood wt.% in dry basis. Treatment (1) between allhardwoods and softwoods showed that hardwoods had a highercontent of ash, fixed carbon, oxygen and sulfur content. They hadthe same average content in hydrogen and nitrogen. Softwoodshad higher volatile matter and carbon content. The study of differ-ent wood species did not result in significant statistical differencesfor treatment (1).Treatment (2) between National hardwoods and National soft-woods showed a higher content of ash, oxygen and sulfur in theNational hardwoods and also the same content of nitrogen of soft-woods. The volatile matter, fixed carbon, carbon and hydrogencontent were higher in softwoods. In the treatment (2) significantstatistical differences were found in carbon contentIn treatment (3), National hardwoods versus tropical hard-woods the higher content of volatile matter, oxygen and sulfurcontent occurs in National hardwoods. There is a difference intheaveragecontentofnitrogenbetweenthesetwotypesofwoods.Tropical hardwoods had a higher content of ash, fixed carbon,carbon, hydrogen, and nitrogen content, the treatment (3) resultin significant statistical differences for volatile matter, fixed car-bon, carbon and oxygen content.The standard deviation for fixed carbon, hydrogen and oxygen,was higher in hardwoods (H) with a variation from 0.3% in hydro-gen to 2.8% in fixed carbon. The standard deviation for nitrogencontent of hardwoods, National hardwoods and tropical hard-woods was the same with a value of 0.1%. The tropical hardwoodsstandard deviation was higher for ash, volatile matter, carbon andoxygen content with a variation from 1.0% (ash) to 3.3% (volatilematter).Table 3 shows the chemical composition of the wood (major,minor and three halogens elements). The major elements in bio-mass, such as Na, K, Ca, Mg, Fe and P, are especially importantfor any thermochemical conversion process. The Table 3 showssome clear differences among the wood species. According toCEN/TS 14961 (2005), the concentration of Na in  P. pinaster   Table 3 Mean of chemical composition of wood (mg/kg) in dry basis. Species Na K Ca Mg Mn Fe Zn Ni Cr Cd Cu F Cl Br P Pinus pinaster   98.5 492.0 1.0 58.5 72.0 49.0 31.0 1.5250 0.4646 0.0030 0.2957 0.9 23.0 0.0 5.7 Pseudotsuga menziesii  34.0 815.0 67.0 20.5 43.0 19.5 9.0 0.8715 0.2440 0.0186 0.5770 0.4 32.7 0.0 73.2 Cedrus atlantica  58.5 495.0 98.0 13.0 22.5 23.5 24.5 1.7925 0.9290 0.0109 0.4584 0.3 28.1 0.1 3.3 Castanea sativa  91.5 174.5 44.0 12.0 38.0 131.0 24.5 1.9325 0.9305 0.0006 0.7635 1.2 1.2 0.0 2.4 Eucalyptus globulus  19.5 3100.0 106.5 83.5 34.5 53.0 80.0 0.3270 0.6160 0.0169 0.4452 0.9 11.7 0.0 1285.6 Fagus sylvatica  152.0 1590.0 148.0 40.5 260.0 38.5 32.5 1.7335 0.4535 0.0593 0.5050 1.2 75.8 0.0 12.5 Quercus robur   61.0 720.0 68.5 11.0 29.0 80.5 18.0 1.1260 0.4432 0.0030 0.2489 0.9 85.2 0.0 9.5 Fraxinus angustifolia  45.0 800.0 111.5 10.0 2.5 11.0 1.0 0.8395 0.1195 0.0056 0.3654 1.0 41.8 0.0 3.6 Prunus avium  58.5 275.0 425.0 111.5 25.5 26.0 16.5 0.9705 0.3924 0.0005 0.1672 0.8 32.0 0.0 2.8 Salix babilonica  600.0 12850.0 3650.0 3.0 170.0 40.5 135.0 0.5105 0.8340 0.2083 1.2385 1.1 37.5 0.0 488.1 Populus euro-americana  418.0 650.0 126.0 40.5 37.5 19.5 46.5 1.0045 0.1525 0.0315 0.0557 1.4 54.5 0.0 10.9  Acer pseudoplatanus  56.5 1610.0 175.0 67.5 1.5 19.5 1.0 0.1168 0.1899 0.0003 0.6465 1.8 17.4 0.0 2074.2 Chlorophora excelsa  48.0 3780.0 4750.0 480.0 5.5 32.0 13.5 0.7825 0.2901 0.0010 0.2008 1.4 10.1 0.9 4.5 Entandrophragma cylindricum  34.0 1495.0 236.5 58.5 3.0 23.5 29.0 1.1785 0.5425 0.0003 0.2958 1.6 10.8 0.8 8.4 Gossweilerodendron balsamiferum  70.5 93.0 143.5 41.5 115.0 57.5 20.5 0.7185 1.1150 0.0243 0.9360 3.3 78.8 0.0 0.5 Bowdichia nitida  43.0 127.5 30.5 501.0 1.5 47.0 12.5 1.9935 0.8810 0.0008 0.4493 0.4 28.3 0.0 4.0 Hymenaea courbaril  60.0 1155.0 123.5 5.5 41.5 42.5 41.0 1.1175 0.4669 0.0001 0.1376 2.2 2.9 0.0 16.7 C. Telmo et al./Bioresource Technology 101 (2010) 3808–3815  3811
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