Hydrothermal Carbonization as an Effective Way of Densifying the Energy Content

eaSpaiortus s/n

Hydrocarbonization

prsunlueateaniedcesshology, characterized by the formation ofmicrosphereswhich grow as temperaturehars are acid in nature and present several oxygen functionalities, as observed from

ssociaton fosstainablhas re

investment and market mechanisms [1]. In the transition to cleaner biomass during hydrolysis processes [6].

Fuel Processing Technology xxx (2011) xxxxxx

FUPROC-03274; No of Pages 6

Contents lists available at SciVerse ScienceDirect

Fuel Processing

e lstechnologies, biomass stands out as one of the most important renew-able energy sources. Apart from the advantage of involving zero netcarbon dioxide emissions, it reduces the environmental impact of or-ganic wastes and can be a key factor for the development of ruralareas. However, the low energy density associated to biomass standsas a drawback since it involves high transportation costs and a lowefciency of gasiers, which are often damaged due to the formationof tars during the pyrolysis processes.

Hydrothermal carbonization (HTC) has recently been suggested as asimple, cheap and effective way of increasing the carbon content of

The process dehydration and decarboxylation reactions at theseexperimental conditions are promoted by using water in the process[7-9], although the addition of different chemicals to provide a specicchemical functionalization on the hydrochar surface has also beenstudied [10].

Recent studies report that the physico-chemical characteristics ofthe two phases generated during HTC processes (solid and liquid) de-pendon the experimental conditions used. Also, the chemical and struc-tural features have been studied on pure organic materials [11] andother complex biomass [12] trying to understand the pathway followedbiomass, thus providing a higher caloric vdened as a thermochemical conversion pro(biomass in this case) is subjected to the actiotures (180230 C) in a suspension with watecan either be provided by the reactor or be d

Corresponding author.E-mail address: [email protected] (S. Romn).

0378-3820/$ see front matter 2011 Elsevier B.V. Alldoi:10.1016/j.fuproc.2011.11.009

Please cite this article as: S. Romn, et al., HProcess. Technol. (2011), doi:10.1016/j.fuping of fuel subsidies tontives for private sector

compounds [5], at the same time that a char (called hydrochar) isformed. Fig. 1 shows typical patterns followed by lignocellulosicClean Energy Progress Report the realignsupport clean energy, by providing more ince1. Introduction

As a result of the several problems ation, the current energy scheme, basedenergy, is moving towards a more susInternational Agency of Energy (IEA) 2011 Elsevier B.V. All rights reserved.

ed to fossil fuel exploita-il fuel derived sources ofe model. In this line, thecently suggested on the

evolved during the decomposition process) for a period of time. Thus,HTC involves the use of mild conditions in comparison with the harshconditions required by other methods used to produce carbonaceousmaterials, such as pyrolysis. During HTC processes, the biomass compo-nents are hydrolysed and the organic compounds are broken intosmaller fragments that are very unstable and repolimerize into oilyPorous material FT-IR and pzc analysis.BiomassEnergy densication

and interesting surfacemorpincreases. Moreover, hydrocHydrothermal carbonization as an effectivof biomass

S. Romn a,, J.M.V. Nabais b, C. Laginhas b, B. Ledesma Applied Physics Department, University of Extremadura, Avda. Elvas s/n, 06006, Badajoz,b Chemistry Department. University of vora, Rua Romo Ramalho 59, 7000671, vora, Pc Mechaniscs, Energetics and Materials Department, University of Extremadura, Avda. Elva

a b s t r a c ta r t i c l e i n f o

Article history:Received 23 June 2011Received in revised form 25 October 2011Accepted 7 November 2011Available online xxxx

Keywords:

Hydrothermal carbonizationmaterials: walnut shell andof increasing the caloric vaon the heating value of the mtively, which corresponds toregarding the variables studthe hydrocarbonization pro

j ourna l homepage: www.alue [2-4]. HTC can becess in which a materialn of moderate tempera-r under pressure (whichue to the gases that are

rights reserved.

ydrothermal carbonization aroc.2011.11.009way of densifying the energy content

c, J.F. Gonzlez a

ngal, 06006, Badajoz, Spain

ocesses were studied under different conditions using two different biomassower stem. Coalication under mild conditions was promoted with the aimof the solid hydrochar. Hydrocarbonization processes brought up an increaserials up to 28.9 and 29.3 MJ kg1, for sunower stem and walnut shell, respec-increase of 1.75 and 1.50 fold when compared with the natural biomass. Also,it was found that temperature and water/biomass ratio were more inuent onthan residence time. The hydrochars show negligible N2 adsorption at 77 K

Technology

ev ie r .com/ locate / fuprocby the precursors duringHTC process; how the breaking up of polymerstake place, which factors can accelerate the process and how the surfacemorphology of the hydrochar particles is modied as the reaction oc-curs giving rise to singular formations such asmicrospheres. The resultsfound in the bibliography show different behaviours depending on thefeedstock used aswell as different interpretations of the process. On theother hand, the studies on the inuence of operating parameters on theenergetic characteristics of the hydrochars are still very scarce.

s an effective way of densifying the energy content of biomass, Fuel

2 S. Romn et al. / Fuel Processing Technology xxx (2011) xxxxxxIn the present study, we investigate for the rst time the hydrother-mal carbonization of two biomass resources: walnut shell (WN) andsunower stem (SF), namely the inuence of temperature, time andratio amount of water/biomass (W/B, wt.). The increase in the energycontent of the produced hydrochars was determined from their heatingvalue.

2. Experimental

2.1. Raw materials

Sunower stem and walnut shell were provided by local manufac-turers and subjected to grounding and sieving (=12 mm)processes.Table 1 shows the lignocellulosic composition (%) of the rawmaterials,as well as their higher heating value (HHV, MJ kg1). As inferred from

Fig. 1. Degradation products and subproducts during hydrolysis of lignocellulosicbiomass.Table 1, sunower stem and walnut shell present some differences.The former precursor has greater cellulose content, while the secondone detaches for its higher amount of lignin and hemicellulose. Regard-ing the energy content, walnut shell shows the highest caloric value,although the values are similar and typical of biomass materials.

2.2. TG/DTG study

The thermal degradationunder inert atmospherewas studied by ther-mogravimetry (Thermobalance Setsys Evolution, SETARAM), using N2 ascarrier gas (50 mLmin1) and a heating rate of 20 C min1. The choiceof these experimental conditions is based on previous results that showthat a low carrier gas ow and moderate heating rate are appropriate toget a net observation of thermal events [13].

2.2.1. HydrocarbonizationThe hydrothermal processeswere carried out using 5 g of rawmate-

rial dispersed in deionised water (100150 mL) and stirred for 2 h at

Table 1Lignocellulosic and higher heating value analysis of precursors.

Precursor Cellulose(wt.%)

Hemicelulose(wt.%)

Lignin(wt.%)

HHV(MJkg1)

Sunower (SF) 45.6 14.5 10.6 16.4Walnut shell (WN) 40.1 20.7 18.2 19.6

Please cite this article as: S. Romn, et al., Hydrothermal carbonization aProcess. Technol. (2011), doi:10.1016/j.fuproc.2011.11.00925 C. The mixture was then transferred to a stainless steel autoclave(Berghof, Germany), which was heated up in an electric furnace atselected temperatures (190230 C), during time intervals of 2045 h.The reaction mixture, consisting of an oily solution and a solid phase(hydrochar) was collected in a glass beaker for separation by ltrationand the solid was washed with abundant distilled water. The solidphase was dried at 110 C for 12 h.

Hydrocharswere named asHPLTt, where P denotes the precur-sor, L the amount of water solution used, and T and t the hydrocarboni-zation temperature and time, respectively.

2.3. Characterization methods

2.3.1. Chemical analyses and high heating valueThe precursor's cellulose and lignin content was determined by

Agroleico (Porto Salvo, Portugal) using Portuguese Standards NP2029and ME-414. The higher heating value (HHV) of the precursors andresulting hydrochars was determined with a Parr 1351 calorimeterbomb (norm ISO 1928) according to the technical specicationCEN/TS 14918, concerning solid biofuels [14].

The natural precursors as well as the hydrochars were also charac-terized with respect to their proximate analysis using the technicalspecications CEN/TS 15148 [15], CEN/TS 14775 [16] and CEN/TS147742 [17] for volatile, ash and moisture content, respectively. Thexed carbon percentage was determined by difference.

2.3.2. Textural characterizationScanning electron micrographs were obtained with a Hitachi S-

3600N microscope. The SEM samples were prepared by depositingabout 50 mg of sample on an aluminum stud covered with conductiveadhesive carbon tapes, and then coating with Rd-Pd for 1 min to pre-vent charging during observations. Imaging was done in the high vac-uum mode at an accelerating voltage of 20 kV, using secondaryelectrons.

The nitrogen adsorption at 77 K was carried out in a Quadrasorb-Tri, Quantachrome Instruments. The samples were initially degassed,in a Masterprep unit, Quantachrome Instruments, at 250 C for a peri-od of 4 h, at a stepwise of 1 C min1.

2.3.3. Surface chemistry characterizationThe surface chemistrywas studied by FTIR spectroscopy and point of

zero charge (pzc) determination. FTIR spectra were recorded with aPerkin Elmer model Paragon 1000PC spectrophotometer, using theKBr disc method, with a resolution of 4 cm1 and 100 scans. The pzcwas determined by mass titration following the procedure given indetail elsewhere [18].

3. Results

3.1. Pyrolysis and hydrocarbonization processes

The proximate analysis, solid yield and heating value for the hydro-chars prepared fromeachprecursor are shown in Table 2.Moreover, theenergy efciency of the process has been determined using the follow-ing expression, the results can be seen in Table 2:

energy ef f iciency heating value of hydrocharsolid yieldheating value of precursor

As it can be observed, themodication of hydrocarbonization condi-tions affects the solid yield, expressed as gram of HC/gram of initialfeedstock. Also, the hydrocarbonization process brings out a decreasein the volatilematter content in all cases, while the xed carbon contentincreases as a consequence of the coalication process. This effect is

lower for samples HWN100/190 and HSF100/190, in coherence with


the softer temperature conditions, which might not be able to removepart of the cellulose of the precursors [11].

As expected, the caloric value follows the same trend as it is relatedto the degree of coalication achieved. A higher hydrocarbonizationtemperature favors the coalication process, while a greater ratioamount of biomass/water (Ratio B/W) causes a decrease on the solidyield. In general, it is found that sunower stem is more reactivetowards HTC than walnut shell. This is consistent with the greaterenrichment of xed carbon of SF compared to WN.

The tendencies found for each feedstock are consistent with somealready published data that had reported work done with differentbiomass materials [9]. We can notice a clear decrease in the solid yieldwith temperature, which can either be due to greater primary decom-position of biomass at high temperatures or through secondary decom-position of the solid residue, as reported by Xiu et al. [9]. On the otherhand, longer HTC times cause a very slight decrease on the solid yield.Some authors [19,20], have reported that a longer treatment time was

Table 2Proximate analysis of precursos and hydrochars (%). Solid yield (%), higher heating value (

Proximate analysis (%)

Moisture Volatile matter Ash Fixed ca

WN 11.0 71.8 1.3 15.9HWN100/230/20 3.7 53.9 2.0 40.4HWN150/230/20 2.3 57.6 2.1 38.0HWN100/230/45 4.6 65.0 3.6 26.8HWN100/190/20 5.1 69.7 2.4 22.7SF 12.7 82.3 1.5 3.6HSF100/230/20 2.2 44.0 2.7 51.1HSF150/230/20 3.2 45.1 3.1 48.7HSF150/230/45 2.6 46.1 2.8 48.6HSF100/190/20 2.6 58.7 4.3 34.3

3S. Romn et al. / Fuel Processing Technology xxx (2011) xxxxxxmore favorable for the production of solid residue, owing to theFig. 2. TG and DTG curves of precursors and respective hydrochars for a) sunowerstem and b) walnut shells under different hydrothermal conditions.

Please cite this article as: S. Romn, et al., Hydrothermal carbonization aProcess. Technol. (2011), doi:10.1016/j.fuproc.2011.11.009formation of solid residue by repolymerization of heavy oil. In ourcase this was not found, although it has to be marked that for bothprecursors the inuence of residence time is not signicant. Regardingthe inuence of B/W ratio, the results obtained indicate bigger ratioslead to lower carbonization. This is consistent with the enhancementof hydrolysis reactions as the quantity of water is increased.

Also, the greater the solid yield, the lowest the heating value, as itcorresponds to a lower carbon densication. In all cases the caloricvalue of the hydrocharswas increased between 18 and 75%with respectwith respective feedstock, depending on the experiment. In principleone could suggest that the HTC is more interesting in the case of walnutshell as it presents higher solid yields and similar HHV than sunowerstem. However, if we take into account the energy content of the hydro-chars in relation to that of the parent material, here deduced by meansof the energetic efciency parameter, we can conclude that this processis more advantageous in the case of sunower stem. This materialretains a greater amount of carbon during the process and provides agreater energy densication.

The decomposition of biomass was followed by thermogravimetry,in particular Fig. 2 shows the TG/DTG proles of both precursors. Thehigher hemicellulose content of WN is consistent with the denedtwo peaks in the temperature range 250400 C. Also, the lower lignincontent of SF is also inferred from the more marked decomposition athigher temperatures, in contraposition to the higher lignin content ofWN, which is harder to decompose. SF exhibits a greater reactivityalong all the range of temperatures, as the main peaks are shiftedtowards lower values of temperature and it shows the lowest residualweight loss under these conditions. From Fig. 2 it is noted that thehydrocarbonization processes brought up some substantial changes inthe TG/DTG proles. First, it is noticeable that the marked differenceswe found among the comparison of the thermal degradation of precur-sors become very small for hydrochars. The TG curves of the HC arealmost identical up to 280 C, where they exhibit a weight loss of9497% (note that at this temperature the weight loss for the parentmaterials was in the range 8291%). This is consistent with the decom-

MJ kg1) and energy efciency (%) of hydrochars.

Energy parameters

rbon Solid yield (%) HHV (MJ kg1) Energy efciency (%)

19.6 36.3 27.1 50.232.8 29.3 49.035.2 27.2 48.848.6 23.2 57.5 16.4 29.2 28.5 50.428.3 28.9 49.629.0 28.7 50.439.7 24.5 58.9position of hemicellulose and a great amount of cellulose during hydro-thermal treatment. The DTG proles, which exhibit one wide peakshifted towards temperatures above 400 C, are also indicative thatmost of the weight loss is related to lignin.

3.2. Textural study

3.2.1. N2 adsorption at 77 KTheN2 adsorption isotherms at 77 K of the hydrochars prepared, not

shown here for the sake of brevity, are all type II according the IUPACclassication. The low N2 adsorption observed from the isotherms wasconsistent with the values of apparent surface area of all hydrochars,determined according to BET method [21], which were situatedbetween 25 and 30 m2g1. Also a negligible effect of experimentalhydrocarbonization conditions on the porosity of the hydrochars wasfound. Sevilla et al. [11] have obtained similar results from N2


adsorption analyses with cellulose-derived hydrochars. In their case,the hydrochars showed a SBET of 30 m2g1, with a very signicantcontribution of SEXT.

3.2.2. SEM analysesFigs. 35 show SEM images corresponding to selected hydrochars. It

can be observed that the materials show a cellular structure typical ofthe parent material. While SF sample (Fig. 3) shows a splinteredmorphology with some large pores and cavities on the surface, WN ex-hibits a plain surface where many different patterns can be observed.Previous papers reporting the conventional pyrolysis at 600 C during1 h, under nitrogen atmosphere, of walnut-shell showed that charsalso conserved the lignocellulosic structure of the parent material [22].

However, some differences betweenWN chars [22] and hydrocharscan be highlighted; thewalnut shell char showed a smooth surfacewithchimney-like cavities, whichwere associated to the condensation of thehot gases released suddenly during pyrolysis process. In the case ofwalnut shell hydrochars, one can see that the surface morphology isquite different; the chimney-like features are much larger (as tunnels)probably because they were slowly formed during the HC process.

On the other hand, numerous microspheres can be found in thesurface of hydrochars for both precursors that was previously associat-ed with the decomposition of cellulose [11]. The recombination of car-bon products from decarboxilation reactions, as well as the breaking

structure of the parent material, although the surface seem to bedeformed as if some spheres were in the process of being formed.These microspheres are much smaller than those of WN/100/230/20and seem to be emerging from the carbon surface.

3.3. FT-IR and pcz analyses

Fig. 6 depicts the FT-IR spectra of raw materials and derivedhydrochars, for the sake of brevity, only two HC samples are shownfor each precursor. It can be observed that with both precursors, thesample hydrothermally treated at 190 C shows negligible differencesin relation to the parent material. Dissimilarly, there are markedchanges for the sample made at 230 C, especially in the case of wal-nut shell, thus indicating that a signicant chemical transformationmight have occurred at these conditions. These changes can be relat-ed to different events occurring to the biomass under HTC processesand are described below:

a) The wide band located at 3400 cm1, associated to OH stretchingvibrations in hydroxyl or carboxyl groups, becomes less intense forsamples prepared the higher temperature with both precursors.

b) The band found around 2900 cm1, which can be related to aliphaticstructures by means of stretching vibrations of aliphatic CH, is clearfor WN and WNH/100/190/20 and very tiny for WNH/100/230/20.

4 S. Romn et al. / Fuel Processing Technology xxx (2011) xxxxxxup of cellulose, might be the driving force to form such new micro-sphere structures, which tend to be placed on the HC surface. Liang etal. [10] have studied the HTC of furaldehyde and found that during de-hydration (polymerization) carbon-containing spheres were formed.With reaction time, subsequent dehydration of these assemblies gaverise to further coalescence of microscopic spheres to larger spheres.Also, these researchers found that increasing HTC time promoted theformation of many micrometer sized carbon spheres which remainedattached the carbon spheres, to form a strawberry-like structure.

Sevilla et al. [11] found an abrupt change on the surfacemorphologyof cellulose hydrochars made at temperatures lower and above 210 C.While the former ones exhibited a structure similar to that of pristinecellulose, the latter ones consisted mainly on aggregates of micro-spheres. Their results suggested that the onset of hydrothermal reac-tions for the cellulose occurred at around 230 C. Our results areconsistent with this hypothesis. Fig. 5 shows the SEM image of sampleWN/100/190/20. As it can be observed, the hydrochar keeps theFig. 3. SEM image of

Please cite this article as: S. Romn, et al., Hydrothermal carbonization aProcess. Technol. (2011), doi:10.1016/j.fuproc.2011.11.009In the case of sunower samples, the changes in this band do notshow any appreciable change.

c) The band located around 1600 cm1 seems to be slightly moremarked for the HC prepared at 230 C. This can be attributed toC=C vibrations in aromatic ring structures, and is consistent withthe tendency found by previous works when studying the effect oftemperature in the chemical surface properties of cellulose [11].

d) We can observe a number of bands in the wavenumber range10001500, which can be associated to a number of different groups:the position of the band at 1250 cm1 is compatible with thepresence of ether structures and epoxides, in which the (CO)vibration occurs at 1270 and 1200 respectively [23]. All these bandsare less intense for the HC produced at 230 C, especially for walnutshell samples.

e) The signal centered at 800880 cm1, more marked for parentmaterials and low temperature HC can be associated to polycyclicaromatic skeleton structures [24].SFH/100/230/20.


Fig. 4. SEM image of HWN/100/230/20.

5S. Romn et al. / Fuel Processing Technology xxx (2011) xxxxxxThese changes are in accordance with the surface acidity of thematerials, as deduced from their point of zero charge values, whichhave been included in Fig. 6. As hydrothermal carbonization tempera-ture increases the hydrochars are less acidic, in accordance with alower presence of acidic groups in their surface. At this point it is inter-esting to highlight the potential use of HC as a precursor for ACs, whichcould have a tunable surface acidity depending on the hydrocarboniza-tion conditions.

4. Conclusions

Walnut shell and sunower stem were subjected to hydrothermalcarbonization in order to increase their energy content so that theyFig. 5. SEM image of H

Please cite this article as: S. Romn, et al., Hydrothermal carbonization aProcess. Technol. (2011), doi:10.1016/j.fuproc.2011.11.009could provide a greater amount of energy per unit of mass. The resultsshowed that this process is clearly inuenced by temperature andwater/biomass ratio, while hydrocarbonization time did not seem toaffect the solid yield nor the heating value of the hydrochars.

TG/DTG studies conrmed that hydrocarbonization processes bringout modications on the thermal behavior of materials, suggesting thata higher temperature promoted the conversion of hemicellulose andcellulose to simpler molecular units.

Moreover, the textural study allowed concluding that hydrocharsshow negligible porosity development and a surface morphology thatkeeps the structure of the lignocellulosic parent material, althoughsome microspheres are formed and remain at the carbon surface. Ahigher temperature seems to cause an increase on the size of theseWN/100/190/20.


Acknowledgements

The authors are thankful to FCT (Portugal), COMPETE, QREN and EU(European Regional Development Fund, FEDER) for nancial support

6 S. Romn et al. / Fuel Processing Technology xxx (2011) xxxxxxspheres. Also, the variables studied affect the chemical surface of thehydrochars, which were all acid. Since most activated carbons derivedfrom biomass are usually basic in nature, this acidity could be taken asan advantage in order to prepare acid adsorbents from them.

through Project FCOMP-01-0124-FEDER-007142 and to the Junta deExtremadura/Universidad de Extremadura for the project associated

74747479.[23] D.J. Pasto, C.R. Johnson, Organic Structure Determination, Prentice-Hall, Englewood

Fig. 6. FT-IR spectra of precursors and derived hydrochars.

Please cite this article as: S. Romn, et al., Hydrothermal carbonization aProcess. Technol. (2011), doi:10.1016/j.fuproc.2011.11.009Cliffs. NJ, 1969, pp. 109158.[24] S. Biniak, G. Szymaski, J. Siedlewski, A. witkowski, The characterization of activated

carbons with oxygen and nitrogen surface groups, Carbon 35 (12) (1997) 17991810.to Programa Propio-Accin VII. B. Ledesma and S. Romn thank theJunta de Extremadura for the predoctoral and postdoctoral ResearchGrants, respectively.

References

[1] Clean Energy Progress Report, IEA input to the Clean Energy MinisterialAvailableonline at:, http://www.iea.org/papers/2011/CEM_Progress_Report.pdf.

[2] P. Azadi, A.A. Khodadadi, Y. Mortazavi, R. Farnood, Hydrothermal gasication ofglucose using Raney nickel and homogeneous organometallic catalysts, Fuel Proces-sing Technology 90 (2009) 145151.

[3] G. Garrote, H. Domngue, J.C. Paraj, Hydrothermal processing of lignocellulosicmaterials, Holz als Roh und Werkstoff 57 (3) (1999) 191202.

[4] G. Bonn, R. Cocin, O. Bobleter, Hydrothermolysis a new process for the utilizationof biomass, Wood Science and Technology 17 (3) (1983) 195202.

[5] A. Demirbas, Biofuels, Springer, London, 2008.[6] E. Palmqvist, B. Hahn-Hgerdal, Fermentation of lignocellulosic hydrolysates. II:

inhibitors and mechanisms of inhibition, Bioresource Technology 74 (2000) 2533.[7] S.M. Heilmann, L.R. Jader, L.A. Harned, M.J. Sadowsky, F.J. Schendel, P.A. Lefebvre,

M.G. von Keitz, K.J. Valentas, Hydrothermal carbonization of microalgae II, Fattyacid, char, and algal nutrient products, Applied Energy 88 (10) (2011)32863290.

[8] S.M. Heilmann, L.R. Jader, M.J. Sadowsky, F.J. Schendel, M.G. von Keitz, K.J. Valentas,Hydrothermal carbonization of distiller's grains, Biomass Bioenerg. 35 (7) (2011)25262533.

[9] S. Xiu, A. Shahbazi, V. Shirley, D. Cheng, Hydrothermal pyrolysis of swine manureto bio-oil: effects of operating parameters on products yield and characterizationof bio-oil, J. Anal. Appl. Pyrol. 88 (2010) 7379.

[10] X. Liang, M. Zeng, C. Qi, One-step synthesis of carbon functionalized with sulfonicacid groups using hydrothermal carbonization, Carbon 48 (2010) 18441848.

[11] M. Sevilla, A.B. Fuertes, The production of carbonmaterials by hydrothermal carbon-ization of cellulose, Carbon 47 (2009) 22812289.

[12] M.M. Titirici, A. Thomas, Y. Shu-Hong, T. Jens-O,M.A. Antonietti, A direct synthesis ofmesoporous carbons with bicontinuous poremorphology from crude plant materialby hydrothermal carbonization, Chem. Materials 19 (2007) 42054212.

[13] J.F. Gonzlez, C. Rayo, S. Romn, C.M. Gonzlez-Garca, B. Ledesma, Thermal degrada-tion behaviour of olivewaste under different conditions, Proceedings of the Third Inter-national Symposium on Energy from Biomass and waste, Venice, 810 November,2010.

[14] CEN/TS 14918, Solid biofuels method for the determination of caloric value,European Committee for Standardization, 2005.

[15] CEN/TS 15148, Solid biofuels method for the determination of the content ofvolatile matter, European Committee for Standardization, 2005.

[16] CEN/TS 14775, Solid biofuels method for the determination of ash content,European Committee for Standardization, 2004.

[17] CEN/TS 147742, Solid biofuels methods for the determination of moisturecontent oven drymethod Part 2: total moisture simpliedmethod, EuropeanCommittee for Standardization, 2004.

[18] P.J.M. Carrott, J.M.V. Nabais, M.M.L. Ribeiro Carrott, J.A. Menendez, Thermal treatmentsof activated carbon bres using a microwave furnace, Micropor. Mesopor. Mat. 47(2001) 243252.

[19] B.J. He, Y. Zhang, T.L. Funk, G.L. Riskowski, Y. Yin, Trans. Preliminary Characterizationof raw oil products from the thermochemical conversion of swinemanure, ASABE 43(6) (2000) 18271833.

[20] E. Chornet, R.P. Overend, Fundamentals of Thermochemical Biomass Conversion,Elsevier, New York, 1985.

[21] S. Brunauer, P. Emmett, E. Teller, Adsorption of gases in multimolecular layers,Journal of the American Chemical Society 60 (1938) 309314.

[22] J.F. Gonzlez, S. Romn, C.M. Gonzlez-Garca, J.M. Valente Nabais, A.L. Ortiz, Porositydevelopment in activated carbons prepared fromwalnut shells by carbon dioxide orsteam activation, Industrial and Engineering Chemistry Research 48 (16) (2009)s an effective way of densifying the energy content of biomass, Fuel

Hydrothermal carbonization as an effective way of densifying the energy content of biomass1. Introduction2. Experimental2.1. Raw materials2.2. TG/DTG study2.2.1. Hydrocarbonization

2.3. Characterization methods2.3.1. Chemical analyses and high heating value2.3.2. Textural characterization2.3.3. Surface chemistry characterization

3. Results3.1. Pyrolysis and hydrocarbonization processes3.2. Textural study3.2.1. N2 adsorption at 77K3.2.2. SEM analyses

3.3. FT-IR and pcz analyses

4. ConclusionsAcknowledgementsReferences

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Hydrothermal Carbonization as an Effective Way of Densifying the Energy Content