June 24 27, 2014 Seville, Spain. Proceedings

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1 June 24 27, 2014 Seville, Spain Proceedings

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3 PROCEEDINGS June 2014 Seville, Spain

4 Institute of Natural Resources and Agrobiology of Seville (IRNAS-CSIC), 2014 Editors: J.C. del Río, A. Gutiérrez, J. Rencoret and Á.T. Martínez Printed in Spain, 2014 Cover design: E.D. Babot ISBN:

5 13th European Workshop on Lignocellulosics and Pulp EVALUATION OF GRAPE STALKS AS A FEEDSTOCK FOR PELLETS PRODUCTION S. O Prozil 1, D.V. Evtuguin 1*, S. M. Lopes 2, L.P. Cruz Lopes 2, A. S. Arshanitsa 3, V. P. Solodovnik 3, G. M. Telysheva 3 1 CICECO, Department of Chemistry, University of Aveiro, Aveiro, Portugal 2 CI&DETS, Department of Environment, Polytechnic Institute of Viseu, Viseu, Portugal 3 Laboratory of Lignin Chemistry, Dzerbenes st. 27, LV-1006, Latvian State Institute of Wood Chemistry, Riga, Latvia *corresponding author: dmitrye@ua.pt ABSTRACT Grape stalks are the massive by-product of winemaking composed essentially of cellulose (ca 30%), hemicelluloses (ca 20%), lignin (ca 18%), tannins (ca 16%) and proteins (ca 6%) and could be an interesting source of solid biomass for energy needs. Among others agriculture residues (e.g. wheat straw or corncobs), grape stalks contain the relatively low ash content (2.90%), which is, however, ten times higher than in softwoods (e.g. spruce or pine). In this work grape stalks were evaluated for the first time as a pelletized solid fuel and compared with those produced from softwood. It was found that the specific energy consumption for pelletizing of grape stalks was approximately 25% lower when compared to that for softwood sawdust. The bulk density of produced grape stalks pellets (670 kg/m 3 ) was similar to that of pellets produced from softwoods (660 kg/m 3 ), whereas the particle density was slightly higher for grape stalks than for softwood pellets (1129 against 1098 Kg/m 3 ). The durability of pellets from grape stalks and softwood was practically the same: 95.8% and 95.6%, respectively. The grape stalks higher heating value was of 16.7 MJ/kg, which is slightly lower than that obtained for softwood (18.2 MJ/Kg). I. INTRODUCTION The present global energy model is mainly based on the use of fossil fuels. However, the growing demand for energy, the high dependence on fossil fuels and the negative impacts on the environment has led the European Union (EU) to review its energy policy strategies. Several reasons have prompted the EU to revise this policy, including: increased use of renewable energy sources in order to reduce carbon dioxide (CO 2 ) emissions, the need to reduce on imported energy sources and the diversification of energy sources and increased international cooperation [2]. The Energy Policy Strategy for 2020 of the European Commission predicts increased use of renewable resources in the energy system. The projections based on renewable energy in the EU includes biomass, which should represent more than 50% renewable energy supply in the EU-27 in 2020 [3]. The utilization of biomass as an alternative to fossil energy sources has emerged recently for domestic heating and electric energy production. Within classes of biomass, forest biomass and agricultural biomass take prominent roles. Agriculture biomass such as, residual stalks, straw, leaves, roots, husk, nut or seed shells, is widely available, renewable, and virtually free. Despite there is an emerging trend in the use of biomass and conversion technologies (combustion, gasification, pyrolysis, pelletization, etc.), the agriculture biomass is still largely under-utilized (abandoned in fields and in water lines or burned openly in the fields), especially in countries lacking strong regulatory instruments to control polluting practices [4]. These polluting practices are damaging to the environmentally and to human health (propagation of odors and fires, disease transmission, contamination of soils and aquifers, etc) and for this reason it is urgent to valorize this type of biomass. The potential of biomass from agricultural sector as an energy source, including the by-products of wine making process, is not enough studied. In particular, grape stalks are the massive by-product of winemaking composed by cellulose (ca 30%), hemicelluloses (ca 20%), lignin (ca 18%), tannins (ca 16%) and proteins (ca 6%) [5]. In apriori, this agricultural residue could be an interesting source of solid biomass for energy needs. Hence the main goal of this work was the evaluation of grape stalks as a pelletized solid fuel. 683

6 13th European Workshop on Lignocellulosics and Pulp II. EXPERMENTAL 2.1. Raw materials Grape stalks of the variety Vitis vinifera L. (Touriga Nacional) used to produce pellets in this study were supplied by Tavfer Group (Quinta do Serrado in Penalva do Castelo in Dão Region of Portugal). The raw material was collected after mechanical destemming, which separate the grapes from woody fraction (grape stalks), and was dried at room temperature. Softwood (essentially spruce) sawdust with small proportion of pine sawdust of ca 1mm fraction were prepared in the laboratory. 2.2 Chemical analyses The elemental composition, the ash content, the moisture content and the sulphur content of grape stalks biomass were determined according to EN 15104:2010, EN 14775:2009, EN : EN standards, respectively. 2.3 Pelletizing and pellets analysis Before pelletizing, grape stalks were grinded in a hammer mill AGICO TSF420C with screening hole diameter of 3.5 mm. The biomass was granulated using a flat die laboratory press KAHL The die hole diameter was 6.0 mm and the channel length of 24 mm. The pellets were produced without any additives or adhesives. The durability and bulk density values of pellets obtained were determined according to EN :2009 and 2011 EN 15103:2009, respectively. The higher heating values (HHV) were determined according to ISO 1928:2009 using PARR 1341 Oxygen Bomb calorimeter. TGA and DTA analyses were realized for samples grinded in a ball Mixer mill Retsch MM 200 and dried in an oven using the Mettler Toledo Star System TOA/SDTA 851 at a heating rate of 10 K/min, air flow rate of 50 ml/min and sample weight of ca 8 mg. III. RESULTS AND DISCUSSION 3.1 Element composition of grape stalks and fuel characteristics Table 1 shows the results on elementary analysis and heating values of grape stalks and commonly used in the European market softwood sawdust (spruce/pine mixture) taken for the comparative reasons. In addition, the literature data on grape pomaces have been also presented. The contents of C and H detected for grape stalks are quite similar to those observed for softwood. The nitrogen content in grape stalks is slightly higher than for spruce wood, but lower than that reported for grape pomaces by other researchers (Table 1). Hence, it could be expected that grape stalks will not cause problems of excessive NO x emissions. The sulfur content observed for the grape stalks is very low compared to the percentages reported by other authors for grape pomaces. The low sulfur content avoids the generation of toxic/corrosive SO x emissions derived from sulphur during the combustion process. The ash content in grape stalks was of 2.9%, a much higher value when compared to woods, but a rather low value when compared to typical agriculture residues such as wheat straw [1]. Note worthy that the heating values of grape stalks and softwood sawdust were close each other (Table 1). Table 1. Quality parameters on DM of biomass used for the pelletizing. Other literature references Characteristics Softwood Grape stalks Grape pomace [6] Grape pomace [7] Carbon content, % Hydrogen content, % Nitrogen content, % Sulphur content, % <0.05 < Ash content, % Higher heating value, MJ/kg Lower heating value. MJ/kg

7 13th European Workshop on Lignocellulosics and Pulp Thermogravimetric analysis has been employed to study the thermal behaviour of biofuels. The thermal analysis in air atmosphere (Figure 1) revealed three major stages of weight loss for grape stalks and softwood sawdust. The first stage takes place at temperatures around 373 K and is attributed to the water evaporation present in the sample, while the second stage ( K) and the third stage ( K) corresponds to the phases of combustion process. The first combustion phase was assigned to gasification stage accompanied by volatile combustion (oxidation) in gaseous phase ( K) and the second to the heterogenic oxidation of charcoal residue ( K). The maximum rates of volatile combustion and charcoal residue oxidation were achieved at ca 583 K and ca 663 K for grape stalks and at ca 593 K and ca 723 K for softwood, respectively. It was suggested that the complete thermodegradation of grape stalk proceeds faster than spruce wood and the char combustion proceeds at lower temperature. According to DTA analysis (curves are not shown) the total amount of heat released by volatile combustion of grape stalks was almost 30% less than that released by combustion of softwood, whereas the total amount of heat released by char oxidation was similar for both types of biomass sources. The incomplete combustion of volatiles at grape stalks combustion was suspected. Figure 1. TGA (left) and DTG (right) curves of grape stalks and spruce wood in air. The results of analyses on densified/pelletized biomass obtained in this study are summarized in Table 2. Under optimized conditions of pelletizing, the moisture content in grape stalks pellets was higher than in pellets from softwood though been in the optimal range of moisture content for biomass (between 10 and 20%). The water content is an important parameter because it has an influence on the basic parameters of fuel, such as calorific value, combustion efficiency, temperature of combustion, and also affecting the storage conditions and durability [8]. Table 2. Physical characteristics of grape stalks and spruce pellets. Parameters Softwood pellets Grape stalk pellets Water content, % Higher heating value, MJ/kg Lower heating value, MJ/kg Length, mm 16.7± ±1.2 Diameter, mm 6.06± ±0.07 Bulk density, kg/m 3 660±10 670±2 Particle density, kg/m ± ±47 Energy density, MWh/m Durability, % Specific energy consumption for pelletizing on DM, kwhe/kg

8 13th European Workshop on Lignocellulosics and Pulp The grape stalks pellets have shown that its particle density, bulk densities and durability values are similar to pellets produced from softwood sawdust. The HHV of grape stalk pellets was 16.7 MJ/kg, a slightly lower value than that one obtained for spruce wood pellets (18.2 MJ/kg). The lower value can be explained by higher content of water (12.6%) and ash (near 3%). Interestingly, the specific energy consumption for pelletizing of grape stalks is approximately 25% lower when compared to that for softwood sawdust. The lower specific energy consumption for pelletizing together with the low cost of the raw material acquisition makes grape stalks one of the promising raw materials for the pelletized fuel from agricultural biomass. IV. CONCLUSIONS The physical properties and energetic value of pellets from grape stalks were evaluated and compared with those of pellets prepared from softwood sawdust. For the main physical properties (bulk/particle density and durability) and heating value, pellets from grape stalks were very close to pellets prepared from softwood, but required almost 25% lower energy for pelletizing. Last fact together with low cost of raw material make grape stalks as an attractive raw material for the production of granulated solid fuel However, the increased ashes content could affect the operating comfort for end users in the residential heating sector and the comparative environmental impact (e.g. emission factors) from grape stalks pellets burning need to be evaluated. V. ACKNOWLEDGEMENT Authors wish to thank the Portuguese Foundation for Science and Technology (FCT project PTDC/AGR- AAM/104911/2008) and the Operation Program of Competitive Factors (COMPETE, ref. FCOMP FEDER ) for the financial support of this work. VI. REFERENCES 1. Demirba, A. Calculation of higher heating values of biomass fuels. Fuel, 1997, 76 (5): p Mantzos, L.; P. Capros. European Energy and Transport - Scenarios on energy efficiency and renewables, E. Commission, Editor 2006, European Commission: Luxembourg. 3. Bentsen, N.; Felby, C. Biomass for energy in the European Union - a review of bioenergy resource assessments. Biotechnology for Biofuels, (1): p Programme, U.N.E., Converting Waste Agricultural Biomass into a Resource - Compendium of Technologies. 2009, United Nations Environmental Programme, Division of Technology, Industry and Economics International Environmental Technology Centre: Osaka/Shiga, Japan. 5. Prozil, S.O., D.V. Evtuguin, and L.P.C. Lopes, Chemical composition of grape stalks of Vitis vinifera L. from red grape pomaces. Industrial Crops and Products, 2012, 35(1): p Celma, A.R., S. Rojasa, and F. Lopez-Rodrıguez, Waste-to-energy possibilities for industrial olive and grape by-products in Extremadura. Biomass and Bioenergy, 2007, 31, Miranda, M.T., et al., Characterization of grape pomace and pyrenean oak pellets. Fuel Processing Technology, , O Dogherty, M.J. and J.A. Wheeler, Compression of straw to high densities in closed cylindrical dies. J. Agric. Eng. Res., 1984, 29,