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Abstract Full Text

Thermochemical properties of several Portuguese and exotic woods and shrubs [Conference Poster].

Abstract

In recent years it has been attended in Portugal a constant increase in demand for forest biomass for energy purposes, which may lead to an overexploitation of these resources. Only an efficient management of biomass can ensure the sustainability of the Portuguese Forest. This can be achieved by the use of biomass resources yet unexplored (shrub component) or by producing more biomass (energy crops). The aim of this study was to evaluate the thermochemical properties of various national wood species, exotic species, and shrubs, most representative of Portugal. With regard to the tree species, the study assessed the following national softwoods: Pinus pinaster, Pseudotsuga menziesii, and Cedrus atlantica; in the national hardwoods: Eucalyptus globulus, Populus euro-americana (cl. I-214), Salix alba, Quercus robur, Castanea sativa, Acer pseudoplatanus, Fraxinus angustifolia, Prunus avium, and Fagus sylvatica; and in the tropical hardwoods: Chlorophora excelsa, Entandrophragma cylindricum, Gossweilerodendron balsamiferum, Bowdichia nitida, and Hymenaea courbaril. As regards the shrub species (bushes), have been studied the Ulex europaeus, Cytisus striatus, Pterospartum tridentatum, Erica arborea, Erica sp., and Hakea sericea. For each species it was determined the gross calorific value-GCV (or higher heating value-HHV) and the following chemical properties: ash content, chemical composition (C, H, O, N, S), Micro and Macroelements (Na, K, Ca, Mg, Mn, Fe, Zn, Ni, Cr, Cd, Cu, P) and halogens (F, Br, Cl). For the Calorific Value, the tropical hardwoods, national softwoods and shrubs have higher calorific value than the national hardwoods. In general it was found that tree species have low ash content (0.1%-0.5%). The shrubs have much higher values (1.5%-2.8%) as well as the Acer p. (1.0%), Entandrophragma c. (1.0%), and the Chlorophora e. (2.8%). Concerning the elementary chemical composition, the different species present very similar chemical compositions. The only exceptions are the national hardwoods with lower levels of C, compared to the tropical hardwoods and the softwoods. The national hardwoods also present higher levels of O comparatively the tropical hardwoods. The fact that hardwoods have less C and more O, can explain its lower calorific value, in relation to other species. For micro and macro elements, the shrubs present levels of Na, Ca, Mg, Mn, Fe, Cr, Cd and Cu much higher than woods (sometimes more than 40X). In turn the K, P, Zn, Ni are identical between shrubs and woods. As regards the halogens, it is clear that shrubs present levels of F and Cl much higher than woods, but identical values of Br. It should be noted that although the shrubs show high calorific value, its use as an energy source can give rise to corrosion and accumulation of ash in burning equipment, as well as the emission of toxic compounds.