Potencial energético da madeira e do carvão vegetal de quatro espécies arbóreas plantadas e irrigadas no semiárido brasileiro.

Abstract

This research aimed at evaluating the energy potential of wood and charcoal from four forest species (Colubrina glandulosa, Handroanthus impetiginosus, Hymenaea courbaril and Azadirachta indica), subjected to two irrigation conditions (12 and 36 months after planting) in a plantation in the Brazilian semi-arid region. The species were planted in 2010 in a town named Acaraú, in the state of Ceará. Four trees of each species with good photosynthetic activity were randomly collected and wood discs were removed from each tree at 0 (base), 20, 40, 60 and 80% of the commercial tree trunk height, used for the physical-chemical and energetic characterization of the wood and charcoal produced from the species. The basic density, molecular, immediate and elemental compositions, higher calorific value, energy density and combustibility value index (CVI) of the wood were determined. As for charcoal, the yields of condensable and non-condensable gases, bulk density, immediate chemical analysis, calorific value and energy density were also determined. There irrigation process demonstrated a significant effect on the basic density of Colubrina glandulosa and Hymenaea courbaril, with the highest value recorded for C. glandulosa (0.67 g cm-³). The chemical and energy characteristics showed a significant interaction between factors involving species and irrigation conditions. H. courbaril wood had the most suitable properties for energy purposes, with high calorific value (4562.31 Kcal kg-1), the highest fixed carbon content (18.28%), high CVI contents (1641.28 and 2394.33) and low ash content (0.73% and 0.53%). The values for the gravimetric yield of both charcoal (CcGY) and condensable and non-condensable gases (GYCo/nCoG) and the specific consumption of wood showed no interaction between the two evaluated irrigation conditions, where the C. glandulosa species presented the highest CcGY (42.02%). The H. courbaril species had the lowest CcGY (36.36%). The charcoal from the C. glandulosa species produced with the highest CcGY, energy density and energy efficiency indexes, suggesting that the basic density of the wood directly influenced the quality of the charcoal.