Calorific value and chemical properties in juvenile and mature wood of thermally-modified Eucalyptus grandis

During thermal modification, timber is exposed to temperatures approaching 200 °C for several hours and wood properties change. This study was aimed at evaluating the calorific value and chemical properties of juvenile and mature wood of thermally modified Eucalyptus grandis. Boards were taken from 30-year-old E. grandis trees and thermally modified at 180°C. Samples of the untreated and thermally modified wood were transformed into chips and then processed into sawdust for the energy and chemical characterization of juvenile and mature wood. The results show that the thermal modification causes: (1) significant increases of 3.7 % and 6.8 %, respectively, in the net calorific value of juvenile and mature wood; (2) significant increases of 24.8 % and 47.6 %, respectively, in the extractive content of juvenile and mature wood; (3) significant decreases of 4.2 % and 8.3 % in the respective holocellulose content; and (4) significant decreases in the galactose, xylose and glucose contents. It was demonstrated that the influence of thermal treatment was lower in juvenile wood than in mature wood.