Influência do tempo de exposição ao solo nas propriedades da madeira e do carvão vegetal da Myracrodruon urundeuva Fr. All

Abstract

The objective of this work was to evaluate the properties of wood and charcoal of the species Myracrodruon urundeuva Fr. All. depending on the time of exposure to the soil, aiming at the viability for energy production. For the study, three trees were randomly collected, coming from residues of a suppression for the implementation of the electrical network in the municipality of Gurupi, TO. The trees were traced on logs from the base, diameter at breast height and top, and sent to the joinery for the manufacture of specimens of 2.5 x 2.5 x 30 cm for installation of the experiment in the field. Five treatments were used: T0 – control, wood without exposure; T1 – with five months of exposure; T2 – with ten months of exposure; T3 – with fifteen months of exposure; T4 – with twenty months of exposure. To determine the chemical properties of the wood, the blocks were transformed into particles to evaluate the content of total extractives, total lignin, holocellulose and solubility in NaOH. The charcoal was produced by means of pyrolysis of wood in a muffle adapted to capture the pyroligneous liquor. After the pyrolysis process, gravimetric yield values were obtained in charcoal, in condensable and non- condensable gases. The apparent density and the immediate chemical analysis of the charcoal were determined and, finally, the calorific value, energy density and carbon stock were calculated. In the wood properties, a reduction in extractives content, basic density (0.91 to 0.72 g cm-3) and holocellulose was observed. There was an increase in lignin content (20.37 to 24.25%), weight loss (8.19 to 27.34%) and NaOH solubility (19.01 to 26.2), thus indicating attack by xylophagous organisms. Regarding the energetic properties of charcoal, the effect of wood exposed to the soil caused a decrease in the volatile matter content, apparent density of charcoal and ash and led to an increase in fixed carbon (64 to 75%), calorific value (7,094 to 7,417 kcal kg-1), carbon stock (317 to 409 kg m-3) and energy density (7,062,530.44 kcal m- 3). Therefore, the time of exposure to the soil negatively affected the properties of the wood, mainly due to the severe attack of xylophagous organisms, which makes it unfeasible for other purposes, but it presented satisfactory results for energy production.