Rendimento volumétrico do desdobro de toras em madeira serrada em indústrias localizadas no município de Itaituba – PA.

Abstract

CONAMA Resolution No. 474/2016 established a volumetric yield coefficient (VYC%) of 35% in the transformation of logs into sawn wood. This provoked a great demand for technical studies to show to licensing agencies the income effectively achieved by industries in the wood sector. In this context, the objective of this work was to evaluate the value of the volumetric yield coefficient (VYC%) of four forest species explored in the municipality of Itaituba – PA compared to the value established in the legislation, as well as whether the diameter class and the technological level of the machinery used has influence on it. The studied species were Handroanthus albus (Cham.) Mattos (yellow Ipe), Handroanthus impetiginosa (Mart. Ex DC.) Mattos (purple ipe), Hymenolobium petraeum Ducke (Mart. Ex DC.) Mattos (Angelim-pedra) and Couratari guianensis Aubl (Tauari). Data were collected in four sawmills, named as S1, S2, S3 and S4. In the analysis of the VYC% for the four species, the values of descriptive statistics (mean, variance, standard deviation and coefficient of variation) were calculated using the Student t test as a parametric test, to compare the sample mean with the mean of the population, at the 95% probability level. In the analysis of the diameter class, three diameter classes were defined using the species yellow Ipe and purple ipe, using analysis of variance (ANOVA) and Tukey's test at 95% probability. In the analysis of the influence of the technological level of the machinery, two groups of sawmills were created using the four species studied, the 1st (S1 and S2) with modern equipment (year 2017) and the 2nd (S3 and S4) with obsolete equipment (year 1995). Student's t test was applied at 95% probability to assess the existence of a difference in the VYC% between these two groups. In total, 89 logs were used in this study, with an average volume of 2.52 m³, which produced a total of 8,535 pieces of sawn wood. The Volumetric Yield Coefficient obtained was 56.78% for yellow Ipe, 57.32% for purple ipe, 58.32% for Angelim-pedra and 59.67% for Tauari. The yields of the diameter classes were 55.80% for class I (40.50cm-62.82cm) with 15 logs, 56.99% for Class II (62.83cm-85.16cm) with 25 logs and 58, 80% for Class III (85.17cm-107.50cm) with 6 logs. Companies in group 1 (with modern equipment) had an average VYC of 62.87%, while those in group 2 (with obsolete equipment) had an average VYC of 53.69%. It is concluded that the VYCs of the four species studied are significantly higher than the 35% parametric value and that the diametric class did not influence the yield. The technological level of the machinery influences the performance significantly, being the most modern with the highest performance.