Productive assessment and energy balance of a horizontal grinder of forest residues recovered from full tree pine harvesting

Abstract

ABSTRACT Diversifying the Brazilian energy matrix by using residual biomass from planted forests requires searching for harvest technologies with sustainable applications. The aim of this study was to access the productive assessment and energy balance of grinding forest residues from full tree pine harvesting using a horizontal grinder in Brazil. A time study and moisture measurement were carried out at 15-year-old Pinus taeda L. stands located in the Santa Catarina State to determine mechanical delay, utilization rate, productivity per productive machine hour and production of a horizontal grinder in which energy balance was also calculated. For these variables, non-parametric bootstrap was performed, resampling a thousand times with replacement and producing new random samples, to calculate bias and confidence intervals at a 95% probability level. Non-working time consumed most of the scheduled machine hours, with only 46% being considered as working time. This was caused by the horizontal grinder’s travel time and time spent waiting for the transport vehicles. The horizontal grinder’s average productivities were 59 Mg per productive machine hour and 219 Mg per shift, considering the low machine utilization. The energy contained in the woodchips is 126.6 times higher than the energy consumed by the grinder, but this calculation only considers the grinding phase and excludes transport to the mill as well as the previous steps of stacking at the side of the field. The sustainability of this production is confirmed as the amount of energy consumed represents a small part of the potential present in the recovered forest residues.