Changes caused by torrefaction on urban wooden waste

Abstract

This work analyzed torrefied wooden waste from urban origin. Five compositions of residues (treatments) were analyzed, made up by solid wood and panels from a recycling station. Torrefaction was performed in an electric furnace, within an inert atmosphere saturated with nitrogen gas, and a temperature of 280 °C for 60 minutes. The physical, chemical and energetic properties of raw and torrefied materials were measured. The analysis showed that the torrefaction process led to an increase of acid-insoluble lignin content, fixed carbon content and higher heating value. Furthermore we observed a reduction of extractives, volatile matter, bulk density and energy density. Torrefaction did not affect the ash content, but proved effective to improving the grinding ability of the residues. In addition, the characteristics of the process and samples composition influenced the gravimetric yield of torrefaction.