Chemical effects of a mild torrefaction on the wood of eightEucalyptusspecies

Abstract

AbstractThe torrefaction is a thermal pre-treatment to improve biomass quality for biofuel applications. In this study, the effects of a mild torrefaction (T) on eight eucalypt species (Eucalyptus botryoides, E. globulus, E. grandis, E. maculata, E. propinqua, E. rudis, E. salignaandE. viminalis) have been compared. Namely, the mass loss (ML), the equilibrium moisture content (EMC), density and chemical composition were determined and FTIR spectra were recorded of the initial and torrefied woods (TWs). The average ML was 11% and the heat-treated woods had an overall 10% density decrement. All the TW had 50% lower EMC compared to untreated wood samples (W). Elemental composition showed that carbon content increased from 48% to 53% and the oxygen/carbon ratio decreased from 0.80 to 0.65. The chemical changes induced by T included an increment of extractives, a 20% higher lignin content and a 16% lower holocellulose content in relation to W. The hemicelluloses modification is manifested by a decrease of xylose, galactose, and acetyl groups in TWs. The fourier transform infrared (FTIR) spectra of the different wood species were very similar, and reflected in a uniform manner the chemical changes upon T. Because of the similar reaction of the eucalypt species, they can also be used in form of mixed eucalypt feedstock as biofuel.