Quality Properties and Torrefaction Characteristics of Pellets: Rose Oil Distillation Solid Waste and Red Pine Sawdust

Abstract

Two different biomass types, rose oil (Rosa damascena Mill.) distillation solid wastes (RDWs) and red pine sawdust (RPS), were pelletized in this study at different moisture and additives. The prepared pellets were also torrefied. This study revealed that the strength of the RPS and RDW pellets decreased as their moisture content increased in both their raw and torrefied forms. However, the tensile strength of the torrefied pellets increased with the increased binder ratio, which is similar to raw pellets. Compared to their raw form, the torrefied pellets generally had higher ash contents, fixed carbon contents, and higher heating values. As a result of torrefaction, the higher heating value of the RPS pellets increased from 17.51–18.80 MJ/kg to 20.20–21.73 MJ/kg, while the higher heating value of the RDW pellets increased from 17.42–18.54 MJ/kg to 19.13–20.92 MJ/kg. For the torrefied RPS and RDW pellets in this study, there was no statistically significant difference between initial moisture content and energy efficiency, energy density, or mass yield. On the other hand, energy density ratios in both the torrefied RPS and torrefied RDW pellets generally increased with increasing binder content. Furthermore, the torrefied pellets were found to be more stable in moisture absorption than the raw pellets.