Torrefaction severity and performance of Rubberwood and Gliricidia

Lab-scale torrefaction experiments of Rubberwood and Gliricidia were conducted at 250-300 oC and 30–60 min in a nitrogen environment to understand the torrefaction behavior. TGA and FTIR were used to characterize raw and torrefied biomass. In the lab-scale experiments, Rubberwood showed 16% mass loss, whereas Gliricidia showed 25% mass loss under the most severe conditions, resulting in 9% and 22% volatile drop, respectively. The higher heating value of the torrefied product increased from 18.9 MJ/kg to 21.39 MJ/kg for Rubberwood and from 19.46 MJ/kg to 22.44 MJ/kg for Gliricidia under the most severe conditions. The calculated Energy Mass Co-benefit Index (EMCI) of Rubberwood at 275 °C and 60 min or 300 °C and 45–60 min and Gliricidia at 300 °C and 60 min indicated favorable torrefaction conditions. Comparatively, Gliricidia was performing well in torrefaction. The severity factor was modified by finding the optimum fitted parameter ω, which establishes a feedstock-specific relationship between torrefaction severity and operating conditions. The normalized severity factor shows a linear correlation with the properties of torrefied biomass, which could facilitate torrefaction modeling.