Increments in higher heating values and energy densities are presented in Figure 3(a) and 3(b). Similarly, as
torrefaction temperatures intensified, HHV increased and correspondingly their energy densities. Energy density is
defined as amount of chemical energy stored in fuel per unit volume and if energy density is more than unity, desired
energy gain can be achieved [30]. HHVs of torrefied biomass samples in this study are comparable to that of subbituminous
coal and energy densities increased by factors of 1.42 and 1.39 for torrefied OPF and LL, respectively, at the maximum torrefaction temperature of 300oC. Notably, energy density rises significantly at torrefaction
temperature exceeding 250oC but with lower solid mass and energy yields. Nam et al. reported that torrefaction
temperature of 250oC can be considered as ‘middle condition’ of average preferred energy density and yield,
depending on the purpose of the torrefied products [27].