## 3 Results and Discussion
### Quality Analysis of Biopellets before and after Torrefaction  
Figure 7 shows the graph comparing the durability of the biopellets before and after torrefaction. Because torrefaction was performed on the premanufactured pellets, there was no remarkable difference in pellet durability before and after torrefaction, regardless of the type of woody biomass feedstock. The excellent durability of the biopellets before and after torrefaction resulted in minimal fine particle generation. The fines content of the biopellets was also measured. The fines content is the percentage of particles that pass through a 3.15 mm mesh. A high fines content is undesirable because it can increase the risk of dust explosions and pose a health hazard when inhaled. Regardless of the types of lignocellulosic biomass before and after torrefaction of the biopellets, very few fines were generated, with a fines content of less than 0.06%. This suggests that, even if the biopellets themselves are torrefied, there is no negative effect on the fines content. Our findings on pellet durability and fines content are consistent with previous studies that reported minimal changes in these properties following torrefaction. For instance, [PERSON] et al. (2012) found that torrefied pellets retained their mechanical strength and had low fines content, similar to our observations [50].  
In conclusion, the torrefaction of biopellets could be considered an ideal technology for producing energy-intensive renewable fuel without any negative effects on the durability or fines content of the biopellets.  
Figure 8 compares the bulk density of the biopellets before and after torrefaction. Bulk density is an important parameter for fuel deliveries on a volume basis, and together with the net calorific value, it determines the energy density. Torrefaction reduced the bulk density of the biopellets by removing volatile substances and other extraneous components, regardless of the type of woody feedstock used. This reduced the mass of the biopellets without remarkably changing their volume. As a result, torrefied biopellets can have a higher energy density, facilitating more efficient energy transport and cost-effective storage.  
Figure 6: Ultimate analysis of the prepared pellets before and after torrefaction.  
These results are in line with previous research by [PERSON] and [PERSON] (2012), who reported a reduction in bulk density and an increase in energy density for torrefied biomass pellets [51].  
Figure 9 is a graph comparing the heating values of the biopellets prepared from various woody biomass before and after torrefaction. Torrefaction treatment increased the heating values of the biopellets by 18-58%, with TA and MT exhibiting the highest increase of 53-58%. HW and CO increased by 48% and 18%, respectively. Nevertheless, the rate of increase in the heating value of the torrefied biopellets varied depending on the type of woody biomass, but the resulting heating values for these biopellets consistently fell within the range of 22 to 24 MJ/kg, indicating a highly favorable heating value. It was finally confirmed that the torrefaction treatment of biopellets made from lignocellulosic biomass was a very useful technology in improving fuel efficiency. The observed increases in heating values are comparable to those reported by [PERSON] et al. (2015), who found that torrefaction significantly enhanced the calorific value of biomass pellets, making them competitive with coal [52].  
Figure 8: Bulk density of the prepared pallets before and after torrefaction.  
Figure 7: Durability of the prepared pellets before and after torrefaction: (**a**) durability; (**b**) fines content.