## 5 Discussion  
Biomass has lower density, higher moisture content, and lower heating value compared with fossil fuels [68]. The diversity of sources and seasonality of some raw materials introduce challenges related to logistics that hinder their use on a larger scale [69]. In an attempt to address these drawbacks, we need to homogenize raw materials in order to produce more energy-dense fuel [70]. Torrefaction is a process that subjects materials to temperatures from 220 to 320 \({}^{\circ}\)C in the absence of oxygen [71]. The thermal decomposition of biomass begins with the evaporation of water and extractives up to 150 \({}^{\circ}\)C. Between 150 and 220 \({}^{\circ}\)C, there is a slow process of depolymerization of hemicellulose with the emission of certain lipophilic compounds, and the material starts to show structural deformity in the plant tissue [72]. Between 220 and 320 \({}^{\circ}\)C, torrefaction is carried out, involving the volatilization of hemicellulose and depolymerization and partial volatilization of lignin and cellulose [73]. The release of hydrophilic extractives such as oxygenated compounds, carboxylic acids with high molecular weight, alcohols, and aldehydes, among other gases, with the complete destruction of the plant cell structure, results in a more brittle material [74]. Above 300 \({}^{\circ}\)C, the other compounds present in the biomass volatilize, resulting in the beginning of the pyrolysis process [75]. In general, the composition of torrefied biomass shows an increase in the fixed carbon content as torrefaction severity increases [76]. Since it has a lower O/C due to the volatilization and transformation of chemical components, the proportion of carbon in the elemental chemical composition is increased, and this directly contributes to the increased heating value [77]. The ultimate analysis of a fuel characterizes its chemical composition in terms of its main chemical elements, which are normally represented by C, H, O, and N. The performance of biomass as a fuel is directly related to its chemical composition. The work of [PERSON] et al. (2015) presented the results of the ultimate analysis of 60 samples of sugarcane bagasse, of which the average values are shown in Table 7[60]. Table 7 shows that the carbon content of biomass is about 45%, with a standard deviation of 1.1%. This deviation is acceptable considering the heterogeneity of the sample and the final objective of this \begin{table}
\begin{tabular}{c c c c c} \hline  & **C (\%)** & **H (\%)** & **O (\%)** & **N (\%)** \\ \hline Average & 44.90 & 6.10 & 48.74 & 0.27 \\ Standard deviation & 1.07 & 0.85 & 1.50 & 0.10 \\ \hline \end{tabular}
\end{table} 
Table 7: Average results of elemental composition of 60 sugarcane bagasse samples (adapted from [60]). material: thermal conversion. According to the results presented in Table 7, these samples had an average carbon/hydrogen ratio of 7:1, an average carbon/oxygen ratio of 1:1, an average carbon/nitrogen ratio of 166:1, and an average oxygen/hydrogen ratio of 8:1 [60]. The decreased atomic ratios of O/C and H/C in relation to untreated biomass make it possible to compare the characteristics of torrefaction biomass with other solid fuels, such as mineral coal and charcoal, using the Van Krevelen diagram (Figure 5). Calculating the H/C and O/C ratios for the analyzed samples, the results shown in Table 8 were obtained; then, they were projected onto the Van Krevelen diagram shown in Figure 5. The black dots represent the analyzed samples. As can be seen, although one of the samples, produced at 200 \({}^{\circ}\)C, already had a higher HHV, it was still projected into the area of untreated biomass,  
When evaluating the use of torrefied biomass as raw material for other thermochemical conversion processes, it was found that for combustion reactions, the solid product can be used as an industrial fuel in boilers for steam production and in co-combustion with mineral coal. In addition, the possibility of storing it for long periods can also facilitate its domestic use [79; 80].