## 3 Results and Discussion
### Thermal Behavior
#### 3.3.2 Combustion
\begin{table}
\begin{tabular}{c c c c c} \hline \multicolumn{5}{c}{**Main Combustion Parameters**} \\ \hline  & **Ma1** & **Ma2** & **Ma3** & **Ma4** \\ \hline T for 5\% weigh loss (\({}^{\circ}\)C) & 135.0 & 137.2 & 164.5 & 183.1 \\ Ignition temperature \(T_{i}\) (\({}^{\circ}\)C) & 266.6 & 266.0 & 264.6 & 266.6 \\ Peak temperature \(T_{p}\) (\({}^{\circ}\)C) & 279.6 & 278.6 & 281.5 & 286.3 \\ Burnout temperature \(T_{f}\) (\({}^{\circ}\)C) & 506.8 & 511.4 & 485.8 & 486.6 \\ DTG max (\%/min) & 35.12 & 36.99 & 42.10 & 39.72 \\ DTG mean (\%/min) & 2.73 & 2.74 & 2.74 & 2.66 \\ Ignition time \(t_{i}\) (min) & 12.18 & 12.15 & 12.10 & 12.18 \\ Peak time \(t_{p}\) (min) & 12.64 & 12.59 & 12.69 & 12.89 \\ Burnout time \(t_{f}\) (min) & 23.96 & 24.12 & 22.9 & 23.00 \\ \(\Delta t_{1/2}\) (min) & 14.0 & 13.8 & 17.0 & 18.6 \\ \(D_{i}\) (\%/min\({}^{3}\)\(\times\)\(10^{-3}\)) & 228.12 & 241.81 & 274.18 & 252.99 \\ \(S\) (\%/\({}^{\circ}\)C\({}^{3}\)\(\times\)\(10^{-7}\)) & 26.62 & 28.01 & 33.92 & 30.55 \\ \(D\) (\%/\({}^{\circ}\)C\({}^{2}\)\(\times\)\(10^{-3}\)) & 9.66 & 10.54 & 8.85 & 7.04 \\ \(D_{f}\) (\%/min\({}^{4}\)\(\times\)\(10^{-3}\)) & 231.93 & 248.59 & 241.45 & 199.96 \\ Residual mass (\%) & 1.22 & 1.24 & 3.10 & 5.23 \\ \hline \end{tabular}
\end{table} 
Table 4: Main combustion parameters (air atmosphere). when this value exceeds 2%/\({}^{\circ}\)C\({}^{3}\)\(\times\) 10\({}^{-7}\), which is amply surpassed by all the wastes studied in this work. Regarding the \(D\) index, it is related to the release of volatile compounds, and its value increases with the increase in the maximum weight loss rate and the decrease in temperature at which these volatile compounds are evolved. Contrary to the \(D_{i}\) index, this value was lower for Ma3 and Ma4 samples (8.85 and 7.04%/\({}^{\circ}\)C\({}^{2}\)\(\times\) 10\({}^{-3}\) respectively), followed by Ma1 with a value of 9.66%/\({}^{\circ}\)C\({}^{2}\)\(\times\) 10\({}^{-3}\); the optimum value was obtained for the Ma2 sample, with an index of 10.54%/\({}^{\circ}\)C\({}^{2}\)\(\times\) 10\({}^{-3}\). Thus, the release of volatile compounds was favored in samples of corncob waste with leaves. Regarding the \(D_{f}\) index, the lowest value was obtained for Ma4 waste, at 199.96%/min\({}^{4}\)\(\times\) 10\({}^{-3}\). This value decreased when \(\Delta t_{2}\) increased, and in this case this parameter was higher because the time at which \(DTG_{max}\) took place was longer. This low value could be due to the higher amount of impurities in this waste, that could make oxygen diffusion and heat transfer difficult [28], delaying the combustion times and producing a higher residual mass after combustion. Additionally, according to ash content results in Table 1, as well as the residual mass in Table 4, it might be concluded that Ma4 waste is not the most suitable residue for combustion. According to the values obtained for \(D_{i}\) and \(S\), it was found that Ma3 and Ma4 had better ignition and combustibility properties, and therefore it can be said that, from that point of view, the wastes containing corn stalk were better than those containing corncob waste, as corncob waste had better characteristics when it was combined with leaves. On the other hand, regarding \(D\) and \(D_{f}\) values, a better behavior for Ma1 and Ma2 was found, that is, the wastes with higher amounts of corncob waste, and in the case of Ma2, there was a considerable improvement (therefore the presence of leaves promoted combustion). In Figure 6, the graphical representation of the comparison of the combustion indexes is included, indicating the relative percentage with respect to the highest value obtained for each index. In this figure, the residue with the best combustion performance appears on the outside, whereas the residue with the worst characteristics appears in the innermost part of the geometric figure.