## 3 Results and Discussion
### Elemental Analysis
Instead, biochars at 600 \({}^{\circ}\)C presented low H/C and O/C ratios, with H/C values near to those reported for anthracite [74; 75], but they had a higher O/C. Therefore, it could be concluded that the biochars from broom and gorse have similar characteristics to those of traditional fossil fuels and eventually could be cleaner substitute energy sources [61]. The biochars from broom and gorse had low S contents (Table 2) compared to those of conventional coals [61; 76; 77; 78]. Therefore, during the combustion of these biochars, lower SO\({}_{2}\) emissions will be produced, reducing their impact on the environment as well as the costs of purifying the emitted gases. \begin{table}
\begin{tabular}{c c c c c c} \hline  & \%N & \%C & \%H & \%S & \%O & (O + N)/C \\ \hline GORSE & 1.55 \(\pm\) 0.05 A & 44.83 \(\pm\) 1.53 A & 6.05 \(\pm\) 0.11 D & 0.08 \(\pm\) 0.04 A & 45.03 \(\pm\) 1.2 D & 0.78 \(\pm\) 0.05 D \\ BG300-1H & 2.09 \(\pm\) 0.06 B & 58.27 \(\pm\) 2.09 B & 5.42 \(\pm\) 0.14 C & 0.04 \(\pm\) 0.01 A & 31 \(\pm\) 1.8 C & 0.43 \(\pm\) 0.04 C \\ BG300-3H & 2.48 \(\pm\) 0.05 C & 62.81 \(\pm\) 1.52 C & 4.87 \(\pm\) 0.11 B & 0.04 \(\pm\) 0.01 A & 25.54 \(\pm\) 1.11 B & 0.34 \(\pm\) 0.02 B \\ BG600-1H & 1.95 \(\pm\) 0.28 B & 71.67 \(\pm\) 2.03 D & 1.72 \(\pm\) 0.38 A & 0.05 \(\pm\) 0 A & 18.81 \(\pm\) 2.86 A & 0.22 \(\pm\) 0.03 A \\ BG600-3H & 1.63 \(\pm\) 0.07 A & 72.32 \(\pm\) 2.19 D & 1.66 \(\pm\) 0.14 A & 0.05 \(\pm\) 0 A & 19.26 \(\pm\) 1.97 A & 0.22 \(\pm\) 0.03 A \\ \hline \end{tabular}
\end{table} 
Table 2: _Cont._  
Figure 1: [PERSON] diagram for broom, gorse, and their biochars. The data with labels correspond to the literature values. LSGC: low-grade sub-bituminous coal [61]; LIG: lignite [73], BIT: bituminous coal [79], ANT: anthracite [75], and ANT2: anthracite [74]. The average HHV of gorse was lower than those found by [PERSON] et al. [54], who obtained values of 20.18 and 20.95 MJ kg\({}^{-1}\), and than those measured and calculated by [PERSON] et al. [50], with HHV values of 19.5 and 19.6 MJ kg\({}^{-1}\) for _U. europaeus_. The average HHV for broom was also lower than that obtained by [PERSON] et al. [50] which ranged between 18.6 and 19.3 MJ kg\({}^{-1}\) or than those reported by [PERSON] et al. [54] of 19.01 and 20.67 MJ kg\({}^{-1}\) for _C. scoparius_. The average HHV of the feedstock increased with pyrolysis time (Table 3) due to increase in C content [50; 58; 61]. In addition, the different formulas used for calculating the HHV did not statistically differ among the biochars, except in the case of BB600-1H and BG300-3H. In the broom and gorse feedstocks, there were statistical differences, especially between HHV\({}_{1}\) and HHV\({}_{3}\) for broom and HHV\({}_{3}\) and HHV\({}_{4}\) for gorse (Supporting Information Table S1). The LHV behaviors were the same, with lower values for broom and gorse feedstock compared with those of the biochars. The CDF, linked to energy production, increased with pyrolysis temperature, as has been reported by other authors [60; 80; 81]. The EEF did not show statistical differences between biochars except in the case of BB300-3H, having a mean value of 1.55 \(\pm\) 0.07; nevertheless, all biochars presented an EEF greater than one, which, according to [PERSON] et al. [60], reflects an improvement in energy densification. In terms of calorific value improvement, the CVI did not show differences between the biochars except in the cases of BB300-1H and BB300-3H, which had the highest values. The ED of broom did not statistically differ between the feedstock and the biochars prepared at 300 \({}^{\circ}\)C, but did differ from that obtained at 600 \({}^{\circ}\)C. The gorse feedstock and the derived biochars did not differ from the feedstock, except in the case of BG300-3H, which had a lower value. All biochars had ED values greater than those reported for old oil palm trees and the respective biochars [61].