## 4 Results and Discussion
### Mass Yields  
The mass yields produced for the vine shoot carbonisation tests as a function of the test method are shown on Figure 4. For all tests, it is observed that, as the temperature increases, as well as the duration time, the mass yields decrease drastically. This is due to the combustion and volatilisation of the raw material, as well as the generation of ash in the part of the mass that has burned [33]. This situation is supported by the literature in this field of research, which shows that a higher pyrolysis temperature results in a lower mass yield of charcoal [32]. In the specific tests of the charring without a lid (WL), it was observed that the results of the mass yield only went up to the value of 300 \({}^{\circ}\)C for 3 h because in later tests, i.e., at higher temperatures, the mass of the vine shoots burned, generating only ashes.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Test** & **E\({}_{\text{Transition\_1}}\)** & **E\({}_{\text{Preheating}}\)** & **E\({}_{\text{Transition\_2}}\)** & **V (\({}^{\circ}\)C/min)** & **E\({}_{\text{Test}}\) (kWh)** \\ \hline
200 \({}^{\circ}\)C for 2 h & & & 0.71 & 0.18 \\ \hline
200 \({}^{\circ}\)C for 3 h & & & 0.47 & 0.29 \\ \hline
250 \({}^{\circ}\)C for 2 h & & & 1.13 & 0.26 \\ \hline
250 \({}^{\circ}\)C for 3 h & & & 0.75 & 0.38 \\ \hline
300 \({}^{\circ}\)C for 2 h & & & 1.54 & 0.34 \\ \hline
300 \({}^{\circ}\)C for 3 h & & & 1.03 & 0.51 \\ \hline
350 \({}^{\circ}\)C for 2 h & & & 1.96 & 0.43 \\ \hline
350 \({}^{\circ}\)C for 3 h & & & 1.31 & 0.65 \\ \hline
400 \({}^{\circ}\)C for 2 h & & & 2.38 & 0.53 \\ \hline
400 \({}^{\circ}\)C for 3 h & & & 1.58 & 0.79 \\ \hline
450 \({}^{\circ}\)C for 2 h & & & 2.79 & 0.63 \\ \hline
450 \({}^{\circ}\)C for 3 h In the cases of the charring of vine shoots with a lid (L), as can be seen in Figure 4, several tests were carried out at higher temperatures than in the case of without a lid (WL) tests, as the temperature could be raised above 300 \({}^{\circ}\)C without combustion occurring. Another relevant aspect shown in the graph is that, as the test temperature rose, the mass yields decreased more smoothly and in a more controlled manner than in the case of the WL tests. Moreover, the trend of the curve reveals that, even if the temperature increased, the mass yields would not decrease drastically, but seem to reach a limit. It is understood that the tendency to stabilise at around 30% mass yield was generated for the highest carbonisation temperature values (>450 \({}^{\circ}\)C). The time variable seems to have more influence at low temperatures than at high temperatures. For example, for the 200 \({}^{\circ}\)C test, going from a time value of 2 to for 3 h implies a decrease in the mass yield of 11.7%. On the contrary, for the 450 \({}^{\circ}\)C temperature tests, the time increase implied a decrease of 1.5%.  
Finally, the test results were plotted for the case where the vine shoots were closed in a can (C). As for their mass yield, the same behaviour appeared as in the case of the L tests, with a slight increase in the yield visible mainly at low temperatures. For example, the 200 \({}^{\circ}\)C for 2 h tests in the case of L yielded a mass yield of 49.5%, while in the case of the feedstock tested in C, the mass yield was 70.7%. This is a difference of 21.2%, which will result in a correspondingly higher carbon content yield. As with the L test, this one tends to decrease slowly to values of about 30% as shown in Figure 4.