## 3 Results and Discussion  
### Biochar Analyses  
Biochar from gasification was analyzed and its ultimate analysis is reported in Table 1. Carbon represented the most abundant element, followed by ashes [26], as previously mentioned, and the oxygen content can be back-calculated as a complementary value to reach 100%. The gasification temperatures adopted ranged from 600 \({}^{\circ}\)C up to 950 \({}^{\circ}\)C, and the average temperature considered was 750 \({}^{\circ}\)C. Particle distribution analysis of the \"as-received\" biochar is reported in Table 2.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **\% Ash** & **\% C** & **\% H** & **\% N** & **\% S** \\ \hline Vine prunings biochar & 32.48 & 67.78 & 0.82 & 0.57 & N.D. \\ \hline \end{tabular}
\end{table}
Table 1: Ultimate analysis of dry vine pruning biochar.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline Size: & \textgreater{}710 \(\mu\)m & 500–710 \(\mu\)m & 125–500 \(\mu\)m & 63–125 \(\mu\)m & 32–63 \(\mu\)m & \textless{}32 \(\mu\)m \\ \hline mass \% & 71.44 & 7.11 & 13.22 & 2.4 & 2.4 & 3.2 \\ \hline \end{tabular}
\end{table}
Table 2: Particle size distribution of “as-received” biochar.  
Imaging of Prepared Biochar and Milled Biochar  
Figure 3a shows the as-received char. It appeared covered with dust and soot. It is possible to notice that the soot and dust material was also present inside the pores of the structure. To select the finest powder, the material sifted under the 32-micron sieve was collected and analyzed with ESEM. It is possible to notice (Figure 3b) that the powder obtained from the \"as-received\" biochar still presented an extended number of impurities on its surface. The final goal of this work was to provide, through the char, a carbon source for the PAN electrospinning process. For this reason, impurities need to be completely avoided. Soot and dust materials have different compositions when compared to char: the ash content does not provide any carbon source, while the organic part (mostly polycyclic hydrocarbon) will behave differently from char in the process [1]. For these reasons, the simple direct use of the \"as-received\" sifted powder cannot be followed and the milling procedure does not solve the problem. In order to produce a cleaner powder, two possible approaches were followed: an attempt was made to mill the char particles, and then a second attempt preceded the milling process with a solvent cleaning stage.  
It was decided to clean the biochar pellets in isopropyl alcohol before the milling process. After 20 h in isopropyl alcohol, the cleaned biochar morphology is depicted in Figure 3c. Biochar particles resulted cleaner from impurities in comparison with the ones that were not solvent-washed, and therefore, they were chosen to be further processed through milling and sifting. Once dried, clean biochar pellets were milled with the described process and then wet-sieved with isopropanol in a 32 \(\upmu\)m sieve. The results are shown in Figure 3d. While, in Figure 3b, the powder was agglomerated, in Figure 3d, the powder was generally deagglomerated and single grains can be seen.  
Figure 3: **(a)** Micro-morphological details from ESEM analysis on “as-received” biochar grain 1000\(\times\) magnification; **(b)** sifted ”as-received” biochar powder, ESEM, 1000\(\times\) magnification; **(c)** cleaned biochar pellet surface, ESEM, 200\(\times\) magnification; **(d)** biochar particles after cleaning and sieving processes (applying 32 \(\upmu\)m mesh).  
The powder composition was analyzed using EDS analysis. Figure 4 shows the results of the composition analysis, outlining the maximum and the minimum of amounts recorded for each element.