## 3 Results and Discussion
### Effect of Temperature and PW Recycling on Hydrochars Properties  
Raw biomass and hydrocarbons' volatile matter (VM), ashes (Ash), and fixed carbon (FC) content determined are reported in Table 2 (deviations of data measured through Er% are shown in Table S2 in Supplementary Materials).  
As expected the highest VM content was found in the raw LP (VM = 75.0%). After step R0, proximate analysis shows a decrease in VM with increasing temperature while FC content follows an opposite trend. This is, as well documented in literature, due the enhanced carbonization of biomass at increasing temperature [54]. In recirculation steps, at 180 \({}^{\circ}\)C, the fixed carbon of hydrocarbons increased while volatile matter decreased. These could be related to the increased extent of condensation reaction (polymerization) of organic intermediates in liquid phase and to the increased decomposition of the staring material possibly promoted by increased acids activity, respectively as recently reported by [PERSON] and co-workers [46].  
At higher temperatures, VM and FC contents were only slightly influenced by PW recirculation.  
With PW recirculation an increase of ash content was observed. This may be as a result of an increased concentration of inorganics into PW resulting on a lower leaching activity from the starting raw biomass [41; 46].  
In order to evaluate the increased ash content contribute in solid yield, obtained after recirculation steps, solid yield dry ash free (d.a.f.) was computed.  
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multicolumn{1}{c}{**Sample**} & \multicolumn{2}{c}{**Proximate Analysis wt\% d.b.**} & \multicolumn{2}{c}{**Energy Properties**} & \\ \hline  & **VM** & **Ash** & **FC 1** ** & **HHV (M) kg\({}^{-1}\))** & **EDR (\%)** & **EY (\%)** \\ \hline Raw & & & & & \\ LP & 75.0\% & 3.8\% & 21.2\% & 17.1 & 100.0 & 100.0 \\
180\_R0 & 65.3\% & 2.3\% & 32.4\% & 22.4 & 130.8 & 65.5 \\
220\_R0 & 58.1\% & 3.1\% & 38.8\% & 24.4 & 143.0 & 70.4 \\
250\_R0 & 50.5\% & 3.2\% & 46.3\% & 26.7 & 156.0 & 63.7 \\
180\_R1 & 63.6\% & 3.0\% & 33.4\% & 22.0 & 128.9 & 72.1 \\
220\_R1 & 59.1\% & 3.7\% & 37.1\% & 23.9 & 139.9 & 71.7 \\
250\_R1 & 51.6\% & 3.2\% & 45.2\% & 26.8 & 156.9 & 65.7 \\
180\_R2 & 62.6\% & 3.0\% & 34.4\% & 22.2 & 129.9 & 71.4 \\
220\_R2 & 58.1\% & 3.2\% & 38.7\% & 24.7 & 144.6 & 72.2 \\
250\_R2 & 51.7\% & 3.3\% & 45.1\% & 27.2 & 159.3 & 67.7 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Proximate analysis and energy properties of raw LP and hydrocarbons. Proximate analysis performed in duplicate; average values showed (Er% \(\leq\) 2.9%). Higher heating values (HHVs) average of two measurements, Er% \(\leq\) 0.9.  
The results showed that the increased ash content slightly affected the solid yield increase at 180 \({}^{\circ}\)C and 220 \({}^{\circ}\)C while at 250 \({}^{\circ}\)C hydrocarbons yield remained almost unchanged (Figure 3).  
All hydrocarbons exhibited higher HHV than the raw feedstock and the increased carbon content of the hydrocarbons obtained at higher temperatures underlines this result (Table 2). By recirculation, HHV of hydrocarbons remained nearly constant [41]. Due to the increase in hydrocarbons yield, energy yield significantly increased after recirculation steps (Figure 4).