## 4 Discussion and Conclusions
The presence of CO\({}_{2}\) in the atmosphere upon heat treatment, however, hindered thermal \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Atmosphere** & **T (K)** & \begin{tabular}{c} **Light Tar** \\ **(GC–MS)** \\ \end{tabular} & \begin{tabular}{c} **Heavy Tar** \\ **(SEC)** \\ \end{tabular} & \begin{tabular}{c} **Char** \\ **DTG Peaks (K)** \\ \end{tabular} \\ \hline \multicolumn{5}{c}{_Pinewoad_} \\ \hline N\({}_{2}\) & 1573 & \begin{tabular}{c} Oxo-aromatics 40\% \\ Anhydrous monosaccharides 30\% \\ Aliphatics:15\% \\ Light PAHs: 15\% \\ \end{tabular} & None & 750 \\ CO\({}_{2}\) & 1573 & \begin{tabular}{c} Oxo-aromatics:40\% \\ Light PAHs: 30\% \\ Heavy PAHs: 10\% \\ \end{tabular} & & \\ N\({}_{2}\) & 2073 & \begin{tabular}{c} Oxo-aromatics:40\% \\ Light PAHs: 30\% \\ Heavy PAHs: 10\% \\ \end{tabular} & & 630; 720; 760 \\  & & \begin{tabular}{c} Oxo-aromatics:30\% \\ Light PAHs: 30\% \\ Aliphatics: 20\% \\ Heavy PAHs: 10\% \\ \end{tabular} & \begin{tabular}{c} Trimodal \\ distribution \\ (higher MW) \\ \end{tabular} & \\ CO\({}_{2}\) & 2073 & \begin{tabular}{c} Oxo-aromatics:30\% \\ Light PAHs: 30\% \\ Aliphatics: 20\% \\ Heavy PAHs: 10\% \\ \end{tabular} & & 630; 720; 810 \\  & & \begin{tabular}{c} _Siraw_ \\ \end{tabular} & \\ \hline N\({}_{2}\) & 1573 & \begin{tabular}{c} Oxo-aromatics: 50\% \\ Light PAHs: 20\% \\ Aliphatics: 20\% \\ Anhydrous monosaccharides: 10\% \\ \end{tabular} & None & 690; 710 \\ \hline N\({}_{2}\) & 2073 & \begin{tabular}{c} Oxo-aromatics: 50\% \\ Light PAHs: 30\% \\ Aliphatics: 15\% \\ Heavy PAHs: 5\% \\ \end{tabular} & \
\begin{tabular}{c} Trimodal \\ distribution \\ (higher MW) \\ \end{tabular} & 710; 810 \\ \hline CO\({}_{2}\) & 2073 &
\begin{tabular}{c} Oxo-aromatics: 35\% \\ Light PAHs: 30\% \\ Aliphatics: 15\% \\ Heavy PAHs: 10\% \\ \end{tabular} & 810 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._annealing of lignin char; in fact, CO\({}_{2}\) chars were more reactive than N\({}_{2}\) chars. In the present work, severe heat treatment and the presence of CO\({}_{2}\) in the atmospheres generated additional char components, which were both more reactive (with peaks at temperature as low as 630 K) and less reactive (with peak temperatures as high as 830 K). It is possible that the newly formed high reactive char component arose from interactions and cross-linking reactions within the solid matrix at the expense of anhydrous monosaccharides (which decrease sensibly in the corresponding tars), whereas the less reactive component arose from thermal annealing of the solid phase. Altogether, the emerging scenario suggests that it is not possible to predict the quality of primary tar and char produced from fast pyrolysis of lignocellulosic biomasses simply by taking into account the behavior of cellulose, hemicelluloses and lignin. Interactions among primary volatile products do exist. Furthermore, it is worth noting that extraction processes for separating cellulose, hemicellulose and lignin from lignocellulosic biomass induce several structure modifications [27; 28; 29], thus making it more and more inefficient to predict the biomass pyrolysis behavior on account of the cellulose/hemicellulose/lignin commercially available. In particular, cellulose extraction methods influence the cellulose crystallinity degree [27]. Extraction processes of hemicellulose generate a lower degree of polymerization, mineral impurities and partial breakage of side chains [28], while lignin extraction methods produce low aromatic products [29]. Additional effects of extractives, proteins and minerals further complicate the phenomena and deserve future work and investigation. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Atmosphere** & **-T (K)** & \begin{tabular}{c} **Light Tar** \\ **(GC-MS)** \\ \end{tabular}  & \begin{tabular}{c} **Heavy Tar** \\ **(SEC)** \\ \end{tabular}  & \begin{tabular}{c} **Char** \\ **DTG Peaks (K)** \\ \end{tabular}