## 3 Results and Discussion
### Qualitative Composition of the VOCs from the Obtained Bio-Based Boards
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Compound** & **RI\({}_{\text{lit}}\)[24]** & **RI\({}_{\text{exp}}\)** & **GA 700** & **GA 1300** & **B 700** & **B 1300** \\ \hline Acetic acid & 580–660 & 666 & 47.3 \(\pm\) 6.1 & 61.9 \(\pm\) 4.6 & 45.9 \(\pm\) 9.4 & 42.3 \(\pm\) 6.2 \\ Furfural & 782–847 & 854 & 31.6 \(\pm\) 10.0 & 29.9 \(\pm\) 5.2 & 31.8 \(\pm\) 8.2 & 51.3 \(\pm\) 6.6 \\ \(\gamma\)-butyrolactone & 861–914 & 940 & \textless{}0.5 & 0.6 \(\pm\) 0.3 & 1.0 \(\pm\) 0.4 & \textless{}0.5 \\
5-methylfurfural & 976–990 & 979 & 3.6 \(\pm\) 0.5 & 1.6 \(\pm\) 0.3 & 4.2 \(\pm\) 0.3 & 0.7 \(\pm\) 0.2 \\ \hline Summed area (peak number) & – & – & 82.5 (3/42) & 93.6 (4/41) & 82.9 (4/31) & 94.0 (3/30) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The most abundant identified VOCs and their relative area % from the total peaks in SPME-GC-MS chromatograms of the woody biomass binder-less boards. \begin{table}
\begin{tabular}{l c c c c} \hline \hline
**Compound** & **RI\({}_{\text{lit}}\)[24]** & **RI\({}_{\text{exp}}\)** & **SA-PB** & **Commercial PB** \\ \hline Acetic acid & 580–660 & 666 & 14.8 \(\pm\) 10.1 & 5.2 \(\pm\) 1.6 \\ Hexanal & 762–822 & 813 & \textless{}0.5 & 13.2 \(\pm\) 5.7 \\ Furfural & 782–847 & 854 & 21.8 \(\pm\) 11.0 & \textless{}0.5 \\ Hepanal & 856–909 & 913 & n\({}^{1}\) & 0.9 \(\pm\) 0.4 \\ \(\alpha\)-pinene & 923–934 & 934 & 0.9 \(\pm\) 0.2 & 38.7 \(\pm\) 16.2 \\ 5-methylfurfural & 976–990 & 979 & 13.1 \(\pm\) 1.9 & n \\
1,2,4-trimethylbenzene & 956–1013 & 999 & 1.9 \(\pm\) 0.3 & n \\ Sylvestrene & 1016–1018 & 1033 & \textless{}0.5 & 1.5 \(\pm\) 0.3 \\ Nonanal & 1069–1130 & 1114 & 0.9 \(\pm\) 0.4 & 2.4 \(\pm\) 0.7 \\ Verbenone & 1164–1217 & 1224 & n & 0.8 \(\pm\) 0.2 \\ \hline Summed area (peak number) & – & – & 53.4 (6/49) & 62.7 (7/62) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The most abundant identified VOCs and their relative area % from theThe qualitative composition of the VOCs emitted from the binder-less boards fabricated from agricultural biomass was similar. The six chemicals identified in Tables 2 and 3 covered approximately 95% of the total peak areas in the GC-MS chromatograms. This clearly shows that the main VOCs from HS- and WS-based binder-less boards were the same--acetic acid, furfural, and other furans, as well as some low-molecular-weight aldehydes, alcohols, and organic acids. However, a difference could be observed within the remaining 5% of the peak area. Namely, the number of total detected peaks in the case of HS-based boards (Table 2) was smaller than in the case of WS-based boards (Table 3), regardless of board density or thickness, which means that the VOCs from hemp shives were more uniform. This could be related to the chemical composition of the species, demonstrating a higher amount of extractives and xylan content in raw wheat straw vs. hemp shives [25]. The xylan content remained higher for the wheat straw after SE too. However, the overall hemicelluloses content was very similar (12.54 \(\pm\) 0.23/13.32 \(\pm\) 0.22 wt %, respectively, in WS/HS): xylan 11.24/9.53, galactan 0.00/0.00, arabian 0.58/0.00, mannan 0.00/0.71, acetyl groups 0.72/3.08, and organic acids such as formic acid 2.16/0.47 and levulinic acid 0.93/0.82. For both HS- and WS-based boards, many other furan derivatives (furoic acid, furfuryl acetate, and methyl furfural isomers), aliphatic carbonyls and carboxyls (levulinic acid), aromatic compounds (eugenol, guaiaicol, benzyl alcohol, etc. ), and terpen (linalool) were detected at trace levels. It is worth noting that the highest peak numbers of VOCs were identified in the boards with high-density, particularly in WS-based board, indicating the impact of density on the increased formation of minor compounds. It has been reported that raw hemp shives as the main VOCs emitted \(\alpha\)-pinene, limone, \(\beta\)-pinene, \(\beta\)-myrcene, benzaldehyde, hexanal, and camphene, with generally decreasing emissions over time except for pentanal and hexanal, which increased by at least twice after 14 days [11].