# Effective Use of Flax Biomass in Biorefining Processes
## 3 Results and Discussion
### Bioethanol Production Process  
#### 3.2.1 Flax Biomass Pretreatment  
Physicochemical pretreatment was carried out, which is a very important stage in the conversion of biomass for energy purposes. The effect of the process is to loosen the compact structure of lignocellulosic, which enables better access of enzymes to cellulose, increasing the susceptibility of biomass to decomposition into simple sugars, which are then converted into ethanol in the fermentation process.  
The selected flax line's biomass was ground using a knife mill on a sieve with a mesh of 2 mm. The biomass was treated with 2% sodium hydroxide and the content of released reducing sugars was determined using the Miller method (Figure 2).  
It was found that the highest content of reducing sugars was obtained for the form of fiber flax--the line PET 16/20, which amounted to 248.1 mg\(\cdot\)g\({}^{-1}\). The linesed turned out to be the most alkali resistant. However, the difference between these forms was not too large and amounted to 27.3 mg\(\cdot\)g\({}^{-1}\), which was 11% of the value obtained for fiber flax.  
Next, the chemical composition of three varieties of flax biomass was assessed, before and after alkaline treatment using chemical methods (Table 6).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Cultivation** & **Sample** & **Cellulose** & **Holocellulose** & **Hemicellulose** & **Lignin** \\ \hline \multirow{2}{*}{Linseed} & BP & 37.42 \(\pm\) 0.62 & 69.31 \(\pm\) 0.99 & 31.89 \(\pm\) 0.41 & 17.83 \(\pm\) 0.43 \\  & AP & 47.82 \(\pm\) 0.17 & 71.61 \(\pm\) 0.39 & 23.79 \(\pm\) 0.51 & 20.30 \(\pm\) 0.60 \\ \hline \multirow{2}{*}{Dual purpose} & BP & 39.94 \(\pm\) 0.21 & 72.13 \(\pm\) 0.26 & 32.19 \(\pm\) 0.42 & 18.44 \(\pm\) 0.10 \\  & AP & 49.20 \(\pm\) 0.56 & 72.31 \(\pm\) 0.44 & 23.11 \(\pm\) 0.54 & 21.26 \(\pm\) 0.04 \\ \hline \multirow{2}{*}{Fiber flax} & BP & 42.17 \(\pm\) 0.29 & 74.27 \(\pm\) 0.47 & 32.10 \(\pm\) 0.63 & 16.93 \(\pm\) 0.31 \\  & AP & 51.40 \(\pm\) 0.58 & 75.72 \(\pm\) 0.21 & 24.32 \(\pm\) 0.55 & 19.86 \(\pm\) 0.30 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Chemical composition of flax biomass before (BP) and after (AP) alkaline treatment (%).  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**No.** & **Breeding Line** & **Fat Content (\%)** \\ \hline
1 & PET 16/16 & 30.9 \(\pm\) 0.4 \\
2 & SW 16/13 & 31.1 \(\pm\) 0.6 \\
3 & PET 16/20 & 28.5 \(\pm\) 0.3 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Comparison of selected lines of flax in terms of fat content in seeds.  
Figure 2: Content of reducing sugars in flax biomass after pretreatment.  
The fiber flax has the highest cellulose content, which is confirmed by the results of the content of reducing sugars. Alkaline treatment resulted in partial degradation of hemicellulose. The seeming increase in lignin content was mainly due to the loss of hemicellulose as a result of the alkaline pretreatment environment.  
Similar values of chemical composition were observed for the biomass of other plants such as hemp. Before chemical treatment, cellulose was in the range of 47-51%, hemicellulose was equal to 28-33% and lignin was 14-16%. Whereas, hemp biomass subjected to chemical treatment with NaOH was characterized by an increased content of cellulose (57-63%), as well as partial degradation of hemicellulose (20-22%). In turn, the lignin content, similarly to flax biomass, slightly increased after chemical treatment (17-18%) [29]. On the other hand, for sorghum biomass treated with 2% sodium hydroxide, an increase in the cellulose content from 37% (before pretreatment) to 71% was observed, and a decrease in the content of hemicellulose from 25% to 16%, and especially lignin from 21% to 6% [41].  
SEM photos of biomass were also taken for all forms of flax before and after treatment with 2% NaOH (Table 7).