## 4 Conclusions  
1. _Festuca arundinacea_ was cultivated on soil with a high concentration of NaCl in the top layer (up to 6 g\(\cdot\)L\({}^{-1}\)), and in the second year of cultivation, it formed a dense sod, produced three cuts and a medium high yield (14.8 Mg\(\cdot\)ha\({}^{-1}\)).  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **Tensile** & **Tensile** & **Flexural** & **Flexural** \\  & **Strength** & **Modulus** & **Strength** & **Modulus** \\  & \(\delta_{\textbf{M}}\) (MPa) & \(E_{\textbf{t}}\) (GPa) & \(\delta_{\textbf{M}}\) (MPa) & \(E_{\textbf{t}}\) (GPa) \\ \hline PLA 3251D & 62.1 \(\pm\) 0.5 & 2.34 \(\pm\) 0.07 & 108.1 \(\pm\) 0.4 & 2.21 \(\pm\) 0.21 \\ PLA-FA\_1 & 47.2 \(\pm\) 0.6 & 3.00 \(\pm\) 0.05 & 83.8 \(\pm\) 0.5 & 2.80 \(\pm\) 0.14 \\ PLA-FA\_2 & 49.3 \(\pm\) 0.9 & 3.14 \(\pm\) 0.09 & 88.2 \(\pm\) 0.9 & 2.92 \(\pm\) 0.20 \\ PLA-FA\_3 & 46.6 \(\pm\) 1.1 & 2.97 \(\pm\) 0.10 & 82.6 \(\pm\) 0.8 & 2.77 \(\pm\) 0.17 \\ PLA-FA\_4 & 47.8 \(\pm\) 0.9 & 3.06 \(\pm\) 0.08 & 84.6 \(\pm\) 0.8 & 2.85 \(\pm\) 0.22 \\ PLA-FA\_5 & 46.1 \(\pm\) 0.7 & 2.93 \(\pm\) 0.07 & 82.2 \(\pm\) 0.8 & 2.74 \(\pm\) 0.09 \\ PLA-FA\_6 & 44.7 \(\pm\) 0.6 & 2.85 \(\pm\) 0.06 & 79.5 \(\pm\) 1.1 & 2.66 \(\pm\) 0.11 \\ PLA-FA\_7 & 46.8 \(\pm\) 0.9 & 2.98 \(\pm\) 0.11 & 83.5 \(\pm\) 1.0 & 2.79 \(\pm\) 0.09 \\ PLA-FA\_8 & 48.0 \(\pm\) 0.6 & 3.06 \(\pm\) 0.09 & 84.9 \(\pm\) 0.9 & 2.83 \(\pm\) 0.10 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Tensile and flexural properties of PLA/tall fescue composites.  
Figure 6: SEM images of adhesion at the interface of PLA/tall fescue biocomposites at magnification of (**a**) \(\times\)500 and (**b**) \(\times\)1000.  
In this work, the tall fescue biomass obtained from the soil with different salinities was used in the process of obtaining bioethanol and green composites based on the biodegradable polymer PLA.
3. It was found that the content of Na\({}^{+}\) in tall fescue biomass had no significant effect on the amount of ethanol obtained (average: 19.32 g\(\cdot\)100 g\({}^{-1}\) of raw material), which may result from leaching of sodium ions during alkaline pretreatment.
4. The possibility of using tall fescue biomass with the lowest Na\({}^{+}\) content in biomass (approx. 2.5 mg\(\cdot\)g\({}^{-1}\)) from an area with high salinity (above 6 g NaCl\(\cdot\)L\({}^{-1}\)) as fillers for composites based on PLA was demonstrated. Moreover, for this biomass, the highest value of bioethanol concentration was obtained, i.e., 10.6 g\(\cdot\)L\({}^{-1}\) (21.2 g\(\cdot\)100 g\({}^{-1}\) of raw material).
5. In summary, _F. arundinacea_ can be successfully used for bioremediation of saline habitats and its biomass for industrial applications such as advanced biofuels and as natural fillers to improve the economics of using biodegradable polymers in composites.  
Conceptualization, J.B., A.A. and K.B.; Methodology, J.B., A.W., K.B., W.G., E.B., A.P., S.R. and A.A.; Software, A.W. and W.G.; Validation, J.B.; Formal Analysis, J.B.; Investigation, A.W., K.B., W.G., E.B., A.P., S.R. and A.A.; Resources, J.B., A.W., K.B., W.G., E.B., A.P., S.R. and A.A.; Data Curation, J.B., A.W., K.B., W.G., E.B., A.P., S.R. and A.A.; Writing--Original Draft Preparation, J.B., A.A., K.B. and A.W.; Writing--Review and Editing, J.B., A.A. and A.W.; Visualization, J.B.; Supervision, J.B.; Project Administration, J.B.; Funding Acquisition, J.B. All authors have read and agreed to the published version of the manuscript.  
Field research was financed by the National Center for Research and Development, Poland under the ERA-NET CO-FOUND FACCE SURPLUS 2 grant (2018-2021).  
Not applicable.  
Field studies were carried out as part of the research project ERA-NET CO-FOUND FACCE SURPLUS 2 (2018-2021): Integrated bioremediation system--biorefining using halophyte species, financed by the National Center for Research and Development, Poland.  
The authors declare no conflict of interest.