## 3 Results and Discussion
### Techno-Economic Analysis  
In the establishment year, total labour requirements and costs for ploughing, harrowing, planting, and weed control were 29.8 man h\({}^{-1}\) ha\({}^{-1}\) and EUR 1036 ha\({}^{-1}\) for the unamended system, and 53.3 man h\({}^{-1}\) ha\({}^{-1}\) and EUR 1222 ha\({}^{-1}\) for the biochar-amended system (Table 2). Diesel consumption and costs were 50.8 L ha\({}^{-1}\) and EUR 75.2 ha\({}^{-1}\) for all experimental treatments. Similar figures were obtained for scenario 2 except labour cost, specifically EUR 836 ha\({}^{-1}\) for the unamended system and EUR 1022 ha\({}^{-1}\) for the biochar-amended system (Table 3). For the second and subsequent years, total labour requirements, labour costs, and diesel usage across all experimental treatments were 3 man h\({}^{-1}\) ha\({}^{-1}\), EUR 824 (or 624) ha\({}^{-1}\), 22.5 L ha\({}^{-1}\), and EUR 33.3 ha\({}^{-1}\), respectively. \begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**Operation**} & \multirow{2}{*}{**Labour**} & **Diesel** & **Materials** & \multicolumn{2}{c}{**Total Inputs**} \\ \cline{3-8}  & & **EUR ha\({}^{-1}\)** & **EUR ha\({}^{-1}\)** & **EUR ha\({}^{-1}\)** & **EUR ha\({}^{-1}\)** & **EUR 200 M m\({}^{-3}\)** \\ \hline \multirow{2}{*}{Tillage} & Ploughing & 15.9 & 37.0 & \(-\) & 52.9 & 529 \\  & Harrowing & 10.2 & 4.93 & \(-\) & 15.2 & 152 \\ \hline \multirow{4}{*}{Soil amending} & Ctrl & \(-\) & \(-\) & \(-\) & \(-\) & \(-\) \\  & Biochar 2.5\% & 186 & \(-\) & 156 & 342 & 3421 \\  & Biochar 5.0\% & 186 & \(-\) & 312 & 498 & 4981 \\  & Biochar 10\% & 186 & \(-\) & 624 & 810 & 8099 \\ \hline \multicolumn{2}{c}{Planting} & 186 & \(-\) & 1700 & 1886 & 18,862 \\ \hline \multicolumn{2}{c}{Weed control} & 23.8 & 33.3 & 74.5 & 132 & 1316 \\ \hline \multicolumn{2}{c}{Harvest} & \(-\) & \(-\) & \(-\) & 800 & 8000 \\ \hline \multicolumn{2}{c}{Total investments} & & Ctrl & 236 & 75.2 & 1775 & 2086 & 20,858 \\ \multirow{2}{*}{1 st year} & Biochar 2.5\% & 422 & 75.2 & 1930 & 2428 & 24,279 \\  & Biochar 5.0\% & 422 & 75.2 & 2086 & 2584 & 25,839 \\  & Biochar 10\% & 422 & 75.2 & 2398 & 2896 & 28,958 \\ \hline \multirow{2}{*}{Following years} & No harvest & 23.8 & 33.3 & 74.5 & 132 & 1316 \\ \cline{2-6}  & Harvest & 23.8 & 33.3 & 74.5 & 932 & 9316 \\ \hline \end{tabular}
\end{table} 
Table 2: The economic costs of valorising _P. tomentosa_ biomass via dual-use production for timber and woodchips (Scenario 1). Figure 5: PCA biplots: (**a**) PC1-PC2; (**b**) PC1-PC3. According to the results presented in Tables 2 and 3, valorisation of the contaminated DS through phytoremediation holds economic preference compared to disposal, which incurs a total cost of EUR 27,400,000 200 M m\({}^{-3}\) (or EUR 2740,000 ha\({}^{-1}\)). In both scenarios for the establishment year, the largest share of the investment was attributed to the cost of plant materials. However, in Scenario 1, the share of plant materials ranged from 58.7 to 81.5% (Table 2), while, in Scenario 2, the share was higher, ranging from 69.6 to 95.5%, which can be explained by the higher planting density (3000 pl ha\({}^{-1}\)) [91]. Moreover, the data obtained for Scenario 2 align with the results of the economic profitability analysis of cultivating _Miscanthus_\(\times\)_giganteus_ in non-agricultural soils [81]. Regarding the cost of biochar amendments at different application rates, in Scenario 1, the share of costs was 6.43, 12.1, and 21.6% for 2.5, 5.0, and 10% application rates, respectively (Table 2). In Scenario 2, the corresponding values were 7.90, 14.6, and 26.6% (Table 3). The economic revenue for both scenarios was estimated conservatively without factoring in expected biomass yield growth over the plantation's lifecycle. This approach was used to confirm that the proposed valorisation strategy is viable and merits deeper investigation. The preliminary findings indicated that (i) phytoremediation of contaminated DS by _P.