###### Abstract
In addition, recent phytoremediation studies give some preference to tree plants since, along with greater yield performance and economically viable valorisation options, they can capture carbon dioxide (CO\({}_{2}\)) and release oxygen into the atmosphere more intensively compared to grass phyto-agents [46; 47]. According to the integrated phytoremediation-bioenergy strategy [48], suggesting to advance the phytoremediation process by utilising soil amendments, incorporation of biochar into the phytoremediation process will provide an additional value due to its climate change-mitigating potential by increasing C storage and decreasing GHG emissions [49]. Biochar is a C-rich substance produced by the pyrolysis of organic wastes; it boosts crop productivity, improves soil biological and physicochemical properties, and increases the activity of soil microbial communities [50]. Biochar is gaining increasing attention as a novel stabilising agent that immobilises organic contaminants and TEs through direct mechanisms such as electrostatic attraction, ion exchange, complexation, and precipitation [51]. Additionally, it alters contaminant availability through indirect mechanisms, i.e., influencing soil properties, i.e., pH, cation exchange capacity, mineral composition, microbial abundance, and organic carbon content [51; 52]. However, the positive effects of biochar depend on factors such as the precursor material, pyrolysis conditions, and application rates [53; 54; 55], and the benefits are not always guaranteed [49; 56]. [PERSON] et al. [57] found that increasing the biochar application rate does not necessarily improve the biomass yield, while [PERSON] et al. [58] highlighted that biochar may introduce environmental risks into phytoremediated systems, such as nitrate leaching [51] or secondary contamination [55]. Recent studies have shown that biochar incorporation can stimulate a removal efficiency of over 77% for Cu, Zn, and Pb [59]. Moreover, a comparative analysis of slaked lime, phosphogypsum, bone meal, and rice husk-derived biochar for their sorption capacity related to As, Cd, and Pb revealed that biochar had a significantly higher sorption capacity [60]. Thus, despite holding a great potential, biochar remains an underexplored \"black gold\" that requires further in-depth research and validation across various systems and environmental matrices. The developing strategy on valorising DS through phytoremediation using the fast-growing timber species _P. tomentosa_ aligns with selected Sustainable Development Goals (SDGs) outlined in the 2030 Agenda for Sustainable Development [61]. Specifically, the approach supports SDG 6.6, which focuses on protecting and restoring water-related ecosystems, is in line with SDG 14.a, which requests to strengthen scientific knowledge and research capacity in improving the state of the environment, and SDG 15.3, which targets the restoration of degraded land and soil by 2030 [61]. The proposed strategy fits within SDG 6.6, as the contaminated DS investigated in this study are fluvial sediments. The valorised (remediated) DS are intended for use as peat substitutes in sustainable agriculture, aligning with SDG 15.3. As of 2 May 2024, progress toward pointed SDGs is varied: 35-50% of targets are experiencing stagnation or regression, 30-65% show moderate progress, and 0-20% have been fully met [62]. These results underscore the urgent need to develop sustainable measures and new technological approaches, including those for DS. The current study aimed to evaluate the phytoremediation potential of _P. tomentosa_ in a'sediment-biochar' system. In the case of positive results, the approach may be proposed for the agriculture sector to receive the cleaned DS to be utilised for improving the soil quality and expanding the land bank.