Phytomanagement of a Trace Element-Contaminated Site to Produce a Natural Dye: First Screening of an Emerging Biomass Valorization Chain  
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1 Department of Green Chemistry and Technology, Ghent University, 9000 Ghent, Belgium; [PERSON]); [PERSON]RESS] (E.M.)  
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2 Clean Technologies and Circular Economy, INERIS, Parc Technologique Alata, BP2, 60550 Vernveil-en-Halate, France; [EMAIL_ADDRESS] (V.B. ); [EMAIL_ADDRESS] (R.G.) [PERSON]  
3 Analytical Methods and Developments for the Environment, INERIS, Parc Technologique Alata, BP2, 60550 Vernveil-en-Halate, France; [EMAIL_ADDRESS] (C.C.) [PERSON]  
the export of TE-enriched plant biomass. This TE removal can be achieved by using hyper-accumator species (e.g., _Arabidopsis hulleri_ L.) that contain high TE concentrations in their biomass or crops with a high biomass yield and lower TE concentration (e.g., _Salix viunitalis_ L.) [3, 7]. Nonetheless, the applicability of phytoextraction can be limited by several reasons, such as multi-TE contamination and a significant time being required to achieve remediation [7]. In contrast, phytostabilization consists of the use of plant species with an excluder phenotype, i.e., a plant with a bioconcentration factor \(<1\), to limit the TE transfer between the soil and the aboveground part of the plant. In addition, such a plant can decrease the TE mobility in the soil through the effects of the root system [4, 7, 9]. In this way, the aim of phytostabilization is not to clean the pollution from the soil but to confine it by controlling the TE transfer pathways. Annual herbaceous plants can be used as phytomanagement tools to manage TE in contaminated soils, but studies to date have mainly focused on species of negligible economic value. The combination of a more gradual improvement of soil quality using plant-based techniques with the economic valorization of the produced biomass is also referred to as phytoattenuation. In this strategy, the economic use of the land as well as the risk mitigation of the contamination itself are the primary goals. The diversity of the plant species involved in phytomanagement (e.g., trees, industrial crops, herbs, and aromatic plant) could allow biomass valorization as a material (fibers, essential oil, eco-catalyst) or as an energy source (combustion, biogas, bioethanol) [6, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]. These non-food purposes might be integrated into the biobased market and can contribute to its development. Specifically, In the European chemical market in 2019, only 3% of the products were biobased, with more than 51% of biomass feedstock being imported. The maturity of this sector was considered low or medium. However, the biobased chemical market is expected to grow in the coming years [20]. This will lead to an increase in biomass needs and in the intensification of land use, which might reduce biomass import-dependency in Europe. In this context, the reuse of marginal land can promote this increase in biomass production without competing with agricultural land [2]. According to the \"paints, coating, inks and dye\" sector, 12.5% of the content of these products were biobased and mainly concern solvents and polymers, not dyes [20]. In this sector, the substitution of synthetic dyes with biobased natural alternatives is a worldwide emerging research subject. These natural dyes could be used in various applications, such as in paint, food, chemical indicators, and textiles, and in emerging ones, such as materials for solar panels or pharmaceuticals [21, 22]. Specifically, the textile sector is one of the most environmentally harmful sectors that use dyes; the use of synthetic metallic dyes composed of TE such as Cr, Co, Cu, and Pb results in a high content of pollutants in the wastewater of the dyeing process [23]. Therefore, the textile sector could highly benefit from biobased natural dyes, enhancing this sector's environmental sustainability [24]. _Malwa sylvestris_ L. (common mallow) is considered a native species in Europe, North Africa, and Asia.