## 1 Introduction
Thus, researchers are actively working to enhance the efficiency of this technique by inducing standard plant species to accumulate high TE concentrations by selective breeding [18; 19], innovative management techniques [20], gene manipulation [21], and soil conditioners [22] such as biological inocula or TE-mobilising agents [23]. Despite recent advances, there is still no empirical evidence that these strategies will significantly reduce the time needed to address the problem of soil pollution. One of the main advantages in using plants to address pollution is that they may provide a valuable contribution toward reducing greenhouse gas emissions to the atmosphere. Whilst it is well established that conventional cleanup techniques for polluted soil are associated with the emission of greenhouse gases through the use of heavy duty construction equipment powered by fossil fuels [24; 25], information on the actual potential of the plants used in phytoremediation to avoid emissions is widely available. For instance, a recent study conducted in Belgium and the Netherlands comparing the CO\({}_{2}\) abatement potential of willow (_Salix_ spp. ), silage maize (_Zea mays_ L.), and rapeseed (_Brassica napus_ L.) grown on contaminated land by means of a life-cycle assessment approach showed the highest net CO\({}_{2}\) abatement for the most productive willow clone compared to the other two crops [26]. The emergence of associated ecosystem services following the application of this technology is a further benefit that should also be considered. Ecosystem services are functions provided by any activity related to the natural environment and ecosystems that could generate externalities. In the field of economics, externalities are defined as costs or benefits that affect a third party who did not choose to incur those costs or benefits ([PERSON] and [PERSON] 1962). The concept of ecosystem services and related externalities has been frequently associated to forest systems because they perform a very complex set of functions for the benefit of society, including the production of raw materials and non-wood products, carbon storage, hydrogeological protection, aesthetic/recreational functions, and biodiversity conservation [27; 28; 29; 30; 31; 32; 33]. Forests belong to the category'mixed goods' which have no market value, or the market is not capable of correctly defining their value. Quantifying the economic value of forest resources is difficult because it requires the assignment of a monetary value to the goods and services without a market value which are additionally provided by forest stands. It should also be noted that the objective to be maximized varies with the bodies considered; private entities focus on profit maximization, while public entities focus on the maximizing social welfare [35]. This implies the existence of different mechanisms for assigning values to the same assets. When estimating ecosystem services of the fast-growing woody species used for phytoextraction, many of the above-mentioned functions cannot actually be considered. TE-contaminated biomass does not represent marketable forest product (e.g., timber production) and its use as energy biofuel is still under evaluation. In addition, most of these stands, compared to actual forest stands, do not perform particular hydrogeological protection activities, they are not optimal for the conservation of biodiversity, and because they are located in contaminated areas, tourism or recreational activities are not allowed. Therefore, the only function that can be considered for these stands is represented by the carbon sequestered by the epigeal biomass that is removed annually and stored in landfills. The aim of the current study was to highlight how, in addition to the benefits derived from phytoextraction, the use of short-rotation coppice plantations creates the opportunity to restore at least one ecosystem service in the form of carbon dioxide storage.