The application of biochar (charcoal or biomass-derived black carbon (BC)) to soil is proposed as a novel approach to establish a significant long-term sink for atmospheric carbon dioxide in terrestrial ecosystems. Apart from positive effects on both reducing emissions and increasing the sequestration of greenhouse gases, the production of biochar and its application to soil is expected to deliver immediate benefits through improved soil fertility and increased crop production. The fertilizing properties of charred plant residues were re-discovered and are nowadays divulged and encouraged within the concept of using biochars produced under controlled combustion conditions as soil amendment. However, the application of biochar as soil ameliorant still presents several major uncertainties. Particularly, the capacity of Mediterranean soils to store and sequester C due to biochar addition has not been well studied, thus this project will comprise for the first time the transport and stabilization of biochar produced from vegetation residues and urban wastes through the soil column. On the other hand, Polycyclic Aromatic Hydrocarbons (PAHs), persistent organic pollutants formed during biochar production due to incomplete combustion process (pyrolysis step), will enter the environment when the biochar is applied as soil conditioner. However, an accurate assessment of the impact of biochar addition on the release of PAHs is still missing and will constitute the other main objective of this proposal.