Pyrolysis for exploitation of biomasses selected for soil phytoremediation: Characterization of gaseous and solid products

Biomasses to be used in the phytoremediation process are generally selected to match agronomic parameters and heavy metals uptake ability. A proper selection can be made greatly effective if knowledge of the properties of the residual char from pyrolysis is available to identify possible valorization routes. In this study a comparative analysis of the yields and characteristics of char obtained from slow pyrolysis of five uncontaminated biomasses (Populus nigra, Salix alba, Fraxinus oxyphylla, Eucalyptus occidentalis and Arundo donax) was carried out under steam atmosphere to better develop char porosity. Moreover, the dependence of the properties of solid residue on the process final temperature was studied for E. occidentalis in the temperature range of 688-967 K. The results demonstrate that, among the studied biomasses, chars from P. nigra and E. occidentalis have to be preferred for applications regulated by surface phenomena given their highest surface area (270-300 m2/g), whereas char from E. occidentalis is the best choice when the goal is to maximize energy recovery.