Characterization, Potential Uses and Soil Leaching of Urban waste/Agricultural residue Ash Mixtures produced from Fluidized Bed Combustion

In the context of exploitation of urban wastes for recycling, valorification, or energy production, present study aimed at investigating the environmental impact and potential uses of ashes produced from co-combustion of such wastes with an olive byproduct in a fluidized bed unit. Bottom and fly ashes were characterized by physical, chemical and mineralogical analyses. Column leaching tests, simulating field conditions, were conducted and key parameters of soil/ash leachate solutions were measured. The results showed that fly and bottom ashes were alkaline, with low electrical conductivity and cation exchange capacity and enriched in Ca, Si, P, K, Mn, Zn, Sr and Cr. The principal mineral phases identified were calcite, quartz, fairchildite, hydroxyapatite and whitlockite magnesian. The elements with higher mobility leached through a soil of quarzitic nature were Na, Mg, Cr and Sr. However, none of the measured values exceeded legislation limits for land disposal. All ashes could be used as secondary building materials, liming agents or soil ameliorants in blends with other byproducts.