Ashes from incinerated municipal solid waste (fly ash) contain high levels of heavy metals such as Pb, Cd and Cu. Deposition of these toxic fly ashes is therefore not without risks. An alternative to deposition is to heat-treat the fly ashes to produce secondary raw materials suited for reprocessing (heavy metal concentrates and detoxified ashes). The potential of the thermal treatment was studied by monitoring the evaporation rate of lead from a certified fly ash (BCR176) during heating between 300 and 950oC under oxidizing as well as reducing conditions. Samples at different phases of the heat treatment process were quenched for subsequent investigation with micro-focused X-ray absorption spectroscopy (XAS) to determine the solid state speciation of lead. Micro- spectromicroscopic data of the quenched heat treated samples were collected at the new MicroXAS beamline at the Swiss Light Source (Villigen, Switzerland). Evaporation data (under oxidizing and reducing conditions) coupled with unique spectromicroscopic observations from the state-of-the-art MicroXAS facility will be discussed. The micro-spectroscopic observations helped to explain the evaporation curves and showed that thermal treatment of municipal waste is a valuable alternative to the deposition of municipal solid waste.