Municipal solid waste incineration (MSWI) is a widespread technology for MSW treatment, but one of its drawbacks is the production of solid residues: bottom ash (BA) and fly ash (FA). They are characterized by high amounts of chlorides and leachable heavy metals, which limit their potential recycle as secondary raw materials (SRM). In this light, we propose to investigate the speciation of Cu, Zn and Pb, which affects their behaviour as leachable species. Such heavy metals represent some of the commonest source of pollution. We aim to exploit XAS, especially in the XANES region, to get insight into Cu/Zn/Pb speciation, using suitable reference minerals. All this is to understand why a novel pre-treatment, i.e. steam washing, is effective in reducing the release of these metals, and to design further developments. The scientific issue of the present investigation is a contribution to valorize such materials towards a general enhancement of the principle of sustainability of our society.