From waste to resource: mineralogical and chemical insights into incinerated sewage sludge ash (ISSA) as a secondary raw material

This study focuses on the characterization and valorization of incinerated sewage sludge ash (ISSA) as a secondary raw material, with particular focus on its mineralogical properties and environmental behavior. Produced as a by-product of municipal wastewater treatment, ISSA presents complex potential both as a source of valuable elements such as phosphorus and selected critical raw materials and as a functional component in industrial material systems. A systematic mineralogical, chemical, and morphological analyses were performed on ISSA samples collected from a Polish wastewater treatment plant. Emphasis was placed on identifying stable and reactive mineral phases, evaluating phosphorus speciation, and assessing the material’s suitability for further processing and application. In parallel, leaching experiments were conducted to ensure the material’s safety in use. The results support the use of ISSA in material production pathways, especially in construction-related applications. Among them, the use of ISSA in cementitious materials was explored in line with circular economy principles, repurposing waste, reducing landfill dependency, and improving resource efficiency. In this context, the potential for passive CO₂ uptake through mineral carbonation was also examined, indicating a measurable contribution to carbon management in sustainable construction materials