Background In municipal waste incinerators, the main waste product is bottom ash, which is equivalent to some 10% by volume of the solid waste input. Fly ash, or the finest, lightest residue, is collected in many plants using a filtration system. Fly ash contains heavy metals (including zinc, lead, cadmium and chromium) and is therefore classified as toxic waste. In most cases, it is disposed of in lagoons, settling ponds, landfills or other sites, such as former mines in Germany. Though different techniques are being researched, there is presently no effective method for stabilising the heavy metals in fly ash. Previous projects that demonstrated the successful reuse of fly ash mainly focused on relatively stable or non-hazardous ash waste. However, the University of Brescia has developed a new method for treating fly ash. Objectives The project will develop the University of Brescia's method for treating fly ash. It will derive silica gel from rice husk ash, and will use the gel to make fly ash from municipal solid waste inert, via a chemical process. The project will: Demonstrate that using rice husk ash as a precursor for silica leads to lower environmental impacts and economic costs, and that the silica gel can be used to treat fly ash; Evaluate the performance of the new materials obtained by the treatment, and the markets for the end products; Reduce the consumption of natural resources, in favour of recycled material; and Generate new knowledge, by combining the know-how and competence of different researchers and staff from industry. Expected results The project's main results will be: Use of rice husk ash as a source of silica gel, and use of the silica gel to treat fly ash. Theoretically in Europe, all rice husk ash could be reused, with a significant reduction in waste destined for landfill; To open up the possibility of fly ash recycling; and To produce a new, environmentally-friendly product, with properties similar to or better than some commercial fillers, which are made from natural resources.