Chemical Stabilization of Municipal Solid Waste Incineration Fly Ash without Any Commercial Chemicals: First Pilot-Plant Scaling Up Laura Benassi, † Michela Pasquali, † Alessandra Zanoletti, † Rogerta Dalipi, † Laura Borgese, † Laura Eleonora Depero, † Ivano Vassura, ‡ Margarida J. Quina, § and Elza Bontempi* ,† † INSTM and Chemistry for Technologies Laboratory, University of Brescia, via Branze 38, 25123 Brescia, Italy ‡ Department of Industrial Chemistry “Toso Montanari”, University of Bologna, Viale del Risorgimento 4, 40136 Bologna, Italy § CIEPQPF-Research Centre on Chemical Processes Engineering and Forest Products, Department of Chemical Engineering, University of Coimbra, Pó lo II-Rua Sílvio Lima, Coimbra, Portugal ABSTRACT: For the first time in Europe, results of chemical stabilization of municipal solid waste incineration (MSWI) fly ash, realized as a pilot plant, are reported. The stabilization technology is based on the use of only waste and byproduct materials (such as coal fly ash, flue gas desulfurization residues, and rice husk ash). In the frame of the COSMOS-RICE project, a pilot plant was built in Italy, with a capacity of more than 0.5 tons of MSWI fly ash/day. The stability of the material obtained was investigated by the evaluation of the pH dependency of the leaching of metals, 6 months after the treatment. The pH dependence of heavy metal solubility was described in terms of unified leaching curves, comparing first- time leaching data of MSWI fly ash from different geographical locations (Italy, Portugal, Denmark, and China), using a polynomial function. Results confirmed that COSMOS-RICE technology can be a promising path for obtaining a stabilized product with likely practical applications, avoiding costly and unsustainable landfilling. KEYWORDS: Fly ash, Stabilization, COSMOS-RICE, Heavy metals, Rice husk ash ■ INTRODUCTION The progressive transition from municipal solid waste (MSW) management mainly based on landfilling to integrated manage- ment systems based on the optimized use of available technologies (i.e., composting, recycling, and incineration with energy recovery) is necessary for the environmental sustainability of European cities. According to EUROSTAT, during the year 2014, in Europe, 122 kg of MSW per capita was incinerated. The available data also show that generally, in places where high incineration rates are reached (>35% of the total waste produced), as for example in Germany and France, the fraction of waste incinerated is constant considering the past years (with the fraction also exceeding 50%). On the contrary, in countries where the incineration rate is <25%, the amount of waste incinerated, with respect to the waste generated, is continuously increasing with time (see Figure 1). Therefore, in the future, the level of incineration of waste is expected to rise in several countries. On the other hand, because Europe faces issues with raw materials, there is an increasing need to encourage resource conservation and promote secondary raw material recovery. The reuse of municipal solid waste incineration (MSWI) fly ash (often by mixing it with corresponding bottom ash) is proposed mainly in construction 1,2 with the development of pretreatment technologies. However, some studies point out that there is high potential for human health risks resulting from exposure to MSWI fly ash. 3 Leaching of pollutants from MSWI fly ash is of major environmental concern with respect to its disposal and/or reuse. When this residue is placed at its final destination, infiltrating water can dissolve solid phases and precipitate secondary phases depending on the leachate composition. In particular, leaching of heavy metals has been shown to be highly variable and may occur over periods of tens to thousands of years. It is governed primarily by the solubility of various solid phases, which in turn is strongly dependent on pH. 4 Over the past three decades, a number of methods to stabilize this hazardous waste have been suggested to reduce the level of leaching. 5−7 Solidification and stabilization (S/S) using cement as a binder is the prelandfill treatment method for MSWI fly ash most commonly used worldwide. 8 This method involves a conversion of the residues into a monolithic or granular material, ensuring easy handling and transportation to landfill Received: June 10, 2016 Revised: August 23, 2016 Research Article pubs.acs.org/journal/ascecg © XXXX American Chemical Society A DOI: 10.1021/acssuschemeng.6b01294 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX