Institute of Geological Sciences, University of Bern, Switzerland; Zentrum für nachhaltige Abfall- und Ressourcennutzung (ZAR), Zuchwil, Switzerland. About 4 million tons of waste are incinerated in Switzerland each year in 29 municipal solid waste incineration (MSWI) plants to reduce the mass and volume of waste, destroy organic compounds, and to recover energy. The mass flow was calculated based on concentrations and amount of FA from all plants in 2016 [ 15]. The addition of an oxidizing agent at low pH conditions is crucial for Cu and Pb recovery, as it enhances the yield greatly ([ 13], Table 1). Likewise, Fe 2+ is converted into Fe 3+, which precipitates as Fe-hydroxide and is accumulated in the remaining filter cake.

Later on, the distribution of HMs in BA and FA are mutually resolved on the basis of physiochemical properties of HMs and their compounds.Further major constituents are Al 2O 3 (35,000 mg/kg), Fe 2O 3 (25,000 mg/kg), P 2O 5 (10,000 mg/kg), MgO (12,000 mg/kg), and TiO 2 (17,000 mg/kg). The remaining plants produce approximately 43,000 t/y of FA, which has to be treated in external or newly constructed facilities. Incineration has gained popularity over landfill as a key solution for the reduction of massively increasing volumes of municipal solid waste (MSW) generation worldwide and in particular China. The content of Al 0 in FA is shown as a boxplot in Figure 4 (a complete table can be found in the Supplementary Materials). S and Cl, which promote the transfer of heavy metals into the flue gas, scatter from 75,000 to 200,000 and 60,000 to 250,000 mg/kg, respectively.

Precious metals and rare earth elements in municipal solid waste—Sources and fate in a Swiss incineration plant. As a basis for the development of defined recovery rates and for the implementation of the recovery process, the authorities and plant operators need information on the geochemical properties of FA. The content of heavy metals is found higher in fly ash than that of bottom ash, as can be seen in Table 4 and Table 5, which enlist the amount of heavy metals for fly ash and bottom ash. As of 2021, there will be 29 MSWI plants in Switzerland producing ~80,000 tons of FA per year that must be treated prior to disposal.Stand der Technik für die Aufbereitung von Rauchgasreinigungsrückständen (RGRR) aus Kehrichtverbrennungsanlagen; AWEL: Zürich, Switzerland, 2013; p. The treated fly ash is then required to be either disposed of or utilized in possible applications such as construction material, geotechnical applications, agriculture, etc. Heavy metals in landfills are a constant threat to the surrounding environment, especially from a long-term perspective, and primary production (mining, excavation, and extraction) have dramatic impacts on the environment and its inhabitants [ 18]. However, the remaining filter cake that is deposited still contains a significant load of contaminants, such as Sb and Sn.

Since some MSWI plants are among the largest in Switzerland, the amount of produced FA is 4300 t per year on average. The availability of chlorine and the formation of metal chlorides may strongly increase the volatility of metals. It is estimated that the amount of fly ash produced accounts for approximately 3–10% of incineration waste [ 9]. these characteristics hinder the use of subsequent applications and demand treatment to make it environmentally friendly. The authors of [ 159] conclude that, at lower temperatures and shorter times, higher integrated control efficiency conditions of heavy metals were achieved.Thermal treatment contains three major ways (vitrification, fusion/melting, and sintering) to stabilize the heavy metals. Of all MSWI plants, 16 out of 29 produce FA that shows very high or high leaching potential, and 13 MSWI plants produce FA that shows moderate or low leaching potential.