Recovery of Metals from Municipal Solid Waste Incineration Plants Wastes: A Comparative Case Study of Pre- and Post-Pandemic Periods

Abstract

Municipal Solid Waste Incineration (MSWI) plants are of great concern, generating solid by-products, namely Fly Ash (FA) and Bottom Ash (BA). These MSWI residues have received significant attention for environmental concerns and the recovery of valuable elements, minerals, and secondary raw materials. The potential recovery of elements in MSW are crucial for circular economy and environmental sustainability (Han et al, 2021; Funari et al, 2016). Therefore, available types of fly ashes samples, i.e., lime- and soda-doped fly ash from bag filters following electrostatic precipitation, and quenched BA samples were sampled during pre- (2013, 2020) and post-pandemic period (2021, 2022) from two grate-furnace MSWI plants, located in Ferrara (FE) and Forlì (FC) cities in Italy. The sample preparation and elemental analysis were performed at ALS Scandinavia laboratory as a part of an international research collaboration between University of Bologna, Luleå University of Technology, and ALS Scandinavia. In this study, we aimed to determine and compare the elemental composition in MSWI samples by Inductively Coupled Plasma-Sector Field Mass Spectrometry (ICP-SFMS) to assess metal abundance by enrichment factor and elemental flows using substance flow analysis and MSWI systems’ mass balance (Brunner and Rechemberg, 2004). Our results showed that recovery of valuable elements (Al, Fe, Si, Zn, and Cu) was high after strong digestion method for all the FA and BA samples. Overall, little variation in elemental composition of FA and BA in both selected periods (pre-pandemic vs post-pandemic) suggests a similar input flow of urban waste. Enrichment factors (EF) show enrichment of Zn, Cu, Al, Fe, Mg, Ca, Na, K, and potentially toxic elements like Pb, Cd in both FA and BA. The chondrite normalized REE patterns of FA and BA are relatively similar suggesting that the BA and FA feeding material are mostly geogenic materials, with possible anthropogenic fluctuation for Ce, Tb, and Yb. The upper continental crust (UCC) normalization patterns were consistent for most elements. In contrast, Ba, K, P, and La patterns vary, likely showing an anthropogenic signal. Mass balance assessment showed that the waste streams can host from low to high concentration of strategic elements as an alternative source of value in the circular economy.