Metal resource potential of residues from municipal solid waste (MSW) melting plants

Fly ash and molten metal residues from municipal solid waste (MSW) melting plants are attracting considerable attention in Japan as an urban mine due to their high metal content. The study aimed at identifying the content of valuable metals in fly ash and molten metal and quantitatively evaluating the metal resource potential through comparison with ore and annual consumption. It was found that not only Zn and Pb but also rare metals such as Ag, Bi, Ga, Ge, Pd, In, Sb, Sn, Te, and Tl were highly concentrated in fly ash, and that the content was mainly influenced by the feedstock supplied to the melting plant. Cu content was extremely high in molten metals. The content of Zn, Pb, Cu, Ag, In, and Pd in fly ash was almost equal to or higher than that in crude ore. Particularly, Zn in fly ash was increased to almost the same level of Zn ore concentrate by simple water washing. Also, the estimated amount of Ga, Ge, Pd, Sb, Sn, and Zn in fly ash and molten metal occupied a high proportion of the annual consumption amount in Japan. These facts revealed that fly ash and molten metals from MSW melting plants have high metal resource potential.