Solid residues from Italian municipal solid waste incinerators: A source for "critical" raw materials

Area of Science:

• Environmental Science
• Materials Science
• Chemical Engineering

Background:

• Municipal solid waste incineration (MSWI) is crucial for waste management.
• Solid residues from MSWI present environmental concerns and recovery opportunities for valuable metals.
• Critical Raw Materials (CRM) are essential for high-tech industries and face supply risks.

Purpose of the Study:

• To quantify the Critical Raw Materials (CRM) content in solid residues from Italian municipal waste incinerators.
• To analyze the distribution of elements within bottom ash and fly ash fractions.
• To evaluate the potential for CRM recovery from MSWI residues.

Main Methods:

• Sampling of untreated bottom ash and fly ash from two MSWI plants.
• Elemental composition analysis using X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS).
• Substance flow analysis integrating chemical data, mass balance, and uncertainty assessment.

Main Results:

• Bottom and fly ashes contain low concentrations of precious and high-tech metals, with Mg, Cu, Sb, and Zn levels comparable to low-grade ores.
• Most elements are enriched in bottom ash, particularly fine fractions, but Sb and Zn show strong partitioning into fly ash.
• CRM concentrations in untreated residues are comparable to those in post-treatment beneficiated residues.

Conclusions:

• MSWI bottom and fly ashes represent a potential secondary source of CRM.
• Separate collection and processing of fresh bottom ash can significantly improve metal recovery efficiency.
• This approach offers an attractive waste management option, especially for older MSWI systems lacking advanced beneficiation.