Strategies for industrial residue valorization through metal recovery, use in construction, or CO2 mineralization.

Effective strategies for waste valorization from industrial residues include metal recovery, use in construction materials, and CO2 mineralization, all of which extend the value of these materials and reduce direct disposal. This study reviews valorization potential across an array of industrial residues, including pyrometallurgical slags, hydrometallurgical residues, power-plant combustion ashes, and mine wastes. Critical metal recovery is prioritized over construction material use driven by metal supply needs, starting with the extraction of rare earth elements (REEs) followed by other metals (Li, Co, Cu, Ni, etc.) depending on the profitability of the extraction and recovery processes. By-products generated from post-metal recovery processes are considered for construction materials. When metal recovery is limited, valorization instead focuses on use in construction materials, first based on their suitability as supplementary cementitious materials (SCMs), followed by structural aggregates, and other civil applications. The study discusses the CO2 mineralization potential and CO2 uptake of varied industrial residues, summarizing their effects on cement hydration and the mechanical performance of carbonated industrial residues used in construction applications, as well as the economic implications and environmental impacts of scaled use. We present two integrated valorization examples for red mud and steel slags. REE concentrations in red mud vary geographically and do not typically provide economic benefit (revenue-to-cost ratio at 1:10). Variability in steel slag composition coupled with operational complexity prevents CO2 mineralization potential, which could be up to about -100 kg CO2 eq./ton.