Extending from reutilization to by-product service: A life-cycle environmental, economic, and risk assessment of heavy metal-containing hazardous waste recycling

The application of waste-derived construction materials represents a critical pathway for high-value reutilization of inorganic heavy metal-containing hazardous wastes, but still poses uncertain environmental risks from residual pollutants within by-products. However, current feasibility assessments of emerging technologies focus primarily on environmental and economic comparative analyses, fails to adequately address the acceptability of potentially pollutant leaching during long-term by-product service, rendering it insufficient. To address this gap, this study presents an extended life-cycle environmental, economic, and risk assessment framework that includes both the reutilization process and the long-term service phase of waste-derived by-products. Using municipal solid waste incinerator fly ash (MSWI FA) as a case, three utilization pathways are evaluated with the proposed framework: (1) co-sintering with zinc-containing waste (FA-SZn), (2) dioxin degradation followed by water-washing (FA-Wash), and (3) co-processing in cement kilns for clinker production (FA-Clinker). Results show that, the emerging FA-SZn outperforms industrialized FA-Wash and FA-Clinker due to the benefits of metal recovery in terms of environmental and economic performance. Additionally, risk assessment demonstrates that FA-SZn-derived supplementary cementitious materials are safer for roadway applications than FA-Wash, with 25.32–49.38% and 39.75–78.80% reductions in non-carcinogenic and carcinogenic risks, respectively. These findings highlight the advantages of emerging MSWI FA reutilization pathway and provide a comprehensive framework for quantifying life-cycle benefits in heavy metal-containing hazardous waste reutilization, supporting sustainable and safe waste recovery strategies.