From rotary kiln to co-incineration with municipal solid waste: A life cycle assessment uncovering key factors for sustainable medical waste treatment

The rapid growth of medical waste (MW) in China faces insufficient treatment capacity, while many municipal solid waste (MSW) incineration facilities remain underutilized. Co-incinerating disinfected MW in existing MSW incinerator provides a synergistic solution, yet its environmental impacts lack systematic quantification. This study conducts a life cycle assessment (LCA) based on site-specific operational data from a facility in Hangzhou to evaluate steam sterilization followed by MSW co-incineration (S2) compared to the current practice of rotary kiln co-incineration with hazardous waste (HW, S1). A comprehensive sensitivity analysis examines key parameters, alternative energy sources, system boundaries, and disinfection technologies (ethylene oxide, calcium oxide, microwave). Results show that S2 significantly reduces environmental impacts across most categories, achieving net benefits in indicators such as terrestrial ecotoxicity and fossil depletion. This improvement derives from higher energy recovery efficiency (26% vs. 4.9%) and bottom ash recycling, which outweigh the added burdens of steam sterilization. Sensitivity analysis identifies electricity generation, caustic soda consumption, and MW feed rate as the most influential parameters. Among alternatives, ethylene oxide performs best due to low chemical and energy inputs, whereas calcium oxide is least favorable. Unlike previous literature relying on disparate data sources, this study provides a transparent, data-driven basis to confirm the environmental advantages of MW co-incineration within existing MSW incineration plants and offer actionable insights for more sustainable MW management.