Blockchain-integrated bilevel optimization for traceable healthcare waste management

Blockchain Technology (BCT) has emerged as a promising mechanism for enhancing traceability and accountability in Healthcare Waste Management (HWM) systems. This study develops a bilevel optimization model for HWM network design that explicitly incorporates blockchain adoption decisions alongside economic, environmental, and public health objectives. The proposed framework captures the hierarchical interaction between regulatory authorities and logistics operators by modeling the government as the upper-level decision-maker responsible for minimizing infection risk and carbon-related impacts, while the lower-level decision-maker minimizes operational costs through waste flow allocation, conditional on the facility configuration and blockchain investments selected by the upper-level decision-maker. Blockchain adoption is modeled as an endogenous binary decision at the hospital level, enabling the evaluation of selective traceability strategies. The model is applied to a real-world case study in Türkiye involving 23 hospitals and multiple collection and treatment facilities. Computational results demonstrate that full blockchain deployment is not always optimal; instead, partial adoption (34.8% of hospitals) achieves 79.39% network traceability while providing a balanced trade-off among cost, risk, and environmental performance. Pareto frontier analysis reveals significant trade-offs between risk reduction and environmental objectives. Furthermore, pandemic scenario analysis and viability-oriented sensitivity analyses incorporating sustainability, resilience, and agility dimensions show that blockchain adoption exhibits threshold-based behavior, increasing sharply under high operational stress and reaching full deployment under extreme conditions. The findings highlight the structural role of blockchain in reshaping Healthcare Waste (HW) network configurations and provide managerial insights for selective and context-dependent blockchain implementation strategies.