A robust bilevel decision-making model for earthquake disaster waste management

Disaster waste management is known as an optimization problem that demands agile, resilient, and sustainable decision-making under rapidly changing and uncertain conditions. In this context, a bilevel optimization model for post-disaster waste management is developed based on the viability approach, explicitly incorporating agility, resilience, and sustainability considerations. In the proposed model, the public authority, acting as the leader, is responsible for the optimal selection of locations and the establishment of Temporary Disaster Waste Management Centers (TDWMCs). Simultaneously, the private sector, as the follower, undertakes waste transportation, separation, recycling, and disposal activities. Establishment costs and carbon emissions are considered at the upper level, while operational costs, recycling revenues, and carbon tax are accounted for at the lower level. The bilevel model is transformed into a single-level formulation using Karush-Kuhn-Tucker (KKT) conditions, and uncertainty in waste generation is addressed through a robust optimization approach. The resulting model is applied to the February 6, 2023, earthquake in Türkiye to demonstrate its practical applicability. The results are analyzed, and sensitivity analyses are conducted with respect to the parameters of the viability approach. The findings indicate that the proposed model realistically captures multi-actor decision-making processes in disaster waste management and provides an effective decision-support tool under diverse policy scenarios.