Designing a Multi-Objective Stable Mathematical Model for Routing Municipal Waste Collection Vehicles

Waste collection poses a significant challenge for contemporary societies. Given the inevitability of ongoing human waste production, the organization of municipal waste collection holds paramount importance. Against the backdrop of escalating environmental pollutants over recent decades and crises induced by global warming, governments have increasingly prioritized addressing sustainability issues. The objective of this study was to formulate an urban waste collection network with a municipal sustainability perspective. To achieve this goal, we proposed a multi-objective mathematical model that incorporates economic, social, and environmental considerations pertaining to the routing of urban waste collection vehicles.

This study introduces an integer multi-objective mathematical model centred on stability components to address the routing problem of urban waste collection vehicles, to design an optimal network for urban waste collection. The model was addressed using real data from waste collection in Iran’s Saveh city. GAMS software was employed for solving the model in small dimensions, while MATLAB software was utilized for solving the model in larger dimensions. The proposed model incorporates a robust approach to handle uncertainty. Multi-objective meta-heuristic algorithms were applied to solve the model in scenarios with larger dimensions. A comparative analysis was subsequently conducted, evaluating solution methods based on both the values of the objective function and the solution time.

The economic objective of this study encompasses the overall costs associated with transporting waste from collection points to processing and recycling centres, along with the expenses related to waste recycling. Its environmental objective focuses on minimizing pollution resulting from the transportation of collected waste. Lastly, its social objective is to maximize citizens' satisfaction with urban waste collection. The results demonstrated that the proposed mathematical model establishes a rational relationship between the incurred costs, the quantity of waste collected, the distance travelled, and the amount of pollution generated during the transportation of waste.

The model presented in this study optimized the urban waste collection system by incorporating dimensions of sustainability. This was achieved by formulating separate objective functions to address various aspects of urban waste collection. The results showed that in the economic dimension, waste collection costs, which account for the largest share of the total cost of waste management, decreased significantly. The collection cost was reduced by optimizing the collection routes and reducing the costs related to recycling collected waste. In addition, in the social dimension, by considering the amount of waste collected compared to the waste produced, the level of satisfaction of citizens was calculated. Finally, the results showed that by reducing the environmental effects related to the recycling and transportation of the collected waste, the proposed model had an acceptable performance.