Towards diesel free logistics: economic and environmental fleet mix optimisation for refrigerated vehicles

EU companies are urged to reduce their logistics emissions to respond to upcoming environmental regulations. Updating the fleet mix can lower the environmental impact of road logistics, which remains key to ensure continuity in first- and last-mile transportation. The fleet mix decision needs to consider also the sustainability performance of refrigerators for temperature-controlled vehicles, which are extensively employed in food logistics. This work thus aims to identify the optimal fleet mix of refrigerated vehicles for a supermarket chain, by minimising operational costs and CO2e emissions, concurrently addressing economic and environmental objectives. A mixed-integer programming multi-objective model was developed and solved using the ε-constraint method. Five power generation systems for trucks and four refrigerator options were considered, while accounting for technical constraints of trucks-refrigerators combinations across three scenarios. The results identify the Pareto front of non-dominated solutions, highlighting an unbalanced trade-offs between costs and CO2 emissions and demonstrating that alternative cost-efficient and environmentally-friendly solutions are available. 67.3% of the solutions on the Pareto front do not select LNG trucks and diesel refrigerators obtaining a fossil fuel-free fleet. Refrigerator systems account for less than 20% of total emissions and their impact is more relevant in economically-oriented solutions. This work contributes to the sustainable logistics literature by exploring the sustainable fleet mix optimisation problem for refrigerated fleets, considering costs and CO2 emissions of both vehicle power generation systems and refrigerator operations. The work can guide practitioners to transition towards sustainable refrigerated fleets for road transportation, supporting the transition towards a low-carbon transport sector.