A Joint economic lot size model for tuna supply chains with battery-constrained electric vehicles and drone-based last-mile delivery

This study proposes a sustainable joint economic lot size (JELS) model for tuna supply chains under stochastic demand. The model considers a multi-echelon network consisting of a processor, a distribution center, multiple retailers, and end customers. Its novelty lies in integrating battery-constrained electric vehicles and drone-based delivery with stochastic demand and variable lead time, aspects rarely addressed simultaneously in previous studies. Lead time is formulated as a function of production, transportation, loading and unloading, transit, charging, and courier delivery activities. To solve the proposed model, an algorithm is developed and validated through a real-world case study. The results show that electric motorcycles achieve annual cost savings of IDR 8.469 billion (80.61%) compared to drones. Conversely, drones reduce delivery time by 2.32 days (55.42%) but increase carbon emissions by 3.13 t.CO₂e (2.65%). Sensitivity analysis identifies product weight, vehicle load capacity, speed, and transport distance as key factors affecting system performance.