A Hybrid Cold-Chain Optimization Framework for Last-Mile Dairy Distribution under Energy Instability: Integrating Formal and Informal Delivery Networks in Urban Nigeria

Abstract

Last-mile delivery of dairy products in many African cities is constrained less by distance and more by infrastructure vulnerability. In urban Nigeria, disrupted electricity networks, fuel volatility, traffic congestion, and the coexistence of formal and informal distribution actors create systemic inefficiencies in the cold chain. This paper develops a theoretical hybrid optimization framework for last-mile dairy distribution under conditions of energy instability. The framework goes beyond technology-centric approaches. It integrates energy reliability parameters, product thermal decay functions, and dual-network coordination mechanisms. It links formal logistics providers with informal micro-distributors. The study draws on supply chain resilience theory, resource orchestration logic, and perishable inventory modeling. It conceptualizes how energy risk can be embedded directly into routing, inventory positioning, and delivery sequencing decisions. The proposed model presents three interlinked design layers: energy-adaptive cold-chain configuration, dynamic routing under erratic power supply conditions, and formal–informal network synchronization. The paper argues that spoilage minimization and customer satisfaction are not automatically aligned and must be jointly optimized through cost–temperature–time trade-offs. The framework contributes theoretically by reframing energy instability as a decision variable instead of seeing it as an external disturbance and by conceptualizing informal actors as strategic assets rather than operational noise. The study concludes with implications for urban food security, supply chain competitiveness, and sustainable distribution design in infrastructure-constrained economies.