Optimizing hydrogen supply chain networks for climate change mitigation: a multi-objective MILP framework with carbon pricing and geographic advantages

Introduction Hydrogen export infrastructure requires decisions—carrier pathway, production location, capacity, and market allocation—with 20-40-year lifespans that lock in emission profiles decades ahead. Existing models focus on import-side networks, treat carriers as emission-equivalent, and ignore multi-coastline geographic advantages, collectively missing 75%-90% of supply chain emissions amenable to export-side optimization. Methods A multi-period mixed-integer linear programming (MILP) model integrating economic and life-cycle environmental objectives was developed and applied to Saudi Arabia over 2025-2045. The model simultaneously optimizes four production zones, three carriers (compressed hydrogen, liquefied hydrogen, and ammonia; 0.8-5.3 kg CO 2 e/kg H 2 ), infrastructure sizing and timing, and market allocation across ten destination countries under four carbon pricing scenarios ($0-$120/ton CO 2 e). A 47,520-variable formulation was solved using IBM ILOG CPLEX via two-phase warm-start at <0.5% optimality gap. Results Dual-coastline routing reduces total costs 18.2% ($107B) while simultaneously reducing transport emissions 18.5%—a no-regret intervention generalizable to Morocco, Egypt, Oman, and Australia. Carbon pricing drives pathway diversification: ammonia share falls from 70.3% to 50.4%, and liquefied hydrogen rises from 24.6% to 35.7%, achieving 31% emission reduction at a marginal abatement cost of $29.7/ton CO 2 e—competitive with industrial carbon capture and storage ($25–$60/ton). Distance thresholds emerge: compressed hydrogen below 2,000 nautical miles, liquefied hydrogen at 2,000–5,500 nautical miles, and ammonia above 5,500 nautical miles, each shifting 1,000–1,500 nautical miles under $60–$120/ton pricing. Capital constraints ($10B/year) achieve 69.3% of unconstrained volume with 39.8% of investment, but worsen specific emissions 19.7% (17.3 → 20.7 kg CO 2 e/kg H 2 ). Discussion Capital availability, not technical feasibility, is the binding constraint for simultaneously meeting volume and emission targets. The framework generalizes to climate infrastructure sharing investment lock-in dynamics, discrete facility sizing, geographic emission constraints, and capital limitations, supporting a phased Saudi strategy reaching 16–21 Mt/year by 2045 ($200–$253B cumulative investment).