Optimal design of decentralized ammonia production via electric Haber–Bosch systems

Abstract

Ammonia production, central to global food and energy systems, is highly centralized and fossil-dependent, consuming ∼5% of global natural gas and creating supply chain risks due to long-distance transport. Decentralized, electrified Haber–Bosch systems offer a resilient alternative that can diversify supply and reduce emissions. This study develops an optimization model to assess the techno-economic feasibility of decentralized ammonia production across six representative locations (Brazil, India, China, the United States, Italy, and Ethiopia). We evaluate three configurations: autonomous (renewables only), grid-connected, and hybrid systems, under 2025 and 2045 cost scenarios. In 2025, decentralized systems remain uncompetitive, with levelized costs of ammonia often exceeding global market prices by more than 500 USD per tonnes in regions with low renewables potential. By 2045, declining renewables and electrolyzer costs narrow the premium: cost-effectiveness is achieved in the United States and Ethiopia, while China, Brazil, and India approach competitiveness with premiums of 175–435 USD per tonnes. Cost drivers vary by design: capital costs and financing conditions dominate autonomous systems, and electricity prices shape grid-connected plants. We show that coupling of intermittent renewables production, buffer capacities, operational flexibility of electrified Haber–Bosch reactors, and flexibility in ammonia demand are key to determining the cost of ammonia supply. High-pressure reactors and the thermal inertia of Haber–Bosch reactors can limit rapid ramping under variable renewable power, highlighting a core green chemistry challenge: current catalytic and reactor designs are poorly matched to fluctuating, low-carbon energy inputs, thus requiring high buffer capacities or a flexible demand. Sensitivity analyses indicate that higher conversion efficiency, lower specific energy use, and reduced dependence on hydrogen and battery storage or oversized renewable capacity are decisive for cost-competitiveness. These system-level results translate into quantitative design targets for green chemistry, indicating that catalysts, electrolyzers, and synthesis pathways that maintain high efficiency under dynamic and part-load operation are essential for sustainable nitrogen fixation. Overall, reductions in system-level cost and energy demand, and enhancements in operational flexibility and part-load operation are necessary to enable next-generation ammonia reactors that embody the principles of energy efficiency, waste minimization, and decentralized, safer chemical manufacturing to reach competitiveness for industrial-scale deployment.