(561g) Low Carbon Ammonia from Distributed H2-N2 Production System

With the anticipated diversification of ammonia applications, the global ammonia market is projected to triple by 2050, reaching over 600 million metric tons annually [1]. However, current ammonia production methods are responsible for approximately 1% of global greenhouse gas emissions, highlighting an urgent need for decarbonization in future ammonia supply chains. Notably, 90% of direct emissions in ammonia production stem from hydrogen production [2], making the provision of low carbon hydrogen essential for achieving sustainable ammonia production.

At present, ammonia production is heavily centralized in regions with access to low-cost natural gas or coal regions, such as the US Gulf Coast as well as China and Russia [3]. This concentration creates a complex and vulnerable supply chain, with production often located thousands of miles from end-users. Geopolitical instability–exemplified by the Russia-Ukraine conflict, which drove prices above $1,600 per ton NH₃–and uneven infrastructure further underscore the risks associated with centralized production [3].

In response, there is growing interest in decentralized ammonia production, particularly through renewable-powered electrolysis for hydrogen supply. While promising, this approach faces cost barriers, with current production estimates ranging between $500 and $1,800 per ton [4]. Additionally, many remote regions lack abundant renewable energy resources, limiting the feasibility of this pathway. Therefore, a more robust decentralized model should not only match local demand but also leverage locally available resources to enable a more flexible and resilient ammonia supply system.

This work explores the feasibility of using a novel blue H₂-N₂ generator [5,6] for decentralized ammonia production. This technology enables the production of low-carbon hydrogen with 82% efficiency and 98% CO₂ capture from locally sourced methane. In our previous work, this system was optimized for small-scale applications, achieving autothermal operation and continuous H₂ and N₂ production, despite periodic switching requirements [6].

In present study, the H₂ and N₂ produced by the system are integrated into an ammonia synthesis unit. The H₂-N₂ generator is coupled with an accumulator, which buffer the flows before feeding them into a Haber-Bosch ammonia converter at 250 bar. The system performance is evaluated at production rates of 1, 3, and 10 metric ton per day (tpd). Preliminary results indicate temperature instability within the ammonia converter at lower production rates (1-3 tpd), highlighting operational challenges at smaller scales. A techno-economic analysis is also conducted to compare this route with other decentralized ammonia production pathways.

This decentralized ammonia production approach offers an alternative for remote regions that lack access to wind and solar energy but have local methane sources. However, methane–a potent greenhouse gas– must be carefully managed to prevent leakage. Furthermore, the local utilization of captured CO₂ should be considered to minimize the economic risks associated with CO₂ transport. Overall, this work offers insights for policymakers and industry stakeholders in developing a more resilient and sustainable decentralized ammonia infrastructure.

References

[1] R. Monis, N. Vasa, S. Mulholland, and S. Wood, “Ammonia Market to Triple by 2050, with Nearly All Growth Coming from Low-Carbon Supply,” 2023. [Online]. Available: https://press.spglobal.com/2023-07-11-Ammonia-Market-to-Triple-by-2050-….

[2] F. Bird, A. Clarke, P. Davies, and E. Surkovic, Ammonia: zero-carbon fertiliser, fuel and energy store. 2020.

[3] T. Kirk, A. Krimer, S. Munasinghe, E. Rodriguez, J. Rosas, and Q. Homann, “Roadmap for Distributed Green Ammonia in Minnesota,” 2024. [Online]. Available: https://rmi.org/insight/roadmap-for-distributed-green-ammonia-in-minnes….

[4] S. Mingolla and L. Rosa, “Low-carbon ammonia production is essential for resilient and sustainable agriculture,” Nat. Food, 2025, doi: 10.1038/s43016-025-01125-y.

[5] A. R. Irhamna and G. M. Bollas, “Intensified reforming reactor for blue hydrogen and nitrogen production,” Int. J. Hydrogen Energy, vol. 80, no. May, pp. 1477–1492, 2024, doi: 10.1016/j.ijhydene.2024.05.428.

[6] A. R. Irhamna and G. M. Bollas, “Enhancing Hydrogen Infrastructure for Domestic Use: A Small-scale Blue Hydrogen and Nitrogen Production System,” [in Prep., 2025].