The Haber-Bosch process, a cornerstone of modern agriculture, faces a critical crossroads. While it has enabled global food production to scale, its reliance on fossil fuels for hydrogen production has become an environmental liability. With ammonia production accounting for over 420 million tons of CO₂ annually, the sector is under pressure to decarbonize. The solution may lie in an unlikely alliance: nuclear energy and high-temperature steam electrolysis (HTSE).
Nuclear energy, particularly from small modular reactors (SMRs), offers a reliable source of both heat and electricity, making it an attractive partner for HTSE. This process, which uses steam instead of liquid water, reduces the electricity demand for water splitting. The integration of SMRs with HTSE and the Haber-Bosch process presents an opportunity to create a carbon-free ammonia production system. The exothermic nature of the Haber-Bosch reaction under high temperatures can further enhance the efficiency of the integrated system by providing the latent heat of vaporisation for feed water.
A project funded by the U.S. Department of Energy is currently developing two reference designs for carbon-free ammonia plants, one using freshwater and the other using seawater or brackish water. The team is focusing on innovative system configurations that integrate an SMR with a cryogenic air separation unit, an HTSE unit, and a Haber-Bosch unit. The current design uses a NuScale Power Module (NPM), which has a thermal power rating of approximately 250 MWt and a gross electrical output of 77 MWe. The HTSE stack operates at 750°C, and the team is evaluating various integration configurations to optimise the use of available thermal energy.
Preliminary case studies have investigated three thermally integrated configurations. Case 3, which preheats the HTSE feedwater using heat generated in multi-stage compressors before receiving additional heating from the ammonia product stream, showed the highest production rate of ammonia. The team is continuing to explore innovative system configurations and perform unit-level design optimisation, with a focus on system-level optimisation and techno-economic analysis.
The potential impact of this research extends beyond ammonia production. The integration of freeze desalination and ice energy storage subsystems when using seawater or brackish water demonstrates the versatility and potential of SMR-powered innovative carbon-free ammonia systems. As the world grapples with the need to reduce greenhouse gas emissions, this research could pave the way for a sustainable future for ammonia production and, by extension, global agriculture.
The development of carbon-free ammonia production systems could also influence other sectors. The integration of nuclear energy with industrial processes could lead to a broader adoption of nuclear energy in industries that require both heat and electricity. Furthermore, the optimisation of the Haber-Bosch process could inspire similar innovations in other energy-intensive industries, driving a wave of decarbonisation across the board.
In the words of the researchers, “The focus will be shifted to perform system-level optimisation and techno-economic analysis (TEA) of the production cost of ammonia.” This shift underscores the importance of not only technological innovation but also economic viability in the transition to a low-carbon future. As the world watches, the Haber-Bosch process stands at the precipice of a transformation that could redefine its role in global agriculture and energy systems.