Ammonia is an essential chemical used across many industries worldwide. Beyond its traditional role as a fertilizer, it is also a promising liquid hydrogen carrier and low-carbon fuel that could help reduce reliance on fossil fuels. However, conventional ammonia production based on the Haber–Bosch (HB) process requires considerable energy and contributes significantly to greenhouse gas emissions, accounting for roughly 1–1.3% of global emissions annually. Given its growing importance, there is an urgent need to reduce the environmental burden of ammonia production.
Recently, chemical looping ammonia synthesis (CLAS) has emerged as a viable alternative method for ammonia production. Specifically, aluminium-oxide (Al2O3)-based chemical looping has shown promise for enabling ammonia synthesis under more energy-efficient conditions.
Building on this concept, a research team led by Assistant Professor Sunghyun Cho from the School of Chemical Engineering, School of Semiconductor and Chemical Engineering at Jeonbuk National University in South Korea, has developed a new dual-chemical looping process combining Al2O3 and iron oxide (Fe2O3). "Our approach combines methane thermal decomposition with Al2O3- and Fe2O3-based chemical looping cycles," explains Dr. Cho. "This method enables ammonia synthesis without the energy-intensive steps, significantly improving both sustainability and efficiency." Their study was made available online on October 29, 2025, and published in Volume 348, Part B of Energy Conversion and Management on January 15, 2026.
The Al2O3-based chemical loop (A-CL) has two stages: nitrogen fixation and hydrolysis. During nitrogen fixation, Al2O3 combines with nitrogen and solid carbon to generate aluminium nitride (AlN). This is followed by hydrolysis, where AlN interacts with steam to produce ammonia. In the proposed dual-looping process, A-CL is complemented by thermal decomposition of methane (TDM) and an Fe2O3-based chemical loop (F-CL).
TDM supplies solid carbon for A-CL, while F-CL provides nitrogen, eliminating the need for additional air separation units. Additionally, carbon monoxide generation within A-CL provides reusable feedstock for F-CL systems. Together, these interactions create a cross-linked circulation of key feedstock materials.
To test practical feasibility, the researchers then conducted a comprehensive energy, exergy, economic, and environmental (4E) analysis of 10 different process configurations, including the proposed dual-looping system and its modified variations, the conventional HB process, and both Al₂O₃-based and Fe₂O₃-based single-chemical looping systems.
Simulation results showed that the proposed configuration outperformed conventional production methods in both energy and exergy efficiencies by 8.4 % and 19.0 %, respectively. It reduced global warming potential by up to 15.85 kg of CO₂-equivalent per kilogram of ammonia produced. It also demonstrated the lowest production costs among all evaluated cases. Sensitivity analysis further confirmed its robustness under varying technoeconomic conditions. Notably, integrating heat exchangers significantly improved energy and exergy efficiencies of all configurations.
"Our dual-looping technology can be applied across industries that require large-scale ammonia production while reducing carbon emissions and maintaining economic feasibility," concludes Dr. Cho. "As the world moves toward cleaner energy systems, this process could support future clean-fuel applications and broader carbon-neutral energy-transition strategies."
