How renewable can green ammonia be? Natural resources exergy footprint on a small-scale ammonia production system

The world energy transition state has significantly increased the weight of renewables infrastructure importance on the development of new energy production systems. This study presents a novel perspective on the production of green ammonia by investigating how renewable it can be based on renewable and non-renewable exergy costs. The primary objective of this research is to verify how the exergy costs of renewable (sunlight, wind, water, and soil) and non-renewable resources (fossil fuels, white hydrogen, and critical raw materials) affect the physical requirements for ammonia production via the Haber-Bosch process under different loads and resources availability conditions. Additional objectives involve comparing the costs of producing ammonia under different plant load operation conditions with the stream recirculation strategy and evaluating how the hybridization of electricity sources affect both the plant load strategy and the flexibility versus efficiency dilemma. The circular thermoeconomic model developed on Aspen Plus and integrated with TAESLab explores ammonia production on a small-scale integrated multi-product ammonia plant with different sources of electricity (based on IEA NZE for solar PV, wind, and (grid), hydrogen (white and green via alkaline, proton and anion-exchange, and solid oxide electrolysis), nitrogen (cryogenic), water, and soil (exergy). Our innovative methodology includes the exergy costs of the processes and materials required for each technology infrastructure construction. Our findings shed a light on how renewable ammonia’s physical costs affect its current and future projected applications based on its overall specific exergy cost (SEC). These values ranged between 13.0 and 44.0 MWh/tNH3 depending on the adopted pathway. Therefore, This work highlights the required energy transition impact on the small-scale ammonia production for regions with different natural resources availability on the world.