Economic viability and CO2 emissions of hydrogen production for ammonia synthesis: A comparative analysis across Europe

Abstract

Ammonia production accounts for 15–20% of greenhouse gas emissions from the chemical sector. Traditionally, ammonia is produced via Steam Methane Reforming (SMR) for hydrogen production, coupled with the Haber-Bosch process. This study compares the SMR-based configuration with emerging alternatives based on water electrolysis – Proton Exchange Membrane Electrolyser Cell (PEMEC) and Solid Oxide Electrolyser Cell (SOEC) – from both economic and CO₂ emissions perspective. Process models for the three plant layouts are developed, incorporating heat integration between different components. The economic results are presented in terms of the levelised cost of ammonia, which accounts for both capital and operating expenses over the plant's lifetime. Sensitivity analyses on electricity and methane prices are conducted to assess the cost-competitiveness of each technology across various scenarios. The outcomes reveal that the optimal technology is highly dependent on electricity prices. PEMEC systems are the most cost-effective option at very low electricity prices (approximately 0.02 €/kWh_e), while SOEC systems become more competitive as prices rise due to their higher efficiency. Above 0.08 €/kWh_e, SMR emerges as the most viable option. Special attention is given to the CO₂ emissions from both SMR and electrolyser systems, also considering the carbon intensity of the electricity used. While electrolysis is often assumed to be carbon-free, this research shows that electrolysers can produce more emissions than SMR, depending on the electricity carbon intensity: when carbon intensity exceeds about 260 gCO₂/kWh_e, SMR results in lower emissions than the electrolyser-based pathways. Finally, future projections suggest that SOEC technology will become highly cost-competitive by 2030–2040.