Cost competitiveness of blue and green ammonia in future energy markets

Low-carbon ammonia can be produced at relevant scales through the conventional Haber-Bosch process paired with carbon capture and sequestration (blue ammonia) or using a renewable-driven Haber-Bosch process with hydrogen sourced from water electrolysis (green ammonia). The feasibility of each technology depends on the cost and availability of methane, green electricity, and the existence of carbon markets. To assess the feasibility of green and blue ammonia, we developed a detailed process model for each system and examined the energy, cost, and emissions associated with each system. We also assessed integration with the grid and intermittent operation from variable renewable energy resources on site. Our results suggest that an effective carbon tax of 50 USD/tCO2 would make blue ammonia feasible. However, for green ammonia to be a viable alternative to gray ammonia in all scenarios, the required carbon tax would be between 100 USD/tCO2 and 200 USD/tCO2. Furthermore, we find that green ammonia is only the preferred alternative over blue ammonia with advanced projections for renewable electricity and electrolysis technologies and with high natural gas price projections. Finally, we discuss the integration of emerging ammonia production routes with the grid and variable renewable power systems and their social impacts in future deployments.