Techno-economic assessment of blue and green ammonia as energy carriers in a low-carbon future

Ammonia is an industrial chemical and the basic building block for the fertilizer industry. Lately, attention has shifted towards using ammonia as a carbon-free energy vector, due to the ease of transportation and storage in liquid state at-33 & DEG;C and atmospheric pressure. This study evaluates the prospects of blue and green ammonia as future energy carriers; specifically, the gas switching reforming (GSR) concept for H-2 and N-2 co-production from natural gas with inherent CO2 capture (blue), and H-2 generation through an optimized value chain of wind and solar power, electrolysers, cryogenic N-2 supply, and various options for energy storage (green). These longer term concepts are benchmarked against conventional technologies integrating CO2 capture: the Kellogg Braun & Root (KBR) Purifier process and the Linde Ammonia Concept (LAC). All modelled plants utilize the same ammonia synthesis loop for a consistent comparison. A cash flow analysis showed that the GSR concept achieved an attractive levelized cost of ammonia (LCOA) of 332.1 euro/ton relative to 385.1-385.9 euro /ton for the conventional plants at European energy prices (6.5 euro /GJ natural gas and 60 euro/MWh electricity). Optimal technology integration for green ammonia using technology costs representative of 2050 was considerably more expensive: 484.7-772.1 euro /ton when varying the location from Saudi Arabia to Germany. Furthermore, the LCOA of the GSR technology drops to 192.7 euro /ton when benefitting from low Saudi Arabian energy costs (2 euro /GJ natural gas and 40 euro /MWh electricity). This cost difference between green and blue ammonia remained robust in sensitivity analyses, where input energy cost (natural gas or wind/solar power) was the most influential parameter. Given its low production costs and the techno-economic feasibility of international ammonia trade, advanced blue ammonia production from GSR offers an attractive pathway for natural gas exporting regions to contribute to global decarbonization.