Geo-storage of ammonia as an energy carrier: A review on the opportunities and challenges

Abstract

Ammonia presents significant advantages over hydrogen as an emerging energy carrier for energy transition. However, the technical feasibility of underground ammonia storage (UAS) in porous media remains largely unexplored. This paper offers a critical and comprehensive review of the opportunities and challenges associated with UAS. A detailed comparison between ammonia and hydrogen is also included. Furthermore, given ammonia's miscibility with water and its reactive nature, this study investigates its geochemical reaction with rock minerals in detail. The results reveal that aqua ammonia does not significantly dissolve rock grains or alter the mineral compositions, particularly in quartz-rich rocks. Furthermore, it was found that reservoir temperature has a more pronounced effect on the ammonia-rock interactions than the reservoir pressure. The results showed that, in carbonate formations, the geochemical reactions are not severe at both low and high temperatures, while in sandstone formations, the reactions primarily occur at mid-range temperatures. According to the detailed review presented here, further development of the UASin porous media depends on multidimensional analysis that includes techno-socio-environmental aspects, economic viability, specific implementation strategies, and a thorough comparison with alternatives such as hydrogen. This review highlights the multifaceted challenges associated with the large-scale deployment of UAS and outlines key priorities for future research. One of the primary concerns and bottlenecks is the dissolution of ammonia in resident water and residual fluids, which must be addressed due to the potential of water contamination and safety hazards, as well as its negative impacts on ammonia purity and loss. Additionally, the lack of laboratory and field data should be addressed in future studies.