Ammonia as an Energy Carrier: Perspectives on Options for Geological Storage

Ammonia is gaining global recognition as a potential energy carrier due to its high energy density and ease of liquefaction at moderate temperatures and pressures. This paper evaluates the subsurface storage options for ammonia, focusing on geological settings. While porous media are not suitable due to ammonia’s solubility in porewater and the associated toxicity risks, and salt caverns are prone to salt dissolution and related contamination of the stored ammonia. However, rock caverns, especially lined rock caverns, offer a promising storage option due to their engineered barrier system, which can limit contact between ammonia, groundwater, and the host rock. Here we review historical case studies of ammonia storage in rock caverns and highlight their operational challenges. We recommend pilot projects and regulatory guidelines for the safe and cost-effective storage of ammonia in lined rock caverns.