Natural gas-based ammonia (NH₃) with carbon capture and storage (CCS) (often referred to as blue ammonia), has become a high-profile candidate fuel and hydrogen carrier in the road to a net-zero energy system. The critical review summarizes peer-reviewed literature and grey-literature sources published in the period 2010 to 2024 to offer a comprehensive, evidence-based evaluation of the processes involved in the production of blue ammonia, its lifecycle greenhouse-gas (GHG) emissions, techno-economic performance, and future applications in power generation, in maritime shipping, and in industrial decarbonization.

Three major production pathways are discussed, which are steam methane reforming (SMR) using post-combustion capture of CO2, autothermal reforming (ATR) using pre-combustion capture, and partial oxidation (POX). Results of lifecycle assessment (LCA) of 42 primary studies show that, at CCS capture rates of 85-95% blue ammonia emits 0.48-1.83 kg CO₂-eq per kilogram of NH₃ compared to 1.93-2.41 kg CO₂-eq/kg of conventional grey ammonia and 0.03-0. In the techno-economic analysis, blue routes cost USD 320-620 per tonne of NH₃, and is bracketed between grey ammonia (USD 200-350/t) and the present green ammonia (USD 580-1200/t). The feasibility of blue ammonia hinges on three parameters, namely the natural gas price, CCS capture efficiency and methane slip along the supply chain, the last of which can negate lifecycle emission savings by 30-60 percent when upstream leakage rates are over 2.5.

Applications that have been examined are co-firing in power plants, direct combustion in gas turbines, cracking to hydrogen in fuel cells, and direct use as a maritime fuel as required by IMO decarbonization regulations. The review outlines five crucial research and policy gaps and suggests an ordered agenda of blue ammonia as a transitional low-carbon fuel by 2050.