As for reducing the carbon footprint of nitrogen fertilizer production, some important research regarding green ammonia synthesis was highlighted. The development of green ammonia production is an important component of sustainable fertilizer production. Green ammonia production involves modification or replacement of the Haber-Bosch process or the use of renewable hydrogen and energy in the Haber-Bosch process to product ammonia. While they do not make up the majority of publications on green ammonia production, publications discussing electrocatalytic and photocatalytic methods have increased rapidly, with electrocatalytic processes more commonly discussed. The reduced complexity of electrocatalytic processes and reactors and the increased availability of green electricity likely leads to a preference for electrochemical methods for ammonia production. Hydrogen evolution (as a competing reaction in ammonia production) is also an important point of study. Tabular inorganic compounds (a class containing metal oxides), small molecules, and elements have been the most studied classes of substances in green ammonia production; the use of inorganic compounds may more easily allow large-scale production of the catalysts, while small molecules may be more easily understood and optimized as catalysts). Improvements in processes for validation of ammonia-producing catalysts (to show that ammonia is produced from nitrogen rather than from other sources and to show that ammonia production depends on the catalyst) and their consistent use are necessary to discover effective ammonia production catalysts. It can be predicted that, given the observed upward publication trend, green hydrogen production and/or catalytic nitrogen reduction for ammonia will have continued active exploration. Like phosphorus recovery, research in this area will be focused on optimizing processes and technology to sustainably gain more yield and for economic viability. From the data profiling of the CAS Content Collection, these efforts are occurring, but those studies using isotope labeled nitrogen in controlled experiments for example, are still a small proportion of the published studies. While renewable-energy powered, electrolytically produced hydrogen for Haber-Bosch is a currently viable solution, electrocatalytic and photocatalytic nitrogen reduction show promise as a new technology to provide sustainably fixed nitrogen for fertilizer production, and we expect we will see more rigorous research in this field.