Ammonia production is a cornerstone of the global chemical industry and plays a critical role in ensuring global food security; however, it is also associated with significant greenhouse gas emissions due to its strong reliance on fossil based hydrogen 1, 12, 19. This review examines ammonia production processes in light of the evolving pathways of hydrogen production. The study provides a comprehensive analysis of conventional and emerging hydrogen technologies, including gray, blue, and green hydrogen, and assesses their implications for ammonia synthesis. Particular attention is given to the environmental performance, technological maturity, and economic constraints associated with each pathway. The review highlights that while gray hydrogen remains dominant, its carbon footprint poses major sustainability challenges. Blue hydrogen may offer a transitional solution through carbon capture technologies, although uncertainties persist regarding its long term viability. Green hydrogen represents a key pathway for decarbonizing ammonia production, although high costs and infrastructure limitations currently hinder its large scale deployment. 7, 10, 12, 16. This work discusses the potential and challenges of low carbon hydrogen pathways in supporting the sustainable transformation of ammonia production.
Eddarraji et al. (Fri,) studied this question.