1. Introduction to Ammonia and Hydrogen for Green Energy Transition

In the pursuit of a sustainable energy future, this comprehensive overview navigates the complexities of alternative fuel combustion, focusing on hydrogen and ammonia, two carbon-free fuels crucial for a low-carbon economy. Hydrogen and ammonia, derived from renewable sources, stand as promising alternatives, their efficient production methods aligning with the world's escalating energy demands. However, their adoption is challenged by nitrogen oxide (NO_x) emissions, prompting an in-depth analysis of NO_x formation pathways. Detailed examinations of equivalence ratios, fuel mixtures, and combustion temperatures provide crucial insights, steering the development of effective mitigation strategies. In the realm of hydrogen-powered engines, where the promise of clean transportation meets the challenge of NO_x emissions, innovative control methods take the spotlight. Techniques such as Variable Valve Timing (VVT), injection timing, and Exhaust Gas Recirculation (EGR) are dissected. Notably, direct hydrogen injection emerges as a pivotal strategy, offering precise control over combustion parameters and NO_x production. These methods, in synergy, present a holistic approach to NO_x reduction and efficient engine operation, shaping the future of sustainable transportation. This holistic exploration not only sheds light on the advancements in hydrogen and ammonia synthesis technologies but also emphasizes the importance of responsible combustion practices. By understanding NO_x formation intricacies and implementing innovative mitigation strategies, researchers, engineers, and policymakers are empowered to pave the way for a greener, more sustainable energy landscape. With a focus on harmonizing environmental conservation and burgeoning energy needs, this discussion provides a comprehensive roadmap, steering the world toward a cleaner, more sustainable energy future for generations to come.