This book explores the potential of ammonia (NH?) as a next-generation fuel for achieving Net Zero emissions in the transport and power sectors. With increasing regulatory pressure to reduce carbon dioxide (CO?) and carbon monoxide (CO) emissions, industries are seeking non-carbonaceous energy sources. Ammonia, with its carbon-free molecular structure, offers a promising alternative, but challenges such as high auto-ignition temperature, slow chemical kinetics, and combustion efficiency must be addressed. This book presents state-of-the-art research on ammonia-fueled internal combustion engines (ICEs), emission characteristics, and combustion enhancement techniques. It covers critical risk factors for ammonia-fueled marine diesel engines, safety considerations, pre-chamber ignition for lean combustion, and advanced optical techniques for soot characterization in fuel spray flames. By providing insights into cutting-edge developments, this book serves as a valuable resource for researchers, engineers, and industry professionals working toward sustainable and low-carbon combustion technologies.