The subject of this book pertains to the applicability of zero-carbon vector fuels, such as ammonia or hydrogen, in a practical scenario. This monograph extensively discusses the applicability or challenges associated with ammonia fuels for both IC-engine and gas turbine applications. It provides insights into ammonia cracking through catalytic membrane reactors for hydrogen production. This book also discusses NOx mitigation techniques for ammonia combustion, such as MILD combustion, two-stage combustion, porous assisted combustion, plasma combustion, and high-pressure combustion. This book also provides details on the chemical kinetics of ammonia and hydrogen combustion. The book can be a valuable reference for researchers and professionals interested in green energy and allied fields.