This book looks deeply into the prospects for using ethanol as a greener alternative to fossil fuels and the technical and scientific issues that surround them. Ethanol, with its numerous advantages, has emerged as a promising contender to replace gasoline as a fuel source. Currently, it is commercially available as a blend with gasoline, commonly known as E10 and E25, utilizing various ratios of ethanol. Despite its clear benefits over gasoline, the widespread adoption of ethanol as a fuel remains hindered by its limited availability. In this insightful book, we aim to explore the multifaceted challenges surrounding ethanol's full integration into our energy landscape, employing a comprehensive approach through review manuscripts. Leading worldwide experts, known for their deep understanding of ethanol as a fuel, have contributed to the book. Their valuable insights and contributions enrich the book's content, offering readers a comprehensive exploration of the subject matter. This book is a compelling resource for researchers, energy professionals, and anyone interested in understanding the challenges and opportunities associated with the integration of ethanol as a substitute for gasoline.