Biofuel is a fuel that is produced in a relatively small time interval from biomass by using modern techniques. It can be derived from plants known as energy crops as well as from the biological wastes produced by agriculture, households and industries. Some of the commonly used biofuels are biodiesel, bioethanol, biogas, syngas, methanol, butanol, bioethers and green diesel. Biodiesel is produced through the process of transesterification by using fats or oils. Bioethanol is produced by the process of fermentation using the carbohydrates which are present in sugar or starch crops. Biofuels are classified into various generations, namely, first generation, second generation, third generation and fourth generation. The topics covered in this extensive book deal with the core aspects of biofuel. It elucidates new techniques and their applications in a multidisciplinary approach. This book will serve as a reference to a broad spectrum of readers.