Any fuel that has been obtained by processing biomass such as plant, algae or animal waste that do not have application as food or feed is termed as a biofuel. It is often considered as renewable sources of energy since the materials involved in its production can be replenished easily. Biofuels can be solid, liquid or gaseous. Wood and grass are common examples of solid biofuels. Bioethanol and biodiesel are liquid biofuels which are produced by fermentation of carbohydrates found in sugarcane and transesterification of oils or fats. Gaseous biofuels include biogas and syngas which are obtained by decomposition of organic matter. Biofuels engineering analyses environmental and economic factors involved in production of fossil fuel alternatives and direct old scientific principles into new technological solutions.. This book attempts to understand the diverse facets that fall under the discipline of biofuels engineering and how such concepts have practical applications. Most of the topics introduced here in cover new techniques and the applications of biofuel engineering. The book is appropriate for those seeking detailed information in this area.