Book excerpt: In face of the increasingly obvious need to ensure the sustainability of the environment, alternative and renewable energy sources are no longer just the concern of environmentalists and have become commitments of governments virtually everywhere in the world. In this context, ethanol emerges as an excellent substitute for petroleum derivatives. This green alternative fuel is sustained by its own burning because when CO2 serves as a carbon source for the growth of plants, it will allow the carbohydrates to be fermented. In addition, currently different generations of this fuel are being proposed, considering the utilization of their own waste. However, challenges still need to be overcome to enable the second, third and fourth generations of ethanol. At the same time, other renewable fuel alternatives emerge to compete with it. The automobile industry, for example, has been developing new engines, hybrids or not, that can be powered by electricity or H2. In this regard, this book addresses, under different aspects, the main strategies to surpass the remaining obstacles, as well as the advantages and disadvantages of ethanol as a fuel of the future. In this context, the "Ethanol as a Green Alternative Fuel" book shows present and future scenarios about bioethanol and perspective in their chain, considering the economic and environmental impact mitigations approach.