Microorganisms are ubiquitous and indispensable for the existence of mankind. They show diversity in size, shape, metabolism and the range of positive functions they perform for sustaining the life on this planet. Bacteria have been exploited by the mankind since times immemorial for the production of various foods and enzymes. They reveal several types of metabolic reactions which are absent in eukaryotic organisms. The present book highlights the potential of microorganisms in solving the global energy crisis. Presently, the world is facing energy crisis due to depleting fossil fuels which are expected to get exhausted during the next 50 yeaOne of the alternative energy resources for the new millennium is expected to be the renewable energy including biomass from which a variety of biofuels can be obtained by the exploitation of microbes. This volume has been organized in 13 s which have been prepared to provide the readers with both an in-depth study and a broad perspective of microorganisms for sustainability of mankind. Further, it makes the readers familiar with the diversity in energy generating pathways among different groups of microorganisms and different types of biomass energy resources available on this planet and the various possibilities which can be exploited for converting these in to alternate energy sources with the help of microbes. A great effort has been made to provide the readers a comprehensive knowledge about different alternative fuels and value added products from microbes for the 21st century. It is hoped that this volume will prove useful to the students and professionals who are pursuing their career in Microbiology, Biotechnology, Biochemistry, Environmental sciences and Energy studies related to the alternate biofuels to solve the global energy crisis.