Rational utilization of different wastes is an important problem of today. It is connected on one hand, with an opportunity of the use of a huge energy potential of a biomass for the production of liquid and gaseous fuel (biogas) and on the other hand with the necessity of the preservation and improvement of the ecology of an environment by the prevention of pollution of reservoirs, infection of ground by pathogenic bacteria and decrease of the cutting down of woods. In this book information presented is not only regarding traditional biogas digesters constructed in a number of Asian and European countries, but it also contains information regarding emerging technologies as bio-reactors for the hydrogen production. This indeed is a very promising emerging technology at present, by taking into account the importance of hydrogen economy for future energy production and storage. A number of topics including production of biogas, its upgrading, utilization, conversion into mechanical and electric power, economic analysis and safety regulations during use are described due to their practical importance at present.