Officially the use of biomass for energy use globally is only 10-13 % of the total energy demand of 140 000 TWh/y. Still, the production of biomass annually is in the range of 270 000 TWh/y. Most of it obviously is not used very efficiently, although some is also used as food. There is thus a need for new methods for converting biomass into refined products like chemicals, fuels, wood and paper products, heat, cooling and electric power. The different type of conversion methods covered is biogas production, bio-ethanol production, torrefaction, pyrolysis, high temperature gasification and combustion. These methods are covered as well as principals for controlling the processes. The suitability for the different methods for different type of biomass as well as different versions of the methods is presented – both existing methods and those being developed for the future. System optimization using modeling methods and simulation is covered as well as analysis of advantages of different solutions. Many key-experts from all over the world are presenting the keys of their specialties to give us an up-to-date view of the situation all over the world. This book has the aim to give facts and inspiration to professionals like engineers and researchers, students as well as those working for different type of authorities or societal organizations.