The first report about methanogenesis was given by Alessandro Volta in 1776. He examined the formation of natural gas bubbles in lake sediments. About a century later studies on the anaerobic degradation of cellulose showed that methane formation is an anaerobic microbial process. The first methane bacteria were obtained in pure culture not before 1947, because special culture techniques had to be developed. Their distinct phylogenetic position, methane bacteria were the first Archaea identified, as well as their specific biochemical and genetic characteristics stimulated intensive basic research on this unique microbial group in the last thirty years. Ecological and geochemical aspects led to further studies on methanogenic Archaea. They play an important role in the third stage of anaerobic degradation of organic material. Furthermore, economic aspects should also be taken into consideration. For cattle breeding methane formation in the rumen of ruminants implies a decrease d use of the food source. In addition, the reserves of fossil fuels such as oil and natural gas will decrease strongly in about 50 years. An important alternative source of energy is the production of biogas from energy crops. In the seminar an overview about important characteristics of methanogenic Archaea will be presented with special emphasis on the formation of biogas from renewable raw materials.