Over the past years, ensuring a sustainable supply of energy has become a matter of public interest. The production of biogas from waste through anaerobic fermentation is without any doubt one of the technologies which not only protects natural resources but is also carbon-neutral. This is also reflected in the increased number and size of biogas plants. However, the production of biogas also involves considerable quantities of digestate which have to be treated in a safe and appropriate way. Due to the high nitrogen content, the most common use as a fertiliser is often only possible with considerable transport costs Therefore, it is vitally important to consider alternative ways for the disposal of digestate before realising a biogas plant. Although there are numerous different process variants, the physical and chemical properties of digestate represent an increasing challenge for the applied technologies. The present thesis focused on those technologies allowing the elimination or recovery of nitrogen. It has been proved that no satisfactory quality of the effluent can be obtained by applying biological technologies and a subsequent filtration step in so called membrane bioreactors. In order to achieve quality standards for direct discharge, further filtration steps are required. In the light of these efforts, the application of the mentioned technology does not seem to be appropriate. However, compared to direct filtration of digestate not involving any biological pretreatment steps -, a better membrane performance could be observed. Although ammonia stripping delivered good results in the laboratory, practice has shown that the operation of biogas plants is often subject to operational disturbances. The relatively young membrane contactor technology has proved to provide very promising results. Under moderate conditions, elimination rates of almost 99 % could be achieved. The mentioned technology is a very interesting process variant for the recovery of nitrogen. Nevertheless, further investigations are necessary in order to provide appropriate technologies for the treatment of digestate.