An alternative strategy is the slow adaptation of the microorganisms present in the reactor to high ammonia concentrationsas well as the strengthening of the microbial community by addition of essential micronutrients. This option was investigated in lab-scale fermentation tests at 38C, which were conducted over a period of 1.5 years. The aims were to determine the limits for organic loading rates (OLR), hydraulic retention time (HRT) as well as the upper limits for ammonia and free ammonia concentration while simultaneously guaranteeing a stable process and high biogas yields