Biomass like poultry manure and sewage sludge have high nitrogen and chemical oxygen demand (COD) concentrations. This can cause disturbances in the anaerobic digestion process, by ammonia as well as accumulation of volatile fatty acids (VFA). Therefore, the target is to develope a high-performance methane stage for mesophilic monofermentation of these substrates. Hence a stepwise increase of the reactors, trickle bed reactor (RB), upflow anaerobic sludge bed reactor (UASB), and anaerobic filter reactor (AF) was done. To adapte the microorganizmen to nitrogen and organic loads plastic pellets have been adapted in RB and AF. The UASB enriches biomass by forming natural pellets through accumulation of the microorganism and the subsequent sedimentation. Altogether, to find out the weakness in the acetogenesis/methanogenesis the feeding process was done with a model substrate, which presents a hydrolyzate. With this one a stable process was determined for organic loads of 15.04 [kgCOD/m(3)*d] in RB and AF. So far, the UASB haven't reached a stable performance. Allover, there wasn't a significant linear correlation between ammonia and the biogas production detectable. The adaption of biomass through the stepwise increase of the organic loads, the immobilization of biomass as well as the reactor type influenced the process stability. (C) 2019 Elsevier Ltd. All rights reserved.