To achieve a sustainable use of energy we must increase our use of renewable energysources, biogas if one such source. One of the greatest potentials for biogas are in theagricultural sector and the Energy Agency calculates that 25% of the available manurecan be used for biogas production. The purpose of this thesis is to contribute withknowledge of co-digestion of manure and how this affects the methane potential andhow co-digestion affects the contents of NH4 in the sludge. The report includes a literature study to understand the digestion process and its partsand allows interpretation of data. The report includes analysis of data from HalmstadUniversitys experiment of anaerobic digestion and an additional digestion. The resultsobtained in this study shows that the effect of co-digestion varies depending on manure.Horse and chicken manure and beef and pig manure gives a positive effect to the codigestion.