This article determines type and amount of non-organic substrates used for biogas production on organic farms in Germany. Furthermore, it discusses determinants and problems of non-organic substrate use. Conventional substrate – mainly maize – is extensively used in larger biogas plants on farms without sufficient land area and/or low stocking rates per kWel. These overcapacities of organic biogas plants may represent maladjustment to external preconditions as a result of bad planning as well as carefully considered exploitations of business opportunities on the basis of external inputs. In order to reduce non-organic substrate use due to bad planning, on one hand biogas consulting services which account for the particular conditions of organic agriculture should be enhanced, on the other hand farmers need to seek independent advice before concluding an agreement with an engineering company