TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The first heat exchanger and third heat exchanger are connected via a circulation line, in which a heat transfer medium circulates.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The amount of the fermentation substrate, which is introduced into the container and the quantity of ammonia-reduced fermentation substrate, which is removed from the container are adapted to one another such that a filling volume of the fermentation substrate in the container is constant of at least 20%. The fermentation substrate is removed azeotropically when a predetermined limit of ammonia for inhibiting the formation of methane concentration is reached. The fermentation is carried out in at least two parallel or series-fermenters, where the fermentation substrate is removed azeotropically from the first, at the beginning and/or during the fermentation process in a subsequent fermenter, and ammonia-reduced fermentation substrate is returned into at least one fermenter for the continuation of the anaerobic fermentation. The fermentation substrate is removed azeotropically only when the calculated concentration of ammonia in the fermenter exceeds a predetermined lower limit value. The ammonia concentration in the fermenter is determined by measuring the ammonia content in the biogas, which is discharged from the fermenter. The location of the azeotropic removal of fermentation substrate, first or subsequent fermentation is determined depending on velocity of the formation of ammonia in the fermentation substrate. The ammonium concentration is regulated in the fermenter via the circulatory amount of fermentation substrate and the amount recycled back to ammonia-reduced fermentation substrate. The ammonia-reduced fermentation substrate discharged from the container is passed to fermenter temperature through a third heat exchanger for cooling. The heat transfer medium heated in the third heat exchanger is supplied by a circuit line of the first heat exchanger and then is returned to the third heat exchanger. The second heat transfer medium is heated separately. The dwell time of the fermentation substrate in the first fermenter (F1) is dependent on the composition of the fermentation substrate, preferably dry matter content. The dry matter content of the fermentation substrate is adjusted by the addition of fermentation liquor and/or water to a value of below 10%. The azeotropically removed fermentation substrate is separated into a liquid and highly concentrated phase, prior to introduction into the first heat exchanger, subsequently only the ammonia concentration of the liquid phase is reduced, and finally the liquid phase and the highly concentrated phase are combined again. EXAMPLE - Cow manure having dry matter content of 10.5%, organic content of 76.5% and ammonia content of 4.5 g/l was used as the fermentation substrate. The fermentation was carried out in two fermenters connected in series, at a temperature of 55 degrees C and pH of 7.2-7.6. The biological desulfurization was carried out in both fermenters. The supply of air or oxygen was carried out via the line (L16). The content of hydrogen sulfide is reduced to below 100 ppm in the biogas of the fermenter by the desulfurization to obtain biogas.