Abstract: Method for anaerobically fermenting biodegradable organic material, whereby this material is mixed with a quantity of already fermented material as an inoculum for the active anaerobic fermentation and this mixture is introduced at the top into a fermentation chamber (1A) in which a fermenting mass is situated, which, while being fermented, moves from an inlet (6A) situated at the top towards an outlet (8) situated at the bottom. Before the mixture is added to the fermenting mass, it is expanded beforehand until its density approximately coincides with the density of the already present fermenting mass at the beginning of this downward movement.

Abstract: A device for determining the aerobic biodegradability in a composting installation of at least one product includes at least two reactors, a temperature device for maintaining the reactors at a temperature above the ambient temperature, a device for passing gas which contains oxygen through the reactors, a device for separately collecting outflowing gas from each of the reactors, a measuring/calculating device for determining the amount of CO.sub.2 in the outflowing gas of each reactor and a calculating device for determining the aerobic biodegradability of the at least one product based on the measured/calculated amount of CO.sub.2 in the outflowing gas of each reactor.

Abstract: Method for determining in an accelerated manner the biodegradability of at least one product under anaerobic conditions which are similar to those in a dump, characterized in that a mixture with a dry substance content of between 25 and 50% is prepared with more than 80 weight-% of an active anaerobic inoculum and less than 20 weight-% of the product, on the one hand, at least one quantity of this mixture and, on the other hand, at least one quantity of the inoculum is subjected in the same manner to a fermentation at a temperature of between 30 and 60 degrees Centigrade in anaerobic conditions, the amount of biogas that is released with both these fermentations is separately measured or calculated, starting with these amounts the amount of biogas produced by the product alone is deduced and starting with the latter amount the degradability of the product itself is determined, this is the amount of carbon which was degraded from the product and converted into CO.sub.2 and CH.sub.4.