the present invention relates to a method for preparing organic material for microbiological fermentations of municipal waste water sludge for reducing the waste water sludge and / or of cellulosic material for the production of biofuels , with at least one of the following steps : disintegrating and / or liquefying the organic and / or cellulosic material by using a jet pump and / or creating a supersonic shock zone in a jet pump the organic and / or cellulosic material is supplied to in order to disintegrate and / or liquefy the organic and / or cellulosic material and / or applying high pressure steam to an annular ring chamber enclosing a tube of a jet pump and directing the steam into the tube of the jet pump thereby sucking organic and / or cellulosic material into the tube and creating a supersonic shock zone in the jet pump in order to disintegrate and / or liquefy the organic and / or cellulosic material . the present invention also relates to an apparatus for preparing organic material for microbiological fermentations of municipal waste water sludge for reducing the waste water sludge and / or of cellulosic material for production of biofuels comprising a jet pump .