An apparatus for producing an organic or organo-mineral fertilizer includes —a main tank receiving water, —a reactor providing cavitation and magnetic field for activating water or for treating a biological suspension, —a mixing tank containing a preliminary shredder, —an injector receiving and saturating the suspension with air, —a fermenter receiving the obtained mixture and creating a volumetric liquid-air flow passed therethrough and fermented by biological humus. The suspension is filtered and passed into a clearing tank. At predetermined conditions, the apparatus carries out a method encompassing a preliminary treatment of water in a looped circuit by connecting the main tank with the reactor via a pump. The activated water is supplied to the mixing tank added with preliminary shredded humus. The circuit is reconnected to further treat the suspension, finally shred its particles, supply it to the fermenter, additionally mix it with humus, filter it and thereby obtain the fertilizer.