The disclosure relates to a device (21) for producing a fertilizer and/or feed, comprising a chamber (26) having a first opening (27) for letting in an emulsion (14′) of wastewater (8, 9) and grease (14), and a second opening (28) for adding organic waste (16), a circulating element (29) arranged in the chamber (26) for circulating a mixture (14′, 16) of the added emulsion (14′) and the added organic waste (16), and a heating element (30) for drying the mixture (14′, 16) by evaporating water (31) from the mixture (14′, 16).