Abstract: The invention relates to a method and a device for producing nitrogen fertilizer, removing phosphate from organic waste products in liquid phase, sanitizing said waste or reducing emissions, and limiting the potassium concentration. According to the invention, the waste product is heated to temperatures ranging between 40 DEG C. at a subatmospheric pressure, the escaping gas that contains carbon dioxide and ammonia is contacted with a mineral-aqueous suspension, the excess gas is conducted within the circuit while the subatmospheric pressure is autogenously stabilized, and the formed nitrogen fertilizer is discharged.