TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The mixture of oxides comprises (wt.%) phosphorus pentoxide (1.3-20), potassium oxide (5-35), calcium oxide (18-45), and magnesium oxide (1.3-16) as the main component ash from organic material. The ash is vegetal or is ash coming from burning animal excrement. The acidic medium is sulfuric acid or carbon dioxide.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Plant: The plant comprises the collection tank, where pumping and shredding unit is arranged which takes care of sending the organic waste, suitably broken down, into a pre-mixing tank that comprises agitation unit and a loading opening in which the mixture comprises phosphorus pentoxide, potassium oxide, calcium oxide and magnesium oxide is inserted; a boiler in which the water or other fluid is heated, which is then made to circulate in a heat exchanger inside the separation unit or in an outer jacket; condensation unit and collection unit under a vacuum, which takes care of creating the vacuum inside the condensation unit and inside the concentrator/evaporator; at least two concentrators/evaporators arranged in parallel; filtering unit between the tank and pre-mixing tank, for separation of a liquid portion of the waste to be treated from the solid portion; drying unit for the solid portion and unit for transferring the dried solid portion into the boiler; and unit for adding the organic ashes of the solid waste, dried and incinerated in the boiler, in the premixing tank. The separation unit is in fluid communication with unit for the vacuum so as to carry out the separation step under a vacuum. The separation unit comprises at least one concentrator/evaporator in which the waste to be treated is inserted, where inside the concentrator/evaporator there is a heat exchanger fed with water or other hot fluid obtained through the boiler or else with the gases/vapors coming out from one of the concentrators/evaporators. There is a heat exchanger in which the waste to be treated passes, which thus undergoes a pre-heating thanks to the latent heat released by the gases coming out from the concentrator/evaporator.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: In the method, ammonia is transformed, downstream of the treatment step, into a salt or its derivative through an acidic medium; process is carried out at 40-100 (preferably 60-95, especially 80-90) degrees C in a vacuum, or else at a relative pressure of -0.5 to -0.95 bar (preferably -0.6 to -0.85 bar) for 40-240 minutes such that the waste stays in the separation unit; the mixture comprising phosphorus pentoxide, potassium oxide, calcium oxide and magnesium oxide is added to the organic waste to be treated in ratio of 0.3-15 (preferably 0.8-8) kg/1000 liters of organic waste; and the organic waste is filtered to give a liquid phase, which is treated in the presence of the mixture of oxides, and a solid phase, where the solid phase is dried and then burnt with formation of an ash from organic material that is used as such, or possibly added to with phosphorus pentoxide, potassium oxide, calcium oxide and/or magnesium oxide, in the treatment of the liquid phase of the waste. ACTIVITY - Fertilizer. No biological data is given.    MECHANISM OF ACTION - None given.    EXAMPLE - No suitable example given.