The invention relates to a method of manufacturing urea as a nitrogen-rich synthetic fertilizer from refuse of any composition, preferably from domestic waste. The organic waste components are first turned into gas in a high-temperature reactor with oxygen (O2) which has been obtained in a cryogenic air separation plant. A synthesis gas arises which predominantly comprises carbon monoxide (CO), hydrogen (H2) and carbon dioxide (CO2). The carbon monoxide (CO) contained in the synthesis gas is subsequently converted with steam into hydrogen (H2) and carbon dioxide (CO2). The hydrogen is subsequently separated and is used for ammonia synthesis together with the elementary nitrogen (N2) which arises as a by-product in cryogenic air separation. In the last process step, urea (CO(NH2)2) is manufactured from ammonia (NH3) and the further synthesis gas component carbon dioxide (CO2).