PURPOSE: To prepare a fuel which generates no harmful gas at a low cost, by subjecting wastes such as barbage to treatments including drying, addition of additives, heating and processing.

CONSTITUTION: Wastes such as garbage 23 in a tank 24 is sent to a drier 28 through a mixer 26 (25 and 27 are metal removers) and is passed through a rotor 40 in a heating oven 39 and a compression drier 43 for drying to a water content of 2W10% (drying process). The dried wastes are sent by a carrier 49 into a mixing tank 18 and waste oil, heavy fuel oil, etc. are added from a tank 51 of a mixing device 30 through a pipe 52 (additive mixing process). The mixture is heated under agitation in a heating tube 54 to gasify harmful substance and discharge the gas through a pipe 60 (harmful substance removal process). The material is sent into a processing unit 34 and crushed in a mixer 66 and the resultant particulate material 65 is sent by a carrier 68 into an additive mixing tank 67 for mixing of combustion improver and additives (e.g. magnesium). The material is crushed in a crusher 70 to a particle size of about 1mm to obtain the aimed powder fuel.