NOVELTY - A solid fuel is obtained by compression-molding and solidifying a material (a) formed by carrying out deodorization-drying of organic waste, and adjusting heat amount to 3300-3800 kcal/kg and moisture content to 15% or less. The material (a) is fermented and dried with a pressure-reduction fermentation-drying apparatus (1) having casing (10), a heating portion, a hollow rotating shaft and sending portion, a rotary component comprising scraping portion fixed to the sending portion, a condensation portion (50), a vacuum pump and a cooling tower (60).    USE - Solid fuel is used for boiler.    ADVANTAGE - The solid fuel is efficiently and economically manufactured, using surplus sludge.    DETAILED DESCRIPTION - A solid fuel is obtained by compression-molding and solidifying a material (a) formed by carrying out deodorization-drying of organic waste, and adjusting heat amount to 3300-3800 kcal/kg and moisture content to 15% or less. The material (a) is fermented and dried with reduced pressure fermentation-drying apparatus having casing to which organic waste to which microorganisms are added is supplied and whose inner portion is pressure-reduced, a heating portion provided in lower portion of the casing, and into which a thermal medium is supplied for heating organic waste in casing, a hollow rotating shaft and sending portion for supplying thermal medium, a rotary component comprising scraping portion fixed to the sending portion, and the rotary component is rotationally driven and organic waste is heated, a condensation portion which condenses vapor produced from organic waste which is provided in the casing, a vacuum pump which sucks air in casing with condensed water condensed in the condensation portion, and a cooling tower which mixes the condensed water and air with cooling water, and microorganisms are added to mixture, and the mixture is circulated between condensation portions.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of the pressure-reduction fermentation-drying apparatus. (Drawing includes non-English language text)    Pressure-reduction fermentation-drying apparatus (1)    Boiler (5)    Casing (10)    Condensation portion (50)    Cooling tower (60)