TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Apparatus: The composite waste disposal system has a carbonization furnace which carries out carbonization process of high calorie waste material, a slurry fuel manufacturing apparatus which mixes high calorie waste material and carbonized material in liquid medium and produces slurry, a wastewater-treatment apparatus which carries out wastewater treatment of fermented liquor produced in methane-fermentation tank, an incinerator which carries out incineration processing of high calorie waste material, a boiler which carries out exhaust-heat recovery from waste gas of incinerator, a modifier, a heat treating furnace, an evacuation unit, a transport unit and a gas separation apparatus. The modifier modifies at least one portion of biogas generated in methane-fermentation tank into carbon monoxide and reformed gas containing hydrogen as a main component. The boiler produces water vapor using waste heat of heat treating furnace, and ejects from methane-fermentation tank. The heat treating furnace heat processes, incinerates and gasifies high calorie waste material. The evacuation unit carries out evacuation of evacuates source gas inside adsorption tower. The transport unit conveys the liquid fuel manufactured using liquid-fuel synthesizing apparatus and used as a fuel for transport of transport unit. The gas-separation apparatus separates and recovers carbon dioxide from biogas, and introduces carbon dioxide into gasifier as fluidization gas.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: The carbonized material manufactured in the carbonization furnace is introduced into gasifier, and gasified. The slurry fuel obtained by slurry fuel manufacturing apparatus is introduced into gasifier, and gasified. The water vapor generated by heating treated water after wastewater treatment is introduced into gasifier as a gasifying agent. Water vapor generated by the boiler is introduced into the gasifier as a gasifying agent. The high temperature waste gas of heat treating furnace is supplied to modifier, and used for heating. The treated water is introduced into boiler, and water vapor is generated. The generated water vapor is introduced into modifier as a modifier. Adsorption agent is arranged inside adsorption tower, and impurity gas contained in source gas is selectively adsorbed and separated by pressure-swing adsorption method. Target purified gas with high purity is recovered. Methane manufactured by liquid-fuel manufacturing apparatus is introduced to a biological-treatment apparatus as a carbon source of denitrifying processing of methane-fermentation liquid.