NOVELTY - A catalyst supported on an active ingredient selected from a metal or metal compound is provided to the gas-liquid mixture phase, obtained from a solid-liquid separation process of organic waste. De-carbonization acid treatment is performed by an alkaline liquid, and a gas-liquid mixture is released. Gas containing methane as a main component is regenerated from the mixture and the alkali liquid is recirculated.    USE - To manufacture heating gas from organic waste, to be used as fuel.    ADVANTAGE - Solid organic waste is converted to heating gas, with high energy conversion efficiency. The generation of toxic substances such as dioxin is effectively prevented. Manufacture of the heating gas reduces the use of fossil fuel.    DETAILED DESCRIPTION - Garbage (1) and/or paper, plastics and ground organic waste (2), raw waste water (5) and industrial waste water (7) are mixed to form liquid organic waste. The waste is ejected through a sewer line pipe (21) to a sedimentation tank (23), where liquid organic waste is separated from solid substances. The liquid is subjected to activated sludge treatment in a tank (13). The solid substance separated from the tank (23) and surplus sludge obtained from the tank (13) are mixed and ground in a concentrator (19). The obtained liquid organic mixture is maintained at 100 degrees C or more, at a preset pressure. Gas containing oxygen in a level of 0.5 times or less of theoretical oxygen level is provided and vapor liquid separation of the gas-liquid mixture phase is performed. A catalyst supported on an active ingredient selected from a metal or metal compound is provided to the gas-liquid mixture phase. De-carbonization acid treatment is performed by an alkali liquid, and a gas-liquid mixture is released. Gas containing methane as a main component is regenerated from the mixture and the alkali liquid is recirculated.    DESCRIPTION OF DRAWING(S) - The figure shows a flow sheet of heating gas manufacture.    Garbage (1)    Paper, plastics and ground organic waste (2)    Raw waste water (5)    Industrial waste water (7)    Sludge treatment tank (13)    Concentrator (19)    Sewer line piping (21)    Sedimentation tank (23)