NOVELTY - Gasholder integrated methane-fermentation tank has methane fermentation tank (5), warm water tank (6) and floating-roof-type gasholder (7) covering upper portion of tank (5). Warm water (16) is passed to heat exchanger of gas engine-electric power generation unit (13), and returned to tank (6), when methane gas generated by tank (5) is supplied to unit (13). Temperature of tank (6) is raised, and utilized for heating of tank (5).    USE - For generating methane gas from organic waste such as human waste, garbage and livestock excrements, used for electric power generation.    ADVANTAGE - The gasholder integrated methane fermentation tank is economical, and enables continuous and stable generation of methane gas with high efficiency.    DETAILED DESCRIPTION - A gasholder integrated methane-fermentation tank has a methane fermentation tank (5) with upper portion opened and having a agitator (8), a warm water tank (6) concentrically arranged around outer side of the tank (5), an inflow pipe (4a) of pressed liquid (4), a pressing installation (2) of organic waste (1), digestive liquor outflow conduit (10a) and a floating-roof-type gasholder (7) covering the upper portion of tank (5). The gasholder (7) consisting of a top wall and a sidewall is capable of floating up and down, and the sidewall is inserted into the water of warm water tank. The tank (5) is heated, and the methane gas (11) is generated from the organic waste. The water (16) of warm water tank is passed to the heat exchanger of a gas engine-electric power generation unit (13), and temperature raised circulating water (15) is returned to the warm water tank, when supplying methane gas to the unit (13) and producing electric power. The temperature of the warm water tank is raised, and utilized for heating of methane fermentation tank.    DESCRIPTION OF DRAWING(S) - The figure shows the block diagram of gas-engine-electric power generation unit system incorporating the gasholder integrated methane fermentation tank. (Drawing includes non-English language text).    organic waste (1)    pressing installation (2)    pressed liquid (4)    pressed liquid inflow pipe (4a)    methane fermentation tank (5)    warm water tank (6)    gas holder (7)    agitator (8)    digestive liquor outflow conduit (10a)    methane gas (11)    gas-engine-electric power generation unit (13)    circulating water (15)    warm water (16)