Abstract: An apparatus for manufacture of combustible gas consisting principally of methane with minor amounts of carbon monoxide, carbon dioxide and hydrogen from organic wastes comprising an inverted vessel positioned in a body of water in a matter of such that the water acts as a "liquid door" to trap plant material and gas within the vessel.The combustible gas manufacturing method provided by the apparatus operates at a temperature of about 21.degree. C. to 37.8.degree. C. Under ideal conditions it is possible to produce as much as about 11 cubic foot of gas per pound of organic waste. A moving current of water agitates the organic material and sweeps the waste products from the bottom of the vessel where they may be recovered and used as fertilizer if desired.