Abstract: Garbage resulting from the preparation, cooking and dispensing of food and containing water-insoluble organic components is treated first heated in the presence of water at a temperature of 100.degree.-400.degree. C. and a pressure higher than the saturated water vapor pressure to convert at least part of the water-insoluble components into water-soluble organic components and to obtain a mixture containing the water-soluble components dissolved in the water. The mixture is then subjected to methane fermentation to convert the water-soluble organic components into methane.

Abstract: An organic material-containing sludge is fluidized and is heat-treated at a high pressure in a reactor disposed underground to obtain an oil having a high calorific value. The heat treatment may be performed using an electrical energy, the terrestrial heat or a reaction heat obtained by oxidative treatment of similer sludge.

Abstract: Hydrogen is produced from a cellulose-containing biomass by heating the biomass in the presence of water and a catalyst at a temperature of 250.degree.-374.degree. C. and at a pressure higher than the saturated vapor pressure of water. The catalyst includes a catalytic metal selected from the group consisting of nickel, iron, cobalt, molybdenum, tungsten, platinum and mixtures thereof.

Abstract: A cellulose-containing biomass such as wood is liquefied by heat-treatment under a pressurized condition in the presence of water and a neutral, oxygen-containing organic liquid such as an ester, ether, ketone or alcohol. An alkaline catalyst such as potassium carbonate may be added to accelerate the liquefaction when the organic liquid is one other than acetone. Also provided is a process for the liquefaction of a cellulose-containing biomass including heat-treating the biomass in an aqueous medium in the pressurized atmosphere of an inert gas or steam at a temperature of 250.degree.-385.degree. C. in the presence of an alkaline catalyst in an amount of 0.01-0.1 part by weight per one part by weight of the biomass on the dry basis.