Carbon-supported Ni catalysts were prepared and used to convert an ethanol/water mixture to CH4. When using 5 wt% ethanol, successful conversion to CH4 and CO2 was achieved at a temperature as low as 250 degrees C. Marginal amounts of undesired by-products such as acetaldehyde were produced even at a low conversion of ethanol. The composition of the product gas was similar to that in the equilibrium state. The rate of ethanol conversion was independent of ethanol concentration, and the activation energy was assumed to be 105 kJ/mol. Our carbon-supported Ni catalysts were found to show high activity for ethanol conversion from the comparison with literature data. The energy balance shows that this process needs little thermal energy to convert the ethanol/water mixture when heat of the outlet stream of the reactor is recovered by heat exchange with the inlet stream since the reaction is a slightly exothermic reaction. CH4 produced in the reactor can be purified by physical absorption of CO2 in water; however, CH4 can be also absorbed in the water at high operating pressure. CH4 can be recovered at 94% when the operating pressure of the absorber is 3 MPa from equilibrium consideration.