Abstract
Using supercritical water (SCW), we produced hydrogen gas efficiently from waste biomass. The advantages of this method are that (1) waste biomass can be converted to a gaseous mixture of hydrogen, methane, carbon dioxide and others, (2) environmentally friendly supercritical water is used as gasification reagent, and (3) the product yield of hydrogen is high because a part of supercritical water is decomposed to hydrogen by water gas reaction and water-gas-shift reaction. Main targets are large amount of waste biomass such as livestock excrement, garbage and so on. They are difficult to incinerate efficiently because of the high moisture content.
We investigated the effects of reaction temperature, pressure, time, molar ratio of water to carbon in biomass and kind of catalyst on the decomposition efficiency of waste biomass and the product yield of hydrogen gas. Almost 100% of the decomposition efficiency and 1500-2300ml (STP) of hydrogen production per gram of dry biomass were realized at 700°C, 10MPa, 20min of reaction time and 20 of molar ratio of water to carbon. Judging from the experimental results, higher temperature, lower pressure and higher molar ratio of water to carbon were favorable for the hydrogen production. Furthermore alkali catalyst gave more excellent performance than nickel catalyst in the hydrogen productivity.
