Hydrothermal conversion of seaweeds in a batch autoclave

In this study, different seaweed species were gasified in supercritical water as biomass feedstock. The experimental conditions were 500 °C of temperature and 1 h of reaction time. The amount of gases, the gas compositions and the amount of water soluble compounds from gasification were determined. The coke yields were found to be significantly lower than those obtained with lignocellulosic and protein contained wastes. The gaseous species detected contain mainly hydrogen, methane and carbon dioxide. The hydrogen yields ranging between 11.8 and 16 g H2/kg seaweed have been obtained. On the other hand, the methane yields were found to be in the range of 39 and 104 g CH4/kg seaweed. The contents of aqueous phases were also determined using various analytical techniques. DOC (dissolved organic carbon) values of aqueous phases showed the high extent of gasification.

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► The seaweed samples were gasified to a hydrogen and methane-rich gas in supercritical water.
► The aqueous phases consist mainly of glycolic, formic, acetic acids and phenols.
► Inorganic salt contents of seaweeds show catalytical effect for the conversion.