Hydrothermal conversion of Ulva macro algae in supercritical water

Abstract Ulva ( Ulva armoricana and Ulva rotundata ) are macro algae which are responsible of environmental damages and are a cause of an eutrophication of the water in the French coast (Mediterranean sea, Brittany). In this study, Ulva were gasified in supercritical water in a batch reactor and in Hydrothermal Diamond Anvil Cell apparatus. Experimental conditions evolve between 400 and 550 °C at around 250 bar. Results show that a short time (7 min) in supercritical condition is sufficient to obtain a significant conversion rate. H 2 and CH 4 concentrations exceed 15 mol.% at high temperature (550 °C) and high algae concentrations are not favorable for H 2 production. The solid residue represents between 7 and 20 wt.% of the initial dry material and is mainly constituted of carbon (20 wt.%) and inorganic compounds: salts (KCl, NaCl), CaSO 4 , SiO 2 and CaCO 3 . The very low dissolved organic carbon (DOC) values of the liquid residue (