Hydrogen production from marine biomass by hydrothermal gasification

Highlights: • Supercritical water gasification of Posidonia oceanica was studied. • The output was mainly composed of hydrogen, methane and carbon dioxide. • Maximum hydrogen yield was obtained with biomass loading of 0.08 (g/mL) at 600 °C. • Maximum hydrogen and methane yields were 10.37 and 6.34 mol/kg, respectively. • The results propose an alternative solution to the landfill of marine biomass. - Abstract: The hydrothermal gasification of Posidonia oceanica was investigated in a batch reactor without adding any catalysts. The experiments were carried out in the temperature range of 300–600 °C with different biomass loading ranges of 0.04–0.12 (g/mL) in the reaction time of 1 h. The product gas was composed of hydrogen, methane, carbon dioxide, carbon monoxide and a small amount of C₂–C₄ compounds. The results showed that the formation of gaseous products, gasification efficiency and yield distribution of produced gases were intensively affected by biomass loading and temperature. The yields of hydrogen (10.37 mol/kg) and methane (6.34 mol/kg) were attained at 600 °C using biomass loading of 0.08 (g/mL). The results are very promising in terms of deployment of the utilization of marine biomass for hydrogen and/or methane production to industrial scale applications, thereby proposing an alternative solution to the landfill of P. oceanica residues