Catalytic supercritical water gasification of wet algae biomass for enhanced hydrogen-rich syngas production using Fe–Ce–Mn oxides

Supercritical water gasification (SCWG) efficiently converts wet algae biomass into hydrogen-rich syngas at high temperature and pressure, eliminating the need for drying. Also, the use of catalysts can enhance hydrogen yield, selectivity, and gasification efficiency, making algae SCWG a promising sustainable energy route. This study explores sustainable hydrogen production from algae biomass by SCWG. Hence, experiments were conducted at temperatures of 500–700°C with a residence time of 20 min and a fixed pressure of 25 MPa. Additionally, Fe–Ce–Mn mixed oxides supported on biochar were applied as catalysts with loadings of 0–8 wt%. Hydrogen yield, gasification efficiency (GE), H2/CO selectivity, and production cost were evaluated. Results showed that increasing temperature significantly enhanced H2 yield from 28.4 to 63.2 mol/kg and GE from 46.2% to 75.4%. Catalyst addition improved performance, with an optimal loading of 6 wt% achieving a maximum H2 yield of 79.6 mol/kg, GE of 86.1%, H2/CO selectivity of 2.96, and a minimum production cost of 1.64 $/kg H2. Tar reduction efficiency reached 95.1% at optimal catalyst loading. These findings demonstrate that high temperature combined with Fe–Ce–Mn catalysis effectively enhances hydrogen-rich syngas production, energy recovery, and economic feasibility, highlighting the algae SCWG approach for sustainable hydrogen generation.