Supercritical water gasification of Botryococcus Braunii algae from textile wastewater through open pond treatment with Ni/Fe2O3−MgO nano-catalyst for hydrogen conversion

• SCWG at 700°C increases H₂ yield to 72.9%, enhancing renewable energy potential. • CH₄ and CO₂ fractions decrease to 17.6% and 12.5% at 700°C, improving syngas. • Gasification efficiency (GE) rises from 31.6% to 66.2% with higher temperatures. • H₂ selectivity improves from 65.4% to 81.5%, confirming better syngas composition. • Ni/Fe₂O₃-MgO catalyst at 700°C boosts H₂ to 72.4% while lowering CH₄, CO₂. This study investigates how treated algae (Botryococcus braunii) can be used sustainably for hydrogen-rich syngas production via supercritical water gasification. Algae serve a dual purpose: taking pollutants out of wastewater and creating biomass for generating energy. The process was carried out by varying the air temperature between 500°C and 700°C to study the gas production and its makeup. A nano-catalyst made from iron (III) oxide and magnesium oxide and nickel (Ni/Fe₂O₃–MgO) was also tested to help with gasification. It was shown that elevated temperatures led to higher production of H₂, with the molar fraction maxing out at 72.9% at 700°C. At the same time, the amount of methane (CH₄) went down 17.6%, while that of carbon dioxide (CO₂) was reduced by 12.5%. The percentage of gasification efficiency increased from 31.6% to 66.2%, and the amount of H₂ selectivity increased from 65.4% to 81.5%. At 700°C, adding a catalyst greatly improved the process, raising hydrogen output to 72.4% and reducing the cost of producing hydrogen to just $1.7/kg. These findings demonstrate that SCWG is an effective method for both making biofuels and improving the quality of wastewater. It improves the quality of the syngas and, at the same time, provides a profitable way to create sustainable energy and protect the environment.