Recover waste greywater to algae biomass for catalytic conversion of higher hydrogen production via supercritical water gasification reaction

Abstract

The algae biomass from waste greywater is activated with 0, 2, 4, and 6 % of cerium oxide nanoparticle (CeO2), which favours specific growth algae, and optimum biomass concentration is used for hydrogen energy production. The supercritical water gasification reaction is implemented for hydrogen production from algae under the processing temperatures of 600 °C with 30 min residence time. During the process, the feedstock is varied from 5 to 20 wt%, and the potassium hydroxide (KOH), potassium carbonate (K2CO3), aluminium chloride (AlCl3), and nickel (Ni) catalyst are utilized to enrich the reforming reaction of organic material and enhance the hydrogen yield. Influences of catalytic conversion on molar fraction, hydrogen gas yield, hydrogen selectivity, gasification efficiency, and Low heating value of the present system are evaluated. An algae biomass concentration activated with 6 % CeO₂ exhibited an improved growth rate of 0.98 μ/day. This biomass was utilized in a supercritical water gasification process with a KOH catalyst, resulting in enhanced output properties, including a high hydrogen molar fraction of 66.8 %, a hydrogen yield of 64.5 mol/kg, improved hydrogen selectivity of 18, optimum gasification efficiency of 67.4 %, and improved lower heating value of 21.4 MJ/Nm3.