Enrichment of algae harvesting and actions of potassium carbonate on hydrogen production from dairy wastewater via supercritical water gasification: performance measures

BACKGROUND The reliance on non‐renewable fossil fuels is prevalent across numerous energy sectors, significantly contributing to global warming. However, the emergence of hydrogen energy technologies presents a promising opportunity for achieving environmental sustainability. By offering carbon‐free emissions, hydrogen could revolutionize our approach to energy, becoming a vital carrier for the future. The main aim of the study was to produce hydrogen energy from dairy wastewater featuring 0.1, 0.2, 0.3, and 0.4 vol% of iron oxide (Fe 2 O 3 ) through a 14 wt% potassium carbonate (K 2 CO 3 )‐configured supercritical water gasification (SCWG) process, followed by 400–600 °C gasification temperature with 25 bar pressure maintained by 30 min residence time. The impact of Fe 2 O 3 concentration on algae growth and harvesting efficiency was measured over consecutive days. RESULTS The 0.4 vol% Fe 2 O 3 concentration facilitates superior algae growth of 0.85 μm d −1 and improved harvesting efficiency by 89%. The optimal algae growth from dairy waste/0.4 vol% Fe 2 O 3 was considered a biomass feedstock for the SCWG process. The influence of an alkaline catalyst with 14 wt% K 2 CO 3 and varying gasification temperatures on molar fraction percentage, hydrogen selectivity, hydrogen yield, and gasification efficiency was experimentally studied. The outcomes demonstrated that the alkaline catalyst with 14 wt% K 2 CO 3 , configured for SCWG, functioned at 600 °C, achieving 58% hydrogen percentage, 18.5% hydrogen selectivity, and 23.65 mol kg −1 of hydrogen yield with a maximum gasification efficiency of 88%. The extracted hydrogen energy is suitable for alternative energy applications. CONCLUSION The dual role of the Fe 2 O 3 and K 2 CO 3 featured gasification process found improved algal growth and superior syngas production (higher hydrogen).