Growing global energy demand and the needs for net-zero alternatives require efficient hydrogen (H2) production. Using the aluminium-water reaction with aluminium from waste sources, this project aims to determine the optimal aluminum–gallium (Al-Ga) ratio to maximise H₂ yield and gallium recovery and to investigate the effects of spent coffee grounds, spent tea leaves, and fruits in seawater on H₂ yield. Experiments were conducted on Al-Ga ratios, temperature, chelators, sodium chloride (NaCl) concentrations, and different aluminium types. H₂ volume, reaction rate and gallium recovery were measured. Higher temperature and chelator concentration increased hydrogen but may impact gallium recovery. An optimal gallium content of 80 wt% achieved 88.33% H₂ yield and 90.30% gallium recovery with 0.05 M NaCl and 1% spent coffee grounds, while 1% spent tea leaves with 0.05M NaCl achieved 85.12% hydrogen yield and 97.40% gallium recovery. Lemon proved to be the most effective chelator, achieving an H₂ yield of 93.15% and 97.30% gallium recovery in seawater. Total gallium recovery was further increased to 99.91% with centrifugation. These results demonstrate a low-cost pathway for on-site H₂ generation using food and aluminium waste, provide quantitative benchmarks for gallium recovery in saline media, and offer a foundation for scaling waste-to-hydrogen processes in coastal, remote, and circular-economy energy systems.
Gui et al. (Wed,) studied this question.