Waste-to-hydrogen via CO2/steam-enhanced gasification of spent coffee ground

Abstract

This paper evaluated steam and CO₂-enhanced gasification of spent coffee ground (SCG) biomass, including energy and exergy aspects focusing on hydrogen production. The waste-to-hydrogen (WTH) conversion was performed via gasification (1000 °C) with a drop-tube-reactor investigating six different steam to biomass (SBR of 0.5, 0.8 and 1.2) and CO₂ to biomass (CO₂BR 0.09, 0.18 and 0.27) ratios. The syngas production indicated clear improvement against O₂/N₂ with an H₂ yield increase up to 69.21% and 18.32% for steam and CO₂ mediums. The energy and exergy analysis points out the 0.8 SBR as the optimum condition with 210% CGE and 48.05% exergy efficiency for H₂ production. As a strategy for carbon capture and usage, the medium with 0.27 CO₂BR provided a 28.52% exergy efficiency for H₂ production and reduced soot formation, showing a potential gasification medium for SCG. Results encourage waste-to-hydrogen prospection within circular economy principles, boosting circular economy principles in urban districts.