Hydrogen-rich syngas production via gasification of lignin-rich agricultural wastes

The global increase in energy demand and the depletion of fossil fuel reserves have accelerated the transition to renewable energy sources. Biomass stands out as a crucial resource for sustainable energy production, contributing significantly to environmental sustainability goals. This study investigates the potential of converting lavender and oregano distillation residues in Turkey into energy through gasification. Aromatic plant distillation residues are rich in lignocellulosic content and exhibit high energy potential, yet they pose challenges in waste management due to their non-biodegradable nature. Experiments were conducted using an updraft fixed-bed gasifier at temperatures of 700℃, 800℃, and 900℃ and gasifying agent flow rates between 0.05–0.4 L/min. Feedstock characterization was performed through TGA, FTIR, XRD, XRF, and elemental analyses. Additionally, the effects of calcined dolomite, travertine, and marble catalysts on tar reduction, carbon conversion efficiency, and syngas quality were analyzed. Lavender residue exhibited a volatile matter content of 88.49%, while oregano residue showed a fixed carbon content of 21.4%. The results demonstrated that calcined travertine reduced tar formation by up to 80% and enhanced H₂ and CO concentrations in syngas. Under optimal conditions, syngas energy content reached 5.8 MJ/Nm³, with a carbon conversion efficiency of 85.59% and cold gas efficiency of 68.5%. Furthermore, solid residues with an ash content of 0.24% and surface area up to 900 m²/g were found suitable for advanced material applications. This study highlights the feasibility of utilizing aromatic plant distillation residues as renewable energy sources through gasification. It demonstrates that marble and travertine wastes can be effectively used as catalysts in gasification studies. It addresses waste management challenges while enhancing energy supply and supporting environmental sustainability goals.