Biochar Production from Sugarcane Residual Biomass Lignin Through Pyrolysis

Lignin is the most structurally complex component of lignocellulosic biomass. Each year, thousands of tons of lignin-rich residues from enzymatic hydrolysis are generated in sugarcane-based cellulosic ethanol biorefineries. The current study specifically utilizes lignin extracted from sugarcane bagasse as the primary feedstock for biochar production, rather than employing the raw bagasse itself. This study investigates, through pyrolytic thermal treatment of two lignin sources, the production of biochars and the evaluation of their potential applications. Kraft commercial lignin and sugarcane bagasse lignin samples, along with their corresponding biochars, were characterized by elemental and proximate analyses, higher heating value determination, spectroscopic techniques, thermogravimetric analysis, X-Ray diffraction, scanning electron microscopy coupled with energy-dispersive spectroscopy, and true density measurements. The results revealed a lower contamination level associated with the extraction process and confirmed the amorphous nature of sugarcane bagasse lignin and its derived biochar. An O/C ratio of approximately 0.3 was obtained for the sugarcane bagasse lignin biochar based on both elemental and Raman spectroscopy analyses. Both elemental composition assessment and Raman spectroscopic analysis indicated that all biochar specimens exhibited hydrogen-to-carbon (H/C) ratios exceeding 0.5. The analyses, therefore, indicated that the biochar derived from sugarcane lignin exhibited higher energy density, moderate stability and a high carbon content. The proposed approach thus provides promising alternatives for the valorizing lignin residues derived from second-generation ethanol production processes.