Produção de biocarvão a partir de ligninas residuais de biomassas pelo processo de pirólise

Abstract

Lignin is the most structurally complex component present in lignocellulosic biomass. Each year, thousands of tons of lignin-rich residues from enzymatic hydrolysis may be generated in a sugarcane cellulosic ethanol bioreûnery. The present study uses lignin extracted from sugarcane bagasse as a feedstock for biochar production, as an alternative to the direct use of raw bagasse. In addition, lignin is also present in the mesocarp of coconut, a residue that is often improperly disposed of. Therefore, the production of biochar from this lignin via pyrolysis, as well as the potential applications of the resulting material, were investigated. The lignin samples derived from sugarcane bagasse and coconut ûbers, as well as their corresponding biochars, were characterized and systematically compared with commercial kraft lignin and its biochar through elemental analysis, higher heating value determination, spectroscopic techniques, thermal analyses, X-ray diûraction, and scanning electron microscopy coupled with energy-dispersive spectroscopy. The results indicated higher efficiency in the lignin extraction process from sugarcane bagasse and further confirmed the amorphous nature of both the extracted lignin and the 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, however, the O/C and H/C ratios in the sugarcane bagasse lignin biochar indicated the occurrence of partially oxidized carbon, with a significant portion of fixed carbon, in a biochar with moderate stability and low levels of contamination. Analyses of the effect of an intermediate pyrolysis temperature on a recalcitrant material such as lignin indicated that the biochar derived from sugarcane lignin exhibited higher energy density, in the value of 25,95 MJ/kg, and a high carbon content, in the value of 61,64%. The proposed approach, therefore, provides promising alternatives for the valorization of lignin waste and the generation of biochar for both energy applications and as a multifunctional material, combining high energy density with structural stability, which significantly expands its industrial application potential.