Potencial energético do biochar produzido a partir da biomassa de carnaúba sob diferentes condições operacionais visando à geração de bioenergia em regiões semiáridas

Abstract

Thermochemical conversion of lignocellulosic residues represents an alternative for renewable energy generation, particularly in semi-arid regions with high availability of underutilized biomass resources. In this context, the present study aims to analyze the energy potential of biochar produced from carnauba (Copernicia prunifera) under different operating conditions, targeting its application in green energy generation in semi-arid regions. The biomass used for biochar production consisted of a mixture of carnauba stalks and leaves obtained from pruning residues in the municipality of Russas, Ceará, Brazil. The mixture was subjected to slow pyrolysis with variations in temperature, heating rate, and residence time. A Central Composite Design (CCD) was employed to evaluate the influence of operating conditions on gravimetric yield and higher heating value (HHV). The produced biochars were characterized by elemental analysis, HHV determination, pH measurement, electrical conductivity, thermogravimetric analysis (TGA), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results indicate an average yield of 26.75% and an average HHV of 22.94 MJ/kg, with temperature exerting the greatest influence on both responses. An increase in carbon content and a reduction in oxygen content were observed as temperature increased. Furthermore, the operating parameters also influenced pH, electrical conductivity, chemical composition, and biochar morphology. Increasing temperature promoted significant improvements in HHV, although nonlinear responses were observed under specific combinations of heating rate and residence time, reinforcing the need for integrated approaches to process optimization. It is therefore concluded that the energy potential of the biochars is strongly conditioned by the interaction among pyrolysis operating parameters, with HHV values ranging from 18.03 to 78.53 MJ/kg.