Energetic potential of pyrolyzed biomass from different sources: a comparative study

Abstract

The use of biomass has been a recent trend as a potential feedstock for char generation with improved energetic value. In this work, agricultural residues such as sugarcane bagasse (SCB) and rice husk (RH) were submitted to slow pyrolysis and their calorific value potential was evaluated in comparison with industrial woodchip biochar (WC) (Pyreg GmbH). The samples were characterized by thermogravimetry (TG), differential thermal analysis (DTA), elemental analysis (CNHS) and Fourier-transform infrared spectroscopy. The chars/biochar had a high energetic profile, as indicated by the prominent exothermic peaks in DTA curves, along with the major mass losses, as demonstrated in the TG curves. The combination of fixed carbon (FC) and ash content (A) proved to be essential to produce a char with enhanced higher heating value (HHV), as observed for SCB (FC = 54.6%; A = 6.2%) and RH (FC = 51.0%; A = 38.4%). SCB and RH chars presented an improved stability reflected by a C/N molar ratio higher than 90%. The low nitrogen content (SCB = 0.8%; RH = 0.6%) and surface area (SCB = 6.0 m2 g−1; RH = 11.2 m2 g−1) of the produced chars suggest that they are not indicated for agricultural applications, unless chemical activation is applied. Furthermore, the post-treatment applied for WC (biological activation) is possibly the cause for the improved physicochemical properties, particularly in terms of potential soil conditioning, at the expense of estimated calorific value.