Kenaf stems: Thermal characterization and conversion for biofuel and biochar production

Kenaf stems are characterized in this present investigation in order to assess their suitability in energy recovery through a pyrolysis process and to identify sustainable applications of the generated biochar. In particular, the raw biomass properties are analyzed using numerous analytical techniques such as thermogravimetric analyses (TGA/DTG), X-Ray Fluorescence (XRF) and Scanning Electronic Microscopy (SEM). First, the thermogravimetric analyses monitor the pyrolysis parameters, control the proportion of its outputs and allow to extract the kinetic parameters. The latter is determined using Friedman, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) models. In a second step, Kenaf derived chars are produced at different pyrolysis temperatures and their physicochemical, morphological, textural and structural properties are determined using different techniques such as CO₂ adsorption, Raman Spectroscopy, and DRIFT Spectroscopy. The main results confirm the Kenaf potential for energy applications as its thermal properties are more interesting compared to other usual crops. The Kenaf stem derived char is also very promising for pollutants removal or gas storage as its surface area as well as its microporous structure are interestingly developed when increasing the pyrolysis temperature. Kenaf char could be also chemically or physically activated in order to be used for pollutants removal from gaseous and aqueous effluents. Finally, the XRF analysis indicated that contents in K and P elements are high. Ca and Mg are also major mineral species in the char. These contents indicate that Kenaf derived char could be also suitable for agricultural soil amendments.