article · Biomass Conversion and Biorefinery
Agricultural residues such as bean husks and sesame stalks can be upgraded into energy-dense biochar through torrefaction. Processing these materials under nitrogen across temperatures from 200 to 300 degrees Celsius for 30 or 60 minutes significantly altered their fuel characteristics and chemical composition. As treatment temperatures increased, hemicellulose and carbohydrates broke down while relative lignin content rose. These changes led to marked increases in fixed carbon and higher heating values, alongside minor reductions in bulk density and moderate decreases in mass and overall energy yields. Analysis indicated that operating at 275 degrees Celsius for 30 minutes achieved an optimal balance between energy retention and heating value for both residues. Pyrolysis kinetic modelling and spectroscopic evaluations further confirmed the systematic thermal degradation patterns and thermodynamic parameters governing the conversion of these feedstocks.
Transforming common agricultural residues into standardized, high-energy biochar provides a pathway to utilize crop waste effectively. Understanding the precise temperatures and reaction times needed to improve calorific value helps advance cleaner, biomass-derived solid fuels that can replace or supplement conventional fossil fuels in heat and power generation.
This research is at an early experimental stage, providing baseline thermal kinetics and processing parameters for upgrading crop waste. The findings could inform bioenergy developers, pellet manufacturers, and agricultural processors seeking to convert sesame and bean residues into higher-grade solid biofuels. However, the abstract does not indicate testing at pilot scale or commercial deployment.
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Abstract Torrefaction encourages homogeneity and enhances the energy-producing capabilities of biomass. In the current study, bean husk (BH) and sesame stalks (SS) were torrefied for 30 and 60 min at operating temperatures of 200, 225, 250 and 275, and 300 °C with nitrogen purging. Mass yield (MY), higher heating value (HHV), energy yields (EY), and torrefaction severity index (TSI) were examined. The variations of the biochar characteristics, pyrolysis kinetics by applying two models (Coats and Redfern (CR) and Direct Arrhenius (DA)), and crystallinity index (CRI) were depicted. Depending on pyrolysis kinetics, thermodynamic activation parameters were derived to elucidate biomass pyrolysis. The alterations in the torrefied materials’ composition were also analyzed using Fourier transform infrared spectroscopy (FTIR). The calculations revealed that the torrefied SS and BH decreased MY by 32.74, 29.02% and decreased EY 26, 20.97%, increased high heating values by 14.1, 13.52%, increased fixed carbon by 55.1, 39.91% respectively, and had a slight reduction in bulk density (approximately 2%). Generally, 275 °C and 30 min were the optimal conditions for a balanced torrefaction of SS and BH based on the HHV that reached to 20.5, 16.2 MJ/kg and EY that reached to 86.16 and 85.56% respectively. The FTIR, XRD, and the thermogravimetric results showed that the torrefaction treatment altered samples owing to carbohydrate breakdown, a rise in lignin, and a reduction in hemicellulose as the temperature of the torrefaction process increased. The CR methodology yielded greater frequency factor (A) and activation energy ( E a ) values than the DA method. The broadest peak width, lowest average E a , and lnA were seen in sesame stalks that had been torrefied at 300 °C and 30 min that reached to 107.85 (kJ/mol) and 13.57 (min −1 ). Results indicated an excellent linear relationship with the index of comprehensive pyrolysis (CPI), CRI, atomic H/C ratio, severity index, and EY.
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DOI: 10.1007/s13399-023-03822-9
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