Thermogravimetric pyrolysis for neem char using novel agricultural waste: a study of process optimization and statistical modeling

Agricultural biomasses are the underutilized sources that have extraordinary potential to synthesize green and cost-effective chemicals. This research focuses on the utilization of novel agricultural residue, i.e., waste neem cake, to produce highly efficient, cost-effective, and environment-friendly fuel, i.e., neem char (NC), through thermogravimetric pyrolysis. To study the effects of process variable on char yield and higher heating value (HHV), statistical modeling was applied by central composite design of response surface methodology. Furthermore, chemical and structural characterization of neem cake and char were carried out by using Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The reaction temperature was the most prominent variable found from the ANOVA (analysis of variances) to affect char yield and its HHV. The optimal result was achieved with 21.46% char yield and HHV value of 6371 kcal/kg at 600 °C, 60 min, and 3 mm. The heating value of char was highly improved indicating the potential application of char as a high-energy renewable fuel. Further, the carbon content and fixed carbon values increased, whereas hydrogen, oxygen, volatile matters, and moisture content decreased in char after the pyrolysis process.