Pyrolysis of low-value waste Trapa natans peels: An exploration of thermal decomposition characteristics, kinetic behaviour, and pyrolytic liquid product

The current work seeks to maximise the bio-oil yield by optimizing the experimental conditions and process parameters for the pyrolysis of water chestnut peels (WCP). The pyrolysis process was carried out in a stainless steel reactor to produce the pyrolysis product. The kinetic analysis was carried out using the model-free techniques such as Ozawa-Flynn-Wall (OFW), Vyazovkin (VZK), and Kissinger-Akahira-Sunose (KAS), while the thermal degradation profile was measured using a thermogravimetric analyzer (TGA) at dynamic heating rates (10, 15, and 20 °C min⁻¹). Additionally, Gas Chromatography (GC) was used to study the non-condensable gases, whereas biochar was characterized according to its physicochemical properties. The results of the kinetic analysis exhibited that utilising the KAS, OFW, and VZK, the average apparent activation energies of WCP were obtained to be 344.37, 337.10, and 325.10 kJ mol⁻¹, respectively. The thermal pyrolysis results revealed that the highest bio-oil yield (42.20 wt%) was achieved at 600 °C temperature, 25 °C min⁻¹ heating rate, and 6 cm bed height. According to GC results, the hydrocarbon levels increased as the temperature increased. Biochar's suitability for usage in various industrial applications was validated by the findings of its characterization.