Pyrolysis of Bioplastics Based on Bovine Gelatin-Potato Flour and Whey Protein-Potato Flour Blends and Their Kinetics and Thermodynamic Analysis

Hypothesis: The pyrolysis process of bioplastics, prepared from a mixture of two animal proteins and whole potato flour, was studied and their kinetics and thermodynamic behavior during pyrolysis was investigated. The proteins used in this study included whey protein and bovine gelatin, which were extracted from the wastes of animal breeding and processing industries. To study kinetics of thermal decomposition, various isoconversional methods including Friedman, Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, and Starink were used and the kinetic parameters of thermal decomposition were calculated for bioplastic samples consisting of bovine gelatin-whole potato flour (BG), whey protein-whole wheat flour (Wh) and whole potato flour (P) as control. The results showed that the variation in activation energy calculated by the Friedman method for BG, Wh and control (P) bioplastic samples was 60.15-214.65 kJ/mol, 59.16-264.07 kJ/mol and 50.38-216.68 kJ/mol, respectively. Prediction of reaction model using Criado’s method in the conversion ranges of 0.1-0.4, and 0.1-0.9, in order to cover the behavior of the bioplastics in two modes of processing and producing renewable energy, respectively, showed that in all investigated bioplastics, Valensi model (D2) in processing mode and Jander model (D3) in the second mode had the best linearity coefficient (R2) between theoretical master plots and experimental reduced rates. Thermodynamic analysis showed that the maximum enthalpy change for BG was observed in the conversion of 0.5 and was equal to ~210 kJ/mol and for the control and Wh bioplastics were observed in the conversion of 0.6 and were equal to ~259 kJ/mol and ~212 kJ/mol, respectively. The results of this study not only determined the thermal behavior of potato-based bioplastics at different temperatures and the thermal decomposition process, but also helped to generate renewable energy from bioplastic wastes.