Drying Kinetics of Papaya (Carica papaya) Seed Waste at Different Temperatures and Pretreatment Conditions for Use in Biofuel Production

Abstract Purpose Excessive reliance on nonrenewable energy sources poses a significant economic and socio-ecological impact. Utilizing underutilized but abundant resources, like waste generated from fruit processing, can help address the need for sustainable feedstock options in biofuel production and tackle challenges associated with reliance on fossil fuels, including poor waste management. The study aims to evaluate the drying kinetics of papaya seed waste and determine the optimal mathematical model that elucidates its drying characteristics, which can be used for biofuel production. Method Accordingly, papaya seed waste was subjected to five drying temperatures ranging from 313 to 353 K. Four semi-theoretical models were used to determine the drying kinetics as a function of drying time, temperature, and seed pretreatment. The fitness of the models was evaluated using a coefficient of determination (R 2 ), chi-square (X 2 ), root-mean-square error (RMSE), mean bias error (MBE), and mean absolute error (MAE). Results The results showed that increasing the drying temperature leads to increased weight loss due to accelerated moisture removal from the seed, consequently shortening the drying time. The minimum energy (activation energy-Ea) required for drying the seeds varied among the mathematical models used and seed pretreatments. For papaya whole seed, the value of Ea ranges from 26.34 to 49.17 kJ mol −1 , whereas for crushed seeds it spans from 32.69 to 54.44 kJ mol −1 . Conclusions The higher R 2 and minimum value of X 2 , RMSE, MBE, and MAE were recorded by Page, and Avhad and Marchetti models for both whole and crushed papaya seeds, implying that they showed superior performance in fitting with experimental data. Graphical Abstract