Natural Antioxidants For Biodiesel Stability: Predictive Modeling, Kinetics, And Economic Feasibility Of Uapaca Kirkiana Extracts
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Date
2025-07
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NM-AIST
Abstract
Biodiesel, a renewable alternative fuel, is susceptible to oxidative degradation, impacting its performance, stability and shelf life. Traditional methods for optimizing antioxidant dosage have relied heavily on trial and error, leading to inconsistent results and increased costs. This study addresses these challenges by integrating experimental analysis with predictive modeling to evaluate and optimize the use of natural antioxidants extracted from Uapaca kirkiana fruit peels, pulp, stem barks, leaves and root bark. The research primarily focuses on enhancing oxidative stability during storage, where degradation is most likely to begin. Antioxidant
potential was assessed through total phenolic content using the Folin–Ciocalteu method and antioxidant activity via 2,2-Diphenyl-1-picrylhydrazyl radical scavenging assays. A predictive model was developed in R software to estimate the optimal antioxidant dosage, using biodiesel's physical-chemical properties as predictors. Storage conditions such as temperature, light and oxygen exposure were standardized to isolate the effects of antioxidant concentration and biodiesel composition. Reaction kinetics were studied to understand antioxidant behavior and degradation pathways. Techno-economic analysis using Aspen Plus® V10 compared the cost-effectiveness of natural and synthetic antioxidants. Results showed that natural antioxidants particularly from fruit peels significantly improved biodiesel stability. Induction periods achieved were 23.9 hours for palm kernel, 21.6 for waste cooking oil, 14.6 for croton, 14.4 for jatropha, and 13.8 for neem seed, all exceeding the 8-hour minimum required by both EN 14112 and ASTM D6751 standards. Predictive model validation with seven biodiesel samples showed close agreement between theoretical and experimental induction periods, with mean absolute percentage errors between 1.69% and 2.44%. Kinetic analysis confirmed that natural antioxidants reduced oxidation rates, with activation energies of 81.39 kJ/mol (fruit peels), 77.73 kJ/mol (pulp), and 63.85 kJ/mol (root bark). The techno-economic analysis demonstrated that natural antioxidants especially from Uapaca kirkiana were not only more effective but also more economically viable, offering shorter payback periods (3.8–12 years) and higher internal rate of returns. In contrast, synthetic antioxidants like BHT and BHA showed negative net present values and longer payback times (11.7–17.8 years). These findings support the use of natural antioxidants as practical, eco-friendly alternatives to
synthetic ones in enhancing fuel stability
Sustainable Development Goals
SDG -7: Affordable and Clean Energy
SDG- 8: Decent Work and Economic Growth
SDG-12: Responsible Consumption and Production
SDG-13: Climate Action