The potential of waste avocado–banana fruit peels catalyst in the transesterification of non-edible Mafura kernel oil: Process optimization by Taguchi

Fruit waste resources are expansive carriers of fundamental minerals and chemicals that are useful in energy generation. In this work, the combination of waste avocado and banana fruit peels as an active, environmentally friendly catalyst was studied in the transesterification of Mafura kernel oil (MKO), a non-edible oil with a high FFA content of 5 %. The catalyst was produced by calcining the burnt waste fruit materials at 700 °C. The calcined biochar was further examined for structural, chemical, and thermal properties using scientific instruments such as FT-IR, XRD, SEM, EDS, and DSC-TGA. The results showed that inorganic minerals and carbonates of Sylvite (KCl), calcium phosphate (Ca₅(PO₄)₃), monticellite (K₂MgSiO₄), and potassium carbonate (K₂CO₃) were obtained after the calcination, which facilitated the conversion of MKO via a one-step transesterification process. The L9 orthogonal Taguchi design-response surface methodology (RSM-L9OTD) was employed to optimize and statistically characterize the transesterification process. The ideal conditions established for the process variables for the optimum yield were CH₃OH: MKO molar ratio of 12:1, catalyst loading of 4.5 wt%, reaction temperature of 65 °C, and time 80 min. The results showed that the Mafura kernel methyl ester (MKOME), which is within the ASTM D6751 and EN 14214 specified standard, was obtained at a confirmatory optimum yield of 96.06 % using the above conditions. Thus, the utilized feedstock offers attractive feasibility to sustainable biodiesel development.