Appraisal of CaO derived from waste fermented-unfermented kola nut pod for fatty acid methylester (FAME) synthesis from Butyrospermum parkii (Shea butter) oil

•Rendering method adopted decreased the viscosity and density of the oil.•Fermentation of kola nut pod increased its calcium and potassium content.•Acid value of 10.76 mg KOH/g of the oil was reduced to 0.37 mg KOH/ g oil.•Optimum FAME content of 95.30 (wt.%) was obtained.•The produced FAME quality is within the biodiesel standard. Fatty acid methylester (FAME) synthesis from Butyrospermum parkii (Shea butter) oil using a CaO derived catalyst derived from waste kola nut pod as a heterogeneous catalyst was examined in this study. Due to the high free fatty acid of the oil, the oil was first esterified with acidic catalyst before transesterified with CaO. In both reactions, response surface methodology was used to model and optimized the reaction conditions. The rendering method adopted produced oil with low viscosity and density. Based on ANOVA, the effect of reaction time, catalyst amount, and methanol/oil molar ratio on acid value reduction were significant. The high free fatty acid of 10.76 mg KOH/g oil was reduced significantly to 0.37 mg KOH/ g oil via statistical optimization in seventeen experimental runs. Submerged fermentation of waste kola nut pod before thermal treatment of the powder increased the calcium and potassium content of the catalyst. Decreased in catalyst reusability was noticed in the 4th and 5th cycles. The optimum reaction conditions ensuring the best FAME content of 95.30 (wt.%) are found to be catalyst amount of 2.5 wt.%, the reaction time of 55 min, reaction temperature of 50 °C, and methanol/oil molar ratio of 5:1 (ml/ml). The produced FAME quality is within the biodiesel standard (ASTM D6751 and EN 14214).