This research explores the production of biodiesel from waste cooking oil using cost-effective catalysts. The study focuses on the efficient application of calcium oxide (CaO) and potassium hydroxide (KOH) catalysts, supported on phosphate-rich soil (PS), named for its significant phosphate content. The experiments were conducted in a reactor equipped with a magnetic stirrer, operating at 63 °C, with a catalyst concentration of 8 wt.% (weight percent of the catalyst relative to the oil) and a methanol-to-oil volume ratio of 1:2 v/v. The study evaluated the effects of reaction time and catalyst loading (the weight percent of CaO or KOH in the catalysts) for both types of catalysts. The results revealed that after 120 minutes, biodiesel with a purity exceeding 98% was achieved using both catalysts. Notably, the highest fatty acid methyl ester (FAME) yield was obtained with KOH/PS and CaO/PS catalysts at catalyst loadings of 33.3 wt.% and 50 wt.%, respectively.
