Design and Development of Small-Scale Biodiesel Production Plant: RSM-Based Parameter Optimization

Abstract

The following study outlines the development, optimization, and physicochemical characterization of a mini-biodiesel plant that uses waste cooking oil as feedstock. A 20-liter-capacity batch-type double-jacketed reactor was developed, in which hot air was injected through temperature-controlled nozzles to maintain the reactor contents at an optimum temperature (60–70°C) throughout the reaction process (esterification and transesterification). The system was constructed from stainless steel 304  to provide corrosion resistance and durability. Using Response Surface Methodology (RSM) with a Box-Behnken Design (BBD), the effects of reaction time, catalyst concentration (KOH), and methanol-to-oil molar ratio on biodiesel production were optimized. This indicated a high level of significance for the quadratic model (F-value = 80.17, p < 0.0001) and an R² of 0.9931, representing excellent predictive power. The optimum conditions were found to be 72.37 minutes and 1.37 wt. A 50% methanol ratio and a predicted conversion of 85.1744 were confirmed experimentally, with an average yield of 85.56%. The support frame was structurally tested and found to be mechanically sound under operational loads. The maximum stress (118.6 Pa) was at least three times lower than the material's yield strength. The biodiesel produced showed that it met all international standards (ASTM D6751 and EN 14214), and its FTIR analysis confirmed that the methyl esters were successfully formed. This integrated method is technically feasible, scalable, and cost-effective, providing a pathway for biodiesel production using WCO as a feedstock, which is expected to contribute to sustainable energy and a circular economy.