Optimization of cavitation-assisted biodiesel production and fuel properties from Neochloris oleoabundans microalgae oil using genetic algorithm and response surface methodology

Abstract

Biodiesel is a promising alternative fuel for diesel engines that provides energy security and significant environmental benefits. But its commercialization is restricted due to the cost and quality as compared to diesel fuel. To address the above, Neochloris oleoabundans microalgae oil, a non-edible, cost-effective, and underutilized third-generation feedstock, is used to produce superior biodiesel by the transesterification reaction using a hydrodynamic cavitation (HC) approach. In this research work, the transesterification model for microalgae biodiesel production is optimized through genetic algorithm (GA) and response surface methodology (RSM) using MATLAB R2020a and Design Expert 8.0.7.1, respectively. Four process input variables (operating pressure (0.5–2.5 bar), catalyst concentration (0.5–1.5 wt.%), reaction time (5–25 minutes), and molar ratio (3:1 to 7:1)) and a five-level L₃₀ array were developed to construct a statistical model. Biodiesel yield and major properties like density, kinematic viscosity, calorific value, and flash point are the model responses. The optimum conditions for microalgae biodiesel production were operating pressure of 2.43 bar, KOH catalyst concentrations of 1.22 wt. %, reaction time of 15.54 minutes, molar ratio of 5.61:1 and at 60°C fixed reaction temperature. The optimum value of response, such as biodiesel yield, was 99.80%, the density was 0.882 g/cc, the kinematic viscosity was 4.06 cst, the calorific value was 41.72 MJ/kg, and the flash point was 146.64 °C. RSM and GA predicted results were validated experimentally. The reaction time for biodiesel produced by HC in the same settings as the conventional method was reduced by 85%. Due to its faster processing time, the HC approach is preferred to the conventional method.