Biodiesel production from a novel renewable source through the ultrasound-assisted transesterification process, using energy efficient nanocatalyst developed from waste material

Abstract

The depletion of fossil fuels created a thrust for an alternative renewable energy source, which could involve sustainable energy formation and cost-reducing catalysts. The catalyst derived from the waste material, specifically a heterogenous nanocatalyst, could economically add value to the process. In this study, a novel microbial strain, Rhodotorula mucilaginosa strain SML (RM-SML), was used as a source of oil for biodiesel production. The nanocatalyst developed from the Central Avian Research Institute – Broiler (CARIB) breed eggshell was used as a catalyst for transesterification, increasing the sustainability and economic viability of the process. RM-SML yielded 68.79 % of oil to its total dry cell biomass. The calcium carbonate-rich CARIB breed eggshell was calcinated in this study to synthesize a highly dynamic heterogeneous CARIB breed eggshell nanocatalyst (CBESNC). The calcination process parameters involved in the nanocatalyst synthesis were optimized using response surface methodology, yielding a maximum calcium oxide of 38.827 %. The synthesized CBESNC was characterized for its size by scanning electron microscopy imaging and its crystallographic nature by X-ray diffraction analysis. CBESNC was used as a heterogeneous catalyst in the ultrasonic-assisted transesterification of RM-SML bio-oil. The effect of the CBESNC in RM-SML bio-oil transesterification was studied and optimized using the response surface methodology, which yielded a maximum biodiesel conversion of 98.33 %. The prediction model in optimization studies was found to fit with the process and was validated experimentally. RM-SML biodiesel was studied for its physicochemical properties and found to meet American Society for Testing and Materials biodiesel standards. It was further confirmed with Gas Chromatography-Mass Spectrum analysis. The energy analysis results proved the commercialization feasibility of the study.