Techno-Economic Analysis of Biodiesel Production from Chlorella vulgaris Using Different Potential Biorefinery Approaches

Biodiesel from microalgae offers a renewable alternative to fossil fuels, with carbon dioxide utilization and capturing lipids without competing with food resources. The extraction, drying, and transesterification processes play a crucial role in converting raw biomass into high-quality biofuel. In this article, Chlorella vulgaris was grown in optimized conditions to improve the lipid content, and biodiesel was synthesized. Lipid content was evaluated from microalgal biomass, and the obtained data were given as input to two different production pathways, viz. solvent extraction and in situ transesterification. When utilizing the extraction and drying processes in the former method, it was discovered that they are the major cost contributors, which were eliminated in the latter through in situ transesterification. Optimization of various operating variables, such as methanol-oil molar ratio, reaction time, reaction temperature, number of stages, feed stage for distillation columns, and water and hexane flow rate for recovery of FAME, was studied in the simulation process. The solvent extraction method achieved 92% oil conversion, with 98% methanol recovery and 96% ester recovery after distillation. The in situ transesterification process achieved 92% oil-to-FAME conversion, with a payback period of 1.72 years for the non-heat integrated process and 1.88 years for the heat-integrated process. Capital costs were $3.48 million (non-heat integrated) and $4.51 million (heat integrated) compared to solvent extraction at $5.05 million (non-heat integrated) and $6.49 million (heat integrated), demonstrating superior economic efficiency. A techno-economic analysis reveals that in situ transesterification has the lowest capital cost and payback period but higher operating costs due to methanol usage; however, with process intensification and optimized configurations, it could become a commercially viable approach for biodiesel production. Regulatory frameworks and infrastructure investment support scalability, while eliminating costly steps like drying enhances economic and environmental sustainability.