Techno-economic and Sensitivity Analyses of Different Biodiesel Production Pathways by Adding Tetrahydrofuran as a Cosolvent

The main objective of this study is to design and simulate three different continuous processes, namely, homogeneous and heterogeneous alkali-catalyzed and supercritical methanolysis processes to produce biodiesel at a production rate of 100,000 t/year from virgin vegetable oil. Tetrahydrofuran (THF) was used as a cosolvent at different concentrations of 25 wt.%, 30 wt.%, and 1.63 wt. % for the homogeneous and heterogeneous alkali-catalyzed and supercritical processes, respectively. An economic assessment and a sensitivity analysis were performed based on the results of the process design and simulation. Technical assessment of the proposed processes indicated that the homogeneous and heterogeneous alkali-catalyzed processes were the simplest, where the least amount of process equipment were used. whereas the supercritical methanolysis process was more complex, which used a large number of transesterification and separation units. The homogeneous alkali-catalyzed process that used THF demonstrated the lowest total capital investment, after-tax net profit, and payback period of M$2.32, M$10.54, and 0.19 years, respectively, and the highest after-tax rate of return of 513%. However, the heterogeneous alkali-catalyzed process that used THF demonstrated the lowest manufacturing cost of M$82.20 and the highest after-tax net profit of M$18.20. The supercritical methanolysis process that used THF demonstrated the highest manufacturing cost of M$90.07 and the after-tax net profit of M$12.40. The results from the sensitivity analyses indicated that the methanol recovery percentage, biodiesel purification tower vacuum pressure, and costs of feedstock oil, methanol, biodiesel, and glycerin by-products are the factors that most significantly affect the economic feasibility of biodiesel production.