Pilot-scale intensified transesterification of waste cooking oil using a combined orifice-venturi cavitation device: performance and techno-economic evaluation

Although hydrodynamic cavitation (HC) has shown promise for intensifying biodiesel synthesis, most reported studies remain limited to laboratory scales or employ either orifice or venturi devices individually, leaving a gap in pilot-scale evaluation and geometric optimization for industrial feasibility. The current study addresses this gap by developing and testing a unique 100 L pilot-scale HC reactor and incorporating a combined orifice-venturi configuration for biodiesel synthesis from waste cooking oil (WCO). Under operating conditions, biodiesel yields of 91.62% in 40 min and 93.16% after 60 min were achieved, with cavitation numbers of 0.40 (orifice) and 0.27 (venturi), confirming strong cavitation activity. The yield efficiency was 1.04 × 10−3 kg/kJ. FTIR, GC-FID, and 1H NMR analyses verified the complete conversion of triglycerides into methyl esters. The resulting biodiesel complied with EN 14214 and ASTM D6751 specifications and exhibited improved cold-flow properties. The process demonstrated strong sustainability, with an Energy Return on Investment (EROI) value of 10.85. Techno-economic analysis revealed substantial commercial potential at scales ≥300 L/day, where ROI and IRR surpassed 91% and payback periods shortened to less than 1.1 years. Overall, the combined orifice-venturi HC system provides a scalable, energy-efficient, and economically viable pathway for decentralized conversion of WCO into high-quality biodiesel.