Economic analysis of a plant for biodiesel production from waste cooking oil via enzymatic transesterification using supercritical carbon dioxide

• Economic analysis of a scCO2-based, enzymatic process, for biodiesel production.
• Design of an envisaged pilot plant to convert 8000 ton of waste cooking oil/year.
• Biodiesel cost of 0.75€/L, with used oil at 0.25€/kg and enzyme at 8€/kg.
• Integration of sustainable approaches for the valorization of a residue.

Enzymatic transesterification is becoming a commercially competitive route to biodiesel. Supercritical CO2 (scCO2) is well established as a solvent for extraction processes. Here we analyze the economy of a scCO2-based, enzymatic process, for the production of biodiesel from waste cooking sunflower oil (WCO). The conversion of WCO to fatty acid ethyl esters (FAEE) catalyzed by immobilized lipase from Thermomyces lanuginosus (Lipozyme TL IM), and downstream separation to recover biodiesel conforming to the EN14214 norm, were studied in a pilot plant unit. The data generated was used to design an envisaged industrial plant, for which an energy balance was carried out. Investment and production costs were estimated for the conversion of 8000 tonWCO/year. This led to biodiesel costs of 1.64€/L and 0.75€/L (for a WCO price of 0.25€/kg; enzyme prices of 800€/kg and 8€/kg, respectively), which already reflect the ca. 10% impact of glycerol sales.

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