Biodiesel production from Nannochloropsis gaditana using supercritical CO₂ for lipid extraction and immobilized lipase transesterification: Economic and environmental impact assessments

The economic and environmental impacts of a commercial biodiesel production process using supercritical CO₂ in lipid extraction and enzymatic transesterification from freeze-dried Nannochloropsis gaditana were assessed. The results were compared with those of compressed natural gas (CNG), which is employed as a transportation fuel in the United Arab Emirates (UAE). The total operation time considered in the techno-economic and environmental impact assessments was 16 years. To produce 1000 ton/y of biodiesel, the manufacturing costs and revenue were estimated to be $21,843,000/y and $27,940,000/y, respectively. The net present value of the profit, payback period, discounted payback period, and internal rate of return were estimated to be $8.31 million, 9 years, 13 years, and 10.5%, respectively. An economic assessment indicated that producing biodiesel using the supercritical CO₂ approach is profitable. Although the economics of CNG appeared more attractive, owing to the lower selling price and better consumption economy, the environmental impact of biodiesel production through supercritical CO₂ was 8 times smaller than that of CNG production. Reusing the produced biodiesel as an energy source in the production process and choosing a location close to the material source and capital items could further improve the economics and environmental impacts of the process.