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.