Life cycle environmental impact assessment of microalgae biodiesel derived from different processes

This study conducts a comprehensive life cycle assessment (LCA) to evaluate the environmental impacts of biodiesel production from microalgae cultivated in freshwater and pretreated domestic wastewater. Utilizing the eFootprint platform, a detailed life cycle model was established, revealing that microalgae-based biodiesel offers substantial carbon sequestration potential, particularly when wastewater is used as the cultivation medium. Compared to the freshwater route, the wastewater-based process demonstrated markedly lower environmental impacts across key indicators, including acidification potential and eutrophication potential. Sensitivity analysis identified the cultivation, harvesting, and drying stages as the primary contributors to environmental burdens. Complementing the environmental assessment, a techno-economic analysis showed that the wastewater-based pathway can reduce operating costs by up to 52 %. This integrated strategy—coupling microalgae cultivation with wastewater treatment—not only enhances carbon capture and mitigates environmental impacts but also yields considerable economic advantages, supporting the advancement of a circular bioeconomy. Nonetheless, the increased energy demands during the harvesting and drying stages of wastewater-based cultivation warrant further optimization to ensure overall environmental sustainability. • A comprehensive LCA of two microalgae biodiesel systems were compared. • Negative CO 2 emissions were observed the lifecycle of microalgae biodiesel. • Microalgae cultivation and harvest drying stages were the key emission steps. • Wastewater cultivation mode reduced more pollutions than freshwater mode. • Electricity was the key emissions factor in the wastewater cultivation process.