Journal of Energy Bioscience 2024, Vol.15, No.3, 171-185 http://bioscipublisher.com/index.php/jeb 179 Microalgae cultivation using palm oil mill effluent (POME) has been studied for its effectiveness in nutrient removal and biomass production. The integration of POME with microalgae cultivation systems has shown significant reductions in nutrient concentrations and organic matter, making it an efficient method for wastewater treatment and biofuel production (Cheah et al., 2016). Figure 2 illustrates the effect of tetracycline (TC) concentration and contact time on the efficiency of TC removal from water by microalgal biomass. The results indicate that: In panel (a), as the initial TC concentration increases, the removal efficiency rapidly increases at low concentrations and then stabilizes, while the biosorption capacity gradually increases at higher concentrations. In panel (b), with increased contact time, the removal efficiency steadily improves and eventually stabilizes. These findings suggest that TC removal efficiency is significantly influenced by initial concentration and contact time, demonstrating that microalgal biomass has the potential to effectively remove TC under appropriate conditions. 8 Economic and Environmental Impact Assessment 8.1 Cost analysis of marine microalgae cultivation and biodiesel production The economic feasibility of producing biodiesel from marine microalgae hinges on several cost factors, including cultivation, harvesting, lipid extraction, and biodiesel conversion. Studies show that the production cost for microalgae biomass is approximately €2.01 per kg, while the cost of biodiesel production is around €0.33 per liter (Branco-Vieira et al., 2020). This relatively high cost is a significant barrier to the commercial viability of microalgae-based biodiesel, particularly when compared to fossil fuels and other biofuel feedstocks. Key cost drivers include the energy-intensive processes of cultivation and harvesting, as well as the costs associated with maintaining optimal growth conditions for the microalgae. Additionally, the infrastructure required for large-scale production, such as photobioreactors and raceway ponds, represents a substantial capital investment. Despite these challenges, the return on investment (ROI) for such projects has been estimated at around 10%, with a payback period of 10 years, indicating potential long-term profitability. To improve economic feasibility, strategies such as optimizing production processes, reducing energy consumption, and integrating co-product valorization (such as extracting high-value compounds alongside biodiesel) are essential. Technological advancements and economies of scale may also help lower costs over time, making microalgae-based biodiesel a more competitive alternative to traditional fuels (Branco-Vieira et al., 2020). 8.2 Life cycle assessment (LCA) of marine microalgae-based biodiesel Life cycle assessment (lca) provides a comprehensive evaluation of the environmental impacts associated with the production of biodiesel from marine microalgae. This approach considers the entire production chain, from microalgae cultivation to biodiesel conversion and use. According to Shimako et al. (2016), the production of biodiesel from microalgae involves several energy-intensive steps, particularly supercritical CO2 extraction and drying, which significantly contribute to the overall environmental footprint. The LCA results indicate that these processes are major contributors to greenhouse gas (GHG) emissions and energy consumption, highlighting the need for technological improvements to enhance energy efficiency. The study also reveals that integrating microalgae cultivation with biogas systems can improve the environmental performance by utilizing waste biomass for energy production, thereby reducing the reliance on external energy sources and lowering GHG emissions. Furthermore, the dynamic LCA for climate change shows that energy consumption in the production steps is the primary factor affecting human health and ecosystem quality due to the associated GHG emissions. These findings underscore the importance of optimizing production processes and exploring renewable energy options to minimize the environmental impacts of microalgae-based biodiesel (Shimako et al., 2016). 8.3 Comparative analysis with conventional biodiesel feedstocks When comparing microalgae-based biodiesel to conventional biodiesel feedstocks such as soybeans and palm oil, several advantages and challenges emerge. Microalgae offer higher lipid content and faster growth rates, making
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