Journal of Energy Bioscience 2024, Vol.15, No.3, 171-185 http://bioscipublisher.com/index.php/jeb 180 them a potentially more efficient source of biodiesel. Unlike terrestrial crops, microalgae can be cultivated in saline water and on non-arable land, thus avoiding competition with food crops and reducing the strain on freshwater resources. According to Dickinson et al. (2017), microalgae-based biodiesel requires less land and can achieve higher productivity compared to conventional feedstocks (Figure 3). However, the production process for microalgae biodiesel is more energy and cost-intensive. The cultivation, harvesting, and lipid extraction processes for microalgae require substantial energy inputs, which can offset some of the environmental benefits. Additionally, the infrastructure and technology needed for large-scale microalgae cultivation and processing are still more expensive compared to traditional agricultural practices. Despite these challenges, ongoing research and technological advancements aim to improve the efficiency and reduce the costs associated with microalgae biodiesel production, making it a more viable and sustainable alternative in the future (Dickinson et al., 2017). Figure 3 illustrates the best production path determined by Ríos et al. (2013). The diagram details the steps from microalgae cultivation to biodiesel production. Microalgae are cultivated in an open pond (OP) system, receiving CO2 and nutrients. The cultivated microalgae undergo dynamic cross-flow filtration and centrifugation to obtain high-concentration biomass (BMII wet and dry). The dried biomass is processed through "Dry route B" direct esterification, using chloroform, sulfuric acid, and methanol. The esterified product undergoes alkali transesterification using KOH, with methanol being recycled. The final product is purified to obtain biodiesel (BD3 and 6), with glycerol produced as a byproduct. The entire process emphasizes the recycling of nutrients and water, enhancing production efficiency. 8.4 Environmental benefits and potential challenges The environmental benefits of microalgae-based biodiesel are significant, but several challenges must be addressed to fully realize its potential. One of the primary environmental advantages is the ability of microalgae to sequester carbon dioxide (CO2) during photosynthesis, which can help mitigate greenhouse gas emissions. Additionally, microalgae cultivation can utilize wastewater, thereby reducing the need for freshwater and contributing to wastewater treatment. This dual role not only enhances water conservation but also provides a sustainable nutrient source for the algae. However, the high energy consumption required for processes such as harvesting, drying, and lipid extraction poses a challenge. These processes can diminish the overall environmental benefits if not optimized for energy efficiency. Figure 3 Best production path determined by Ríos et al. (2013) Furthermore, the use of chemical flocculants for harvesting and the potential nutrient runoff from cultivation ponds can impact local ecosystems negatively. Addressing these issues requires the development of more energy-efficient technologies and environmentally friendly practices. Economic feasibility also remains a hurdle,
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