Journal of Energy Bioscience 2024, Vol.15, No.5, 301-313 http://bioscipublisher.com/index.php/jeb 307 particularly if large-scale harvesting is implemented. Therefore, it is crucial to develop sustainable practices that minimize environmental impacts and ensure the long-term viability of biohydrogen production (Jiménez-Llanos et al., 2020; Sharma et al., 2021). 6.3 Technological bottlenecks in scaling biohydrogen production Scaling up biohydrogen production from marine algae faces several technological bottlenecks. One significant challenge is the low hydrogen yield and productivity in current systems, which hinders commercial-scale operations (Goswami et al., 2020). The efficiency of biohydrogen production is influenced by various factors, including the metabolic pathways of algae, reactor design, and operational conditions (Show et al., 2019). For instance, the optimization of bioreactor configurations and the manipulation of light and nutrient conditions are critical for enhancing biohydrogen yields (Rajesh Banu et al., 2021). Additionally, the development of continuous bioreactor systems, as opposed to batch systems, is necessary for industrial-scale implementation. Addressing these technological challenges requires ongoing research and innovation to improve the efficiency and scalability of biohydrogen production processes (Show et al., 2019). 7 Commercialization and Industrial Scale-Up 7.1 Status of commercial biohydrogen production using marine algae The current status of commercial biohydrogen production using marine algae is still in its nascent stages (Figure 3). While there have been significant advancements in the laboratory and pilot-scale studies, large-scale commercial operations are limited. The primary focus has been on optimizing the biological fermentation processes, which are considered more eco-friendly and economically viable compared to thermochemical processes (Goswami et al., 2020). Despite the potential of marine algae as a sustainable and renewable feedstock for biohydrogen production, the transition to commercial-scale operations faces several challenges, including low hydrogen yield and high production costs (Jiménez-Llanos et al., 2020; Sharma et al., 2021). Figure 3 Potential metabolites exchanged among different H2-producing microorganisms during growth conditions (A) and H2-producing conditions (B). The secretion and uptake of metabolites are indicated with plain and dotted arrows, respectively. Depending on the specific culture conditions the same metabolites can be secreted or accumulated. Organic Acids (OAs) mainly include ethanol, glycerol, formate, acetic acid, lactate, succinate and butyrate. When predominant, the specific OA is indicated next to the arrow (Adopted from Fakhimi et al., 2020) 7.2 Case studies of pilot projects and commercial ventures Several pilot projects have been initiated to explore the feasibility of biohydrogen production from marine algae. For instance, an 11 m³ pilot-scale bioreactor was used to investigate biohydrogen production via dark- and photo-fermentation, utilizing solar energy to reduce production costs and carbon emissions. This project
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