Current status and obstacles in the sustainable synthesis of biohydrogen from microalgal species

• Hydrogen production from microalgae is critically reviewed. • Progress and encapsulates technological advancements in hydrogen is emphasized. • Engineered microalgae cells could produce biohydrogen. • Culturing in different photobioreactors for biohydrogen production is compared. • Modified photobioreactor performance for hydrogen production is summarised. Hydrogen production from microalgae is a promising field of study for many reasons, enabling it to be a sustainable and renewable energy source. In recent decades, research in this area has seen its prime, with the increasing shift of focus to hydrogen production through microalgae, eyeing technological advancements and enhancing understanding of its production through microalgae. Techniques such as optimizing growth conditions, genetic engineering, using microalgal consortia, innovative photobioreactor design, and enzymatic processes are used to develop a concise understanding and thus formulate methods and techniques to increase hydrogen production from microalgae. Challenges such as low production rates, high costs incurred for different phases of incubating the desired trait (s) of microalgae, decoding the evolutionary pattern when subjected to the production conditions, environmental factors, and the many hindrances in harvesting have posed grave setbacks, which are stern reminders for the much-needed advancements in genetic engineering, photo-biochemistry, and photobioreactors. Economic viability is another setback that can be countered with improvements in understanding the current generative model. Techniques that remain dubious with current technology but hold great promise for future advances in the current model of inference and synthesis include artificial photosynthesis, synthetic biology, advanced materials for photobioreactors, better microalgal consortia, usage of nanomaterials and advanced process control systems. This review emphasizes the progress and encapsulates technological advancements in the hydrogen lineage inching towards a sustainable circular hydrogen economy from microalgae.