Current strategies and future perspectives in biological hydrogen production : A review

Biohydrogen is a green and eco-friendly energy carrier with the potential to reduce our dependency on fossil fuels. Renewable biohydrogen production from waste biomass sources is potentially cheap; however, large-scale commercial production has not yet been achieved. Problems that need to be tackled include identifying industrially competent microorganisms, and appropriate bioreactor designs enabling novel hybrid methods such as integration of dark fermentation with electro-fermentation and utilization of microbial organisms doped with semiconducting nanomaterials for enhanced production. This review focuses on the production of hydrogen by biological methods, highlighting various fermentation processes, the role of enzymes, and different pretreatment methods. The waste materials used are briefly summarized, and current strategies in biological hydrogen production, including biomimetic and synthetic biology approaches, are assessed for their economic feasibility and their potential to contribute to net zero carbon emission. The lignocellulosic waste and the dynamic membrane bioreactor are the best suitable biomass and bioreactor, respectively for biohydrogen production. The integrated method of dark fermentation and electro-fermentation yields 41% higher hydrogen compared with dark fermentation alone. Finally, this review points out that significant efforts focusing on the development of hybrid fermentation technologies along with the development of novel engineered strains are needed for the commercial-scale production of biohydrogen in the future.</p

Microalgal Biorefinery Concepts&rsquo; Developments for Biofuel and Bioproducts: Current Perspective and Bottlenecks

Microalgae have received much interest as a biofuel feedstock. However, the economic feasibility of biofuel production from microalgae does not satisfy capital investors. Apart from the biofuels, it is necessary to produce high-value co-products from microalgae fraction to satisfy the economic aspects of microalgae biorefinery. In addition, microalgae-based wastewater treatment is considered as an alternative for the conventional wastewater treatment in terms of energy consumption, which is suitable for microalgae biorefinery approaches. The energy consumption of a microalgae wastewater treatment system (0.2 kW/h/m3) was reduced 10 times when compared to the conventional wastewater treatment system (to 2 kW/h/m3). Microalgae are rich in various biomolecules such as carbohydrates, proteins, lipids, pigments, vitamins, and antioxidants; all these valuable products can be utilized by nutritional, pharmaceutical, and cosmetic industries. There are several bottlenecks associated with microalgae biorefinery. Hence, it is essential to promote the sustainability of microalgal biorefinery with innovative ideas to produce biofuel with high-value products. This review attempted to bring out the trends and promising solutions to realize microalgal production of multiple products at an industrial scale. New perspectives and current challenges are discussed for the development of algal biorefinery concepts