Recent advances in biological hydrogen production from algal biomass: A comprehensive review.

• Metabolic pathways for algal biohydrogen production are discussed. • Hydrogen-producing hydrogenases and nitrogenases in microorganisms are reported. • Current innovations towards genetic modification to increase biohydrogen are reviewed. • Scaling of biohydrogen production using innovative integrated strategies is presented. • Commercial biohydrogen production projects are cited. Clean fuels play a crucial role in the industrialized world's efforts to combat greenhouse gas emissions. Among the cleanest fuels available, hydrogen stands out as it produces water as a byproduct during combustion. To ensure the sustainable generation of clean fuels, it is imperative to produce hydrogen from environmentally friendly and renewable sources. Biological processes present a promising avenue for the production of hydrogen from affordable and sustainable bio-resources, including biomass and solar energy, using diverse techniques such as direct/indirect photolysis, photo-fermentation, dark-fermentation, and Microbial electrolysis cell. This comprehensive study delves into various aspects of biological hydrogen production, encompassing discussions on microorganisms, different types of substrates and their concentrations, the role of chemical additives, and key operational parameters like temperature, pH, agitation, and insights into hydrogenase and nitrogenase properties. For light-dependent processes, the study also explores the influence of illumination systems. Furthermore, the research examines different configurations of biological processes, integrating light, dark, and photo-fermentation in two- and three-component systems. By investigating these critical factors, the study aims to shed light on optimizing biological hydrogen production. The findings offer valuable insights for advancing the sustainable and efficient utilization of clean fuels in the global effort to mitigate greenhouse gas emissions. [ABSTRACT FROM AUTHOR]