Biohydrogen production from algae: Perspectives, challenges, and prospects

Hydrogen is a promising future fuel because of its clean and high energy content properties. It is an ideal energy carrier to reduce greenhouse gas emissions, as its conversion to energy yields only pure water. A challenging issue in establishing hydrogen as a source of energy for the future is the way it is produced. Biohydrogen, produced from biological processes, is a potential renewable biofuel to replace current unsustainable hydrogen production technologies, which rely on nonrenewable fossil fuels through thermochemical processes. One of the promising biohydrogen production approaches is the use of microalgae. Unlike other well-developed biofuels, such as bioethanol and biodiesel, algal hydrogen production is still in the early stages of development. This review examines the state-of-the-art of algal hydrogen, with particular reference to metabolic pathways of hydrogen production, the factors influencing biohydrogen production, bioreactor operation and design, and economic considerations. The challenges and prospects of algal hydrogen production are also outlined. © 2019 Elsevier B.V. All rights reserved.