Dark Fermentation of Microalgae and Cyanobacteria for Hydrogen Production

Hydrogen is an effective energy carrier, having high-energy density and releasing no pollutants upon combustion. Indirect biophotolysis is a two-stage process wherein photosynthesis and hydrogen evolution are effectively decoupled. In the first stage, microalgae or cyanobacteria use sunlight to fix carbon dioxide and fuel their growth. In the second stage, dark anaerobic fermentation of the accumulated biomass is used to generate hydrogen by the action of hydrogenases. This chapter presents an overview of the metabolic processes leading to the formation of hydrogen in dark anaerobic conditions, and the factors affecting hydrogen formation rate. Recent developments in dark fermentation for hydrogen production from microalgae and cyanobacteria and different strategies to improve hydrogen production efficiency are also presented.