Hydrogen production by microalgae

The production of H2 gas from water and sunlight using microalgae, 'biophotolysis', has been a subject of applied research since the early 1970s. A number of approaches have been investigated, but most proved to have fundamental limitations or require unpredictable research breakthroughs. Examples are processes based on nitrogen-fixing microalgae and those producing H2 and O2 simultaneously from water ('direct biophotolysis'). The most plausible processes for future applied R D are those which couple separate stages of microalgal photosynthesis and fermentations ('indirect biophotolysis'). These involve fixation of CO2 into storage carbohydrates followed by their conversion to H2 by the eversible hydrogenase, both in dark and possibly light-driven anaerobic metabolic processes. Based on a preliminary engineering and economic analysis, biophotolysis processes must achieve close to an overall 10