Microalgae: a green source of renewable H-2

This article summarizes recent advances in the field of algal hydrogen prod uction. Two fundamental approaches are being developed. One involves the te mporal separation of the usually incompatible reactions of O-2 and H-2 prod uction in green algae, and the second involves the use of classical genetic s to increase the O-2 tolerance of the reversible hydrogenase enzyme. The e conomic and environmental impact of a renewable source of H-2 are also disc ussed.