Microbiological photosynthesis is a promising tool for producing hydrogen in an ecologically friendly and economically efficient way. Certain microorganisms (e.g. algae and bacteria) can produce hydrogen using hydrogenase and/or nitrogenase enzymes. However, their natural capacity to produce hydrogen is relatively low. Thus, there is a need to optimize their core photosynthetic processes as well as their cultivation, for more efficient hydrogen production. This review aims to provide a holistic overview of the recent technological and research developments relating to photobiological hydrogen production and downstream processing. First we cover photobiological hydrogen synthesis within cells and the enzymes that catalyze the hydrogen production. This is followed by strategies for enhancing bacterial hydrogen production by genetic engineering, technological development, and innovation in bioreactor design. The remaining sections focus on hydrogen as a product, that is, quantification via (in-process) gas analysis, recent developments in gas separation technology. Finally, a discussion of the sociological (market) barriers to future hydrogen usage is provided as well as an overview of methods for life cycle assessment that can be used to calculate the environmental consequences of hydrogen production

Over the past decades, the economic and environmental soundness of manufacturing systems are often questioned because of the large consumption of energy and primary materials. In order to investigate potential opportunities towards achieving the material and energy efficiency in these systems, it is essential to model these flows and associated complexity in detail. An isolated consideration of individual processes which in themselves are comprised of sub-processes is not a sufficient approach. To obtain a reasonable level of detail from the system, hierarchical structure of energy and material consumers in the system is required. In this paper a simulation based approach is presented to model energy and material flows. This approach considers hierarchical structure of energy and material consumers within the system. It can be served as a base to identify hotspots and to assess the effectiveness of retrofitting exercise through what-if scenarios. An industrial case study is used to demonstrate the applicability and the validity of the proposed approach.

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