L09-prod5 - Hydrogen Production 1 8/19/2005 LECTURE LECTURE...

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Unformatted text preview: Hydrogen Production 1 8/19/2005 LECTURE LECTURE LECTURE LECTURE # # # # 9 TOPIC TOPIC TOPIC TOPIC: H y d r o g e n P r o d u c t i o n Hydrogen Production 2 8/19/2005 Biological Methods s Hydrogen can be obtained from biological process involving organic compounds s Two fundamental ways of biological hydrogen production are b Fermentation of the bacteria b Biophotolysis Hydrogen Production 3 8/19/2005 Hydrogen generation reactor (Algae) Hydrogen generation reactor (Bacterium) Solar energy Pretreatment device Feeder of inorganic salts Hydrogen gas separator Bacterial cell separator Separation and production of useful by-products Physiological active materials Sea Water, Etc. CO 2 H 2 ,CO 2 H 2 ,CO 2 O 2 H 2 W aste W ater containing organic materials * Adapted from Miyake et al. Journal of Biotechnology 70 (1999): p.90, Figure 1. Figure: Concept of biological hydrogen production Biological Methods Hydrogen Production 4 8/19/2005 Fermentation of the bacteria: s This is an anaerobic process that converts organic substances to H 2 and CO 2 without the need of sunlight and oxygen s Fermentation is carried on material like starch, cellobiose, sucrose, xylose to produce hydrogen s Valuable metabolites are butyric acid, lactic acid and acetic acid Biological Methods Hydrogen Production 5 8/19/2005 Fermentation of the bacteria: s Theoretical efficiency of conversion from substrates to hydrogen 33% s It is much lesser than conversion efficiency of methane formation 85% s Bacterial fermentation is water pollution that creates a need to further treat the fermented broth before disposal Biological Methods Hydrogen Production 6 8/19/2005 Biophotolysis: s Involves the use of microalgae - cynobacteria and green algae to generate hydrogen from sunlight and water s Microalgaes are uses two classes of enzymes to produce hydrogen b Hydrogenase b Nitrogenase Biological Methods Hydrogen Production 7 8/19/2005 Biophotolysis: s Nitrogenase enzyme works in the absence of nitrogen gas .to reduce protons to molecular hydrogen s The reaction is irreversible as it utilizes ATP molecules and converts to ADP s Hydrogenase reaction are reversible as they do not require ATP molecule Pi ADP H ATP e H 4 2 2 4 2 2 2 + + + +- + 2 2 2 2 H e H +- + Biological Methods Hydrogen Production 8 8/19/2005 Biophotolysis: s Both enzymes are oxygen intolerant in nature s Hydrogenase-mediated systems have no methods to protect from oxygen s Nitrogenase is protected by O 2 by various biological mechanisms b Spatial separation b Temporal separation s But nitrogenase requires a large amount of metabolic energy reducing efficiency and making it impractical process Biological Methods Hydrogen Production...
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L09-prod5 - Hydrogen Production 1 8/19/2005 LECTURE LECTURE...

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