Biological H{sub 2} from syngas and from H{sub 2}O
- National Renewable Energy Lab., Golden, CO (United States)
The two stand-alone objectives of the research are to economically produce neat H{sub 2} in the near term from biomass (thermally gasified to syngas) and in the mid term from H{sub 2}O using cyanobacteria or algae with an oxygen-tolerant bacterial hydrogenase. Photosynthetic bacteria have four different terminal enzymes that mediate their H{sub 2} metabolisms-nitrogenase, uptake hydrogenase, fermentative hydrogenase, and carbon monoxide-linked hydrogenase. Each has been microbiologically and biochemically examined for their potential to specifically generate H{sub 2} in large-scale processes. Based on measurements of maximal activities, stabilities, energy requirements, equilibria, and partial pressures of the H{sub 2} producing reactions, the CO-linked hydrogenase is easily the most suited for practical applications. The enzyme mediates H{sub 2} production from CO at rates up to 1.5 mmol/min/g cell dry weight at near ambient temperature and pressure. Hydrogen can be produced and evolved at linear rates up to at least 2 atmospheres of partial pressure (100% CO). The rate-limiting step with high cell density suspensions is the mass transfer of CO into the aqueous phase. Bioreactor designs have been examined which enhance the mass transfer. Hollow-fiber bioreactors with bacterial cells immobilized on the fiber surfaces evolve H{sub 2} at ambient pressure at rates of about 0.3-0.7 mmol/min/g cdw. One such reactor has been producing H{sub 2} from CO continuously for 9 months with only occasional changes of liquid medium. A trickle-filter reactor with bacteria immobilized on beads removed from a bulk water phase and a pumped-bubble coil reactor with bacteria in suspension are also being examined.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- OSTI ID:
- 447147
- Report Number(s):
- NREL/CP-430-21968-Vol.1; CONF-9605195-Vol.1; ON: DE97000053; TRN: 97:001172-0015
- Resource Relation:
- Conference: 1996 annual hydrogen peer review for DOE, Miami, FL (United States), 1-3 May 1996; Other Information: PBD: Oct 1996; Related Information: Is Part Of Proceedings of the 1996 US DOE hydrogen program review. Volume 1; PB: 575 p.
- Country of Publication:
- United States
- Language:
- English
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