Content | ©S.R. Guiot, AHGSET workshop, IEA, Paris -6/7 May 2008 —20 R&D needs : to improve H2yield ¾better understand thermodynamics of H2catabolismby mixed cultures, to guide pH, temperature and pH2 optimization ¾screen for high-yield H2-producing mixed& stable populations-based inocula from fertile biota ¾novel isolated strains, namely in the upper-thermophilic domain ¾cloning and expression of hydrogenasesmore efficient ¾manipulation of metabolic pathwayse.g. in Clostridia Microbiological issues ¾designs with high cell density(immobilization) ¾designs integrating methods to lower dissolved H2(to prevent end-product inhibition) : pressure release; vacuum; submerged membrane for dissolved gas extraction; integration with H2sinks. ¾2stages-processsecondstage: 9photofermentation:highyieldsbutlimitedbylightcaptureefficiency(photoreactors)and nitrogenases(slow,neednon-growingconditionswithoutnitrogensource,energy-intensive) •CH3COOH + 2 H2O o4 H2+ 2 CO2 •CH3CH2CH2COOH + 6 H2O o10 H2+ 4 CO2 9biocatalyzed electrolysis Process issues |