Enhancement of hydrogen production from glucose by nitrogen gas sparging

The effect on hydrogen yield of N-2 Sparging was investigated in non-steril e conditions using a hydrogen-producing mixed culture previously enriched f rom soya bean meal. A continuous stirred-tank reactor (CSTR) at 35 degrees C and pH 6.0 was operated on a mineral salts-glucose (10 g l(-1)) medium at a hydraulic retention time (HRT) of 8.5 h, and organic loading rate of 27. 02 g glucose litre reactor(-1) day(-1). Results are reported from an 8 week period of continuous operation, and the enrichment culture gave stable res ults over an extended period. A hydrogen yield of 0.85 moles H-2/mole gluco se consumed was obtained after 5 HRT, the gas produced being 53.4% H-2 With N-2 Sparging at a flow rate approximately 15 times the hydrogen production rate, the hydrogen yield was 1.43 moles H-2/mole glucose consumed. The spe cific hydrogen production rate increased from 1.446 mi hydrogen min(-1)g(-1 ) biomass to 3.131 mi hydrogen min(-1) g(-1) biomass under sparging conditi ons. It is suggested that hydrogen partial pressure in the liquid phase was an important factor affecting hydrogen yield. Energy could be recovered as hydrogen from processes generating volatile fatty acids for fine chemicals and liquid bio-fuels or from acidification reactors preceding normal anaer obic biological treatment of sugary wastewaters. (C) 2000 Elsevier Science Ltd. All rights reserved.