Bio-hydrogen production by anaerobic fermentation of waste

Labscale experiments were carried out at the Department of Environmental Engineering, Technical University of Denmark. A two steps process for hydrogen production in the first step and methane production in the second step in serial connected fully mixed reactors was developed and could successfully convert organic matter to approx. 20-25 % hydrogen and 15-80 % to methane. Sparging with methane produced in the second stage could significantly increase the hydrogen production. Additionally it was shown that upflow anaerobic sludge blanket (UASB) reactor system was very promising for high effective biohydrogen production from glucose at 70 degrees C. Glucose-fed biofilm reactors filled with plastic carriers demonstrated high efficient extreme thermophilic biohydrogen production with mixed cultures. Repeated batch cultivations via exposure of the cultures to increased concentrations of household solid waste was found to be most useful method to enhance hydrogen production rate and reduce lag phase of extreme thermophilic fermentation process. Low level of pH (5.5) at 3-day HRT was enough to inhibit completely the methanogenesis and resulted in stable extreme thermophilic hydrogen production. Homoacetogenisis was proven to be an alternative competitor to biohydrogen production from organic acids under thermophilic (55 degrees C) conditions. With respect to microbiology, 16S rRNA targeted oligonucleotide probes were designed to monitor the spatial distribution of hydrogen producing bacteria in sludge and granules from anaerobic reactors. An extreme thermophilic (70 degrees C), strict anaerobic, mixed microbial culture with high hydrogen producing potential was enriched from digested household waste. Culture members were phylogenetically affiliated to the genera Bacillus and Clostridium. A thermophilic (60 degrees C) bacterial strain Thermoanaerobacterium thermosaccharolyticum PSU-2 with high yield (2.53 mol H_2. mol-"1 hexose) and production rate of hydrogen 1.12 mmol H_2.L"-"1.h"-"1 was isolated from a biohydrogen reactor fed with palm oil mill effluent. The biofilm of T. thermosaccharolyticum strain PSU-2 developed on heat pretreated methanogenic granules substantially enhanced biomass retention and enhance the hydrogen production. It appeared to be most preferred process configuration for thermophilic continuous hydrogen production from organic wastes. The project is fully reported in 10 journal articles. (from final project report)