| Summary: | 碩士 === 逢甲大學 === 環境工程與科學所 === 95 === Hydrogen is one of the alternative energy carriers that countries all over the world develop actively at present. Starch is a carbohydrate that plants produce via photosynthesis, and it exists in extensive quantities in the nature. Fermentative hydrogen production with mixed cultures is more practicable compared with pure cultures. In addition, fermentative hydrogen production generates liquid metabolites (alcohols and volatile fatty acids), which are all rich in heat energy. If we can reclaim these metabolites, we can gain additional energy, and reduce the pollution of the biochemical oxygen demand in metabolotes.
In this study, the influences of various seed sludge (sewage sludge, fructose mill sludge, food mill sludge, paper mill sludge, and beach soil) on the fermentative hydrogen production with starch were investigated. The effects of different environmental factors for the hydrogen production were further studied. When different initial pH (5.0~7.0), substrate concentration (20~60 g COD/l), and operation temperature (30~55oC) were studied, an optimum hydrogen production rate and yield of 619.6 mmol H2/l/d and 2.2 mol H2/mol hexoseremoved, respectively, was obtained at pH 5.5, 20 g COD/l as substrate concentration, and 35oC and paper mill sludge as the inoculum. Bioenergy yield was depended on the amount of liquid metabolites generated and ranged from 2073 to 3793 KJ/mol hexose. More ethanol was obtained at high temperature (40~55oC) with energy production potential of 300-760 KJ/mol hexose. The optimum condition for hydrogen production for the beach soil was the same as for paper mill sludge. The hydrogen production rate and yield were 199.2 mmol H2/l/d and 2.2 mol H2/mol hexose removed, respectively. About 1125-2861 KJ/mol hexose of energy could be produced depending on the amount of the liquid metabolites resulted.
Hydrogen production with starch was further investigated in continuous stirred tank reactor operated at the optimum condition described above. Hydrogen production rate and yield was optimized by decreasing the hydraulic retention time (HRT). Optimum hydrogen yield (1.32 mol H2/mol hexose) was obtained at HRT 12 h, while the optimum hydrogen production rate (0.42 mol H2/l/d) was obtained at HRT 4 h. with about 500.4 KJ/l/d of energy generated using paper mill sludge as inoculum .
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