Study Of Gradient Fermentation Of Food Waste For Hydrogen And Methane Production

Food waste is a kind of pollutant which is harming the environment. The resource utilization is important significant to the purifying environment and alleviating the energy shortage.Among the many kinds of disposal methods of organic solid waste, the way of anaerobic treatment has dual advantages. On the one hand, there is at least seventy percent of organic substrate could be removed from FW after anaerobic digestion, the method of which is very effective for waste disposal. On the other hand, a great deal of biogas (a mixture of mainly methane and carbon dioxide) was simultaneously generated during the process of anaerobic digestion. Therefore, anaerobic treatment of FW has received wide attention from scientists in recent years.In this paper, FW was used as the substrate for anaerobic digestion, was digested successfully via hydrogen production phase and methane production phase. Firstly, the raw biogas (RBE) effluent was mixed with FW according to a certain proportion, the mixture was prepared to be used the feedstock of hydrogen production phase. Secondly, the effluent of hydrogen production phase was transported into methanogenic phase. Lastly, the effluent of methanogenic phase was mixed with FW according to a certain proportion used as the feedstock of hydrogen production phase. Therefore, a cycle was formed with the above three steps, which could achieved the goal of gradient utilization of FW. In addition, the effects of different pretreatment methods of biogas effluent on the performance of hydrogen production were also investigated in this paper. The main conclusions obtained in this paper as follows:In batch experiments, the optimal range of hydrogen production rate (50-58mL/g) was obtained at the ratio of1/3(RBE/FW, TS/TS), the sum of content of acetate and butyrate was above80%. In the semi-continuous experiments, the hydrogen production phase could operate successfully for15days. The average hydrogen production rate was39.59mL/g, the total organic acids concentration was13220mL/g, the sum of content of acetate and butyrate82.45%.Similarly, under the back-flow ratio of1/3, another batch experiments was carried out to study the effect of different pretreatment methods of biogas effluent on the performance of hydrogen production. The result showed that the hydrogen production rate of ultrasound treatment was the highest (64mL/g). The order of the total concentration was as follows: ultrasound>heat>aeration> RBE.In the semi-continuous experiment of pretreated biogas effluent (PBE), the effect of different hydraulic retention times (HRTs) on the performance of hydrogen was studied. The result showed all the treatments performed normally under the HRTs of2d,3d and4d, and running for15days. The hydrogen production rates of the former two HRTs were closed, and better than HRT of4d.The optimal parameters obtained in the dual phases were as follows:the HRT of hydrogen production phase was2days; the HRT of methanogenic phase was50days.1g volatile solids (FW) could convert to hydrogen of49ml and methane of554ml in the dual phases, and the sum volume of the value gas was603ml, however,1g volatile solids (FW) could obtain561ml methane in single-phase methane fermentation.