Engineering Control Measures And Microbial Community Analysis Of Hydrogen Production System From Sugarcane Juice

Economic development and industrial progress can not go without energy. The development and utilization of fossil fuel have brought about a disaster to the environment and human health, therefore, the development and utilization of clean and renewable energy is the urgent problem to be solved of the contemporary world. Hydrogen is considered as the most promising new energy and been a focus in energy research since it is clean, high-efficiency and sustainable energy. Biohydrogen production has great research and application prospect as a technology of utilize biomass to produce energy. The crucil probems of the technology are industilization of fermentative hydrogen production, the materials that can be used by microorganism with high-efficency and improvement of the hydrogen production stability and hydrogen production continuity.Anaerobic biohydrogen production system from sugarcane juice using anaerobic sludge was established in this study. The ecological factors influencing the hydrogen production efficiency of the fermentation system were discussed. The optimization of engineering control parameters and mechanisms of improving the hydrogen producing capability of the fermentative hydrogen producing system were also discussed. Molecular biology methods were used to analyse the the dynamics of microbial community.Difficulties in starting the reactor are the engineering constraints of anaerobic fermentative biohydrogen production system. The effects of initial volume loading rate and pretreatment of sludge on the start-up of the reactor were discussed. The results showed that initial volume loading rate has a decisive role to the start-up of the reactor. It is illustrated that butyric acid type fermentation was formed when the initial volume loading rate was 6.0kgCOD/m3. The initial organic loading rate should not be too high, otherwise, the pH value of the system will decline sharply, resulting in over-acidification state and leading to the failure of the start-up of the system. Either Aerobic sludge or heating pretreated sludge can be used as the seed sludge for biohydrogen production. Butyric acid type fermentation was formed after starting for 25d, and the butyric acid and acetic acid content fluctuated between 72% and 83% when using aerobic sludge as the seed sludge. The maximum hydrogen production rate of 8.04L/d was acquired. The ethanol type fermentation was formed for 20d operation using the heating pretreated sludge with ethanol and acetic acid content exceeding 80%, and acquired the maximum hydrogen production rate of 16.11 L/d. The results of the start-up show that the type of sludge and the pretreatment method are key factors influencing the formation of the fermentation type. Both the biogas yield and hydrogen yield of ethanol type fermentation are all higher than that of butyric acid type fermentation, indicating that ethanol type fermentation has better hydrogen production stability and the microorganism has better adapt capability to the change of the environmental conditions than that of the butyric acid type fermentation.The increase of volume loading rate can improve biogas production rate and hydrogen production rate, however, if the volume loading rate exceeded the carrying capacity of the system, it will lead to the declining of COD removal efficiency and biogas production rate and hydrogen production rate since some microorganisms eliminated from the reactor due to changes and resulting in the system collapse finally. Metal element has an important role in microbial activity, it would be beneficial for peed up the rate of hydrogen production by adding suitable amount of Fe2+ and Mg2+ to the hydrogen production system.The performance of hydrogen production nearly stoped when the volume loading rate exceeded the carrying capacity of the system in ethanol type fermentation. However, if adjust the influent organic loading rate timly, the biohydrogen system can recover for hydrogen production. The results show that the volume loading rate for the operation of butyric acid type fermentation stably should not be higher than 20kgCOD/m3·d. Hydrogen production revealed to be the best with initial pH value of 8.5 and fermentative temperature of 35℃using sugarcane bagasse as the substrate.The results show that the content of various VFA are high during the initial start-up of the reactor, presenting mixed acids type fermentation with low biomass and the biomass would increase with the operation of the hydrogen production reactor. Ethanol type fermentation presented better performance stability and hydrogen production capacity compared to butyric acid type fermentation. Moreover, it is beneficial to improve hydrogen production efficiency by regulating parameters to form ethanol type fermentation. Identification of bacteria in activated sludge showed Clostridium and Ethanoligenens were predominant bacterias in ethanol type fermentation.