Hydrogen Research Influence Of The Carbon-nitrogen Ratio Of Anaerobic Fermentation Organisms

With the increasing crisis of fossil fuel shortage and environmental pollution, hydrogen, a high combustion value and renewable energy carrier, has received considerable interest from researchers and scientists in recent years. Hydrogen production by anaerobic fermentation has higher hydrogen production rate and less operative limitations such as no requirement of sunlight. Besides, anaerobic fermentation hydrogen production is able to take advantage of carbohydrate-rich wastes to produce very clean energy, which is of great significance as a potential source for hydrogen production.In the anaerobic fermentation process, the carbon/nitrogen ratio (C/N) in the feed is a critical factor representing nutrient balance, which is important for cell synthesis, growth, and metabolism. The cow dung compost was co-digested respectively with glucose and apple pomace (AP) in the batch experiments to investigate the effect of C/N ratio on hydrogen production and determine the optimum C/N ratio for anaerobic fermentative hydrogen production with cow dung compost.Firstly, the effect of C/N ratio on anaerobic fermentative hydrogen production for the co-digestion of glucose and cow dung compost was studied. The results showed as follows: as a whole, when the C/N ratio elevated from6.6to9.3, the cumulative hydrogen yield (CHY) increased with the increase of C/N ratio, while the CHY gradually decreased with the increase of C/N ratio when the C/N ratio rose from9.3to11.4. The CHY peaked with1232.7ml/L-culture at a C/N ratio of9.3and the concentrations of glucose and cow dung compost were5.0g/L and180.0g/L, respectively.Secondly, AP was used to substitute for glucose as the substrate. The AP was co-digested with cow dung compost at different mixture ratios to investigate the effect of C/N ratio on fermentation hydrogen production. The results showed that when the mixture ratio of cow dung compost and apple pomace was1:5, the CHY reached the maximum (1398.0ml/L-culture) and the optimum C/N ratio was10.6. Compared with glucose, AP contains only approximately13%reducing sugars except for cellulose, hemicellulose, and lignin, while the co-digestion of AP and cow dung compost got higher CHY than the co-digestion of glucose and cow dung compost.Finally, when the glucose was used as the single substrate and the microorganisms existing in the electrode of pH meter as bacteria source which was from previous hydrogen production with cow dung compost, at a C/N ratio of10.3, the CHY peaked with945.7ml/L-culture and the concentration of glucose was10.0g/L. Meanwhile, at the optimum C/N ratio, the main component of liquid end-products were ethanol, acetate and butyrate and the percentage of butyrate was highest.