Study On Scale-up Experiment Of Bio-Hydrogen Production From Cornstalk By Fermentation

The reduction of energy resource and the pollution of environment are two great problems to human being. Comparing with the other fossil fuel, hydrogen is an ideal, clean and sustainable energy resource for future. It has many advantages as follows: high energy density, high heat conversion, low cost of transportation, and no recontamination. Biological hydrogen production processes, including photosynthesis and anaerobic fermentation, are environmentally friendly and less energy intensive compared to chemical processes. Between two biological processes, fermentative process that uses wide range of organic substances is technically simpler and more attractive than photosynthetic process. The fermentative bio-hydrogen process is environment friendly and reaches two aims: getting rid of wastes and emitting hydrogen. So it must have a good future.In the present study, taking corn straw as substrate, the scale-up experiment of bio-hydrogen production by cow dung compost in 301itre reactor basing on shaking culture and small-scale experiment was carried out. We got the significant study results.The results showed:1. The method of enriching and culturing natural anaerobic microorganism bacterium from the cow compost was investigated in this experiment. The effective way to harvest hydrogen bacteria was that the compost aerated for 2 hours after boiling for 15 min, and then was cultured by the mixture of sucrose and corn straw as substrate in a 5-liter reactor. The hydrogen productivity achieved 3.5mol H₂/mol sucrose. After culturing for 18 hours, the bacterium was inoculated to the 30-liter bioreactor, and the delay time to produce hydrogen was shortened to 4 hours. Pretreated by demolition, marinating, acidolysis, the hydrogen productivity of the corn straw was 220mlH2/g cornstalk, about 47 times of those un-pretreated corn straw.2. According to the variety of the organic loading COD of culture fluid, semi-continuous culture method was introduced, fresh culture medium or potassium hydroxide were added into bioreactor to adjust PH value every 12 hours. And the by-product was moved away in time in order to balance the degradation efficiency of the substrate and the hydrogen production rate. The favorable condition can extend the steady period of the bacterium.3. The optimal controls parameter in the 30-liter bioreactor as follows: T36±1℃, PH 5.0～5.2, speed of agitator 100r/min, initial concentration of cornstalk 12～15g/l, interval of feeding 12h. Under this optimal experimental conditions, the scale-up reactor obtained a hydrogen yield of 433ml/(l×h) continuously, the maximum hydrogen productivity of cornstalk was 220 ml/g, the highest hydrogen concentration in the biogas reached 61%. The detection results revealed that the fermentation was butyrate acid type fermentation according to the by-products.