Biohydrogen Production From Solid Organic Waste By Anaerobic Fermentation

Biogas is a potential alternative fuel that is renewable in nature and thereby does not contribute to the net atmospheric concentration of the greenhouse gas. It is a colorless combustible gas produced by the fermentation of biomass and other wastes. Three times experiments have been studied aiming at the solid organic waste hydrogen fermentation. To investigate the mechanisms of biohydrogen production by anerobic fermentation of solid organic waste, gas chromatography is used to analysis the biogas and volatile fatty acid in anaerobic bio-reactor.Firstly, the ability of hydrogen production by digested sludge from the West Lake, Enteobacter aerogences, digested sludge from sewage farm, the fluid of methane pool and dejecta (pig) have been studied. The rule of the ability of hydrogen production by different bacteria under different control condition. Simultaneity, the importance of the synergistic effect on hydrogen production has been proved. Under the same suited control condition, the hydrogen production of the mixed cutler is higher than the single one.Secondly, the biohydrogen production from three food wastes mainly composed of undissolved carbohydrates by anaerobic fermentation of digested sludge is studied. It is found by experiments that the degradation rates of potato, greengrocery and rice in the fermentation are respectively 45.7%, 89.2% and 30.5%. The biohydrogen yield of per gram of dried potato, greengrocery and rice are respectively 82.4 ml·g^-1, 62.6 ml·g^-1 and 37.7 ml·g^-1. No methane is detected in the biogas, because the methane-producing activity is restrained and the hydrogen-producing activity is simultaneously kept when the digested sludge is preheated in the boiling water for 30 min. Ethanol concentration is much higher than other volatile fatty acids in the fermentation solution when the pH value is controlled around 4.5. The biohydrogen production rate firstly increases to a peak and then decreases with an increase of propionic acid concentration in the fermentation solution.Finally, the extraction of hydrogen from the fermentation of eichhornia crassipes by digested sludge is demonstrated. The results show that: The contents of H₂ and CO₂ are 10%～20%, 75%～90% and no CH₄ respectively. Ethanol, acetate, propionate and butyrate are detected, and the trace of valerianate is not found in the liquid of fermentation. Associated with the hydrogen production potential, the pH value of 5.5 is better than that of 4.5, the fermentation temperature of 55 ℃ is better than that of 35 ℃ and the food-to-microorganism ratio of 1:1 is better than that of 3:7 . The high hydrogen production potential of 122.3 ml·g^-1 occurred when the pH value of fermentation liquid is 5.5, the fermentation temperature is 55℃ and the food-to-microorganism ratio is 1:1.