| The amount of kitchen wastes is increasing with the social and economic development as well as improvement of living standards. Due to the huge amounts, high content of organic matter and easy corruption, they will cause serious pollution to the environment if was not treated properly, such pollution includes the odor pollution of atmospheric environment, the various infectious diseases, serious pollution of surface water and groundwater form the leachate. Kitchen wastes have been a threat to the people. Therefore, effective for kitchen wastes disposal imminent, which also can solve the growing problem of rubbish to the cities.Hydrogen production from kitchen wastes by anaerobic digestion, not only can solve the disposal of kitchen wastes, but also obtain clean and efficient energy. This approach can achieve the reduction of kitchen wastes, harmless and resource utilization. Hydrogen is considered to be a completely clean and efficient energy. Hydrogen also is the best choice to alternative for fossil fuels, with the energy crisis and worsening environmental pollution. The quantity of combustion from hydrogen is higher than any fossil fuel, and combustion produces only water, no greenhouse gases generated. Hydrogen has a wide range of applications, such as food industry, chemical industry and so on.As the complicated characterization of kitchen wastes and diverse inoculum, the control factors which affect the efficiency hydrogen yield from kitchen wastes were various. The control factors were diversely because of the different conditions. Although many scholars had studied the control factors for their own experiments of hydrogen production, most of them only considered the single controlling factor. Studing the full control factors, including the inoculation ratio, pH, temperature, enhancement hydrolysis of substrate, active microbial activity of hydrogen producing microorganism et al, can optimize hydrogen generation mode from kitchen wastes.This paper studied on property control factors of hydrogen generation from kitchen wastes. The basic conditions, including inoculation ratio, initial pH, carbon and nitrogen ratio and temperature were investigated. The initial conditions for hydrogen generation were obtained based on these four aspects; Hydrolysis is considered to be the limit step of digestion from organic wastes, pH pretreatment of substrate was adopted to enhance the hydrolysis efficient; Improving the activity of hydrogen-producing sludge can enhance the hydrogen production efficiency during production process; Adding metal ion can activate the activity of hydrogen-producing sludge.The "hormesis" effect of rare earth element La3+ on hydrogen-producing sludge was studied in order to explore the optimal concentrations; It was the "butyric acid-type" fermentation of hydrogen production in this study. Thus, butyric acid stress to improve the acid tolerance of sludge was investigated, with proposed to increase hydrogen-resistant acid sludge, improve the hydrogen production; Finally, the change of characterization in sludge during butyric acid stress process was performanced, the changes of physically and biochemical in sludge were analysised in order to obtain the basic parameters. Through the above aspects, the control factors of hydrogen generation from kitchen wastes were optimized to establish the optimum model of hydrogen generation. The main conclusions of this paper were as follows:1. Through the analyse of inoculation ratio, initial pH, carbon and nitrogen ratio and temperature, the optimization of the inoculation ratio was 2.5:1, initial pH was 7.5, carbon and nitrogen ratio was 18:1 and temperature was 35℃. The hydrogen yield reached to 28.34 mL/ gVS under this condition. The fermentation type was"butyric acid-type".2. pH pretreatment was adopted to enhance the hydrolysis step from kitchen wastes. After pH 2 and pH 13 treatment conditions, the concentration of carbohydrate, protein, lipid and SCOD increased 87.0%,41.3%,134.7%,78.8% and 283.1%,203.2%,259.1%,108.2% compared with the control. The largest hydrogen yield was 105.38 mL/gVS under pH13 pretreatment, which increased 2.66 times compared with the control. The concentration of organic acids increased rapidly in the first 19 hours of all groups, but changed little from 19th hour to the end, which was similar as the change of hydrogen yield. It showed that the concentration of carbohydrate and protein were decreased throughout the whole process under pH13 pretreatment group, while they first increased then decreased under pH2 and control groups. During the whole process, the concentration of lipids in three components was almost no change. Overall, the priority substrate which micro-organisms utilized was carbohydrate. In the three groups, the concentration of protein and extracellular polysaccharides in EPS increased in the first 14 and 9 hours, but then declined, while the DNA in the whole process of hydrogen generation increased. The maximum value of EPS was 78.60 mg/gVS (pH13 pretreatment)> 65.54 mg/gVS (pH2 pretreatment)> 45.75 mg/gVS (control). The main and most obvious changes component of EPS in sludge was extracellular polysaccharide during hydrogen generation process. The results indicated that pretreatment with acid and alkali for breaking the organic matters in kitchen wastes had obvious effect, and pretreatment could improve the hydrogen yield from kitchen wastes.3. Hydrogen yield initial increased with the added concentration of La3+, but decreased from addition concentration up to 0.5 mg/L. The maximum hydrogen yield was 43.11 mL/gVS occurred under addition La3+with 0.5 mg/L, which was 1.45 times of control. Gompertze model showed, Rm was 0.5 mg/L groups>0.1 mg/L group>control>0.05 mg/L group>1 mg/L group> 5 mg/L group. With the added concentration of La3+, the delay timeλof hydrogen production became longer. VS and SCOD showed a rapid growth in the first 20 hours, but remained stable since 20th hour. However, the pH in the whole process declined. The maximum of P-glucosidase enzyme, BAA-protease and dehydrogenase was 9912.09μmolPNP/(gTS.h),104.67μmolNH4-N/(gTS.h) and 6216.15μgTF/(gTS.h) under La3+ concentration was 0.5 mg/L, which was 1.85,1.48 and 1.69 times of control, respectively. The effect of addition La3+ on hydrogen producing sludge showed "hormesis", and the optimization added concentration of La3+was 0.5 mg/L.4. When the concentration of butyric acid stress reached 4.0 g/L, final butyric acid was 8417.1 mg/L, which increased 31.3% compared with the control. The hydrogen yield reached 63.72 mL/gVS under 4.0 g/L butyric acid stress, which was 214% of control. VS and SCOD reached maximum of 22.68 g/L and 21034.9 mg/L under 4.0 g/L butyric acid stress, which was 1.32 and 1.30 times of control, respectively. (3-glucosidase enzyme, BAA-protease and dehydrogenase showed increased trend in the first 10,5 and 10 hours, respectively, but then decreased. The results indicated that acid tolerance of sludge could increase by stress, and then enhanced hydrogen yield.The feasibility of producing methane from the hydrogen remaining broth was investigated, the results showed that the sequential methane was 287.4 mL/gVS, which increased 34.0％compared with the independent methane. The main degradation of organic acids was butyric acid during sequential methane process, while it was acetic acid during independent methane process.5. The change of characterization of sludge during butyric acid stress was studied. The results showed that the average settlement time and VS of granular sludge in the stress process was decreased. The diameter of flocculation decreased, while the average area of flocs increased in the whole process. Final concentration of glutamic acid decarboxylase first increased with the stress concentration and then decreased. The maximum concentration of glutamic acid decarboxylase was 12.06μg/(TS.h) under 4.0 g/L butyric acid stress, which increased 77.0% compared with the control. The change of physical and chemical properties of sludge during stress process was represented.
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