| As a byproduct of the ethanol industry,the yield of vinasse is large,and there is a great amount of organic compound in vinasse making the COD high.In this paper,the theory of anaerobic digestion and the researchs about digestion of straw and pig manure had been discussed in order to achieve the purpose of environmental protection and utilization of vinasse.Conclusion are as follows:To simulate the effects of vinasse to the straw AD fermentation system,exogenous volatile fatty acid had been added into the batch.It improved the content of methane.But with the volume of added acid increased,methane production efficient of exogenous fatty acid reduced,concentration increased from 4g/L to 8g/L,the gas production by ethanol from the theoretical value of 87.13% down to 70.24%.Acetic acid decreased from 73.04% to 60.45%.The performance of sodium acetate was similar to that of acetic acid.The gas production at the initial concentration of 8g/L was 79.26% of the theoretical value.The addition of ammonium acetate resulted in inhibition of rice straw fermentation,the yield in the experiment group lower than in the control group.The conversion rate of butyric acid at the initial concentration of 8g/L was 57.86% of the theoretical value.The temperature under the condition of exogenous 1g/L,2g/L and 3g/L of the volatile acid initial concentration,gas production of ethanol were 56.32%,59.04% and 42.26% by the theoretical value.For acetic acid the gas production was 190.3%,107.2% and 1.8%,respectively.The gas production rate was 54.53%,103.8% and 69.2% respectively for butyric acid.The results showed that exogenous VFA would not have hameful effects to the AD system.Due to the uneven nutrient content vinasse is difficult to digest by anaerobic fermentation.While mixed with additional carbon source such as straw and swine manure under suitable conditions,vinasse can be digest effectively.When the addition amount of vinasse accounted for 12.5% of the total volume,the biogas yield of straw mixed with vinasse were 627.8,585.6 and 443.9 mL·g TS-1 at TS 3%,6% and 9% respectively,which were much higher than 292.5 ml·g TS-1 in straw control without vinasse.The CH4 concentration has improved to above 70% from 60%.The highest biogas yield 676.7 ml·g TS-1 with substrate of swine manure mixed with vinasse obtained at TS 3%.For the mixed substrate of straw and manure with vinasse addition,the optimal TS ratio of straw to manure was 1:1,and the highest biogas yield was 425.3 ml·g TS-1.The maximum VFAs of straw and vinasse group were 2.8-4.7 times higher than the straw control group.The fermentation type tuned from mixed fermentation to typical butyric type fermentation.The VFAs of swine manure and vinasse group was relatively lower,while the fermentation type changed from mixed fermentation to propionic type.The results show the biogas mixed with vinasse in the substrate of straw and manure will create a highly efficient anaerobic co-digestion system.The vinasse can effectively stimulate and accelerate the biogas yield of straw and swine manure while the degradation and utilization of itself also enhance efficiently in the cofermentation.Under the condition of mesophilic temperature,when the vinasse adding amount accounted for 25% of the total volume,the co-fermentation of straw and vinasse in TS concentration of 6% and 9% both failed.The fermentation of swine manure was successful,and the biogas yield were 271.52 and 237.75 ml/gTS,respectively.Under the condition of thermophilic temperature,the co-fermentation of straw and vinasse sucessed in both TS concentation,and the gas production is 478.54 and 475.58ml/g TS respectively for swine manner.It is 426.20 and 353.93ml/g TS for swine manner.Under the condition of thermophilic temperature,when the adding amount of vinasse accounted for 12.5,25,37.5,50,62.5% respectively,both the straw and swine manure could be used as the external carbon source.After deducting the biogas from vinasse,the gas production yield of each group for rice straw was 373.26,474.95,490.35,and 561.85ml/g TS,respectively.When the swine manure was used as the external carbon source,the gas production was 371.03,436.20,423.26,385 and 307.50 ml/g TS,respectively.Both rice straw and swine manner had improved to the contrast.Therefore,the purpose of using anaerobic digestion to degrade the vinasse and realize the combination of ethanol and biogas production is realized. |
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