Biogas Production By Anaerobic Fermentation Of Green Vines And Utilization Of Biogas Slurry

With the increasing Chinese economic level,the consumption of vegetables is increasing,which produces lots of green vine solid waste.Because of the high ratio of water in green vines,it is easy to breed decay.Only a small part of green vine solid waste is used to feed livestock,and more is randomly discarded which makes our environment seriously polluted.Therefore,it is highly necessary to properly process these discarded green vines and to utilize the biomass energy effectively.Combining a special scientific research of the national public welfare industry?Agriculture?,i.e.,"rural biogas centralized gas supply technology integration and supporting equipment and demonstration?201403019?",the research compares the physical and chemical properties of three kinds of green vines?fresh potato rattan,fresh tomato rattan and fresh soybean rattan?,and analyses anaerobic fermentation characteristics of green vines to investigate the impact factors of the anaerobic fermentation of vines in order to provide a new way for the utilization of green vine solid waste resources.In view of the residual biogas liquid of high nitrogen and phosphorus concentration produced after anaerobic fermentation,it is purified and treated with Chlorella pyrenoidosa to provide data and theoretical support for rural biogas engineering.The main conclusions are as follows:?1?Experiments exploring the characteristics of three green vines found that green vine is rich in lignocellulose,and it is a good material for anaerobic fermentation,which can produce methane through the action of microbes.Although the theoretical gas production of three green vines has a high fermentation potential,the structure of fresh green vines is too loose,along with the poor thermal stability of chemical bonds,the three kinds of vine appeared excessive acid accumulation or even rancidity in the mixed anaerobic fermentation experiment.In addition,the characteristics of the high lignin content and the low hemicellulose content of the fermentation substrate lead to the relatively slow hydrolysis acidification process,but they can be normally fermented after self-regulation.?2?The following conclusions were drawn from the experiment of green vines mixed with anaerobic fermentation.The pH,temperature and FeCl₂ have greater effects on the anaerobic fermentation of green vines.First of all,anaerobic digestion of tomato vine and soybean vine can be carried out only if the pH is adjusted to more than 7 during the early stage of anaerobic fermentation.In addition,among the normal anaerobic fermentation of potato vine experiment group,it was found that the total gas production and methane volume fraction did not change significantly after the initial pH was raised.Secondly,under the three different temperatures of 25?,35?and 45?,the three green vines obtained better anaerobic fermentation at 35?degrees.The maximum material conversion rate was 39.53%,42.41%and 54.54%respectively,and the cumulative gas yield and the maximum VFA were significantly different?P<0.05?.Finally,adding FeCl₂ enhances the activity of methanogens in the green ferment anaerobic fermentation system.In the three green vines test group,when the dosage of FeCl₂ was less than 20 mg/L,the peak arrival time of gas production increased with the increase of dosage,and the fermentation period was negatively correlated with the dosage,but there was no significant change in the output of VFA and the overall gas yield.Under the optimal reaction conditions,the conversion rate of three green vines was positively correlated with the content of hemicellulose and cellulose in vines?R²=0.997?,the accumulative gas yield and the volatile solid content of green vines were positively correlated?R²=0.9622?.?3?The biogas liquid had higher nitrogen and phosphorus content after the anaerobic fermentation.It was found that Chlorella pyrenoidosa had a certain purification effect on the anaerobic fermentation of green vines,and the concentration of biogas liquid had a great effect on the growth of Chlorella pyrenoidosa and the removal of pollutants.The 25%concentration test group had the best effect,the removal rate of ammonia nitrogen and total phosphorus were above 95%,the removal rate of COD was above 70%,and the growth rate of algae dry weight was above250%.As the concentration of biogas slurry continued to increase,the growth rate of Chlorella pyrenoidosa and the removal of pollutants appeared to decrease,and the concentration of 100%biogas slurry would prohibit the growth of Chlorella pyrenoidosa.