Thermophilic Anaerobic Digestion Of Vegetable Wastes For Biogas Production And Analysis Of Microbial Community

Anaerobic fermentation technology for the treatment of solid wastes is conducive to the energy recovery and reuse of various solid organic wastes.It has been applied to the treatment of wastewater,animal waste,food waste and agricultural residues.And the main objectives of anaerobic fermentation technology are bioenergy production and waste recycling.Vegetable waste is one of the main organic solid wastes in biogas production because of its high moisture content,high organic content and biodegradability.Based on vegetable waste as raw materials,the effects of the factors of substrate concentration,particle size,different vegetable wastes and stirring methods on biogas production by anaerobic fermentation were studied at thermophilic condition?55±1??.In addition,the effects of mixed vegetable residue juice and mixed vegetable waste of Chinese cabbage,cauliflower and sow thistle on biogas production by anaerobic fermentation were studied at thermophilic condition?55±1??.And the methanogen community structure under optimum technological conditions was analyzed.The results are as follows:1.Under the conditions of 3%substrate concentration,0.85 mm?20 mesh particle size?,and Chinese cabbage waste,the degradation rate of TS and VS,the second daily biogas peak,the highest methane content and the cumulative biogas yield are 56.75%,68.32%,515 mL,65.32%and 4251 mL,respectively.These indexes were all higher than the corresponding indexes of other experimental groups?the experimental group that the substrate concentration was 2%,5%,and 7%respectively,the particle size was 5 mesh,broccoli and cabbage vegetable waste are used as raw materials.?.And the pH of before and after fermentation at the conditions of 3%substrate concentration,4.00 mm?20 mesh particle size?,and Chinese cabbage waste are 7.4and 7.6,respectively.They are within the normal pH range of Methanogens.2.Under the condition of 3%substrate concentration,20 mesh particle size,the study of mixed vegetable residue juice showed that the degradation rate of TS and VS,the second daily biogas peak,the highest methane content and the cumulative biogas yield of the vegetable residue+water group were 56.23%,61.06%,525 mL,66.19%and 3390 mL,respectively,which were all higher than the corresponding indexes of other experimental groups.The pH of before and after fermentation of vegetable residue+water group are 7.2 and 7.6,respectively.They are within the normal pH range of Methanogens.3.The study of mixed vegetable waste showed that the degradation rates of TS and VS,the second maximum daily biogas capacity,the highest methane content and the cumulative biogas yield of 3%substrate concentration,under the same conditions,were 42.25%,56.35%,210 mL,64.51%and 2070 mL,respectively,were all higher than the corresponding indexes of other experimental groups.4.There was no accumulation of VFAs and ammonia nitrogen concentration in the continuous stirring group.And its pH value fluctuated between 6.9 and 7.9.In addition,its degradation rates of TS and VS,maximum daily biogas yield,methane content and cumulative biogas yield were 42.25%and 56.35%,42 L,63.80%and297.1 L,respectively,which were better than the corresponding indexes of other experimental groups.5.The results of high-throughput sequencing revealed that at the class level,Archaea were mainly composed of Methanobacteria and Methanomicrobia.At the genus level,Methanothermobacter was the most important Methanogenic bacteria in the reactor,accounting for 55⁸1%of the total bacteria.Methanosarcina is the second leading Methanoarcina,accounting for 16⁴2%of the total bacteria.During continuous stirring,CO₂ and H₂ were used by Methanosarcina to produce methane by the hydrogen generation pathway.That is,Methanosarcina played a leading role in the experimental group of the continuous stirring.