Study On Near-synchronized Anaerobic Co-digestion Of Naoh Modified Sugarcane Leaves And Animal Manure

China is a country with a vast agricultural base and a large amount of tropical agricultural wastes including sugarcane leaves(SL).The annual yield of SL in China is as high as 36 million tons,while the utilization ratio is less than 20%.Lots of SL is abandoned or open burned,causing severe environmental pollution.At the same time,South China is traditional dominant area for pig and herbivore,and great amounts of animal manure(AM)are produced every year,which cause ecological and environmental issues.Anaerobic digestion(AD)technology is considered to be an effective way to deal with the wastes from planting and breeding.The methanogenic properties,key influencing factors,substance transformation,efficiency change and microbiological characteristics of CTP under gradient load of NaOH modified SL and AM in mesophilic condition were studied in this thesis.The internal mechanism of NaOH modification was revealed by the micro-physical structure,chemical composition and chemical structure.The near-synchronized anaerobic co-digestion method was proposed and the research results were applied in biogas plant.The main research was as follows:1.Effects of NaOH modification on AD performance of SL.AD tests were carried out of 4 particle sizes and 12 NaOH concentrations of SL,respectively.The results showed that the kinetic constant of SL was were 0.015-0.038 d-1 and particle size 2-10 mm has the maximum methane yield.Compared with unmodified ones,the methane yield of modified SL was promoted by 22.02%-89.45%and AD time T80 was shortened by 1 to 3 days,in which 6%NaOH-5d has the best performance(methane yield was 154.08 mL TS-1).2.Physical and chemical mechanism of NaOH modification on SL.The internal mechanism of methane yield enhancement of modified SL was investigated by modern analysis method including SEM and FTIR.NaOH modification destroyed the physical and chemical structure of SL and increased the amount of organic matter that could be decomposed and utilized by microorganisms.The epicuticular wax and cell walls were significantly damaged and dissolved,the specific surface area increased and the content of surface elements changed.The content of cellulose,hemicellulose and lignin decreased by 4.65%-17.77%,8.21%-21.51%and 3.04%-27%,respectively.The degradation rate of LCH was improved.The cold water and hot water extractive content was increased while the benzene-alcohol extractive content decreased.Some functional groups of lignin broke down,parts of hydrogen bonds of cellulose were destroyed,and the intermolecular and intramolecular degradation of the hemicellulose took place.3.Near-synchronized anaerobic co-digestion performance and mechanism of NaOH modified SL and AM.The AD performances of modified SL with pig manure(PM)and dairy manure(DM)at different mixing ratios were investigated.The effects of temperature,mixing ratio and inoculation ratio of three substrates above were determined by Box-Behnken design method.The results indicated that SL and AM have great differences in digestibility,and presented obvious asynchronism in co-digestion.The biodegradability of SL was significantly improved by NaOH modification,and near-synchronized digestion between SL and AM was realized.The macronutrients(C,N,P,S)and trace elements(Fe,Co,Ni)of mixture were more balanced and the system was more stable,and a synergistic effect had been created.The start-up time was shortened and the biodegradation rate of organic matter was accelerated.The best mixing ratio was 1:2 and the maximum methane yield of mixture was increased by 22.82%.Temperature and inoculation ratio had significant effects on AD,while the effects of mixing ratio were not obvious.The optimal process conditions were determined by response surface methodology(RSM),with the temperature of 36?,mixing ratio of 1:1.2:0.8 and inoculation ratio of 38%4.AD performance and microbiological characteristics of the Combined Two Phase(CTP)reactors with NaOH modified SL,PM and DM.Continuous AD tests of the mixture under gradient load were carried out Miseq high throughput sequencing was used to analyze the microbial community structure.When the feeding rate was not higher than 4.5 gTS·L-1·d-1,the system could keep steady with methane content of 57.8%-62.23%and volumetric biogas production rate of 1.36 m3·(m3·d)-1.The acidification and ammonia inhibition occurred while the feeding rate was increased to 5 gTS·L-1·d-1.The substrates in CTP reactors basically achieved phase separation,the upper was the feeding zone,the middle was the hydrolysis acidification zone and the lower was methanogenic zone.Relatively independent microflora was fonned in different regions and large amounts of methanogens were enriched in methanogenic zone.Methanomicrobiaceae,Methanosarcinaceae and Methanosaetaceae were the dominant species of archaea.Bacteria which could degrade cellulosic material was enriched in hydrolysis acidification zone.5.Engineering application research.Based on the modification methods and process conditions determined above,the application research on biogas plant was carried out in Guangxi province.The system process design,material and water balance calculation were accomplished,and the economic,social and ecological benefits were analyzed and evaluated.The results show that the NaOH modification method was feasible and had good prospects for popularization.