Study On The Effects Of Aerobic Hydrolysis On The Anaerobic Fermentation Characteristics Of Corn Straw

China produced a large variety of agricultural wastes every year,the annual production of corn straw rich in carbohydrate polymers accounts about 30% of the total.The transformation of corn straw into available resources is attracting more and more attention.Biogas fermentation is one of the most important ways to transform crop straw to clean energy.In the process of anaerobic fermentation of corn straw,the carbon source required for anaerobic microbial activity is mainly supplied by cellulose.However,carbohydrate-rich microfibrils such as cellulose are tightly surrounded by lignin in the straw,impeding the use of microorganisms.Many studies have demonstrated that lignin has better degradation under aerobic conditions.Therefore,the aerobic hydrolysis technology can effectively improve the gas production performance of anaerobic fermentation.In addition,the aerobic hydrolysis technology has the characteristics of low energy consumption and no pollution.In order to further explore the effects of different influencing factors on material conversion and gas production in the process of aerobic hydrolysis of corn straw,this study was analyzed the time,substrate concentration and aeration interval of aerobic hydrolysis of corn straw as variables.The main conclusions obtained are as follows.(1)The degradation rate of lignocellulose and utilization rate of substrate were significantly improved after aerobic hydrolyzing.Lignin,cellulose and hemicellulose were degraded by 8.02%,25.73% and 28.80%,respectively,after 24 hours of aerobic hydrolysis.The accumulation rate of volatile fatty acids(VFAs)begins to slow down greatly after the hydrolysis proceeds to 16 h.The cumulative concentration of acetic acid at this time was 223.16 mmol/L.The aerobic hydrolysis of the 16 h performed the best gas production.The cumulative Volatile solids(VS)methane production rate was 21.33% higher than the control group.In addition,the VS degradation rate after anaerobic fermentation in this group was 3.97% higher than the control group.Therefore,aerobic hydrolysis is an effective method to improve the anaerobic fermentation performance of the substrate,and 16 h is the suitable hydrolytic time.(2)Increasing the concentration of aerobic hydrolytic substrate in a certain range can promote the degradation efficiency of the substrate and increase the gas production performance of anaerobic fermentation.The test group with aerobic hydrolytic concentration of 10% performed well.The degradation rates of lignin,cellulose and hemicellulose after aerobic hydrolyzing for 16 h were 8.53%,22.74% and 27.82%,respectively.From the perspective of acidification,acetic acid and butyric acid were the main constituents of VFAs in the aerobic hydrolysis process.The sum of these in each group accounts for more than 70% of the total VFAs content.The gas performance of the 10% group was also better than other groups.The Total solids(TS)and VS methane production rates were 209.18 mL/g and 251.01 mL/g,respectively.(3)Different aeration intervals have a significant effect on the lignocellulose degradation of corn straw.The degradation of lignocellulose in two groups with aeration interval less than 4 h is better,the degradation rates of lignin and hemicellulose could both reach more than 9% and 28% after 24 h of hydrolysis,respectively.At the end of the hydrolysis,the cellulose degradation rate of each group fluctuates in the range of 27.97% to 16.2%.From the perspective of gas production,the aerobic gas production was better than the single-phase anaerobic control group.The gas production performance of the aeration interval 4 h group was the best.The methane production rates of TS and VS were 215.87 mL/g and 259.05 mL/g,respectively,which was 30.37% higher than control group.From the perspective of gas production performance and energy conservation,it is appropriate to select 4 h as the ventilation interval.(4)The multivariate quadratic regression equation obtained by the Response Surface Methodology has a good fit to this study.The optimal aerobic hydrolytic parameters for corn straw were 17.33 h for aerobic hydrolytic time,10.47% for substrate concentration,and 2.88 h for interval aeration.Under this condition,the predicted cumulative methane production was 15.91 L,VS methane production rate is 256.61 mL/g.The concentration of aerobic hydrolyzed substrate is the largest among the three factors that affect cumulative methane production.The text values were close to the model predictions.Response surface methodology has certain reliability for the simulation of anaerobic fermentation of corn straw after aerobic hydrolysis.