Research On Kinetics Of Anaerobic Fermentation Biogas Production Based On ADM1 Model

In view of the huge yields of agricultural straw and low efficiency of comprehensive utilization,livestock manure pollution,antibiotic pollution and energy shortage,this study modified the ADM1 model to characterize the dynamic process of anaerobic co-fermentation with cow dung and corn straw as feedstocks.Methane yields were predicted after model calibration(sensitivity analysis and parameter estimation),model validation,and model analysis(Pearson correlation coefficient and RMSE),and compared with the original ADM1 model.The modified ADM1 model was used to simulate the anaerobic co-fermentation of cow manure and corn straw under the influence of antibiotics(erythromycin and sulfadimethylpyrimidine).The key parameters affecting the fermentation were analyzed.The main results are shown as follows:(1)The original ADM1 model was not able to characterize the methane production kinetics of the anaerobic co-fermentation with cow dung and corn straw as feedstocks,while the modified ADM1 model was able to characterize the methane production kinetics more accurately.After sensitivity analysis,the key parameters that had significant effect on methane were given:disintegration rate coefficient of cow dung(kdis,cd),disintegration rate coefficient of corn straw(kdis,cs),maximum absorption ratio of acetic acid(km,ac),maximum absorption ratio of hydrogen(km,h2),maximum absorption ratio of sugar(km,su),half-saturation coefficient of acetic acid(Ks,ac),propionic acid(Ks,pro)and sugar(Ks,su).The recommended calibration values for these parameters were 0.43,0.31,16.30,42.97,30.20,0.39,1.11 and 8.50,respectively.The Pearson correlation coefficients of the modified ADM1 model in the calibration group and the four validation groups were>0.958(p<0.05),and the RSME values were<0.3.According to the results of kinetic study and statistical indicators,the modified ADM1 model accurately predicted the methane production of the anaerobic co-fermentation with cow dung and corn straw as feedstocks.(2)The modified ADM1 model was used to simulate the methane-producing process of anaerobic fermentation under the influence of antibiotics.The key parameters influencing the anaerobic co-fermentation under the stress of erythromycin were km,ac and Ks,ac,and the key parameters influencing the anaerobic fermentation under the stress of low concentration of sulfadimethylpyrimidine were kdis,cd and kdis,cs.Under the influence of erythromycin,the recommended values of kdis,cd,kdis,cs,km,h2,Ks,pro,Ks,su and km,su in the modified ADM1 model were 7.79,0.00001,4.35,9.99,99.66 and 0.53,respectively.At this point,the correlation coefficient of each group were>0.977(p<0.05)and RMSE were<3.27,indicating that the model was able to simulate the methane production by anaerobic fermentation under the influence of erythromycin.Under the influence of low concentration of sulfadimethylpyrimidine,the modified ADM1 model was able to simulate the experimental results(correlation coefficient>0.988,p<0.05;RMSE<2.09);Under the influence of high concentration of sulfa dimethylpyrimidine,the RMSE value of each group was higher(>9.59),and the model was not able to simulate the methane production accurately by anaerobic fermentation.In this study,the ADM1 model was modified.After model calibration,verification and analysis,the modified ADM1 model was able to realize the prediction of methane production by anaerobic co-fermentation with cow dung and corn stalk as feedstocks,and obtain the key parameters and recommended values of model simulation of anaerobic co-fermentation with cow dung and corn stalk as feedstocks under the influence of antibiotics.It provides theoretical guidance for further exploration of accurate characterization of anaerobic fermentation biogas production process and the study of anaerobic co-fermentation under the influence of antibiotics.