Study On The Influence Mechanism And Evaluation Model Of Methane Production Performance Of Pig Manure

China has abundant pig manure resources and pig manure has great potential for large-scale biogas production.An important parameter to evaluate the methanogenic performance of anaerobic digestion of organic materials is biochemical methanogenic potential,which is also one of the key parameters for greenhouse gas emission accounting of pig enterprises.In this paper,we investigated the relationship between polymaterials and methanogenic potential by measuring the content of organic fraction and elemental analysis of pig manure in different growing periods in different pig farms;we studied the stability of pig manure anaerobic digestion system and material transformation rules in different growing periods,analyzed the influence of pig manure in different growing periods on methanogenic potential,and determined the characteristics of microbial community in pig manure anaerobic digestion system in different growing periods.The main conclusions are as follows:The methanogenic potential value of pig manure was significantly and positively correlated with the easily decomposable fraction of pig manure.The methanogenic potential value was correlated with the content of C,H,O and N in pig manure,and the higher the content of C,H,O and N elements,the higher the methanogenic potential value of pig manure.The correlations of the empirical model for predicting BMP of pig manure in different growth periods based on the content of VFAs were0.334,0.370,0.188 and 0.550 for VFAs,refractory components,and the total content of easily decomposed components,VFAs and refractory components,respectively.The correlation of the empirical model for single-component BMP prediction was lower than that of the multi-component BMP prediction.FTIR,EEM,thermogravimetric and DTG analyses,elemental and chemical fraction analyses were performed on lactating pig B,gestating sow R and fattening pig Y samples,respectively.The results showed that the content of cellulose and hemicellulose difficult to degrade substances was higher in sample Y,followed by sample R and the lowest in sample B.The material composition characteristics of pig manure samples at different growth periods were one of the important reasons for their anaerobic digestion and methane production characteristics.Sample B and R had higher content of easily degradable components such as protein-like and lipid-like,and high hydrolysis efficiency,while sample Y had higher content of hard-to-degrade components such as cellulose,hemicellulose and lignin-like,which were not easily hydrolyzed;the concentration of TVFAs increased first and then decreased during anaerobic acid production of pig manure in different growth periods.In the anaerobic digestion process,the concentrations of TVFAs in the reaction systems of samples Y,R and B were in the order of Y>R>B.This difference was attributed to the composition characteristics of pig manure in different growth periods and the digestion and decomposition characteristics in the intestinal tract of pigs.The methanogenic characteristics of the pig manure samples differed between growth periods.The cumulative biogas production of different pig manure samples was in the order of B>R>Y.The methane production potential values of the three samples were 246.2,223.7 and 206.9 mLCH₄/g VS,respectively;sample Y produced the highest average proportion of CO₂ in the biogas,followed by sample B,and the lowest was sample R.High-throughput sequencing technology was used to characterize the microbial populations in the anaerobic digestion system of pig manure at different growth stages.At the phylum level,the main bacterial microorganisms in each sample included Bacteroidota,Firmicutes,unidentified＿Bacteria,Proteobacteria,Desulfobacterota,Synergistota,Verrucomicrobiota.There were some similarities and differences in the composition of bacterial microorganisms at the genus level in the three pig manure samples.The archaeal genera in each sample mainly included the genera Methanobacterium,Methanosarcina,Candidatus＿Methanofastidiosum,Methanomassili icoccales,unidentified＿Bathyarchaeia and RumEn＿M2（also known as Methanomassiliicoccales archaeon RumEn M2）.The highest relative abundance of unidentified＿Bathyarchaeia in fattening pig manure samples may be related to its higher cellulose,lignin and hemicellulose content in the system,as unidentified＿Bathyarchaeia was shown to be involved in cellulose degradation.However,the relative abundance percentage of unidentified＿Bathyarchaeia in fattening pig manure was not significantly superior compared to the remaining two pig manure samples.