Effects Of Pore Characteristics Of Membrane On Ammonia Emission From Chicken Manure Compost

Aerobic composting is one of the important measures of livestock and poultry manure harmless handling,however,a large amount of ammonia emission limited the promotion of composting application.In present study,the different porosity membranes were used to discuss the effect of membrane cover composting on the NH₃emission and its mechanism,and provided the references for the ammonia emissions effectively reducing in composting process.In this experiment,layer manure was used,mushroom and sawdust as the litter.In the experiment,blank group covered without any membrane（CK）,non-porous polytetrafluoroethylene（PTFE）membrane covering the compost pile labeled as group A,and another two groups used the porous membrane,PTFE group（moisture permeability is8.06×10³g/（m²·24h）,air permeability is 9.01 mm/s）labeled as group B,PTFE group（moisture permeability is 8.29×10³g/（m²·24h）,air permeability is 13.60 mm/s）labeled as group C,there were 3 repeats in each group,the weight of each repeat approximated 1 ton,and the compost process carried 21 days,during experiment,the gas and the samples of compost pile were collected for the determination of ammonia,physical,chemical and microbial parameters.The main results are as follow:（1）By the comparison of group CK,the total ammonia daily emission（the sum of ammonia inside and outside of the membrane）of the group A,group B and group C decreased 13.25%,32.05%and 14.46%respectively.By the comparison of group A,the total ammonia emission in group B and C decreased 21.67%and 1.39%respectively.The ammonia emissions of group B decreased 20.57%by the comparison of group C.Throughout the composting process,by the comparison of group CK,the ammonia emission of membrane outside in group A,B,and C decreased 87.94%,83.52%and 74.15%,respectively,and the ammonia emission of membrane outside in group A was significantly lower than that in both group B and C（P<0.05）.（2）By the comparison of group CK,the content of ammonium nitrogen decreased in group B and C and the organic matters also was promoted in group B and C during the high temperature period of composting.At the end of composting,the p H value in group CK,A,B and C were 8.50±0.29、8.81±0.37、8.06±0.14、8.01±0.12,respectively.The p H value of group A was significantly higher than that in group B and C（P<0.05）.The nitrate nitrogen content in groups A,B,and C were 0.72±0.05 g/kg,0.69±0.03 g/kg and 0.67±0.07 g/kg,respectively,which all higher than that in group CK（0.60±0.02 g/kg）.（3）Membrane cover increased the number of total bacteria in the compost pile,changed the relative abundance of microorganisms,increased the content of nitrifying bacteria,and promoted the conversion of ammonium nitrogen to nitrate nitrogen in compost pile.During the whole composting process,the abundance of Proteobacteria increased.Among them,the abundance of Proteobacteria in group B and C was higher than that in group A.In the later period of composting,the relative abundance of Actinomycetes bacteria in the three groups of membrane cover（groups A,B,and C）were 13.22%,12.35%and 12.49%,respectively,which were higher than that in group CK（7.17%）.At the end of composting,the relative abundance of Bacilli in the three groups of membrane cover（groups A,B and C）were:39.21%,36.66%,and 57.72%respectively,which were significantly higher than that in the group CK（16.71%）（P<0.05）.In summary,membranes cover can reduce the ammonia emission during compost process.PTFE composting membrane（group A,no pores）was better than expanded PTFE membrane（groups B and C）in reducing ammonia emission of membrane outside,and expanded PTFE membrane with low air permeability（group B）was better than high-permeability（group C）in reducing ammonia emissions of membrane outside.The composting membrane covered with different porosity changed the relative abundance of microorganisms in the composting process（21 days）.The total number of bacteria in the membrane-covered group increased.The Firmicutes was the dominant phylum in the composting process.The bacteria relative abundance increasing promoted the conversion of ammonium nitrogen to nitrate nitrogen.