Research On Characteristics And Influencing Factors Of Methane Generation-oxidation On Livestock Manure Composting

The level of agricultural intensification has the continuous improvement in China,so,the concentrated feeding of livestock has led to aggravation of the pollution of manure.Aerobic composting is a biological treatment to sanitizing and recycling livestock manure.Compost products can be applied to the soil as organic fertilizer after screening.However,the composting of livestock manure is an important source of anthropogenic methane emissions.Therefore,it is necessary to study the change of methane emission rates during swine,cow,and chicken manure aerobic composting process as well as its application in soil.This paper discussed the correlation between environmental factors and methanogens,methanotrophs,mcr A,mxa F,mmo X and pmo A genes during swine,cow,and chicken manure aerobic composting process.Methanobrevibacter was the dominant methanogen in the swine and cow manure composting,and Methanocorpusculum was the dominant methanogen in the thermophilic period of the chicken manure composting.VS/Ash and moisture were crucial factors affecting the abundance of Methanobrevibacter.Methylococcaceae＿norank was the detected dominant methanotroph of the three livestock manures composting,which had a significant positive correlation with p H and ORP.Temperature,p H value and VS/Ash were major environmental factors affecting mcr A,mxa F,mmo X and pmo A.And the mcr A gene has higher heat resistance than mmo X,mxa F and pmo A genes in the cow manure composting.This paper also discussed the variation of the structure and abundance of methanogens and methanotrophs.The correlation between environmental factors and mcr A,mxa F,mmo X and pmo A genes in the soil samples that manures and their composting products added to after 125 days were also been studied.The acceleration on methane oxidation capacity was the most significant for applying cow manure composting product.Methanobrevibacter and Methanobacterium were the dominant methanogens in the soil samples that swine manure applied.Methylococcaceae＿norank was commonly detected in the soil samples that compost products applied.Verrucomicrobiaceae＿norank was only detected in the treatment of cow manure composting products.All the three manures application reduced the abundance of methanotrophs.The adding of swine and cow manure and composting increased the relative abundance of mcr A gene.The increasing of p H and EC promoted methane oxidation by increasing the activity of pmo A gene.In addition,this paper simulated the important parameters of the methane metabolism process through the methane generation-oxidation kinetic model of livestock manures,and further revealed the changes of methanogens and methanotrophs activity in aerobic composting.The CH₄ generation-oxidation kinetic model could effectively simulate the change of methane emission rate(CH_4,out)during the aerobic composting process of swine and cow manure,but both of models showed the phenomenon of peak time delay.The hydrolysis rates of microorganisms in the three aerobic manures composting reactors were consistent with the change of temperature,and showed a decreasing-rising-steady change trend.The amount of CH₄ oxidation accounted the CH₄ production by 41.14%,40.19% and 30.09% of swine,cow,and chicken manure composing,respectively.The high free air spaces gave methanotrophs stronger relative oxidizing capacity,and the activities of methanogens and methanotrophs in the swine manure were higher than those in cow manure and chicken manure.