Emissions Of Greenhouse Gas And Transformations Of Substance During Dairy Manure Composting

With the rapid development of large-scale farms, a lot of manure is produced. Manure is rich in nutrients, but the accumulation process will produce large amounts of greenhouse gases, which is an important source of greenhouse gas emissions. In order to study the process of greenhouse gases during dairy manure composting and provide a basis for reducing greenhouse gas emissions and efficient use of manure, this study chose manures of different lactation dairy (high yield group, the middle yield group, low yield group) to compost. The composting continued for 90ds. The static chamber-GC sampling system with manual is established to measure GHG (CH4, CO2 and N2O) emission. Changes of various forms of organic carbon (TOC, dissolved organic carbon, hot water soluble organic carbon, et al) and total nitrogen, nitrogen, ammonia nitrogen, protein, free amino acids were observed. Relationship between these indicators and greenhouse gas emissions were analyzed. The main conclusions are as follows:(1) In the first week of composting, emissions of CO2 and CH4 were at a high level, and then decline rapidly. N2O basically did not emissions in the early composting. With the temperature improving and moisture reducing, CO2 and CH4 emission rate increased and maintained at a high level, N2O emission rate also increased rapidly and then decreased rapidly after the peak. The total size of greenhouse effect were high yield group> middle yield group> low yield group. CO2 contribute more than half of the total greenhouse effect while CH4 and N2O contribute almost the same.(2)Highly active organic carbon in each treatments rise slowly at first and then increased rapidly. It decreased rapidly later and kept stable at the end of decomposing. There was a weak increase compared with content at first. LOC content fluctuated upward through composting and all treatment groups increased by over 60%. Low activity organic carbon content fall and then rise, and there was a downward trend after that. At the end of composting each treatment to reduce the magnitude of higher organic carbon and high activity below the active organic carbon. Water-soluble organic carbon content of each treatment and trends DOC/TOC were increased and then decreased after the first, and then remained relatively stable. Alkali-soluble organic carbon change at first declined, after rising last fall trends. To the end of the compost, high yield group, the middle group, low-yielding group alkali-soluble organic carbon content decreased by 38.53%,31.53%,36.09%.(3)At the beginning of composting, hot water-soluble organic carbon content continued to decline, with the extension of the composting time, the hot water-soluble organic carbon produced than consumed by microbial activity, its content rises. In the late composting, hot water-soluble organic carbon content decreased. At the end of composting, three groups of handling hot water-soluble organic carbon content was not significantly. The protein content of each group showed a fluctuating upward trend to the end of the compost, the protein content of the order of low yield group> high yield group> middle group. Free amino acid content of each treatment after the first increase in the last lower decreased. All these groups did not reach maturity dung as the standards of NH4+-N/NO3-N≤0.5. NH4+-N contents was high when started composting and it declined after slightly increase. NO3--N contents increased during composting. N2O-N emissions had some correlation with HN and FAA content.(4)The emission size of CH4-C and N2O-N in these three groups were the same, which was high yield group> middle yield group> low yield group. There were both significant differences among the treatments. The low yield group emissions least cumulative of CO2-C and there was no significant difference between high and middle yield group. Cumulative emissions of N2O-N was significantly positively correlated with TN content and significantly negatively correlated with C/N ratio. During composting, cumulative emission of CH4-C, CO2-C, CO2-C+CH4-C had no significant correlation with TOC content or C/N ratio.