Greenhouse Gases And Ammonia Emission From Flush-manure And Solid-liquid Separation System In Large-scale Dairy Farms

With the rapid development of large-scale dairy farms,treating manure and sewage is becoming a big issue to be solved urgently.Because of its advantages of high efficiency and saving labour force,the flush-manure and solid-liquid separation system is gradually applied to large-scale dairy farms.However,wastewater and fecal residue produced by the system would emitted a large amount of greenhouse gases?GHGs?and ammonia?NH₃?.A dairy farm appling the flush-manure and solid-liquid separation system was selected to measure emissions of greenhouse gases and NH₃.GHGs were measured by the static chamber-gas chromatography technique and NH₃ was measured by the venting method in this present study.The seasonal variation of GHGs and NH₃ from wastewater,fecal residue,and the entire system were analyzed.Global warming potential?GWP?and particulate matter 2.5 forming potential?PMP?were evaluated in the seasonal and annual variation.The main results are as follows:?1?Emissions of CO₂ and CH₄ were mainly affected by the temperature and organic carbon content during the wastewater storage processes.For CO₂,its emission were mainly concentrated in the early stage of storage,while in spring was in the early and late stages of storage.The fastigium of CH₄ emission rates in spring and summer were consistent with CO₂,while in winter and fall its emissions were lower and almost zero,respectively.At the end of the experiment,cumulative emissions of CO₂ from high to low were spring?3.73 g?kg-1?,summer?3.32 g?kg-1?,autumn?2.10 g?kg-1?and winter?0.23 g?kg-1?,and that of CH₄ were also spring?1.71 g?kg-1?,summer?0.86 g?kg-1?,autumn?0.51 g?kg-1?,and winter?4.06×10-4 g?kg-1?.The emission rate of N₂O in each season was very small,and its cumulative emissions were all less than 21.30 ?g?kg-1.The emissions rate of NH₃ were mainly affected by wastewater temperature and p H during the period of trial,and its cumulative emissions from high to low were summer?177.24 mg kg-1?,spring?168.13 mg kg-1?,and autumn?162.00 mg kg-1?and winter?144.93 mg kg-1?.?2?The main GHGs was CO₂,and the emissions of CH₄ and N₂O were very small during the fecal residue storage processes.The emission of CO₂ was mainly affected by the temperature of the fecal residue,and the cumulative emissions from high to low were spring?81.85 g?kg-1?,summer?61.86 g?kg-1?,autumn?58.50 g?kg-1?and winter?36.46 g?kg-1?.The emissions of CH₄ and N₂O were mainly affected by the temperature of the fecal residue,and the cumulative emissions of CH₄ and N₂O in each season were less than 63.39 and 1.71mg?kg-1,respectively.The emission of NH₃ were mainly affected by the stack temperature,p H,and turnover frequency,which run through the entire process.Its cumulative emissions from high to low were winter?0.67 g?kg-1?,autumn?0.54 g?kg-1?,summer?0.42 g?kg-1?and spring?0.36 g?kg-1?.?3?Fecal residue was the main source of CO₂ and N₂O emissions in the flush-manure and solid-liquid separation system,while the emissions of CH₄,NH₃,GWP and PMP were resulted from wastewater.In spring,summer and autumn,the contribution rates of annual system GWP were basically the same which were all between 31.70% and 34.63%,while winter contribute less to the system.The contribution rates of annual system PMP in different seasons from high to low were summer?38.02%?,winter?26.57%?,autumn?18.45%?,and spring?16.95%?.In summary,the CO₂ and CH₄ emissions from wastewater and fecal residue storage processes are mainly affected by the temperature,while the emissions of NH₃ are mainly influenced by the temperature and p H.CH₄ emission from wastewater storage is the main source of GWP.By controlling CH₄ emissions from wastewater in spring,summer and autumn can reduce the annual GWP of the system.However,in order to reducing the annual PMP,it is necessary to control the NH₃ emissions from wastewater and fecal sludge in different seasons.