Life Cycle Assessment Of Manure Management Systems In Intensive Dairy Farms

Intensive dairy farm waste is one of a major source of environmental problems.It is significant to choose a reasonable manure management system to reduce the pollution of manure from the dairy industry.Therefore,this study used life cycle assessment（LCA）method to evaluate the environmental impact potentials of three manure management systems,namely dry manure-aerobic composting,flush-manure and solid-liquid separation and slurry.The main impact stages and pollutants were analyzed.The environmental impacts of three manure management systems were comprehensively compared,and the sensitivity analysis of the results was conducted.The results showed that:（1）The energy use（EU）,global warming potential（GWP）,acidification potential（AP）,eutrophication potential（EP）and particulate matter potential（PMP）of the dry manure-aerobic composting system for treating 1t of feces in dairy farms were 7.526 MJ,5.753 kg CO₂ eq,0.438 kg SO₂ eq,0.133 kg PO₄^3-eq and 0.019 kg PM_2.5 eq,respectively.Fecal aerobic composting,field application and wastewater storage were the major stages which affect global warming,acidification,eutrophication and particulate matter forming.The manure collection was the major contributor to energy consumption.The major pollutant of GWP was N2 O,while NH3 was the main source of AP,EP,and PMP.（2）The EU,GWP,AP,EP and PMP of the flush-manure and solid-liquid separation system for treating 1t fecal of dairy cattle in dairy farms were 9.724 MJ,14.576 kg CO₂ eq,0.184 kg SO₂ eq,0.571 kg PO₄^3-eq and 0.008 kg PM_2.5 eq,respectively.The wastewater storage was the major stage could influence global warming,acidification and particulate matter.The wastewater discharge was the major contributor to eutrophication.And the solid-liquid separation was the major contributor to energy consumption.The major pollutant of GWP was CH4,while NH3 was the main source of AP and PMP.And the TN and TP were the major pollutant of EP.（3）The EU,GWP,AP,EP and particulate matter potential of the slurry system for treating 1t of feces in dairy farms were 11.401 MJ,15.794 kg CO₂ eq,0.670 kg SO₂ eq,0.230 kg PO₄^3-eq and 0.028 kg PM_2.5 eq,respectively.Slurry storage and field application were the major contributor to global warming,acidification,eutrophication and particulate matter.Slurry transfer and field application were the major contributor to energy consumption.Themajor pollutant of GWP were N2 O and CH4,while NH3 was the main source of AP,EP,and PMP.（4）The comprehensive impact of different manure management systems were0.206 for dry manure-aerobic composting system,0.42 for flush-manure and solid-liquid separation system,0.769 for slurry system.The comprehensive index was insensitive to the NH3 emission factor and weight coefficient.In summary,none of the three manure management systems could resolve all five environmental problems.However,the dry manure-aerobic composting system is better to improve environmental problems such as EU,GWP and AP than other two systems.and had the lowest comprehensive environmental impact,so it is suggested being applied in dairy farms.