Dynamics And Driving Factors For The Ammonia And Greenhouse Gases Emissions Of Dairy Industry In Beijing-Tianjin-Hebei Region

With the rapid development of economy,atmospheric contamination has become a serious problem in Jing-Jin-Ji district recently.Frequent haze days have caused the deterioration of air quality and affected people’s normal life and physical health.Dairy farming is an important component of the livestock industry.With the increasing scale and intensification of dairy farming,the produced manure has resulted in large amounts of ammonia and greenhouse gas emissions,thus caused a series of environmental problems.In order to reveal the drivers of the evolution of ammonia emissions and GHG emissions from dairy farming in the Jing-Jin-Ji region,this study uses the emission factor method to estimate the emissions in 2008,2012,2016 and 2020 and investigate the emission trends.The driving factors to the emissions were examined using the constructed Kaya constant equation extension model and the LMDI method.Finally,the gas emissions in 2025 were projected,and the mitigation potentials were evaluated by using different mitigation practices.The main conclusions are as follows:(1)NH3 emissions from the dairy industry in the Beijing-Tianjin-Hebei region in 2008,2012,2016 and 2020 were estimated to be 51.8,46.1,40.7 and 33.8 kt,respectively,showing a gradual decrease;greenhouse gas emissions were estimated to be 5 950.7,6 730.3,5 769.9 and 4 229.8 kt CO2eq,respectively,showing a trend of first increase and then decrease.(2)Methane emissions from enteric fermentation and manure storage of dairy cattle are the most important source of GHG emissions from dairy farming in Beijing-Tianjin-Hebei region,with emissions of 4 723.6,5 429.2,4 648.0 and 3 175.2 kt CO2eq in 2008,2012,2016 and 2020,accounting for 79.38%,80.67%,80.56%and 75.07%of the total GHG emissions in the four years,respectively.N2O emissions from manure management and field application are another important source of GHG emissions from dairy farming in the Beijing-Tianjin-Hebei region,with emissions of 1 227.1,1 301.1,1 121.9 and 1 054.6 kt CO2eq in the four respective years,accounting for 20.62%,19.33%,19.44%and 24.93%of the total GHG emissions in that year,respectively.(3)During the period 2008—2020,the NH3 emission intensity based on net benefits peaked with a maximum of 0.22t per 10 000 Yuan.The GHG emission intensities(calculated in CO2eq)show a trend of increasing and then decreasing,with the emission intensity based on net benefits peaked with a maximum of 31.77 t per 10 000 Yuan.(4)The analysis of the driving influencing factors indicated that the breeding cost factors was the most important factor contributing to the increase of NH3 emission in the Beijing-Tianjin-Hebei region,with a cumulative contribution of 26.0 kt of ammonia emissions,while the benefit per kg of milk and the manure management were the most important factors contributing to the decrease of NH3 emission,with a cumulative reduction of 24.2 and 11.4 kt of ammonia emissions.The analysis of the driving influencing factors indicated that the breeding cost factors was the most important factor contributing to the increase of GHGs emission in the Beijing-Tianjin-Hebei region,with a cumulative contribution of 3 416.0 kt of CO2eq emissions,while the benefit per kg of milk and the farming scale factors were the most important factor contributing to the decrease of GHGs emission,with a cumulative reduction of 3 166.1 and 915.1 kt of CO2eq emissions.(5)The results of the scenario analysis show that with the existing management methods,by 2025,ammonia emissions from dairy farming in Beijing-Tianjin-Hebei region will increase by 45.56%and CO2eq emissions will increase by 34.81%compared to 2020;by strengthening the management of emissions from the feeding house and manure storage,ammonia emissions will still increase by 28.99%and CO2eq emissions will increase by 37.48%compared to 2020;while through the whole chain management of feeding house,manure storage and field application,the ammonia emissions will be reduced by 50.89%and CO2-equivalent emissions will be reduced by 37.84%compared to 2020.(6)When GHG emissions are calculated using GWP*,cumulative GHG emissions peaked in 2017 with a contribution of 35 423.1 kt CO2we,at which point the contribution to temperature is 0.02 mk.When full chain reduction measures are taken,the contribution of GHGs from dairy farming in the Beijing-Tianjin-Hebei region to climate warning will gradually decrease in the future.In summary,breeding cost,benefit per kg of milk,and the manure management were the major factors affecting ammonia and greenhouse gas emissions from dairy industry in Beijing-Tianjin-Hebei region during the period of 2008—2020.Implementation of mitigation management along the whole-chain of feeding houses,manure storage and field application may restrain the ammonia and greenhouse gas emissions(CO2eq)in 2025 below those in 2020,and the CO2we emission may become negative and would not contribute to the global warming.Therefore,this study provides a new perspective and important support for the green and sustainable development of dairy farming in China,and will play important role in the accelerated realization of the carbon peaking and carbon neutrality in China’s agriculture.