Manure Management And The Discharges Of COD,Total Nitrogen And Total Phosphorus Of Animal Operations In Different Scales In Hebei Province

With the increasing number of large-scale livestock and poultry farms in Hebei province,the risk of environmental pollution has become increasingly prominent.Therefore,the realization of environmentally friendly large-scale livestock and poultry farming is of great significance for the prevention and control of livestock and poultry environmental pollution.Based on this,this paper first analyzes the current situation of livestock and poultry pollution in Hebei province through estimating pollutant discharge and performing spatial analysis using ArcGis10.2,and then uses EKC model to empirically analyze the relationships between COD,total nitrogen and total phosphorus against the livestock and poultry farm scales in Hebei province.The theoretical values of suitable animal farm scales in Hebei province were calculated and the main sources of pollutant discharges were identified.In addition,the differences in manure management modes of livestock farms of different scales were analyzed.Finally,livestock and poultry pollution prevention and control recommendations for Hebei province were provided.The main findings are as follows:?1?Shijiazhuang is the first city in Hebei province with more than 20 million tons of manure,which is mainly cattle manure.Tangshan and Baoding have 16.14 and 16.02million tons,respectively.They rank in the top three;Qinhuangdao has the least amount of livestock and poultry manure,which is 5.39 million tons.Pig,cattle,poultry and sheep farming are the main sources of livestock manure.The livestock and poultry manure land load in Hebei province is 14.1t/hm²/a,the warning value is 0.47,and the grade is II,indicating that livestock manure has a“slightly”threat to the environment.The cultivated land load in Qinhuangdao reached 24.5 t/hm²/a,the warning value was 0.82,and the graded grade was III,which was seriously polluted.The total nitrogen cultivated land load in Hebei province is 128.8 kg/hm²/a,and the total phosphorus farmland load is22.0 kg/hm²/a,which is lower than the EU limit standard,but the total nitrogen in Shijiazhuang,Tangshan,Qinhuangdao and Chengde,the cultivated land load has exceeded the EU limit.The total phosphorus load of Qinhuangdao is 40.1kg/hm²/a,which exceeds the EU limit.?2?The dependence variable y in the EKC model was tested for correlation with other variables.The x,x² and x³ of the total pollutant emissions were significantly correlated with the total y emissions.The x and x² in COD,total nitrogen and total phosphorus emissions were significantly correlated with y_COD,y_TN and y_TP.The regression equations of each model can pass the F test,and the constant term of the model of the total pollutant emission model and the respective variables pass the T test;the simulated curve is“inverted U-shaped”.And through the calculation and calculation of the total pollution emission model equation,it is concluded that the theoretical scale of the optimal size of livestock and poultry farms in Hebei Province is 22,000 pig equivalents,which is a large scale.At present,the main source of pollutant discharge from livestock and poultry farming in Hebei province is a small and medium-sized livestock and poultry farm with a proportion of 78.8%.?3?Analysis of the data of 312 pig farmers in Gaobeidian,the farms using full price materials,concentrated materials and premixed materials accounted for 25.32%,36.54%and 38.14%,respectively.In terms of feed selection,large and medium scale farmers tend to choose full-price materials and concentrates,and small-scale farms tend to choose pre-mixes.In the treatment and utilization of liquid manure,large-scale farms mainly use slurry storage and anaerobic fermentation,where the proportion of biogas liquid returning to the field is high but the proportion of fertilizer and water use is low,and the proportion of commissioned treatment is also low;medium-scale farms mainly use unfermented slurry storage and anaerobic fermentation,where the proportion of biogas slurry returning to the field is low but the proportion of fertilizer and water use is high,and the proportion of entrusted treatment is low;the small-scale farm mainly uses fertilizer and water storage,the proportion of biogas slurry returning to the field is low,the proportion of unfermented slurry is high,and the proportion of entrusted treatment is low.In terms of solid manure treatment and utilization,small-scale farms mainly use composting and anaerobic fermentation,where the proportion of farmyard manure is high,the proportion of biogas residue returning to the field and the proportion of entrusted treatment are low.The medium-scale farm mainly uses composting and anaerobic fermentation and.The proportion of utilizing farmyard manure is high,the proportions of biogas residue returning to the field and the entrusted treatment are low;large-scale farms mainly use organic fertilizer production,composting and anaerobic fermentation,and production of biogas.The proportion of farmyard manure is lower than that of small and medium-sized farms,but the proportion of returning to the field is high,and the proportion of commission processing is low.In terms of the willingness to pay for pollution control,most of the large-scale farms are willing to pay 10%to 30%of pollution control costs.Most of the medium and small-scale farms are willing to bear 0-10%of pollution control costs,and more of them are willing to bear 10%the cost of pollution control is medium-scale farms,and small-scale farms tend to pay less than 10%or 0 in the willingness to pay for pollution control.In terms of government regulation,large-scale farms are the most regulated,followed with medium-scale farms and small-scale farms.The livestock and poultry subsidy policy should be tilted to small and medium-sized farms.In summary,the scale of livestock and poultry emissions in Hebei province has an“inverted U-shaped”curve relationship with their pollutants dischage.Shijiazhuang,Baoding and Tangshan are the most polluted areas,and 78.8%of medium and small-scale farms are mostly located here.The three cities are the main sources of pollution emissions,while the mode of manure management for small and medium-sized farms is simply poor,resulting in serious pollution of livestock and poultry in these areas.Therefore,these areas should be the main ones,and the animal farms of these areas should be encouraged to reach 22,000 pig equivalent with a focus on increasing subsidies for small and medium-sized farms in these areas.