The Study On Construction And Estimation Of Nitrogen Footprint Model For Large-Scale Livestock Breeding Industry

With the rapid growth of global population,the rapid development of industrial and agricultural production,the burning of fossil fuels and the production and use of nitrogen fertilizer,the nitrogen load of the earth ecosystem has rised rapidly.The total amount of livestock and poultry industry in China is large,which causes the nitrogen pollution,and there are obvious differences among the breeding mode,the methods of disposing the waste and technical level.But now,considering the regional or watershed scale,the means of estimating the process of livestock and poultry and emission load of the whole chain of nitrogen in terms of the waste disposal is lack,which makes it hard to control the real contribution to the environmental nitrogen pollution caused by the livestock and poultry under the specific mode of situation.In Jiangsu Province,the swine production accounts for the largest proportion in the livestock and poultry breeding system,followed by the meat and egg poultry.This artical will take the hoggeries and henneries in typical regions as the research objects,based on the core idea of N-PRINT.By combining the analysis of lifecycle and the basic method of balance in human and nature systerm,the writer will construct the evaluation model of livestock and poultry breeding nitrogen footprint which is suitable for Chinese situation,and use it to carry on the empirical analysis.It also discusses different nitrogen footprints under different reuse of the waste and different management modes.It is significant for the nitrogen emission and environmental pollution of livestock and poultry breeding industry with scientific and quantitative cognition degree in terms of theoretical research and practical management decision.The main research results are as follows:(1)The feed conversion rate of laying hens(30.6%)is generally higher than that of commercial pig feed(27.8%-30.8%),which is much higher than that of pigs(15.0-16.9%).Among them,the feed conversion rate of boars is 18.0%,and the number of gilts is about 17.3%,and the basal sow is about 7%.(2)Farm management,manure utilization and management of different farms have a significantly different effect on nitrogen emissions or losses in livestock and poultry farming.Pigs are treated with biogas and compost,and the heap is mainly composted.There are also significant differences among the different treatments of the same animals.Among them,the nitrogen loss rate was 78.9%-83.5%under different manure management modes during pig breeding.(3)Nitrogen footprint analysis results of manure management models in different regions showed that the biogas treatment is one of the most effective ways of management of fecal nitrogen loss.The nitrogen loss in biogas treatment was only 13%of the total nitrogen loss during the whole process of livestock and poultry breeding,which is lower than the nitrogen loss of composting process by 29%.(4)Gas loss is also an important way of nitrogen loss.The nitrogen loss of gas is 51%-72%,NH3 is the main part of gas loss,accounting for 65%-78%.(5)The case study showed that the nitrogen loss of commercial piglets(3.5 kg)and the nitrogen loss of the laying hens were(1.57 kg)per 1 kg of livestock and poultry products.Comprehensive consumption structure,production structure and environmental emissions,we can find poultry farming is a more ideal choice,the choice of livestock and poultry breeding species is an important aspect of the future development of animal husbandry in China.(6)The development of a cycle of farming with biogas as a link should be the focus of future development,but it also brings new challenges to the anaerobic fermentation process,equipment and technology.It is worth mentioning that the biogas system in the construction process of the consumption of raw materials and the process of running CH4 gas leakage,but also on the environment have a negative effect,and thus in the future biogas project operation process requires special attention and improvement.(7)Nitrogen livestock and poultry manure comprehensive treatment methods and techniques have not yet attracted enough attention.At present,the breeding waste disposal method is single and extensive.And the single technology of processing and utilization has been unable to effectively solve the environmental pollution problem of large-scale livestock farming,we need to consider the comprehensive utilization of fertilizer and energy,etc.,to seek technical economical and environmental harm minimization of long-term livestock waste control mode.