Comparative Study On The Cost-benefit Of Manure Resource Utilization Models For Scale Pig Farming In Hunan

Hunan,as a large pig exporting province,ranks first in the country in terms of number in the list of large pig exporting counties announced in 2021,and ranks third in the country in annual pig stocking volume and second in pig slaughtering volume.The proportion of live pig scale farming(annual slaughter volume over 500 head)increased from 34.5% in 2010 to57% in 2020,and the pig farming changed from traditional decentralized type to modern intensive type.With the increasing level of pig farming,the intensification and separation of farming brings a severe test to the ecological environment.Pig manure is a kind of misplaced resource,and the manure and urine actually contain a large amount of organic matter and nutrients such as nitrogen,phosphorus and potassium,which can better meet the nutrient demand of crops in the process of growth,and will not cause damage to the ecological environment as long as the process of manure storage,treatment and utilization is reasonable.On the one hand,the resource utilization of pig manure can reduce the total amount of pollutant emissions,continuously improve the quality of rural environment,enhance the quality and stability of the ecosystem,and comprehensively improve the efficiency of resource utilization;on the other hand,it is important to expand the supply of organic agricultural products and improve the quality,efficiency and competitiveness of agricultural products,and promoting the resource utilization of manure is an inevitable choice for the high-quality development of the farming industry.Based on circular economy theory,sustainable development theory,environmental resource value theory and cost-benefit analysis theory,this paper systematically organizes and summarizes relevant literature on the impact of pig manure on the environment,direction of manure resource utilization and evaluation and analysis of manure resource utilization model,and analyzes the current situation and shortcomings of manure resource utilization research.And combined with the field research,we summarize the current situation of manure resource utilization and mode of pig farming in Hunan Province,and take the combination of farming-full volume return model,combination of farming-energy model,clean reuse model and standard discharge model in different scales as the entry point to explain the operation mode and advantages and disadvantages of each scale,and select the operation the demonstration sites with mature and significant effects are selected for case studies.The cost-benefit of each model is accounted for,and the TOPSIS comprehensive evaluation model is used to evaluate the ecological,economic and social benefits of each model,and the cost-benefit of different manure resource utilization models under different pig farming scales is analyzed in depth.The results show that:(1)among small-scale farms,the average pig manure resource utilization cost is the lowest in the combined breeding-farming-all-volume return model and the highest in the clean reuse model;the economic benefits are the best in the combined breeding-farming-all-volume return model;the ecological benefits are the best in the clean reuse model;the combined breeding-energy model the social benefits are the best;the overall benefits of the clean reuse model are the best,slightly better than the combined farming-all-volume return model.(2)Among medium-scale farms,the clean reuse model has the lowest cost per pig and the highest standard discharge model;the clean reuse model has the best economic benefit;the combined farming-all-volume return model has the best ecological benefit;the combined farming-energy model has the best social benefit;the combined farming-all-volume return model has the best overall benefit.(3)Among large-scale farms,the average pig cost of manure resource utilization is the lowest in the standard discharge model and the highest in the clean reuse model;the economic benefit is the best in the clean reuse model;the ecological benefit is the best in the combined farming-energy model;the social benefit is the best in the clean reuse model;the comprehensive benefit of the clean reuse model is significantly higher than the other three models,and it is the preferred model for manure resource utilization in large-scale farms.It is the first choice of large-scale farm manure resource utilization model.Finally,we propose the following points for constructing a long-term mechanism for resource utilization of pig farming manure: cultivating third-party service entities and carrying out diversified services;improving the incentive system and amplifying the role of economic induction;implementing classification management and enhancing the role of demonstration;and grasping the technical team and improving the level of technical services.It provides a reference for farming households to select the appropriate manure resource utilization model,and also provides a basis for the optimization and adjustment of relevant policies of the government and public utilities.