| China is a big pig breeding country.Greenhouse gas emission from pig breeding is one of the key emission sources of agricultural greenhouse gases,especially in the process of manure management.To promote green and sustainable development of pig breeding process and industry chain,is the inevitable requirement for China to cope with the climate change and comply with the policy of greenhouse gas emission reduction.However,at present,the domestic research on greenhouse gas emission of pig-breeding enterprises is obviously deficient.The problems include the lack of uniform accounting system and target of accounting standard,the lack of concrete accounting process and the lack of practice,and the accounting method unclear.This study combed the greenhouse gas accounting system and standards in the level of enterprises and products both domestic and foreign,and referred to the existing accounting methods standard,finally,put forward the standardization of greenhouse gas accounting steps for pig breeding enterprises.By summarizing the accounting methods of enteric fermentation methane emission,manure management methane emission and manure management nitrous oxide emission,it is suggested that we should solve the problem of lack of characteristic emission factors by actual measurement of large amount of data.In the accounting method of enteric fermentation methane emission,we have explored the high-level accounting method of enteric fermentation methane emission on the basis of existing research data.According to the standardized accounting process proposed in this study,this paper takes twenty-four pig breeding enterprises in Beijing as an example,and calculates the greenhouse gas emissions of enterprises by using scientific accounting methods and standardized accounting processes.The main conclusions are as follows:（1）This study summarized the greenhouse gas accounting system and standards in the level of enterprises and products both domestic and foreign,and the standardized accounting process of greenhouse gas emission in pig breeding enterprises is determined.Includes two elements for the determination of greenhouse gas emission accounting boundaries and the calculation of greenhouse gas emission.In determining the boundary link for the accounting of greenhouse gas emissions,it is divided into three steps to determine the culture model,determine the accounting boundary（fuel combustion emissions,process emissions and emissions from the purchase of electricity and heat）,and determine the range of greenhouse gases to be accounted for.The calculation of GHG emissions involves the identification of sources of greenhouse gas emissions and greenhouse gas types,the selection of appropriate accounting methods（collection of activity levels,the identification of emission factors）and the calculation of aggregate emissions.（2）Based on the survey data of twenty-four scaled pig farms in Beijing,this paper calculates the emission factors of enteric fermentation methane emission by method 2.The enteric fermentation methane emission factors of weanling piglets,growing fattening pigs and sows were 0.53 kgCH4 per head per year,1.46 kgCH4 per head per year and 2.34 kgCH4 per head per year respectively.The default value of enteric fermentation methane emission factor in Beijing is 1.41 kgCH4 per head per year,which is less than the default value 1.5 kgCH4 per head per year given by the Standard Guidelines of the Greenhouse Gas Emission Accounting for Animal Husbandry in Beijing.According to the standard of Construction of scale pig farms（GBT 17824.1-2008）in China,in the scale of piggery of 600base sows,the default value of enteric fermentation methane emission factor in China is 1.32 kgCH4 per head per year,which is greater than IPCC Guidelines for National Greenhouse Gas Inventories by Intergovernmental Panel on Climate Change,and Guidelines for Provincial Greenhouse Gas Inventories in China.The default value is 1 kg CH4 per head per year in these standards.（3）Based on the production data of twenty-four scaled pig farms in Beijing,it is calculated that the greenhouse gas emissions of the unit pigs are 2.19kgCO2e per kilogram pig.Among them,enteric fermentation methane emission,manure management process emission and energy consumption emission accounted for 7.40%,49.32%and 43.28%of total greenhouse gas emissions,respectively.CH4,N2O and CO2 emissions accounted for 12.68%,44.04%and 43.58%respectively.Regardless of energy consumption emissions,greenhouse gas emissions of a total of130.68kg CO2e kilogram pig,piglets,growing pigs,finishing pigs and sows accounting for 16.18%,23.43%,49.87%and 10.52%,enteric fermentation methane emission and manure management process emissions accounted for 13.05%and86.95%respectively. |
