Estimation of NH3 emission factor for pig manure in China

The environmental pollution resulting from emission and deposition of ammonia (NH3) from animal manure has become a global concern and an important topic in the environmental diplomacy. To make the control strategies of ammonia emission, it is a key task to identify NH3 emission factor (NH3 EF) for different kinds of animals. Pig production is one of the main domestic animal productions in China, from which large quantities of manure are produced each year. NH3 emission from pig manure was studied by using nutrient flow methodology applied in the RAINS model. Based on extensive literature review and investigations for several provinces of China, the NH3 EFs for different pigs were calculated and characteristics of NH3 EFs under different breeding types and manure management options were analyzed in the course of “housing-storage-field application”, aiming to supply methods for identification of NH3 EF for other animals, and then to estimate NH3 emission from animal production of China. The results showed: 1) Under housing-holding breeding, the NH3 EFs of “household biogas model” (which refers to that manure was stored in household biogas pool) and “composting model” (with manure stored and composted on open place) for fattening were 4.75～4.93, 7.36～7.50 kg·(animal·a)-1 and for sow were 8.64～8.97, 13.38～13.64 kg·(animal·a)-1, respectively. Under intensive breeding, the NH3 EFs for fattening, sow and piglet were 3.13～3.29, 5.76～6.12, 0.57～0.60 kg·(animal·a)-1, respectively. 2) Characteristics of NH3 emission in the link of “housing-storage-field application” between two breeding types were different. For intensive breeding and “household biogas model” under housing-holding breeding, emission in house was the largest; while for “composting model”, emission during storage was the largest. 3) Compared with data from foreign literature, NH3 EFs for fattening in “composting model” under housing-holding breeding was slightly larger than UNECE’s data, but NH3 EF for fattening in “household biogas model” was slightly smaller than UNECE’s data. Moreover, NH3 EFs for sow under housing-holding breeding and for pigs under intensive breeding were all smaller than UNECE’s data.