AMMONIA EMISSION FACTORS FROM SWINE FINISHING OPERATIONS 

D. Bruce Harris, Richard C. Shores, and Larry G. Jones, Environmental Protection 

Agency, Office of Research and Development, National Risk Management Research 

Laboratory, Research Triangle Park, NC 

ABSTRACT 

Concentrated animal feeding operations (CAFOs) are being examined in several regions 

of the U.S. as major sources of ammonia and particulate matter precursors. The National 

Risk Management Research Laboratory (NRMRL) has previously measured ammonia 

concentrations around and estimated emissions from a swine production facility. In this 

paper we present the results from two new studies at swine finishing facilities. New data 

are collected for tunnel-ventilated pull-plug swine finishing barns using 

chemiluminescent ammonia measurements from the exhaust fans. Open-path Fourier 

transform infrared (OP-FTIR) measurements of a naturally ventilated pit recharge barn 

and its lagoon are used to develop emission factors in the second study. The data suggest 

that the barns are a significant source of ammonia, and that the current emission factors 

are not markedly different from these new data. 

INTRODUCTION 

Ammonia (NH3) is the major alkaline component of Earth’s atmosphere.’ Ammonia has a 

relatively short lifetime due to its rapid conversion to the ammonium (NHh+) radical and 

deposition of NH3 to natural surfaces.2Y3 Its reaction with the acid gases produced by 

fossil fuel combustion provides a major portion of the ambient fine particulate matter.4 

The Heath Effects Institute recently intensively reanalyzed two studies that associated 

increased mortality with increased fine particles in urban areas and found no reason to 

change those conclusions.’ Excess reduced nitrogen has induced adverse effects in forest 

systems.6’7 Pearl reports advanced signs of eutrophication in several estuarine and coastal 

ecosystems impacted by atmospheric nitrogen deposition.8V9 

EPA’s inventory of ammonia sources nationally, based upon 1996 data, shows animal 

husbandry operations responsible for 73%.” For 15 states these operations contribute 

more than 75%. Emission factors for individual operations were reviewed by Battye et 

al.” which relied upon data from the European Community. Many European swine farm 

operations are very similar in comparison to American practices, but there are some 

significant exceptions, and the existing European ammonia emission factors should not 

be used for American inventories without verification. As part of its mission to 

understand processes that emit air contaminants, NRMRL’s Air Pollution Prevention and 

Control Division initiated a program to examine American swine farm emissions. 

MEASUREMENTS 

Reported elsewhere are measurements we previously made as part of a larger site 

characterization effort by the State of North Carolina to understand the environmental 

impact of swine waste.l* While others concentrated upon the emissions from the lagoon, 

we explored the concentration of ammonia and other gases around the pit recharge 
production barns of a farrow-to-finish swine facility. A single-beam OP-FTIR system 

was situated along several downwind paths that allowed separation of the different 

production phases. The long path capability of the OP-FTIR enabled us to measure all the 

exhaust plumes from the nine finishing barns continuously. To isolate the hogs from 

human contact and risk of infection, a fence ringed the facility. We could not sample the 

exhaust ducts directly with a probe; nevertheless, we could monitor the ammonia 

emissions by aiming the OP-FTIR beam through the fan plume 1 m from the duct exit. 

By monitoring the number of fans operating and estimating their flows from the 

manufacturer’s literature, we developed seasonal emission factors.13 Because we had to 

make several assumptions regarding the air flow around the facility to estimate the 

emission factors, an opportunity to sample a finishing-only facility with direct access to 

the exhaust ducts presented by a major swine producer was accepted. 

This new study facility consists of four separate farms each consisting of ten tunnelventilated pull-plug barns and a fifth farm with five tunnel-ventilated barns. We tested a 

minimum of two barns at each farm housing young (Y), middle (M), and older (0) 

animal age groups. Two chemiluminescent ammonia analyzers sampled the exhaust from 

a rake mounted inside the exhaust cones. Collocation studiesI have shown very good 

agreement between paired analyzers, which we confirmed during these tests. Data were 

stored as l-minute averages. Exhaust fan flow rates were calculated from factory 

calibration curves provided by the fan manufacturer. The pressure difference, measured 

from inside to outside the barns, was measured and used to calculate the individual fan 

flow rates. Sail switches were used to record the frequency of operation for each of the 

fans operated. The total flow rate was determined by adding together the flow rate of all 

the fans operating. Mass emission rate was determined from the product of total flow 

rate and concentrations measured. These data are summarized in Table 1 by farm (F), age 

group (Y, M, or 0), and test (T) number. 

The second study used an OP-FTIR to monitor the emissions from a small (0.30 hectare) 

swine lagoon holding the waste from a single, naturally ventilated finishing barn. The 

sampling was done to evaluate the control capability of a porous bioactive cover 

system.15 A scanning OP-FTIR system” was combined with a radial computed 

tomography technique”-” to develop a concentration profile of the lagoon plume. The 

vertical wind profile, obtained with weather sensors located at 2 and 10 m heights, was 

integrated across the plume concentration to yield the mass emission fluxes shown in 

Table 2. The lagoon was not covered for the first test, but was for the second. The 75% 

reduction observed in the ammonia emissions represent the initial effects of the cover 

before surface bioactivity was established. Increased retention of nitrogen in the lagoon 

waste liquid was also observed. Methane emissions were unaffected by the cover, and 

their flux increase may result from the higher wind speed. 
Table 1. Swine finishing barn ammonia emissions. 

Emission Rates 

F4-Y-T1 13 1000 60,000 5.40 8.60 0.516 

F4-Y-T2 15 970 67,900 7.29 12.29 0.760 1.086 

FS-Y-T1 14 936 65,520 3.28 6.04 0.387 0.553 

F5-Y-T2 17 912 9 1,200 4.62 7.21 0.474 0.474 

Average Y 14 949 66,940 5.14 8.69 0.548 0.796 

Fl-O-T1 30 370 92,500 5.51 8.51 1.380 0.552 

Fl-O-T2 26 760 160,600 2.67 4.35 0.343 0.163 

F2-O-T1 26 822 180,840 3.38 6.13 0.447 0.203 

F2-O-T2 29 570 142,500 3.08 9.18 0.966 0.387 

1 Average 0 ( 28 1 631 1 144,110 1 3.66 1 7.04 1 0.784 0.326 

Table 2 - Summary of methane and ammonia emissions from lagoon along with 

meteorological data. 

711 l/O0 

8/16/00 

Ammonia Methane Flux 

Flux (g/min) (g/min) 

15.0 27.6 

3.66 33.6 

Wind Speed 

Ws) 

2.1 

3.0 

Wind Direction 

(degrees) 

254 

254 

RESULTS AND CONCLUSIONS 

Van Der Hoek, et al.*’ reported that the European Expert Panel on ammonia had 

determined default ammonia emission factors for animals across Europe. These factors 

for swine stables are 2.89 and 7.43 kg NH3 per animal per year for “Fattening pigs” and 

“Sows,” respectively. The “Fattening pigs” stables correspond to the hog finishing barns 

included in our test program, and the “Sows” stables that include the young animals 

3 
correspond to our fat-rowing barns which are to be included in a future program phase. In 

North Carolina, all but the very youngest animals are housed in a finishing barn as are the 

older animals after being weaned. Thus, none of the barns in this study housed animals 

less than 10 weeks old. The measured ammonia emissions reported in Table 1 for this 

study are representative of the summer season. We annualize them for presentation in 

Table 3 as the summer factor for comparison to other reported annual ammonia emission 

factors. We expect actual annual emissions to be lower due to the effect of ambient 

temperature on the vapor pressure of ammonia. Based on our previous work, annual 

emissions for North Carolina fattening barns are estimated at 3.69 kg/hog/year (Table 3). 

The age of the hog at 10 to 30 weeks did not have a statistically significant 

influence on ammonia emissions unless the data are normalized for weight. All fattening 

hogs older than 10 weeks had about the same impact on ammonia emissions on a per 

animal basis (Table 1). Only when the data are expressed on a per 100 pounds basis do 

the younger hogs appear to have higher emissions. In addition to the five mechanically 

ventilated barns tested (Table l), a naturally ventilated barn was examined in the second 

study. The ammonia emissions from this barn (4.0 to 12.0 g/minute) are in the same 

range as the mechanically ventilated barns. Other factors influencing the emissions 

results which will be examined in future work include the use of recycled lagoon water 

used to flush the holding pit below the barn floor, the influence of the diurnal cycle, and 

seasonal variation. 

The summer emission factor developed from our current data for the 16 tunnel-ventilated 

barns tested is slightly higher than the summer value included in our earlier work (4.8 1 

versus 4.75 kg/hog/yr), but within the variation of the method. Recent data2* from 

Midwestern deep-pit barns yield similar emissions for the summer (4.68 kg/hog/yr). 

Our data and other recent tests suggest that an annual emission factor for the tunnelventilated barn currently being used by the industry is not markedly different from the 

one developed by Battye et al.” The seasonal effect is real and may lower total emissions 

in areas or seasons where temperature control is not the reason for fan operation. 

Completion of the seasonal component of our current studies should provide additional 

data to examine possible modifications to the current EPA emission factor. 

Table 3. Swine confinement facility emission factors, kg/hog/yr. 

4 
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