Air emissions from livestock production facilities are receiving increased attention due to potential human health and environmental implications. The goal of this project was to collect currently available measured emissions data or property line concentration data and integrate the results through meta-analysis for air emissions of NH3, H2S, VOCs, PM10 and PM2.5 from live swine production facilities in North America, including manure storage systems; and to interpret implication of these data relative to existing or potential federal regulations. Results from more than 80 studies were identified though a thorough literature search and data from these studies were extracted using standard data extraction sheet. Together with results from the 11 swine sites in the National Air Emissions Monitoring Study (NAEMS) the data are compiled. Extracted data from all studies were analyzed statistically.
The median emission rates from various studies were more robust because the mean emission rates were sensitive due to a few large values. The median emission rates from swine houses were 2.78, 0.09, 0.44, 0.09, and 0.015 kg yr-1hd-1, for NH3, H2S, VOCs, PM10 and PM2.5, respectively. The median emission rates from swine storage facilities were 2.08, 0.20 and 0.75 kg yr-1hd-1, for NH3, H2S and VOCs, respectively. Large variations in emission rates among different studies were observed, resulting from different conditions in studies. The standard deviations of emission rates from the different studies were usually close to, or larger than, the values of the mean emission rates. Causes of variations or uncertainties in the emission rates were analyzed. Potential causes that may influence emission rates include: stage of production, manure system for swine houses, type of manure storage facilities, area of manure storage facilities, average pig weight, size of operation (number of pigs), air temperature, ventilation type, and measurement method. Farrowing operations had significant higher emission rates than finishing operations on a per head basis for all the pollutants of interest (NH3, H2S, VOCs, PM10 and PM2.5). Gestation houses had the highest NH3 emission rate, but H2S and VOCs emission rates were lower than farrowing houses. The manure management system was also a significant factor in determining whole farm emissions. Hoop systems had higher NH3 emission rates than other types of manure systems. Deep pit systems produced higher H2S emission rates than pit drain or pit recharge systems. The NH3 emission rates from manure storage were significantly influenced by ambient air temperature and the area of storage per head. Slurry storage systems had higher H2S emission rates compared with lagoon systems, especially when emission rates were expressed in kg yr-1m-2. The VOCs emission rates from swine housing were positively related with indoor air temperatures and were negatively related with size of operation, while the VOCs emissions from manure storages were positively related with size of operation. Regression models for emission rates were developed for each of the pollutants, which could be used for estimation of emission rates under various conditions.
Air emissions from industries are subject to permitting requirements under the Clean Air Act (CAA) as well as reporting requirements under the Emergency Planning and Community Right-to-Know Act (EPCRA) and the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) if their emissions reach specified thresholds. For example, operations that exceed 100 lb/day H2S or NH3 emissions are required to report under EPCRA. Based on results of this study, sizes of swine farm that may trigger the need to report NH3 and H2S emissions were calculated for finishing, farrowing, gestation, and nursery operations respectively. For example, swine farm size that may trigger the need to report NH3 emissions were estimated to be 1,819 to 3,074 head for finishing operations, and 885 to 1,313 head for farrowing operations (emissions exceeding 100 lb NH3/day).
Data of measured concentrations of air pollutants in the vicinity of swine operations in literature were also collected and compiled. The Agency for Toxic Substances and Disease Registry (ATSDR) has suggested minimum risk levels (MRLs) for NH3 and H2S designed to protect sensitive populations. At the distances from 30 to 1185m from swine facilities, the ambient NH3 concentrations did not vary greatly, and the average NH3 concentration in literature was 66±66 ppb, which is 66% of the chronic minimum risk levels (MRL) for NH3 (100 ppb). At distances of 30 to 1185m from swine facilities, the ambient H2S concentrations in literature was 3.1±6.2 ppb, which is only 16% of the intermediate MRL for H2S (20 ppb). The average contribution of swine operations in near-source (~15 to 50 m distances) ambient concentrations were 5.8±2.9 µg m-3 for PM10 and 1.7±1.1 µg m-3 for PM2.5. There are limited data for VOCs emissions from swine operations and more science-based information is needed.
Contact information: Zifei Liu, 785-532-3587, [email protected]
