Location: Northwest Irrigation and Soils Research2013 Annual Report
1a. Objectives (from AD-416):
The purpose of this project is to address atmospheric emissions of trace gases from concentrated dairy operations and manure management systems. The goal is to develop emissions factors which will allow decision makers to evaluate the contribution of these constituents from dairy production with other agricultural and industrial sectors and assist in long-term planning efforts aimed at improving air quality and reducing emissions. Additionally, this project examines emissions of bioaerosols from dairy production facilities as well as airborne transport of pathogens during the reuse of dairy wastewater for crop irrigation. This information will be used to determine the potential for off site transport of bioaerosols and pathogens from dairy production, which is a community concern. The specific objectives and goals of the project are listed below (investigator involved and their time commitment). Objective 1. Determine emission rates of gases and bioaerosols from dairy operations. (Leytem 0.3, Dungan 0.2, Bjorneberg 0.2) • Research Goal 1.1. Estimate on-farm emissions of ammonia, methane, nitrous oxide, and carbon dioxide from dairy production facilities to determine emission factors that account for diurnal and seasonal fluctuations in emissions. • Research Goal 1.2. Compare gas monitoring equipment effects on estimates of ammonia and methane emissions. • Research Goal 1.3. Develop on-farm emissions factors for ammonia, methane, and nitrous oxide from dairy wastewater storage ponds based on wastewater characteristics, management practices, and climatic conditions. • Research Goal 1.4. Measure airborne concentrations of culturable bacteria, virus, and filamentous fungi and endotoxins downwind from a concentrated dairy operation to assess diurnal and seasonal variations. Objective 2. Utilize fecal contamination indicators to assess the downwind transport of pathogens in dairy wastewaters delivered via sprinkler irrigation systems. (Dungan 0.3, Leytem 0.2, Bjorneberg 0.1) • Research Goal 2.1. Assess the transport of aerosolized bacterial and viral pathogens generated during the land application of dairy wastewaters using sprinkler irrigation systems.
1b. Approach (from AD-416):
A year long study will determine the emissions of ammonia, methane, nitrous oxide, and carbon dioxide from the barns and wastewater storage pond of a large freestall dairy. Additionally, bioaerosol transport from the barns to downwind locations will be assessed. The emissions of ammonia, methane, and nitrous oxide from dairy liquid storage ponds will also be assessed in order to determine the factors affecting these emissions and develop better methods for predicting emissions from these systems. An assessment of the transport of pathogens from sprinkler irrigation of dairy wastewater will also be undertaken to determine the risk of pathogen drift to human receptors and potential health risks. A better understanding of the type and amount of constituents released into the air from animal production and manure storage areas are expected results. This information will allow us to develop emissions factors and assess the risk of pathogen drift from these systems.
3. Progress Report:
Significant progress has been made in 3 out of 4 objectives, all of which directly contribute to quantifying the extent of agricultural emissions of air pollutants. Under Objectives 1.1 and 1.4, emission factors for ammonia, methane, and nitrous oxide were developed for the housing area and wastewater storage ponds at a freestall dairy. The emission factors were subsequently published in a peer-reviewed journal. Under Objective 1.3, methane and nitrous oxide emissions are currently being monitored at two dairy production facilities, which will continue through the next fiscal year. Under Objective 2, substantial progress has been made using a model to estimate the dispersion and transport of bioaerosols generated during the spray irrigation of dairy wastewaters. A peer-reviewed publication on this topic is anticipated in FY 2014.
1. Quantification of pathogens in dairy wastewaters. ARS researchers in Kimberly, Idaho, conducted a study to quantify pathogens in dairy wastewaters. Understanding the type and quantity of pathogens in wastewaters is important, as dairymen in the arid west typically apply their manure wastewaters through sprinkler irrigation. During irrigation events, the pathogens can become aerosolized and subsequently inhaled by exposed individuals. The data from our study indicates that a variety of zoonotic bacterial pathogens are present in most dairy wastewaters, but at relatively low concentrations. The results are a critical component of a quantitative microbial risk assessment that is currently being developed to estimate the risk of infection in individuals that are downwind from wastewater application sites.
2. Estimating trace gas emissions from dairy production. Concentrated dairy operations emit trace gases such as ammonia, methane, and nitrous oxide to the atmosphere which are a concern from human health and climate change perspectives. The implementation of air quality regulations in livestock-producing states increases the need for accurate on-farm determination of emission rates. ARS researchers in Kimberly, Idaho, determined the emission rates from the open-freestall and wastewater pond areas on a commercial dairy. The combined on-farm emissions on a per cow per day basis from the open-freestall and wastewater pond areas averaged 0.20 kg ammonia and 0.75 kg methane. Data from this study can be used to develop trace gas emissions factors from open-freestall dairies in southern Idaho and other open-freestall production systems in similar climatic regions.
3. Assessing model inputs to improve on farm emission rates of trace gasses. Inverse dispersion models are useful tools for estimating emissions from animal feeding operations, waste storage ponds, and manure application fields. Atmospheric stability is an important input parameter to such models. ARS researchers in Kimberly, Idaho, compared emission rates calculated with an inverse dispersion model (WindTrax) using three different methods for calculating atmospheric stability: sonic anemometer, gradient Richardson number, and Pasquill-Gifford stability class. Predicted emission rates were similar between the sonic anemometer and Richardson methods, while Pasquill-Gifford method resulted in emission rates that tended to be 50% to 100% greater. This research suggests that the gradient Richardson method may be used to determine atmospheric stability for inverse dispersion modeling if a sonic anemometer is not available.
Dungan, R.S., Klein, M., Leytem, A.B. 2012. Quantification of bacterial indicators and zoonotic pathogens in dairy wastewater ponds. Applied and Environmental Microbiology. 78(22):8089-8095.