Air emissions are a local, regional and global concern. Rural residents and state and federal regulatory agencies have an increased interest in the air emissions from livestock operations. With that in mind, it is in a livestock farmer’s best interest to take steps to better understand the pollutants emitted from their facilities.
Fresh and stored manure emits volatile organic compounds (VOCs). Up to 300 different VOCs have been identified within manure air emissions, including phenyls, acids and indoles. Although emitted from manure in small amounts, the VOCs are largely responsible for manure’s offensive odor character.
Odor is a local concern and contributes to community unrest and neighbor dissatisfaction with nearby livestock facilities. Most states have some type of odor regulation though although between states their application to livestock facilities is highly variable. In Michigan, odor is addressed within the Michigan Department of Agriculture and Rural Development (MDARD) Generally Accepted Agricultural and Management Practices (GAAMPs) for Site Selection and Odor Control for New and Expanding Livestock Facilities. Although not a regulation, the GAAMP suggests increased property line setbacks based on the number of animal units housed at a livestock production site. The property line setbacks rise as the number of animal units at a site increase.
Ammonia is emitted from livestock manure both from livestock housing and the manure storage area. Ammonia has been associated with atypical forest growth as well as excessive plant growth and decay in surface water. Ammonia emissions may combine with other air emissions to form small atmospheric particulates similar to smog. These particles may drift long distances before they are deposited making ammonia emissions a regional concern.
Greenhouse gas (GHG) emissions present a global concern. Carbon dioxide, methane and nitrous oxide are all greenhouse gases emitted from livestock production sites. During the normal respiratory process, animals release carbon dioxide and plants absorb it. The generation of carbon dioxide from respiration is not included when considering a “carbon footprint.” Carbon dioxide is released from manure storages and can be stored in soils as soil organic carbon. Methane is emitted from manure storage facilities and fields, and by ruminants during the digestive process. Manure storage facilities and fields also emit nitrous oxide. Using information provided by the United States Environmental Protection Agency (EPA), Pitesky, Stackhouse and Mitloehner (2009) reported that livestock production contributes only 2.8 percent of the total U.S. GHG emissions. The GHG emissions from livestock sites are comparatively small and at present these emissions are largely unregulated.
Emitted from stored manure, hydrogen sulfide presents both an odor and a health concern. The EPA has defined exposure limits to hydrogen sulfide. With respect to livestock farms, the greatest concern and risk to both human and animals from exposure to hydrogen sulfide occurs during the agitation and pumping of deep-pitted barns.
NAQSAT was first made available in 2010. Currently, the tool will evaluate air emissions from dairy, beef, swine, turkey, broiler chicken, layer hens and horse farms. As an online tool, it is not intended to be downloaded on to the user’s computer. Users of the tool provide inputs in eight management categories: animals and housing, feed and water, manure collection and transfer, manure storage, land application, mortalities, on-farm and nearby roads, and neighbor relations (perception). Users answer questions that pertain only to their situations since the program generates questions determined by answers to previous questions. Photos provide a useful visual comparison to aid users in answering. Users do not need to input facility size, number of animals and farm location to utilize the tool. Data entered into the tool can’t be identified back to the user, making all entries strictly confidential.
The tool’s output page includes seven air emissions ‒ odor, dust, ammonia, hydrogen sulfide, methane, volatile organic compounds (VOCs) and nitrous oxide ‒ in each of the eight management categories. Estimates of the quantity of each air pollutant are not part of the report. Rather, the tool utilizes a bar graph to indicate how well the farm is doing at controlling emissions for each of the seven pollutants in each of the management categories. In the sample results shown in the graphic, the green area in the boxes indicates how well the farm is doing for each pollutant and the white area indicates opportunity for improvement. Within the “Animals and Housing” management category the report indicates less opportunity for improvement of four emissions and greater opportunity to reduce ammonia and methane. (The seventh emission, nitrous oxide was not applicable for this category in this sample.) The user may either click on the boxes associated with the emissions of concern (in this case, ammonia and methane) to find suggested resources or run additional scenarios to determine where improvements may be made to reduce those emissions. The amount of white showing in each bar for mortalities indicates there are many opportunities to improve management of dead animals on this farm.
In the future, addressing air emissions may become a component of conservation planning. Tools such as NAQSAT will play an important role in helping livestock farmers incorporate air emissions into those plans.