Background

Emissions from livestock operations cover a wide range of compounds. The largest public concern is the generation and transport of malodorous compounds across the landscape. Policy issues focus more on transport and deposition of ammonia, methane, nitrous oxide, and particulates. Humans can detect as odors a large number and mixture of volatile organic compounds or even single compounds, e.g., ammonia or hydrogen sulfide. These volatile organic compounds and gases may potentially interact with particulates in the atmosphere to change their dispersion characteristics and reaction in the human nose.

Odors result from the digestive process of microorganisms in manure. Odorous compounds commonly associated with livestock facilities include ammonia, volatile organic compounds including amines and fatty acids, and sulfur-containing compounds. In addition, significant quantities of gases can be released as by-products of engineering processes designed to dispose of manure or reduce odors. Odors, however, are only a small part of the overall emission profile; other gases of environmental and ecological concern, e.g., ammonia, methane, nitrous oxide, and hydrogen sulfide, are released as part of the overall digestion process.

Particulates generally are a consequence of interactions of animals with their environment. In concentrated housing facilities, bedding, manure, litter, and animal byproducts such as feathers; and the activities of mixing and distributing feed; can generate particulates. Animal activity within housing, during transport, or due to other husbandry efforts can cause particulates to become airborne. In external housing facilities, animal movement on dry soil and manure can produce significant dust problems. Aerosols can be generated any time in the presence of a water source and air movement. Numerous farm management procedures generate aerosols, including misting or spraying to cool animals, manure separation techniques, spray irrigation, and spraying to control dust. PM-10 standards and the pending regulation of PM-2.5 increase the urgency to address the sources and amounts of particulate emissions.

Little is known about the interaction of ammonia with other nitrogen or sulfur species in the atmosphere that would suggest a difference among locations (urban environments with large production of these compounds compared to rural environments with relatively low concentrations). Ammonia as a compound or as a precursor of PM-2.5 is of concern both environmentally and ecologically, and understanding the role of livestock production systems on ammonia emission and dispersion is critical to regulating and managing air quality in the context of confined animal feeding operations (CAFOs).

Odors can impact the well-being of workers and animals. Perceptions of odors by neighbors and government regulation of odor emissions can have serious economic consequences for farmers. Greenhouse gases contribute to global warming and the reduction of stratospheric ozone. Unfortunately, most of the greenhouse gases released from livestock facilities are a necessary consequence of production. The major exceptions are methane production related to storage and use of manures and gas production from manure processing systems.

Particulates can cause respiratory problems in humans and animals, either directly or by carrying pathogens, endotoxins, or allergens. Pathogen distribution via particulates can be a source of disease. Health problems of workers and animals in concentrated housing situations are a particular concern.

Given our lack of understanding of the emission and dispersion of gases and particulates, we can not reliably predict the environmental impact of current animal production systems. Given further our lack of understanding of the human perception of odors and our inadequate ability to quantify odor emissions, it is difficult to assess the dispersion pathways over complex terrain and to develop gaseous and particulate emission control practices.

The objectives of the Manure and Byproduct Utilization National Program are to (1) address the measurement of compounds associated with animal production and manure storage; (2) elucidate the mechanisms responsible for the formation of these gases; (3) determine the rates of emission; (4) evaluate the role of environmental conditions on emission generation and transport; (5) define impacts of emissions; and (6) develop cost-effective methods to control emissions. The Air Quality National Program focuses on determining emission rates from different systems and practices of livestock production, manure storage and handling, and manure application and dispersion of these emissions across the landscape. The linkages between these two programs are critical to the needs of the public. Additionally, collaborative linkages will be important with EPA, NOAA, FDA, CSREES, Natural Resource Conservation Service (NRCS), U.S. Forest Service (FS), DOD, Department of Energy (DOE), universities and land grant institutions, and the equipment industry.

Vision

Livestock production systems with no atmospheric impact

Mission

Develop practices and technologies for animal production systems that minimize gaseous and particulate emissions and human health impacts and provide information for science-based policy and regulation decisions