Airborne emissions from livestock and poultry operations include numerous odorous gases and associated particulates that are easily transported in the air. The sources of odor are the building housing the animals, associated manure storage units, and the mostly intermittent land application of the manure onto cropland. The odorous gases released are by-products of mostly anaerobic decomposition / transformation of livestock wastes by microorganisms. The wastes include manure (feces and urine), spilled feed and water, bedding materials (straw and wood shavings), wash water, and other wastes. This highly organic mixture includes carbohydrates, fats, proteins, and other nutrients that are readily degradable by microorganisms under mostly anaerobic conditions. A large number of volatile compounds are produced in this decomposition process with at least one study identifying 168 different compounds. Release of these compounds occurs at exposed surfaces such as pens floors, surfaces of manure storage lagoons or tanks, and when manure is spread onto cropland for nutrient recovery. Once in the air these compounds diffuse through and are transported by air currents where they disperse into the atmosphere. Some compounds adsorb onto airborne particles and other surfaces and react chemically, which can have detrimental effects on the environment and atmosphere.

Presently, emission rates of these compounds are beginning to be measured and determined. Regulatory agencies, both federal and state, are becoming concerned about air emissions from livestock and poultry operations. Research is proceeding to develop control technologies that will reduce the environmental and human impact of these emissions.