Air quality can be affected by aerial emissions of pollutants from poultry production facilities. Ammonia emitted into the atmosphere is arguably the most environmentally significant aerial pollutant associated with poultry production. The transport and fate of ammonia once it is emitted into the atmosphere are not well understood, but its presence in high concentrations can trigger environmental effects that have impacts on local ecosystems and human health.
As such, consideration of the environmental effects on airsheds and watersheds of nutrient loading from poultry production is important for long-term sustainability. Ammonia from poultry operations is derived from nitrogen, which is an essential component of dietary protein, amino acids and other biomolecules necessary for life. However, dietary nitrogen not converted into meat, eggs or other tissue is excreted in the form of organic nitrogen, which is rapidly converted into ammonia under most, but not all, poultry production practices.
The amount of ammonia actually emitted into the atmosphere depends on multiple variables, including climate, poultry housing design, and manure and litter storage and treatment practices, such as methods for applying them to land. Hydrogen sulphide and other VOCs can result from the metabolic breakdown of poultry waste products, generally under low-oxygen conditions such as occur when manure is allowed to ferment (anaerobically digest) in a pit beneath the birds, in an earthen lagoon or in other open-air containment. This type of waste operation is more common with swine or dairy livestock than poultry, but may occur in some locations with layer operations.
Under open-air fermentation, hydrogen sulphide and VOCs can be emitted into the atmosphere as pollutants, and can also be components of nuisance odour. Hydrogen sulphide can be dangerous to humans at certain concentrations.
Particulate matter (or dust) is an aerial pollutant of more concern than hydrogen sulphide and VOCs. It occurs in typical poultry operations where appreciable numbers of birds are confined.
Dust emissions can contain dried fecal matter and may include bacteria, endotoxins, moulds, mites and insect parts. Dust emissions from housing facilities are highly variable, depending on the climate, building design, feed consistency (dry or pellet) and control mechanisms for preventing large dust particles from leaving the area near the building – in recent years, considerable progress has been made in developing low-cost dust barriers to prevent dust dispersion.
Fine particulate matter (e.g., PM-fine) resulting from the conversion of ammonia gas in the atmosphere into ammonium salts can have greater consequences for human health, and is less likely to be mitigated by dust barrier approaches for preventing larger dust particles. This is another of the factors that make aerial ammonia emissions so important.
Climatic conditions play a very significant role in the impacts from aerial poultry pollutants, regardless of flock size. For example, excessively dry conditions, especially in litter, result in increased respiratory conditions affecting birds’ productivity, while excessively wet litter results in increased ammonia concentrations (and pathogenic microorganisms), which are also detrimental to productivity.