PARTICULATE MATTER EMISSIONS FROM ANIMAL FEEDING OPERATIONS

Abstract

Animal feeding operations (AFOs) are a fast-growing sector of production agriculture in theUnited States. In general, AFOs are facilities in which livestock or poultry are fed in confined areasor buildings in which native vegetation cannot be sustained and to which manufactured, processedor mixed feed must be supplied from without. They exist and grow primarily as a result of economiesof scale, affording producers the opportunity to minimize costs associated with transportation,feeding and harvest.<br><br>The concentration of animals in an AFO puts stress on the environment in several ways. Mostbroadly, because conversion of feed to marketable end products is inherently inefficient, AFOs tendto accumulate unused nutrients and other feed-derived by-products until they are somehow exportedfrom the system. Moreover, because the boundary of a livestock system is of arbitrary extent,this net accumulation of nutrients or other by-products may occur at multiple scales, from thefarmstead to the watershed to the geographical region depending on the relative marketability ofby-products at each of those scales.<br><br>The accretion of by-products in localized areas increases environmental stress by (a) providing areservoir of potential environmental contaminants and (b) increasing the gradient by which thosecontaminants can move into an otherwise nave environment. For example, accumulation of phosphorusin stream sediments may increase both (a) the concentration gradient driving the diffusionof phosphorus from the sediments into the streamflow and (b) the length of time required to depletethe phosphorus reservoir in those sediments. Virtually every environmental stress associated withanimal feeding can ultimately be traced to system inefficiencies and lack of markets for the lowvalueby-products resulting from them.<br><br>One of the ascendant forms of environmental stress associated with AFOs is air pollution. Traditionallydefined, air pollutants are compounds or materials that, when suspended in or mixed withair, degrade air quality and impair its utility for any of a wide range of purposes. Although the publicassociates air pollution most commonly with haze, smog or other low-visibility conditions, pollutantshaving little to no effect on visibility may threaten the health of humans, animals and otherliving organisms. One class of pollutants having both health and visibility implications is particulatematter.