Feedlot Runoff

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Feedlot runoff

Feedlots are containment areas used to raise large numbers of animals to an optimum weight within the shortest time span possible. Most feedlots are open air, and are thereby subject to variable weather conditions. A substantial portion of the feed is not converted into meat, and is excreted, thus degrading the air, ground, and surface water quality . The issues of odor and water pollution from such facilities center on the traditional attitudes of producers that farming has always produced odors, and manure is a fertilizer , not a waste from a commercial undertaking.

Animal excrement is indeed rich in nutrients, particularly nitrogen , phosphorus , and potassium. A single 1,300 lb (590 kg) steer will excrete about 150 lb (68 kg) of nitrogen; 50 lb (23 kg) of phosphorus; and 100 lb (45 kg) of potassium in the course of a year. That is almost as much nutrient as would be required to grow one acre of corn, which needs 185 lb (84 kg) of nitrogen; 80 lb (36 kg) of phosphorus; and 215 lb (98 lb) of potassium. Unfortunately, manure is costly to transport, difficult to apply, and its nutrient quality is inconsistent. Artificial fertilizers, on the other hand, offer ease of application and storage and proven quality and plant growth.

Legislative and regulatory action have increased with encroachment of urban population and centers of high sensitivity, such as shopping malls and recreation facilities. Since odor is difficult to measure, control of these facilities is being achieved on the grounds that they must not pose a "nuisance," a principle that is being sustained by the courts.

Odor is influenced by feed, number and species of animal, lot surface and manure removal frequency, wind, humidity, and moisture. These factors, individually and collectively, influence the type of decomposition that will occur. Typically, it is an anaerobic process which produces a sharp pungent odor of ammonia, the nauseating odor of rotten eggs from hydrogen sulfide, and the smell of decaying cabbage or onions from methyl mercaptan.

Odorous compounds seldom reach concentrations that are dangerous to the public. However, levels can become dangerously elevated with reduced ventilation in winter months or during pit cleaning. It is this latter activity, in conjunction with disposal onto the surface of the land, that is most frequently the cause of complaints. Members of the public respond to feedlot odors depending on their individual sensitivity, previous experience, and disposition. It can curtail outdoor activities and require windows to be closed, which means the additional use of air purifiers or air-conditioning systems.

Surface water contamination is the problem most frequently attributed to open feedlot and manure spreading activities. It is due to the dissolving, eroding action of rain striking the manured-covered surface. Duration and intensity of rainfall dictates the concentration of contaminants that will flow into surface waters. Their dilution or retention in ponds, rivers, and streams depends on area hydrology (dry or wet conditions) and topography (rolling or steeply graded landscape). Such factors also influence conditions in those parts of the continent where precipitation is mainly in the form of snow. Large snow drifts form around wind breaks, and in the early spring, substantial volumes of snow-melt are generated.

Odor and water pollution control techniques include simple operational changes, such as increasing the frequency of removing manure, scarifying the surface to promote aerobic conditions, and applying disinfectants and feed-digestion supplements. Other control measures require construction of additional structures or the installation of equipment at feedlots. These measures include installing water sparge-lines, adding impervious surfaces, drains, pits and roofs, and installing extraction fans.

See also Animal waste; Odor control

[George M. Fell ]