The swine industry has moved rapidly toward specialized, highly concentrated production systems and a vertically integrated business organization. That trend is expected to continue not only in the United States but, as integrated companies expand offshore, the production systems developed in the United States will be replicated elsewhere. Specialized, concentrated production systems in agriculture, and especially those for poultry and swine, are responsible for the high efficiency and ability to deliver consistent products at increasingly affordable prices in all markets. Because concentrated production is often not located close to the cropland that is the site of feed production, which has historically served as the recipient of the animal waste for fertilizer, land application of waste has often exceeded the capacity of the crops growing on the land to assimilate the nutrients. This results in the possibility of surface and groundwater contamination by the nutrients and pathogens in the waste. In addition, high concentrations of animals have been associated with local concerns about emitted odors and regional concerns about emitted ammonia.

Swine production is substantially conducted in confinement facilities in which animals are housed in pens with slatted floors and without bedding. Currently, swine waste (solid and liquid), as well as spilled drinking water and feed, drops through the slats in these floors into a pit where it is held for variable lengths of time depending on the subsequent handling system. Currently used swine handling systems, new technologies, new developments, and criteria for evaluation of swine waste management systems are addressed in this article.

United States.[1] Lagoons are usually formed by excavation and embankment of earth to a depth of 8 10 feet (depending on the position of water table) and lined with compacted clay, rubberized fabric, or other impervious material (depending on the prevailing regulations). The lagoon receives the waste from the production facilities flushed by either release of large volumes of liquid recycled from the top portion of the lagoon (traditionally 800 gallons/flush/half of building, repeated two to six times daily) or release of 30,000 40,000 gallons of pit-recharged liquid and waste, approximately once weekly, from a recharge of lagoon liquid. In both systems, the high flow volume and the slight slope of the waste-receiving pit under the pens (1 1.5% slope) result in effective gravity waste removal from the barns. The waste streams from each of these two commonly used systems (containing less than 2% solids) may be passed through a short-retention settling basin to allow heavy solids to be retained. Once the waste materials are in the lagoon, anaerobic breakdown occurs in a complex series of reactions. While there is a loss of volatile materials from the lagoon surface (carbon dioxide, methane, ammonia, nitrogen gas, and other volatile compounds), most of the nutrients are retained in the organic phase as microbial cells (settled to bottom as sludge) or inorganic elements.[1]

Periodically, material from the lagoon is applied to cropland as a source of nutrients, with application rate governed by the requirement for nitrogen (and, more recently, phosphorus) of that specific crop. Application schedule is governed by regulations including weather and growing season. Occasionally hydraulic loading rate of the application field is a limitation.

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