Waste Stabilization. Stabilization is the treatment of manure to reduce odor and volatile solids prior to land application. Run-off from drylots and liquid manure from flush alleys are often stabilized in anaerobic lagoons. Anaerobic lagoons use bacterial digestion to decompose organic carbon into CH4, CO2, water and residual solids. Single-cell systems combine both stabilization and storage in one earthen structure whereas two-cell systems separate stabilization and storage (i.e., anaerobic lagoon followed by a storage pond).
Waste Stabilization. The anaerobic lagoon has emerged as the overwhelmingly predominant method used for the stabilization and storage of liquid swine manure. Methods of aerobic stabilization (e.g., oxidation ditches or aerated lagoons) were abandoned many years ago due to high electricity costs and operational problems such as foaming. Solids separation is typically not practiced at swine facilities. Several factors have contributed to the use of anaerobic lagoons for swine waste management. One is the ability to handle the manure as a liquid and use irrigation for land application. A second is the potential to reduce noxious odors by maximizing the complete reduction of complex organic compounds to CH4 and CO2, which are odorless gases. Finally, the use of anaerobic lagoons in the swine industry was driven, in part, by the potential to maximize nitrogen losses through NH3 volatilization thereby reducing land requirements for ultimate disposal. With the shift to phosphorus as the basis for determining acceptable land application rates for animal manures, maximizing nitrogen loss is ceasing to be an advantage. The design and operation of anaerobic lagoons for swine and other animal manure has the objective of maintaining stable populations of the microorganisms responsible for the reduction of complex organic compounds to CH4 and CO2. The microbial reduction of complex organic compounds to CH4 and CO2 is a two-step process, in which a variety of VOCs are formed as intermediates. Many of these VOCs, such butyric acid, are sources of noxious odors when not reduced further to CH4. Methanogenic microorganisms have slower growth rates than the microbes responsible for the formation of VOCs. Therefore, anaerobic lagoons must be designed and operated to maintain a balance between the populations of these microorganisms and methanogens to avoid accumulations of VOCs and releases of associated noxious odors. Both single cell and two cell systems are used for the stabilization and storage of swine manure. In single cell systems, stabilization and storage are combined. In a two-cell system, the first cell has a constant volume and provides stabilization while the second cell provides storage. With two cell systems, water for pit recharge or flushing is withdrawn from the second cell. In climates with low precipitation and high evaporation rates, there may be one or more additional cells for the ultimate disposal of excess liquid by evaporation. Anaerobic lagoons use bacterial digestion to...
