Poultry Manure Treatment And Utilization

Most poultry manure is used for crop and pasture fertilization as a cost-effective alternative to inorganic mineral fertilizer. Land application also recycles nutrients, enhances soil fertility, and improves soil physical properties. However, a balance must be maintained between maximum utilization of nutrients by crops and the risk of health and environmental impacts. Proper managing of poultry manure from its production through utilization is the key to maintaining this balance. This includes proper design and siting of housing, manure storage, and mortality management facilities; and comprehensive nutrient management planning. Education and training of managers and operators of poultry production systems are essential for good manure management.

Manure and soils receiving manure should be tested for available nutrients before application. Application rates have typically been based on N requirements of crop. For soils testing high in P, manure application should be based on the crop's P requirements. Manure application that exceeds a crop's ability to take up N may threaten water quality. Nitrogen as nitrate is a highly mobile compound that may cause human and animal health problems if drinking water concentrations are greater than 10 mg/l. Soil P enrichment occurs as a result of overfertilization with P. Phosphorus applied to fields as inorganic fertilizer or from manure can move into bodies of water through erosion and runoff events and can accelerate eutrophica-tion (the natural aging process of lakes and streams), leading to excessive algae growth, oxygen deficiency, and fish mortality.

Some of the liquid or solid manure may be put to alternative uses, with or without undergoing a treatment process. Liquid manure from layer operations is sometimes stored and treated in anaerobic (oxygen-free) lagoons and further diluted with additional water, while anaerobic bacteria biodegrade volatile organic compounds. Part of the total solids in manure are settled as sludge at the lagoon bottom, while the supernatant (the liquid standing above suspended solids and sludge) can be recycled for flushing layer houses and irrigated as a source of nutrient and water for plants.

Liquid poultry manure may also be anaerobically digested in insulated, airtight containers (digesters) to produce biogas (methane and carbon dioxide). The methane gas produced with this treatment process is combustible and can be harvested to produce energy. This energy can be converted to electricity. The closed biogas digesters also control manure odors.

A small portion of the litter and straw, hay, or crop residue may be used as a carbon source for animal mortality composting, with the resulting compost used as fertilizer. In some parts of the United States, broiler litter or dried layer manure is used in the microbial mixture to supply nutrients for Agaricus mushrooms.[4]

Broiler

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turkey

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Chicken Litter Storage Methane Alarmwww.dekker.com.)"/>
Fig. 1 Waste storage management and utilization options for poultry operations. (Adapted from USDA NRCS Agricultural Waste Management Field Handbook, Part 651.) (View this art in color at www.dekker.com.)

Direct incineration of raw broiler litter with high ash content (soil and other incombustibles in the litter) in conventional furnaces has proven difficult due to incomplete combustion, slag formation, odor, gas, and particulate emissions to the environment. On a commercial scale, electric power generation plants in the

United Kingdom are firing poultry litter as a furnace fuel to generate boiler steam. The ash produced from litter combustion is recovered and sold as nutrient-rich fertilizer.[5]

The feasibility of cofiring biomass (poultry litter and beef feedlot manure) with coal as a fuel for energy generation is currently being studied in the United States.[6'7] Preliminary results from small-scale boiler experiments show that blends of coal and biomass can be successfully fired, and that nitrogen oxide pollutant emissions were similar to or lower than those from firing coal only.

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