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Waste Composting

Manure composting guidelines may be found in numerous sources, including the following: Summary:

Composting involves decomposition of organic manure materials (USEPA, 2001a), and is a common and relatively inexpensive method of handling livestock manure. This is a natural process that converts animal wastes, bedding, and other raw products into humus, and is enhanced and accelerated by the mixing of organic waste with other ingredients in a prescribed manner for optimum microbial growth (USDA, 1999).

Composting manure reduces many of the typical drawbacks associated with raw manure use. Well-composted material is typically odorless, fine-textured, and low in moisture, and can be bagged and sold for use as a fertilizer with little odor or fly breeding potential. Using composted waste as soil fertilizer instead of raw manure can greatly reduce odors emanating from those areas. The availability of phosphorus, potassium, and micronutrients is greater in most compost than the raw manure, while nitrogen in compost is not as readily available.

Aerobic composting reduces the mass and volume of the waste, reduces odors, can inactivate pathogens and kill weed seeds, stabilizes manure for easier handling, converts inorganic ammonia to an organic form of nitrogen (stable humus has virtually no free ammonia or soluble nitrate), and can result in a valuable soil amendment. Aerobic composting generates carbon dioxide, water vapor, and heat. Temperatures often reach 40 to 65°C during the active composting phase, and are capable of inactivating or killing assorted animal pathogens and parasites as well as weed seeds.

Anaerobic composting is used less frequently, as it is a less rapid process than aerobic composting, is not nearly as good at eliminating odors (odor production is a primary reason anaerobic composting is not frequently used), and does not result in high temperatures like aerobic composting. Anaerobic composting produces methane and carbon dioxide, and may also generate ammonia, organic acids, and hydrogen sulfide.

Compost sites should be covered if possible to prevent precipitation from soaking the plies, and if not then rainfall runoff should be contained and controlled. Sites should not be located near drinking water wells and surface waters, and should be on relatively flat ground where water does not run off or collect (USEPA, 2001a). Proper carbon-nitrogen ratios need to be maintained, so organic material is often added to the waste piles. Appropriate moisture content is also important for optimal composting. Aerobic compost piles need to be turned periodically to provide oxygen (or provided some other method of aeration). Aerobic composting should take place at the correct temperature, and pathogens can be killed if an appropriate length of time is used.