This publication provides a general overview of anaerobic digestion and the current status of biomethane technology on livestock farms in the United States. It is part of the Bioenergy Engineering Education Program (BEEP) of the Biological Systems Engineering Department at Virginia Tech. Most of the discussion uses dairy manure as an example of feedstock for an anaerobic digester. Resources which provide more detailed information on anaerobic digesters are listed.

An acceptable system of disposal for dead birds is essential to any well run poultry farm operation. Moreover, Virginia law requires that poultry producers have an approved means for disposing of dead birds. There are generally two categories of disposal problems: (1) Normal mortality, which is typically about 0.1 percent per day, but fluctuations up to 0.25 percent per day are not uncommon, and (2) Whole flock disposal.

Poultry litter (poultry manure and a bedding material such as sawdust, pine bark, or peanut hulls) is a good source of nutrients and organic matter for growing crops. Land application of poultry litter on farms has been the mainstay of effective and safe usage for years. Unfortunately, improper management of litter applications may cause nutrient enrichment and/or contamination of surface and ground water resources. The key to proper management is an understanding of the nutrients available in the litter, the nutrient requirements of the crops to be produced, and the potential for the litter and/or nutrients to reach surface or ground waters.

In recent years, large concentrations of poultry on small parcels of land have made the manure disposal problem more critical. When nutrients from manure or commercial fertilizers exceed the ability of crops to utilize them, surface runoff and groundwater pollution problems develop. This fact sheet outlines management steps to take advantage of the fertilizer value of poultry litter while minimizing potential damage to Virginia’s water resources.

Storage of livestock wastes involves accumulating manure and wastewater in an environmentally sound manner until they can be applied to land or otherwise utilized. Manure storage facilities allow farmers to spread manure when conditions are right for nutrient use by crops. Storing manure in a concentrated area, however, increases risk to the environment and to human and animal health. Fecal bacteria in livestock waste can contaminate groundwater, causing such infectious diseases as dysentery, typhoid and hepatitis.

Wastewater from the dairy milking center includes wastes from the milking parlor (manure, feed solids, hoof dirt) and milk house (bulk tank rinse water and detergent used in cleaning). The amount of wastewater generated varies with milking preparation, equipment use, and the number of cows. A milking center for a 100-cow free-stall operation may use anywhere from 100 to 1000 gallons of water per day, and sometimes more.

Nearly all broiler, pullet, and breeder operations grow the birds on concrete, wooden, or earthen floors. A 2-to 6-inch layer of wood shavings, peanut hulls, or other bedding material is used as an absorptive base. The manure and bedding mixture is commonly called litter, and it is removed one or more times a year and replaced with fresh bedding material. Most broiler operations produce 1.1 to 1.4 tons of litter per 1,000 birds. For a flock of 18,000 to 20,000 birds, this amounts to between 22 and 34 tons of litter per flock.

Silage can be made from corn, grain, or alfalfa, or from canning wastes, such as those resulting from sweet corn processing. The amount of leachate (silage juices) produced varies with the material stored, its moisture and nitrogen content, and handling and storage conditions. Of these, moisture content is the most crucial.