Animal feeding operation

The Environmental Protection Agency defines an animal feeding operation (AFO) in the Code of Federal Regulations (CFR, Federal Register, V. 68 No. 1, page 7265) as a lot or facility (other than an aquatic animal production facility) where the following conditions are met:

The definition of an AFO was developed by EPA as a regulatory definition to delineate confined feeding of beef cattle, dairy cattle, horses, swine, sheep, poultry, or other livestock from pasture-based systems (grazing systems were not meant to be regulated by EPA) for enforcement of the clean water act. The AFO classification is meant to apply to all sizes of operations and is the first step in defining an operation as a Concentrated Animal Feeding Operation. Concentrated Animal Feeding Operations are facilities that require federal National Pollutant Discharge Elimination System (NPDES) water quality permits, irrespective of size. While state regulations differ from state to state, changes in 2003 to the NPDES permit program forced most state programs to adopt the AFO and CAFO designations, and thus the regulatory definition of an AFO is common across the United States.

EPA did not explicitly differentiate AFOs by size in the Code of Federal Regulations, but is commonly understood as follows.

Classification of AFOs follows the delineation of CAFOs, small, medium, and large. Large AFOs are automatically termed Large CAFOs based on size designation alone.

A small AFO would be delineated as follows:

A medium AFO would be delineated as follows:

Small and medium AFOs can be designated as Concentrated Animal Feeding Operations based on their risk to surface water. There are two conditions EPA and state regulatory authorities consider that if either are met, change the designation of an AFO to that of a CAFO.

This is often interpreted by regulators to mean that water runoff, manure, or process wastewater that can leave a facility and can come into contact with surface water, such as a road ditch, stream, river, pond, dam or similar watercourse, meets this definition, and thus pull medium AFOs into the permit program. EPA means for a medium AFO that meets this contact with surface water criteria to apply for coverage under the NPDES permit program (then designated a medium CAFO). However, for small AFOs the state regulatory authority must designate the operation as a CAFO in order for them to meet the definition of a small CAFO.

...
Wikipedia