Air Emissions and Animal Agriculture

What is a CAFO?

CAFO is an acronym originally adopted by state and national government agencies. The term was subsequently adopted by the public press and the general population. CAFO is currently a term used to generally define a large livestock farm.

CAFO originates from AFO or Animal Feeding Operation. The United States Environmental Protection Agency (EPA) defines an AFO as a lot or facility where animals are confined for a minimum of 45 days, or more, in any 12 month period and where crops, vegetative growth, forages or post-harvest residue are not sustained during the normal growing period over any portion of the lot or facility (EPA, 2011A). This definition includes barns, coops, open concrete lots and fenced dirt lots stocked at a density that will not allow pasture to grow. Animals permanently on pasture, or on pasture and then rotated to fields with crop residue, are not considered an AFO as long as they are not housed for more than 45 days. 

CAFO, or Concentrated Animal Feeding Operation, is a term EPA uses to define AFOs who may be regulated under the National Pollution Discharge Elimination System (NPDES) permitting program (EPA, 2011B).  Table 1 provides a listing of the three sizes of CAFO’s, small, medium and large, based on EPA’s definition.  Small and medium CAFO’s would only be permitted based on past violations of the Clean Water Act. All large CAFO’s are permitted under the NPDES program based solely on the number of animals/birds housed at the site.

Most state regulating agencies use the federal EPA terms AFO, farms that do not require an NPDES permit, and CAFO, those farms that may require an NPDES permit. Other states, such as Indiana, use the term AFO interchangeably with other terms such as CFO, Confined Feeding Operation.


Table 1: CAFO designation based on size of AFO *


Size Thresholds (number of animals)

Animal Sector

Large CAFOs

Medium CAFOs**

Small CAFOs***

Cattle or cow/calf pairs

1,000 or more


Less than 300

Mature dairy cattle

700 or more


Less than 200

Veal calves

1,000 or more


Less than 300

Swine (weighing >55 lbs)

2,500 or more


Less than 750

Swine (weighing <55 lbs)

10,000 or more


Less than 3,000


500 or more


Less than 150

Sheep or lambs

10,000 or more


Less than 3,000


55,000 or more


Less than 16,500

Layers or broilers (liquid manure handling)

30,000 or more


Less than 9,000

Chickens other than layers (other than liquid manure handling systems)

125,000 or more


Less than 37,500

Layers (other than liquid manure handling systems)

82,000 or more


Less than 25,000

Ducks (other than liquid manure handling systems)

30,000 or more


Less than 10,000

Ducks (liquid manure handling)

5,000 or more


Less than 1,500

*Table adopted from EPA’s Regulatory Definitions of Large CAFOs, Medium CAFOs and Small CAFOs (EPA, 2011)

**Must meet one of the two "method of discharge" criteria to be defined as a CAFO

***Never a CAFO by regulatory definition, but may be designated as a CAFO on a case-by-case basis

Some United States residents may in general believe, though not technically correct, the term CAFO is used in reference to any large livestock farm without any knowledge of actual numbers of animals housed at the facility or type of manure handling system utilized. Unfortunately some may also assume, based on that designation, that the farm is not environmentally friendly. 

It is important to recognize the regulatory designation as a large CAFO only recognizes the potential to discharge in to the waters of the state and the CAFO designation for small and medium livestock farms only recognizes a past discharge. Potential to pollute is not in any way a condemnation for polluting. Small and Medium CAFO’s may have already addressed their past environmental concerns. Therefore one should be cautious about assuming a livestock farm is not environmentally friendly based strictly on its AFO – CAFO status.  

Last Updated 11/02/2011