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CAFO Home > Facts About CAFOs

Facts About CAFOs

Table of Contents:

What is a CAFO?

A concentrated animal feeding operation (CAFO) is an industrial-sized livestock operation. CAFOs are a type of animal feeding operation (AFO), which the U.S. EPA defines as operations in which animals are confined in a grass- and vegetation-free area for at least 45 days out of the year. The "concentrated" part of CAFO comes from the fact that many animals are housed in close quarters in CAFOs. Large CAFO in Lenawee County, visible are 4 barns and 3 pits.

According to the Wisconsin DNR, farms that meet one of the following criteria qualify as CAFOs:

  • Includes 1000 or more "animal units" (roughly the equivalent of 700 milking and dry cows or 100,000 laying chickens)
  • Includes fewer than 1000 animal units but discharges waste into navigable waters or contaminates a well


CAFOs are designed to maximize output from limited land. Because space is limited, hundreds or thousands of animals are packed together, often with restricted movement. These close confines can become a breeding ground for disease. To counter the threat of disease, farmers often administer antibiotics to their livestock.

Due to their size, CAFOs generate an enormous amount of waste. According to the Wisconsin DNR, one dairy cow produces about as much waste as 18 people. That means that a single 2000-cow dairy operation can produce roughly as much organic waste as the city of Greenfield, WI (pop. 36,720). This waste has to end up somewhere. Often, it ends up in our water and air.

In Wisconsin, there are currently 233 CAFO operations that hold waste discharge permits. You can find a map of statewide CAFOs here.


What are the different kinds of CAFO?

CAFOs can be classified into two main types: barns and feedlots. The type of CAFO dictates the method of waste disposal used on the farm.

In barns, animals are housed in buildings that they seldom leave. Removing wastes from these buildings is a major challenge.

  • Dairy and swine CAFOs often use clean water to wash animal wastes and contaminants from the buildings into waste-storage structures or lagoons.
  • Poultry CAFOs use dry-waste systems. The waste falls from animal cages to the floor, where it is scraped out of the building periodically or collected on conveyer belts and moved to composting or storage sites.

On feedlots, animals are kept outdoors in pens. Here, the manure waste accumulates on the ground, often washing off with rainwater into nearby ditches and streams.


What pollutants do CAFOs produce?

Brown liquid enters Lime Lk Drain, with plume clearly visible.
CAFOs produce huge amounts of animal sewage and other pollutants. Animal waste can contain the following substances that threaten human and wildlife health:

  • Pathogens. Manure can contain bacteria such as E. coli, Listeria, and salmonella and other microscopic organisms like cryptosporidia. These organisms can cause severe illness and even death in people and animals that consume them, especially those with compromised immune systems.
  • Pharmaceuticals. Because the close confinement in CAFOs facilitates the spread of disease, farmers often administer antibiotics and other medicines to their livestock. Those medicines end up in animal waste, possibly contributing to the growth of antibiotic-resistant bacteria.
  • Excessive nutrients. Manure is full of nutrients like nitrogen and phosphorus, which is why manure is used as a fertilizer on crops and gardens. However, too much of these nutrients can have adverse effects. When nitrogen compounds called nitrates get into drinking water, they can cause a potentially fatal disease in infants known as blue baby syndrome. Additonally, excessive phosphorus leads to blue-green algae growth, which is detrimental to water quality, health, and property values.
  • Harmful gases. Bacteria in manure storage pits break down the manure, releasing gases as a byproduct. These gases include methane, carbon dioxide, ammonia, and hydrogen sulfide, which can cause serious issues. Hydrogen sulfide, for instance, can cause irreversible neurological damage. Meanwhile, carbon dioxide and methane are greenhouse gases. Aside from effects on public health and the environment, CAFOs and the fields that receive their waste emit a strong stench that can diminish quality of life for neighbors.

CAFO waste can also include heavy metals, hormones, cleaning agents, milkhouse wastes, ammonia, and silage leachate.

Although CAFOs are often regulated by waste discharge permits, accidents or oversight can happen. Manure lagoons can overflow, a well's containment system can fail, or farmers can consciously or unconsciously dispose of waste inappropriately. In these cases, there can be drastic consequences for neighboring humans and ecosystems. However, even CAFOs operating within regulations can release harmful substances into our water and air.


How do CAFOs pollute water?

Water pollution is possible at virtually any point in a CAFO's operation.

Truck spraying manure onto white snow covered field in February 205.

  • In the production area, spills, overflows, and tracking of wastes on tractor and truck tires can cause surface runoff of contaminants.
  • Stormwater that mixes with manure wastes, silage leachate, or milkhouse wastes can flow into drains.
  • Pipes or hoses carrying wastes can break or become unattached. Waste storage structures can overflow or burst.
  • Field tiles or catch basins can drain waste directly into surface waters.

When CAFO wastes are applied to farm fields, the waste can pollute water bodies through overapplication, washing away with stormwater, or directly entering water bodies from field drainage systems. Water pollution can also occur due to equipment failure, such as an improperly calibrated manure spreader.

CAFO wastes can also contaminate groundwater by seeping into the water table from leaking waste storage structures or from fields on which waste has been over-applied. CAFO waste in groundwater can threaten wells. Groundwater is difficult to monitor, so the extent and source of contamination are often harder to pinpoint than surface water contamination.


How do CAFOs pollute air?

The malodorous and potentially harmful gases that CAFOs produce can come from the following sources:

  • Barns where the animals are housed


The air pollution inside the buildings is potentially harmful to the animals and humans inside if the fans ever stop operating. Normally, the fans simply blow the contaminated air to the outside where it can pollute the whole community. Poultry operations blow ammonia and particulate matter, including feathers and chicken feces, out of the buildings.

  • Waste storage structures
  • Handling of the wastes


The CAFO wastes stored in waste storage structures is not treated or aerated, often resulting in extreme off-gassing of pollutants such as hydrogen sulfide (H2S) when the wastes are transported and sprayed onto farm fields. 

  • Land application of waste


Once or twice a year, waste storage structures are scraped and the thick, fermented wastes are spread onto farm fields, causing even worse air pollution.


How efficient are CAFOs?


One of the arguments for the shift to a CAFO-based agricultural system is the supposed efficiency of CAFOs. It's true that CAFOs can produce large amounts of ostensibly cheap food. However, this seeming benefit of CAFOs comes at a high cost to taxpayers. According to a report on CAFOs by the Union of Concerned Scientists, "the CAFO system is driven not by efficiency but primarily by the market power held by large processors and public policy" (Gurian-Sherman 2008). The report points out that agricultural policies such as the subsidization of feed corn and waste removal are behind-the-scenes perks for CAFOs that keep their operating costs (and, therefore, the cost of CAFO-produced food) artificially low.

CAFOs receive many subsidies, such as milk price support guarantees, federal EQIP money through the Farm Bill, tax abatements, grants, bonds, even economic development funds for roads. Meanwhile, smaller farms that can't compete with the low prices CAFOs can afford are driven out of business.

Finally, CAFOs' impact on public health and the environment diminishes their relative cost-effectiveness. If taxpayers have to shoulder the burden of cleaning up contaminated drinking water and treating diseases caused by CAFO byproducts, the additional costs negate the low cost of CAFO-produced food.


How are CAFOs regulated and permitted?

Federal laws establish minimum standards for the regulation of any activity that causes air pollution or water pollution. However, through aggressive lobbying by the promoters of CAFOs, federal laws for the environmental oversight of CAFOs are extremely weak.

Currently, the U.S. Environmental Protection Agency provides no regulation of air pollution problems from CAFOs. The Emergency Planning and Community Right-to-Know Act (EPCRA) is designed to help local communities protect public health, safety, and the environment from chemical hazards. Under this act, large CAFOs are exempt from federal reporting responsibilities. The only requirement for large CAFOs is that they must report large ammonia or hydrogen sulfide emissions to state and local emergency response officials.

The federal Clean Water Act does provide some regulation of CAFOs, although interpretations of the extent of those requirements are being litigated. State laws must be at least as restrictive as the federal law, but in Wisconsin and some other states citizens have needed to bring challenges to state's delegation under the Clean Water Act to force the agencies to implement the laws. Federal law requires that any CAFO which has had an illegal discharge into surface waters must obtain a National Pollutant Discharge Elimination System (NPDES) permit in order to continue operations.

Wisconsin is authorized by the federal government as a permitting agency requiring CAFOs to obtain a Wisconsin Pollutant Discharge Elimination System (WPDES) permit. CAFOs are considered point sources, which are specific, identifiable sources of pollution. However, regulation of CAFOs and their impact on environmental quality can be less stringent than regulation of other polluters. For example, according to this fact sheet from Midwest Environmental Advocates, CAFOs are not required to treat waste before spreading on land or to obtain an air pollution permit, unlike other waste dischargers.



This content was adapted from materials developed by the Sierra Club Michigan Chapter Water Sentinels Program, with support from The Sierra Club, and are used here with permission. If site visitors wish to use these materials, please contact Rita Chapman at or Lynn Henning at for permission. Original materials can be found at