Jump to main content or area navigation.

Contact Pacific Southwest Animal Waste

Pacific Southwest, Region 9

Serving: Arizona, California, Hawaii, Nevada, Pacific Islands, Tribal Nations

What's the Problem?

On this page:


What Are AFOs?

Animals crowded together form a Concentrated Animal Feeding Operation
This large feedlot meets the criteria of an AFO and a CAFO.
Rainfall plus manure produces sewage overflow
Stormwater runoff from an agricultural field where manure was applied.
Animals crowded together form a Concentrated Animal Feeding Operation
Concentrating animals puts more emphasis on proper manure management.
This full cesspit will likely overflow when rain comes
Improperly designed facilities can lead to improper discharges.

Animal feeding operations (AFOs) are farms or feedlots where animals are kept and raised in confined areas for at least 45 days over a 12-month period. AFOs cluster animals, feed, manure and urine, wastewater, dead animals, and production operations on a small land area. Feed is brought to the animals rather than the animals grazing in pastures, fields, or on rangeland. There are approximately 450,000 AFOs in the United States. Common types of AFOs include dairies, cattle feedlots, and poultry farms.

Benefits and Costs of AFOs

A strong livestock industry is essential to our nation's economic stability, the viability of many rural communities, and a healthy and high-quality food supply. However, the growing scale and concentration of AFOs has contributed to negative environmental and human health impacts. Pollution associated with AFOs degrades the quality of waters, threatens drinking water sources, and may harm air quality.

Animal Waste and Waste Management

By definition, AFOs produce large amounts of waste in small areas. For example, a single dairy cow produces approximately 120 pounds of wet manure per day. The waste produced per day by one dairy cow is equal to that of 20-40 people. If properly stored and used, manure from animal feeding operations can be a valuable resource. Applying manure to land can be an environmentally sound approach to fertilizing fields. Manure can also be used in digesters (machines which decompose manure and capture the methane gas emitted) to produce electricity, and other useful by-products such as ethanol. However, if not managed correctly, the waste produced by AFOs can pollute the environment – especially water.

Consequences of Waste Mismanagement

Improperly stored or used, animal waste can pollute rivers and underground drinking water supplies. Inadequately sized and poorly-lined ponds or other storage structures allow manure to escape into the surrounding environment. Poorly maintained and unlined corrals let contaminated wastewater containing to seep into ground water.

Many AFOs also lack necessary stormwater runoff controls, such as berms, that divert rain water and snow melt from the animal confinement area. Stored manure gets washed into nearby streams. Applying too much AFO wastewater to fields too quickly or by inadequate methods, can also cause the contaminants in animal waste to pollute streams or ground water before they can be completely absorbed by the land and crops.

In some cases, an AFO's location -- for example, on hillsides, along streams, and atop sensitive ground water areas -- complicates sound animal waste management. Animal waste has the potential to contribute pollutants such as nutrients (e.g., nitrate, phosphorous), organic matter, sediments, pathogens (e.g., giardia, cryptosporidium), heavy metals, hormones, antibiotics and ammonia to the waters we use for drinking, swimming and fishing. In addition to water quality problems, AFOs can also contribute to significant air quality problems, including dust, smog, greenhouse gases, and odors.

Top of page

Drinking Water Impacts

This waste-filled corral will leak into groundwater supplies
The build up of wastewater and manure in a corral can leach nitrates into groundwater.

When contaminants from animal waste seep into underground sources of drinking water , the amount of nitrate in the ground water supply can reach unhealthy levels. Infants up to three months of age are particularly susceptible to high nitrate levels and may develop Blue Baby Syndrome (methemoglobinemia), an often fatal blood disorder.

The microorganisms found in animal wastes, such as cryptosporidium, can also pose significant public health threats. For example, after a severe rainstorm in 1993, an outbreak of cryptosporidium in Milwaukee's drinking water supply caused 100 deaths and sickened 430,000 people. If the presence of these microorganisms exceeds the standards set by the Safe Drinking Water Act, community and private well owners will not only face health risks, but will also have to find new sources for their drinking water supplies. This can be extremely costly and impractical.

River and Stream Impacts

Nutrient runoff from manure has choked this pond with algae
Excess nutrients can lead to algal blooms.

Manure, and wastewater containing manure, can severely harm river and stream ecosystems. Manure contains ammonia which is highly toxic to fish at low levels. Increased amounts of nutrients, such as nitrogen and phosphorus, from AFOs can cause algal blooms which block waterways and deplete oxygen as they decompose. This can kill fish and other aquatic organisms, devastating the entire aquatic food chain.

Air Impacts

In general, air quality problems associated with AFOs are caused by gases emitted from the decomposition of animal wastes and by the dust generated by animal activity and farming practices. These air pollutants can cause respiratory illness, lung inflammation, and increase vulnerability to respiratory diseases, such as asthma. Emissions of reactive organics and ammonia from AFOs can play a role in the formation of ozone (smog) and particulates, air pollutants regulated by Clean Air Act to protect public health. Soil disturbance by animals or farm equipment can generate particulate matter. Emissions from AFOs are a major concern in areas, such as the San Joaquin Valley and California's South Coast, where ozone and particulate matter often exceed national health standards.

In addition to negative health impacts, ozone can reduce agricultural yields and make plants more vulnerable to disease. Odorous and potentially toxic gases, such as sulfur dioxide, produced by the decomposition of animal wastes, may also cause nausea, headaches, and throat and eye irritation after prolonged exposure. Methane emissions from waste decomposition at AFOs also contribute to global warming. EPA's AgStar program encourages the use methane recovery technologies at animal feeding operation. Recent studies of air emissions from AFOs are listed in the bibliography.

Cross-Media Recognition

As mentioned above, animal feeding operations can affect multiple pollutant media streams. In addition, methane emissions from an AFO can provide a potential energy source and nutrients in the manure and wastewater are a valuable fertilizer. Recognizing the need to look at animal feeding operation waste management in a comprehensive or systems approach, EPA helped form the Dairy Manure Collaborative, which has begun working with stakeholders to develop voluntary, multimedia approaches towards managing waste streams at animal feeding operation. For example, the San Joaquin Valley Dairy Manure Technology Feasibility Assessment Panel recently produced a report assessing technologies for management and treatment of dairy manure.

Top of page

Pacific Southwest NewsroomPacific Southwest Programs Grants & FundingUS-Mexico Border News & EventsCareers About EPA Region 9 (Pacific Southwest)A-Z Index

Jump to main content.