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Environmental Consequences Of Animal Factories
The Natural Resources Defense Council

Factory farms, which mass-produce animals in assembly-line fashion, have harmed aquatic life, human health and ecosystems across the nation. As industrial-sized farms stagger under the vast burden of manure they are generating, environmental disasters are inevitable. The scale of this unprecedented outpouring of animal waste is staggering: 130 times the waste generated by humans in this country each year.

This section details how animal waste is poisoning our water and air. It also explains why more disasters are likely to occur unless the nation takes serious steps not only to regulate the way animal factories currently handle their waste but also to turn towards more benign methods of raising animals and managing the wastes they generate.

Water Pollution

Bursting and overflowing manure lagoons have spawned environmental disasters around the country, sending animal waste gushing into rivers, groundwater and coastal wetlands. In 1995, an 8-acre hog waste lagoon in North Carolina burst, spilling 25 million gallons of animal waste into the New River. The spill killed as many as 10 million fish and closed 364,000 acres of coastal wetlands to shellfishing. In 1998, a 100,000-gallon spill into Minnesota's Beaver Creek killed close to 700,000 fish. In 1997, animal feedlots were responsible for 2,391 spills of manure in Indiana. Sixty-three percent of Missouri's factory farms suffered spills between 1990 and 1994, according to Missouri's Department of Natural Resources. In 1996, forty spills killed close to 700,000 fish in Iowa, Minnesota and Missouri.

A North Carolina study of nearly 1,600 wells adjacent to hog and poultry operations showed that 10 percent of the wells tested were contaminated with nitrates above the drinking water standard, and 34 percent were contaminated with some level of nitrates. Another study in that state found severe seepage losses of nitrogen from more then 50 percent of the lagoons tested by the state, posing a risk to groundwater. While seepage can be reduced with the use of clay liners, even clay-lined lagoons may leak from several hundred to several thousand gallons per acre per day.

While spills capture public attention, the more common problem is over-application of waste onto cropland, which sends polluted runoff into waterways and leaches pollutants into the groundwater.

Too Much Manure on Too Little Land

Animal manure can be a valuable fertilizer source. But the sheer quantity of manure that is the byproduct of large-scale animal confinement operations makes it more difficult to apply manure at a rate at which it can be absorbed by crops. The quantity of manure is magnified since feedlots are often clustered in close proximity to each other in small geographic areas in order to be close to slaughterhouses and inexpensive feed supplies.

Applying too much manure to farmland sends pollutants into rivers, streams, groundwater and air, which serves as yet another pathway to water. In a North Carolina state study, the nitrates in shallow groundwater below fields sprayed with liquid manure have been measured at rates five times the human health standard; in long-term sprayfields, the rates have been as high as thirteen times the human health standard.

Pollutants of Concern

The pollution from animal waste can harm waterways, human health and aquatic life. The primary pollutants of concern are nutrients (nitrogen and phosphorus), pathogens like bacteria and viruses, and heavy metals.

Phosphorus and nitrogen from manure are major water pollutants. At high levels, phosphorus is acutely toxic to fish; at lower levels, phosphorus and nitrogen over-enrich water bodies, causing an excess of algae (a process called "eutrophication").

Oxygen in water is a basic requirement for a healthy aquatic ecosystem. Severe oxygen depletion usually results when large quantities of organic matter, such as animal manure, pollute waterways. Prolonged exposure to low oxygen conditions can suffocate adult fish and their eggs or starve them by killing their prey. An example of the possible harm that may be caused by excessive nutrients is the development of a large oxygen-depleted "hypoxic" area known as the "dead zone" in the Gulf of Mexico. This dead zone, responsible for massive fish kills, now covers extensive areas of the continental shelf south of Louisiana at certain times of the year. Related problems of nutrient enrichment and eutrophication include noxious algae that have toxic effects on marine life. Nutrient pollution has been linked to the growth of a type of organism known as Pfiesteria piscicida, which has been implicated in major fish kills in coastal waters in North Carolina. In 1997, Pfiesteria piscicida killed more than 30,000 fish in the Chesapeake Bay, whose Eastern Shore suffers from the over-application of poultry manure on farmland. Pfiesteria is also toxic to humans.

Ammonia is a toxic form of nitrogen that causes algae blooms and fish kills in coastal waters. Open-air lagoons emit ammonia into the air. Sprayfields and barns also contribute to the problem. Some of the ammonia emitted from factory farms is deposited into waterways or fields about 50 miles away through water or fog, and the rest changes into a drier, airborne form that can travel hundreds of miles away. In Sampson County, North Carolina, the amount of ammonia in the rain doubled between 1985 and 1996, a period of major expansion in the hog industry.

Another pollution concern is the long-term contamination of soil from heavy metals added to livestock feed. For example, zinc and copper are added to swine and poultry feed to prevent disease and improve digestion. Plants absorb a small amount of these metals, but a significant quantity builds up in the soil. When the level gets too high, it can stunt plant growth. Human waste, which is applied to land as sludge, also contains heavy metals, and EPA regulations impose restrictions on the permissible level of heavy metals in sludge. These restrictions do not apply to the land application of animal waste, however. In 1995, 17 percent of the soil samples in North Carolina's largest poultry-producing counties and 10 percent of the soil samples in the state's largest swine-producing counties had zinc levels that exceeded by ten times the levels needed by the crops for their growth. The number of soil samples from these counties that exceeded this level had doubled since 1985. Already this level of zinc makes it hard to grow peanuts, and other crops will begin to suffer in future decades as the metals reach higher concentrations. Application onto the land of lagoon sludge, the buildup left on the bottom of the cesspool, poses another environmental threat. Lagoons are abandoned after ten or twenty years and the sludge that has accumulated over the years contains high concentrations of heavy metals, such as zinc and copper, from animal feed.

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