What should be a valuable agricultural fertilizer—animal manure—often becomes a toxic environmental and social liability. CAFOs simply generate too much of it to safely go around. Communities reek from the stench of it. And it can contain all kinds of pollutants that end up in the air, soil, water, and even back into the animals themselves when it is fed to them to minimize production costs.

Myth: CAFO Manure is a Benign Resource


Confining more animals whose wastes cannot safely be absorbed by the surrounding land, watershed, and atmosphere is detrimental, if not illegal. CAFO wastes (including fish farms) can contain a slurry of toxins, including viruses, infectious bacteria, antibiotics, heavy metals, and oxygen-depleting nutrients that run off the land, contaminate groundwater and aquatic systems, and pollute the atmosphere.

According to one estimate, if the amount of confined livestock and poultry waste produced in the United States each year were packed in boxcars, they would track around the world fourteen times.1 To offer just a few more comparisons, a new hog plant in Utah will produce more animal waste than all the human sewage created by the city of Los Angeles; California’s 1,600 Central Valley dairies churn out more waste than a city of 21 million people; and the 600 million chickens living on the Delmarva Peninsula near Washington, DC, generate as much nitrogen as a city of almost 500,000 people.2 The key difference is that while human waste is treated in plants that must meet rigorous processing standards, the management and disposal of most animal wastes are poorly regulated.

Toxic Storage “Lagoons” Lagoon storage and sprayfield applications on land are two common methods of dealing with CAFO wastes. Neither is problem-free. Spraying liquid manure onto croplands can spread viruses, bacteria, antibiotics, metals (such as zinc, arsenic, copper, and selenium),3 nitrogen, phosphorus, and other compounds that run off the land, contaminate the groundwater, travel through subterranean field drains (tiles), and pollute the atmosphere. Spraying more animal waste than the surrounding land can safely absorb is common. When lagoons burst, develop leaks, or are overwhelmed by flood events, as often happens, millions of gallons of manure reach waterways and spread microbes that can cause gastroenteritis, fevers, kidney failure, and death. One bacteria, Pfiesteria piscicida, produces a powerful toxin that has been responsible for massive fish kills in waters polluted by hog manure.

Harmful Gases According to the Pew Commission on Industrial Farm Animal Production:

Decomposing manure produces at least 160 different gases, of which hydrogen sulfide (H2S), ammonia, carbon dioxide, methane, and carbon monoxide are the most pervasive. These gases may seep from pits under the building or they may be released by bacterial action in the urine and feces on the confinement house floor. Possibly the most dangerous gas common to industrial food animal production (IFAP) facilities is hydrogen sulfide. It can be released rapidly when the liquid manure slurry is agitated, an operation commonly performed to suspend solids so that pits can be emptied by pumping. During agitation, hydrogen sulfide levels can soar within seconds from the usual ambient levels of less than 5 ppm to lethal levels of over 500 ppm. Animals and workers have died or become seriously ill in swine industrial farm animal production (IFAP) facilities when hydrogen sulfide has risen from agitated manure in pits under the building. Hydrogen sulfide exposure is most hazardous when the manure pits are located beneath the houses, but an acutely toxic environment can result if gases from outside storage facilities backflow into a building (due to inadequate gas traps or other design faults) or if a worker enters a confined storage structure where gases have accumulated.4

Airborne Pollution For people living anywhere near these animal factories, the stench can be horrific: smells like rotten eggs and rancid butter are commonly reported. But this is just a beginning. Airborne toxicity travels long distances. Ammonia can be carried more than 300 miles through the air before being dumped back onto the ground or into the water, where it has the potency to cause algal blooms and fish kills.5

Pathogen and Antibiotic Transfer CAFO manure also frequently carries pathogens such as Salmonella, E. coli, Cryptosporidium, and fecal coliform, which can be 10 to 100 times more concentrated than in human waste. In fact, more than forty diseases can be transferred to humans through manure. Furthermore, if humans get sick from one of the diseases in CAFO manure, our antibiotics may no longer be able to cure us. Antibiotics are regularly administered to most CAFO animals in “subtherapeutic” doses— regardless of whether there is a medical need. Constant exposure to antibiotics, has, in turn, created new generations of disease pathogens resistant to the very antibiotics we invented to fight them. A significant percentage of those antibiotics are later discharged in animal waste and can seep into aquifers, creeks, rivers, and lakes with potential consequences along the way.

Foul Waters According to the Pew Commission on Industrial Farm Animal Production, over 1 million Americans are estimated to take their drinking water from groundwater that shows moderate or severe contamination with nitrogen-containing pollutants, mostly owing to the heavy use of agricultural fertilizers and high rates of land application of animal waste.

Wendell Berry eloquently described the difference between traditional diversified farms and CAFOs: “Once plants and animals were raised together on the same farm—which therefore neither produced unmanageable surpluses of manure, to be wasted and to pollute the water supply, nor depended on such quantities of commercial fertilizer. The genius of American farm experts is very well demonstrated here: they can take a solution and divide it neatly into two problems.”6

1. Michael W. Fox, Eating with Conscience: The Bioethics of Food (Troutdale, OR:, NewSage Press, 1997), 37. This estimate was updated with information from the Pew Commission on Industrial Farm Animal Production, Putting Meat on the Table: Industrial Farm Animal Production in America (Washington, DC: Pew Charitable Trusts and Johns Hopkins Bloomberg School of Public Health, 2008), 23.
2. “Behind the Odors from Factory Farms: What the Nose Doesn’t Know,” the diary of Stanley Cooper, image links compiled by Kathleen Jenks, MyThing Links.org.
3. Fox, Eating with Conscience, 39.
4. Pew Commission, Putting Meat on the Table, 16.
5. Robbin Marks, Cesspools of Shame: How Factory Farm Lagoons and Sprayfields Threaten Environmental and Public Health (Washington, DC: Natural Resources Defense Council and Clean Water Network, July 2001).
6. Wendell Berry, “The Pleasures of Eating,” in Bringing It to the Table: On Food and Farming (Berkeley, CA: Counterpoint, 2009).

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