In this section:
Mountains of Manure
Animal Waste, the Environment, and Human Health
Regulation and Technology in Managing Waste
What You Can Do
Did You Know
For More Information
Related Information:
Air Pollution
Biodiversity
Health
Environment
Fossil Fuel and Energy Use
Pasture-Raised
Water pollution
Workers
Where there are animals, there is animal waste, and as the growth of industrial farming concentrates thousands of animals on increasingly fewer farms, it produces massive amounts of animal waste on relatively small plots of land. When too much waste is produced in one place, there's no safe, cost-effective way to either use it productively or dispose of it. While government regulation and better waste management practices can make a difference and should be encouraged for existing farms, the problem of livestock waste will never end so long as we rely on concentrated industrial farms to produce our food.
Mountains of Manure
The USDA estimates that more than 335 million tons of "dry matter" waste (the portion of waste remaining after water is removed) is produced annually on farms in the United States, representing almost a third of the total municipal and industrial waste produced every year1. What's more, animal feeding operations annually produce about 100 times more manure than the amount of human sewage sludge processed in US municipal wastewater plants2. One dairy farm with 2,500 cows produces as much waste as a city with around 411,000 residents3. Unlike human waste, however, in most cases the law does not require that livestock waste be treated.
At farms where animals are allowed to graze on pasture, much—if not al—of their manure is excreted directly onto the land, serving as a fertilizer and recycling nutrients back into the soil. On industrial livestock farms, however, animals drop their manure in the houses where they live. From there, the manure must be cleaned out, transported, and stored, each step of which can negatively affect the environment. Simply cleaning out livestock houses can waste vast amounts of water—a dairy operation that utilizes an automatic "flushing" system can use up to 150 gallons of water per cow per day4.
Manure is usually stored for many months, often in giant outdoor pits known as lagoons5. As it decomposes, the manure emits harmful gases such as ammonia and hydrogen sulfide6. Meanwhile, these lagoons can leak or rupture, polluting the surrounding soil and water systems. One study conducted by North Carolina State University in 1995 estimated that as many as 55% of the manure lagoons on hog farms in that state were leaking7. Even without leaks, manure lagoons are so fragile that major storms often result in overflows. Perhaps most famously, in 1999, the majority of North Carolina's manure lagoons spilled over into waterways during Hurricane Floyd, leading to widespread water contamination. What made matters even worse was that North Carolina, like most states, requires no treatment of animal waste8.
Since manure is produced on factory farms in excess of what can safely be absorbed by the farm's soil, it is often shipped to neighboring farms for use as fertilizer. Unfortunately, manure is quite heavy, so transporting it both consumes large amounts of fuel (needed to power the trucks that haul it) while at the same time contributing to air pollution (due to emissions from the trucks that haul it)9.
Once the manure arrives at its destination, it is sprayed onto farm fields as fertilizer. Under the current system of animal production, however, there is always more manure available than can possibly be absorbed by the soil as fertilizer. In fact, studies show that between 1982 and 1997, as industrial agriculture grew, the US experienced a 64 percent increase in the amount of manure that could not be absorbed by our soils10. This practice is not only harmful to the soil, but can also result in contamination of human drinking water and lead to serious public health problems.
Animal Waste, the Environment, and Human Health
People often believe that animal manure is harmless, but in truth it can be quite hazardous. Factory livestock facilities pollute the air and release over 400 separate gasses, mostly due to the large amounts of manure they produce11. The principal gases released are hydrogen sulfide, methane, ammonia, and carbon dioxide12. Gasses can be dangerous air pollutants that threaten both the environment and human health. Nitric oxides are also released in large quantities from farms through manure application13, and are among the leading causes of acid rain14.
The risks of lagoon leakage, overflows, and illegal discharge of waste also pose a direct threat to the quality of soil and water systems. A report for the U.S. Geological Survey documented over one thousand spills and dumps of animal waste in the ten Midwestern states it surveyed over the course of three years15. Manure from leaky lagoons or saturated farm fields has also been known to enter public water sources and infect humans16. For example, a study of waterborne disease outbreaks from 1986 to 1998 conducted by the Centers for Disease Control demonstrated that in every case where the pathogen could be identified, it most likely originated in livestock17.
Among the many nutrients usually present in high concentrations in animal waste are phosphorous and nitrogen, which are beneficial to the soils when the manure is added in small concentrations. However, the volume of manure usually found in lagoons and storage systems, and subsequent very high concentrations of nutrients, can cause a range of ecological problems like fish kills or a loss in biodiversity when released into the environment18 and can affect human health when leached into drinking water. Nitrogen in manure is tied up in its organic state until, through decomposition, it is converted to a soluble form (ammonium nitrate). When ammonium nitrate is mixed with water, nitrates can leach into groundwater systems and threaten the water quality19. According to the Environmental Protection Agency (EPA), drinking water with nitrate concentrations above ten parts per million (ppm)20, can cause developmental deficiencies in infants and death in severe cases due to oxygen deprivation. Nitrates introduced into the body through affected water significantly reduce the blood's oxygen carrying capacity21 and deprive the body of oxygen. High nitrate concentrations are also believed to have caused spontaneous abortions and possibly cancer22.
The storage of animal waste under industrial livestock facilities and in manure tanks also poses a direct health risk to both animals and humans. Since animal waste is often stored directly beneath the barns in which the livestock live, livestock commonly die from poor ventilation that allows for the buildup of toxic gases inside confinement facilities23. What's more, manure pits have been known to claim the lives of farm workers, and between 1992 and 1997 at least twelve workers died due to asphyxiation by manure gases and drowning while trapped in manure lagoons24. The gases in livestock facilities can also pose other risks to workers; for example, methane is highly flammable, and if not vented properly from manure tanks it can cause explosions25.
Regulation and Technology in Managing Waste
Until recently, there has been very little regulation of animal waste. Federal law changed in 2002 to require virtually all confined animal feeding operations (CAFOs) to apply for National Pollutant Discharge Elimination System (NPDES) permits for their waste discharge. In 2005, the rule was revised requiring only CAFOs that discharge waste (i.e. into streams, rivers, or lakes) to apply for a NPDES permit26. However, these new regulations make it clear that Federal law prohibits any CAFO from discharging waste, even accidentally, without a permit and will face fines if this is violated. Additionally, CAFOs applying for this permit are now required to submit a nutrient management plan (NMP) with the permit application that is open for public review27. This new regulation makes nutrient management a Federal regulation (no longer leaving it up to the states to enforce) and requires a plan of action for the management of waste to ensure that no waste is discharged from the CAFO site. The Environmental Protection Agency has the right to prosecute those who discharge animal waste illegally under the Clean Water Act28, although these cases are brought infrequently.
Apart from regulation, there are some other innovations that may help control the potential problems associated with animal waste. Researchers have discovered that adding sodium carbonate—a mineral commonly found in laundry detergents—to manure can dramatically decrease the amount of the harmful bacterium E. Coli O157:H7 present29. There are also feed additives for cattle—including one derived from a type of seaweed which is already widely used in human foods and cosmetics—that can significantly reduce the amount of this dangerous strain of E. Coli in cattle manure30.
Another proven and simple way to reduce the presence of E. Coli in cattle manure is the method of sending them out to graze on pasture, and taking them off of industrial feed made of corn and other grains.
While feed additives are a creative way to address some problems, ultimately they do nothing to address the fact that too much waste is being produced in areas that are too concentrated. Eliminating E. Coli bacteria does nothing to address the problems of harmful gases or the detriment high concentrations of manure (and therefore nitrogen and phosphorous) have on the environment and human health. While methane digesters can partially reduce the discharge of harmful gasses, they can't eliminate the solid waste which still must be stored and discharged, nor do they protect against leaks or overflows that can contaminate water supplies.
What You Can Do
It's clear that the best way to deal with industrial agriculture's mountains of manure is to de-concentrate the animals and likewise de-concentrate their waste. Sustainable, pasture-based systems allow for the animals to distribute their waste in amounts that the soil can absorb, without using large quantities of water for washing or fuel to power trucks for transportation and spraying. By shopping at small, local sustainable farms and supporting pasture-based methods of waste management, we can all encourage change and promote healthier and more environmentally-friendly farming.
Did You Know?
- Dairy cows in confined feeding operations throughout the US produce more than two billion pounds of manure nitrogen per year31.
- The most recent available Census of Agriculture data shows that there were almost 95.5 million cows and calves in the United States in 200232 There were also about 60.4 million hogs and pigs33, each producing waste every day.
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Page updated November 2008
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