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Manure Gun
near houses.
Manure Sprayer near houses
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Sustainable Table Issues:  Waste

Printer FriendlyWhere 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.

Comparing Animal and Human Waste Production

In order to compare the impact of different types of animals, livestock statistics are often cited in terms of “animal units.”

One animal unit equals 1,000 lbs. of the live weight of an animal, (for example, four 1,250-pound cows equal 5 “animal units” of cattle, while 125 eight-pound chickens make up 1 “animal unit” of chicken).

By this measure, one animal unit of broiler (meat) chickens produces an average of 14.97 tons of manure each year, fattened cattle 10.59 tons per year and dairy cows 15.24 tons per year.iv

In comparison, one “animal unit” of humans produces a mere 5.48 tons of waste per year.v

Mountains of Manure
The USDA estimates that more than 335 million tons of “dry matter” wastes are produced annually on farms in the United States, representing almost a third of the total municipal and industrial waste produced every year.i 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 plants.ii One dairy farm with 2,500 cows produces as much waste as a city with around 411,000 residents.iii Unlike human waste, however, in most cases the law does not require that livestock waste is treated.

At farms where animals are allowed to graze on pasture, much - if not all - 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

Manure is usually stored for many months, often in giant outdoor pits known as “lagoons.”vii As it decomposes, the manure emits harmful gases such as ammonia and hydrogen sulfide.viii Meanwhile, these lagoons often 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 leaking enough to cause environmental damage.ix 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 waste.x

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.xi

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 soils.xii 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 produce.xiii The principal gases released are hydrogen sulfide, methane, ammonia, and carbon dioxide.xivgasses 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 application,xv and are among the leading causes of acid rain.xvi

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 years.xvii Manure from leaky lagoons or saturated farm fields has also been known to enter public water sources and infect humans.xviii 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 livestock.xix

Among the many minerals usually present in high concentrations in animal waste are phosphorous and nitrogen, which can cause a range of ecological problems like fish kills or a loss in biodiversity.xx The ammonia present in manure waste can be converted to nitrates in water systems,which in turn can cause sickness and even death in humans.xxi These include dangerously low blood-oxygen levels in babies (known as “blue-baby syndrome”), spontaneous abortions, and possibly cancer.xxii

New York State Dairy Manure Lagoon Spill

In August 2005, three million gallons of cow manure spilled from a ruptured tank on a 3,000-head dairy farm in upstate New York, spilling into the Black River and polluting an area one-fourth the size of the Exxon Valdez oil spill.xxiii

The New York State Department of Environmental Conservation cited the farm for numerous environmental and permit violations, and estimated the spill caused the deaths of 200,000 to 250,000 fish.xxiv

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 facilities.xxv 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 lagoons.xxvi 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 explosions.xxvii

Regulation and Technology in Managing Waste

Until recently, there has been very little regulation of animal waste. Federal law changed in 2002 to require large livestock facilities to apply for National Pollutant Discharge Elimination System permits for their waste discharge. Although this still leaves it up to the individual states to define and enforce pollution guidelines, it is a step towards tighter regulation of agricultural waste.xviii The Environmental Protection Agency also has the right to prosecute those who discharge animal waste illegally under the Clean Water Act, xxix although these cases are brought infrequently and regulation of animal waste in the US still lags far behind much of the rest of the world. For instance, Denmark, Japan, the Netherlands, Sweden and the United Kingdom all have programs to ensure that no more animal waste is applied to soil than can be absorbed as

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 present.xxxi 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 manure.xxxii

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 presence of nitrogen and phosphorous in the manure. 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.

  • Use the Eat Well Guide! Find local farms, stores, and restaurants serving sustainably-raised meat and dairy products by entering your zip code.
  • If you live near a factory farm and want to do something about the problems it creates, organize a local group and read the GRACE Factory Farm Project’s Guide to Confronting a CAFO.

Did You Know?

  • Dairy cows in confined feeding operations throughout the US produce more than two billion pounds of manure nitrogen per year.xxxiii
  • The most recent Census of Agriculture shows that there were almost 95.5 million cows and calves in the United States in 2002.xxxiv There were also about 60.4 million hogs and pigs,xxxv each producing waste every day.

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