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Animal Agriculture: Waste & Inefficiency

Compared to growing plants for human consumption, the farming of animals is shockingly inefficient and wasteful. In fact, animal agriculture takes more from the global food supply than it provides. (1). First, in order to eat the animals, we have to grow all the crops needed to feed them, which is vastly more crops (and resources) than it would take to feed humans directly.  According to the USDA, it takes thirteen pounds of grain to yield one pound of beef — while the protein yield from crops such as soy and lentils is already, pound for pound, as high as beef, and sometimes higher.  Secondly, only a tiny part of the energy eaten by an animal is converted into edible protein–the rest is burned off. This is simple biology: most of the energy from crops fed to farm animals is used to fuel their own metabolic processes, and much of the rest is turned into parts of their bodies we don’t eat (such as bones, feathers, cartilage, feces), with only a fraction of those grains and other plants being turned into meat. In the case of pigs, 90% of the protein from grain feeds is lost, while chickens fed a diet of corn and soybeans can only use 20% of the protein present in those grains, meaning that 80% is wasted. (2)

When we include all the resources that go into raising livestock — the land, fertilizers, pesticides, fossil fuels and water — factory farming practices are shown to be even more inefficient, wasteful, and environmentally costly. It takes more than 11 times as much fossil fuel to make one calorie from animal protein as it does to make one calorie from plant protein. (3) The reasons for this become clear if we add up the energy-intensive stages of raising animals for food: (1) grow massive amounts of corn, grain, and soybeans (with all the energy required for tilling, irrigation, crop-dusters, and transport of fuel, fertilizers, pesticides and herbicides); (2) transport the grain and soybeans to feed manufacturers on gas-guzzling 18-wheelers; (3) operate the feed mills (requiring massive energy expenditures); (4) transport the feed to the factory farms (again, in fuel-guzzling vehicles); (5) operate the factory farms; (6) transport the animals many miles to slaughter on more 18-wheelers; (7) operate the slaughterhouses; (8) transport the meat to processing plants; (9) operate the meat-processing plants; (10) transport the meat to grocery stores; (11) keep the meat refrigerated or frozen in the stores until it’s sold.

This waste and inefficiency has profound effects on political, economic, and food security across the world. Half the world’s grain crop is fed to animals raised for food, while an estimated 1 billion people are malnourished, and 6 million children starve to death every year. (4) The Global Hunger Alliance, among many other organizations, warns that developed countries must radically decrease livestock agriculture because it is robbing developing countries of proper nutrition, and economic and political stability. They write, “Most hunger deaths are due to chronic malnutrition caused by inequitable distribution and inefficient use of existing food resources. At the same time, wasteful agricultural practices, such as the intensive livestock operations known as factory farming, are rapidly polluting and depleting the natural resources upon which all life depends. Trying to produce more foods by these methods would lead only to more water pollution, soil degradation, and, ultimately, hunger.”  

Moving away from the wasteful and harmful production of meat and toward a plant-based diet is essential to the health of human and non-human animals. Doing so will allow us to feed more people for less money and ecological cost. Dr. Aaron Altschul, in his book Proteins: Their Chemistry and Politics, estimates that in terms of calorie units per acre, a diet of vegetables, beans and grains will feed twenty times as many people as a meat-based diet.

Water: Depletion & Pollution


It is estimated that to produce one pound of animal protein takes 100 times as much water as it takes to produce one pound of grain protein. (Pimentel and Pimentel 2003, 662s, as quoted in Henning). A typical chicken slaughterhouse in the U.S. uses 1 to 2 million gallons of water a day (5, 6), while large-scale hog slaughtering plants use between 3 and 4 million gallons of water daily. (7)  When we add up all the water required for livestock production: irrigation of the massive amounts of feed crops grown for 60 billion farmed animals a year; drinking water supply for these animals; water for cleaning away the filth in factory farms and transport trucks; water for processing and cooling carcasses in slaughterhouses, and for flushing out millions of gallons of blood and waste, daily–the farmed animal industry places an inordinate strain on our water supply. In fact, in the U.S., livestock production accounts for almost half of all the nation’s freshwater use. (8)

Just as we have seen a four-fold increase in meat consumption since 1960, humans now use three times more water than they did fifty years ago. Yet, worldwide, one in six people can’t get access to fresh water. In many areas of the world today, the use of fresh water far exceeds the replenishment rate. Rivers are drying up. Aquifer levels are sinking dramatically. The United Nations Food and Agricultural Organization (FAO) estimates that by 2025 64% of the world’s population will be living in water-stressed regions. The standard animal-based diet of a person in the United States requires 4,200 gallons of water per day (for animals’ drinking water, irrigation of feed crops, processing, cleaning, waste-treatment and disposal, etc.), while a person on a vegan diet requires only 300 gallons a day. (9)


The number one source of freshwater pollution in the U.S. is excess levels of nitrogen and phosphorous, most of which comes from fertilizer runoff. The massive amounts of excrement from factory farms are either stored in large underground holding tanks, sprayed into the air in a fine mist, or spread on crops as manure fertilizer. Waste from spraying and spreading reaches rivers when it rains, poisoning drinking water and aquatic wildlife ecosystems. In the Southern U.S., where there is a high concentration of chicken factory farms, as many as one-third of all underground wells fall below EPA safe drinking water standards for nitrate, a form of nitrogen that super-accumulates in chicken waste.

Excrement from animal waste holding tanks, or “lagoons,” also leaches through the soil into nearby groundwater. In numerous instances across the country, hog waste cesspools have ruptured and spilled millions of gallons of untreated waste into nearby rivers, killing hundreds of millions of fish. In California, the leading dairy producer state, dairy operations have been cited as the largest source of nitrate pollution in more than 100,000 square miles of toxic groundwater. Overall, animal excrement from U.S. factory farms has polluted 35,000 miles of rivers in 22 states.

Factory farm runoff also causes algal blooms that kill fish by removing oxygen from water, causing huge “dead zones” where aquatic life cannot survive. The largest of these, in the Gulf of Mexico, is roughly the size of New Jersey.

Global Warming & Greenhouse Gases

The farm animal sector annually accounts for:

- 9% of human-induced emissions of carbon dioxide (CO2),

- 37% of emissions of methane (CH4), which has more than 20 times the global warming potential (GWP) of CO2,

- and 65% of emissions of nitrous oxide (N2O), which has nearly 300 times the GWP of CO2. (10)

Carbon Dioxide: Burning fossil fuels (such as oil and gasoline) releases carbon dioxide, the primary gas responsible for global warming. Producing one calorie from animal protein requires 11 times as much fossil fuel input—releasing 11 times as much carbon dioxide—as does producing a calorie from plant protein. Feeding massive amounts of grain and water to farmed animals and then killing them and processing, transporting, and storing their flesh is extremely energy-intensive. In addition, enormous amounts of carbon dioxide stored in trees are released during the destruction of vast acres of forest to provide pastureland and to grow crops for farmed animals. On top of this, animal manure also releases large quantities of carbon dioxide.

Methane: The billions of animals, free-roaming and factory-farmed, raised for food globally produce enormous amounts of methane, both during digestion and in the billions of of tons of manure they excrete. Methane is more than 20 times as effective as carbon dioxide at trapping heat in our atmosphere. The EPA lists animal agriculture as the single largest source of methane emissions in the U.S.

Nitrous oxide is about 300 times more potent as a global warming gas than carbon dioxide. According to the U.N., the meat, egg, and dairy industries account for a staggering 65 percent of worldwide nitrous oxide emissions.


Biodiversity is essential to ecological harmony and stability, and affects many aspects of human and animal well-being. Ecosystems that are biodiverse are less toxic, more resilient, and better able to adapt to change. Worldwide, biodiversity is in rapid decline. There is now scientific consensus that we are currently living through the sixth mass extinction known to have occurred in the natural record. Extinction is occurring at rates roughly 120,000 times faster than normal background extinction rates. (11) According to UN scientists, 200 species of plants and animals now go extinct every day. (12) In the place of these lost species, meat and dairy animals now account for 20 percent of the earth’s terrestrial animal biomass. (13) This irreversible change in global biodiversity is so distinctive that many scientists no longer refer to our geologic epoch as the Holocene but as the Anthropocene, to underscore human activity as the singular causal driver behind this radical change.

Key to this anthropogenic (human-caused) crisis is livestock production. (14) Modern agriculture is the largest cause of genetic erosion, species loss and conversion of natural habitats worldwide(15). Within agricultural sectors, livestock farming is the major driver of deforestation, currently using 30 percent of the earth’s entire land surface for feedlots and pastures, while another 33 percent of all global arable land is used to produce livestock feed.  In Latin America, some 70 percent of former forests in the Amazon have been razed for grazing (16), while more than 260 million acres of U.S.forest have been cleared to create cropland to grow grain to feed farmed animals. (17)

Slash and burn clearing of forest for livestock grazing in Indonesia.  Photograph: Yusuf Ahmad/Reuters

The conversion of natural habitats to cropland or grazing pasture entails the replacement of rich ecosystems with monocultures poor in biodiversity, reducing the potential to provide ecosystem services other than food production. Habitat modification already affects more than 80% of all globally threatened mammals, birds and plants. (18) Livestock grazing is the number one reason that plant species in the United States become threatened or extinct, and it leads to soil erosion and eventual desertification of once fertile land. (19) Deforestation, field consolidation, and drainage of wetlands for farming reduce the overall area available for wildlife, and fragment natural habitats. On converted cropland, pesticides and herbicides directly destroy many insects and unwanted plants, reducing or eliminating food supplies for birds and other animals. Many of these impacted life forms may be important soil nutrient recyclers, crop pollinators and predators of pests. Loss of biodiversity is thus not limited to the land clearing stage of livestock production but continues long afterward. (20)


(1) Henning, Brian. “Standing in Livestock’s ‘Long Shadow’: The Ethics of Eating Meat on a Small Planet,” in Ethics and the Environment, Vol. 16, No. 2 (Fall 2011), p. 68

(2) A Humane Society Report: The Impact of Industrialized Animal Agriculture on World Hunger

(3) Pimentel, David and Pimentel, Marcia, “Sustainability of Meat-Based and Plant-Based Diets and the Environment,” in American Journal of Clinical Nutrition, 2003.

(4) A Humane Society Report: The Impact of Industrialized Animal Agriculture on World Hunger

(5) Water Online, “Sanderson Farms Exec Says Chicken Slaughterhouse Will Tap 1.5 Million Gallons From Well Water In Nash County”

(6) United Poultry Concerns: Intensive Poultry Production: Fouling the Environment

(7) Midkiff, Ken. How Corporate Farming Has Endangered America’s Food Supply, Macmillan, 2005, 240 pp; p.47

(8) Food Empowerment Project, Water Usage and Privatization

(9) WorldWatch Institute, “Is Meat Sustainable?”

(10) A Humane Society Fact Sheet: Greenhouse Gas Emissions From Animal Agriculture

(11) Leakey, Richard and Lewin, Roger: “The Sixth Extniction”

(12) Vidal, John: “Protect Nature for World Economic Security, Warns UN Biodiversity Chief,” in Guardian UK, 2010

(13) Food and Agriculture Organization of the United Nations, “Livestock a Major Threat to Environment”

(14) Food and Agriculture Organization of the United Nations, “Livestock’s Impact on Biodiversity”


(16) Food and Agriculture Organization of the United Nations, “Livestock a Major Threat to Environment”

(17) People for the Ethical Treatment of Animals, Meat Production Wastes Natural Resources


(19) People for the Ethical Treatment of Animals, Meat Production Wastes Natural Resources

(20) Food and Agriculture Organization, “Prospects for the Environment: Agriculture and the Environment”