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A farm with 2,500 dairy cows produces the same amount of waste as a city of 411,000 people.

From http://www.cowspiracy.com/facts/ per “Risk Assessment Evaluation for Concentrated Animal Feeding Operations.” U.S. Environmental Protection Agency – Office of Research and Development. 2004.

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  • Explanation: That link has been thrown about a lot in pro-vegan discussions... so I am picking three of their more juicy claims more or less randomly to see how they fare.
    – David Mulder
    Nov 27, 2014 at 18:13
  • They source it to the EPA. If that source does not convince you, what source does?
    – gerrit
    Nov 27, 2014 at 20:08
  • @gerrit Unlike the other article this indeed is an actual EPA document. Guess I will just self answer then.
    – David Mulder
    Nov 27, 2014 at 20:54

2 Answers 2

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Searching the document shows that the actual numbers put forth by EPA are

Animal farms produce as much manure as small and medium-size cities. A farm with 2500 dairy cattle is similar in waste load to a city of 411,000 people.

The quote on cowspiracy.com takes this entirely out of context and talks about generic waste instead of specifically about manure. Additionally this difference is not surprising as even a Turkey produces 13x as much manure per year as a human. What biological difference causes this huge difference I do not however know.

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  • 4
    "Waste" is such a vague term. CO2? Methane? Water? NO2? PCBs? But manure? Sure human sewerage may be considered waste, but is cow manure? That's not waste. It's pretty much evidence that the claim is false.
    – Oddthinking ♦
    Nov 27, 2014 at 23:06
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    @Oddthinking Well, in their defense (though I fully agree the claim is false), waste is the term used in the EPA document as well in the second line.
    – David Mulder
    Nov 28, 2014 at 0:36
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    One of my uncles owns and runs a ranch. Most of the manure produced by his cows ends up being sprayed over his crop fields. I'd call that the exact opposite of "waste"
    – Shadur
    Nov 28, 2014 at 5:52
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    For cattle I guess the difference is merely that they're larger animals and they eat food that can't be converted to fat as easily as what we eat. For birds I know the biological difference: birds have evolved to retain as little solid waste in their body as possible, often pooping while eating. This is because they need to be as light as possible to reduce power requirements of flight yet need to absorb as much energy as possible for the power requirements of flight. Since evolution rarely fix what's not broken even chickens retain some of this characteristic
    – slebetman
    Jul 25, 2016 at 7:31
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    @Oddthinking When I read the claim, I immediately thought of excreted waste. I only realized after reading the answer how the claim might be seen in a more vague light.
    – called2voyage
    Jul 25, 2016 at 19:13
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Summary:

2500 dairy cattle, with an average size of about 1200 lbs, produce roughly 75,000 lbs of manure each day.

411000 people, with an average size of about 178 lbs, produce roughly 381,031.25 per day.

Thus a single dairy farm of 2500 cattle is severely lacking, if we consider only manure, compared to a city of 411,000 people. You need 4 more farms to get close.

Bovine pooping, https://www.daf.qld.gov.au/environment/intensive-livestock/cattle-feedlots/managing-environmental-impacts/manure-production-data

Queensland's Department of Agriculture and Fisheries enter image description here

Human pooping

With average human weight of 177 lbs, and roughly an ounce of poo generated per 12 pounds of body weight, per day. http://greatist.com/health/poop-health-embarrassing-questions

we may calculate (177.913/12)/16 ~= 0.9kg/day output @ 1 oz per pound

enter image description here http://www.fastcodesign.com/1672008/infographic-everything-you-were-afraid-to-ask-about-poop

Clearly, cattle produce more dung per pound of body weight and per capita. Humans have a body-to-stool ratio of about 192:1 while cattle seem to be about 40:1.

This means, with ~1.4 billion cattle on the planet, we are close to tied for total crap per populace. There's about 5 times more of us, but their daily average amount of poop is about 5 times more massive per unit of body mass.

Note: there is a fair discrepancy between sources on how much an average human poops. It seems to vary between 1-2 pounds per day roughly. I'm working with the lower amount. If we work with the higher estimates then humans are beating cattle by a fair margin.

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    "Humans have a body-to-stool ratio of about 192:1 while cattle seem to be about 40:1." Hmm, I wonder why that is. Perhaps it's because cows eat lots of food? And perhaps the reason why cows eat lots of food is because they eat food that is low in caloric density, while human eat food with high caloric density ... such as beef?
    – Acccumulation
    Dec 4, 2019 at 5:06
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    @Acccumulation that could well be one reason that cows would have more 'poop per pound' than people. the lower caloric value of grasses and higher cellulose/fiber content requires cattle to have four stomachs just to digest it all. combine that with the fact that they need more volume of grass to match the same amount of energy found in a volume of steak... bam
    – That Realtor Programmer Guy
    Dec 4, 2019 at 7:00
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    Last two paragraphs, which discuss only the cardinality of humans and bovines, appear to have completely forgotten the difference in average weight.
    – Ben Voigt
    Dec 6, 2019 at 21:49
  • @BenVoigt ah indeed I have worded this poorly saying "larger" when the intent is to reference the prior mass-to-mass ratio. They are brought into common basis vectors thanks to the "per day" metric of each. The average weight and diet per cattle and per human are all rolled up into the average daily weight of flow. I've corrected the wording to clarify the relation to daily average weight
    – That Realtor Programmer Guy
    Jan 25 at 3:32
  • But you still have the incorrect "we are close to tied" claim in there.
    – Ben Voigt
    Jan 25 at 15:36

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