Do Cow Farts Really Significantly Contribute to Global Warming?

Matt Blitz 12
Shawn asks: Do cow farts really significantly contribute to global warming?

cow-backsideThere are currently approximately 1.3 to 1.5 billion cows grazing, sleeping, and chewing their cud at any given time on planet Earth. And these 1,300 pound (average weight for both a beef and dairy cow) animals eat a lot. Much like humans, when they eat,  gas builds up inside of their guts and has to be expelled. (See Why Beans Make You Fart) Cows fart and burp… a lot.  The result is a large amount of methane being introduced into the atmosphere.

In a 2006 United Nations’ Food and Agricultural Organization report, it claims that the livestock sector, most of which are cows, “generates more greenhouse gas emissions as measured in CO2 equivalent – 18 percent – than transport.” According to a Danish study, the average cow produces enough methane per year to do the same greenhouse damage as four tons of carbon dioxide.  So is this significantly contributing to global warming?

Let’s start with how and why cows produce so much methane gas. Cows, sheep, goats, giraffes, and deer belong to a class of mammals called ruminants. Most ruminants have four stomachs, two-toed feet, and store their food in the first chamber of the stomach, called the rumen, before regurgitating it. This regurgitated food is called “cud” and the animals chew it again to help further break it down to make it easier to digest. Inside of the rumen, over four hundred different kinds of microbes exist that also play a critical role in the digestion process. Several of these microbes create methane gas as a byproduct. Due to the sheer number of cows on the planet, along with the large size per cow, our tasty friends produce more methane gas than all other ruminants combined.

Why could this potentially be bad? Methane is twenty one times more potent at trapping heat from the Sun than carbon dioxide. Though it is less prevalent in the atmosphere than carbon dioxide, it is, by unit, the most destructive of the greenhouse gases. Since the turn of the 19th century, methane gas emissions have increased by 150%, according to NASA’s Goddard Institute.

Methane gas, like all other greenhouse gases (which includes water vapor), acts like a blanket around our planet, trapping heat. The right amount and the planet has an average temperature of a life-supporting 59 degrees Fahrenheit. Too little and the greenhouse effect becomes weak, like on Mars. Too much and the surface of the planet becomes so hot “it can melt lead,” like on Venus.

Livestock is the largest source of methane gas emissions worldwide, contributing over 28 percent of total emissions. Wetlands, leaks from oil refineries and drills, and landfills also contribute methane gas to the atmosphere. In fact, unlike the ratios on a global scale, in the United States livestock is only the third largest contributor, behind the mining and transportation of natural gas and rotting landfill waste.

In actuality it’s not as much the farting that’s the problem, cows’ burping and manure contribute more methane gas than flatulence. According to researchers at New Zealand’s largest Crown Research Institute, AGResearch, up to 95 percent of the emissions comes from the cow’s mouth rather than its behind. It’s estimated, through whichever orifice, that each individual cow lets out between thirty and fifty gallons of methane per day.  With an estimated 1.3 to 1.5  billion cattle in the world today, this adds up fast.

Exactly how significant this it to our global environment isn’t something that anyone can easily put a number on, but the EPA, NASA, various global agriculture organizations, and the United Nations all recognize that this is a real problem. In recent years, several different solutions have been proposed. Scientists and experts have experimented with cows’ diets to see if that could help cut down on the amount of methane gas. For instance, Welsh scientists studied the effects of putting garlic into cows’ feed. According to BBC News, “Garlic directly attacks the organisms in the gut that produce methane.” So far, results have been positive.

Researchers have also studied adding plants that are high in tannins to the diet, which are believed to lower methane levels in ruminants. Another branch of study focuses on not lowering the amount of methane gas, but figuring out a way to contain it and repurpose it. Some farms have experimented with having their livestock live in a plastic bubble, which takes the expelled gas and converts it into electricity. But this process is both expensive, inefficient, and considered somewhat inhumane, forcing animals to live inside an artificial bubble.

Methane gas emitted by cows and other livestock does have a significant impact on the amount of greenhouse gases in our atmosphere, which are the main culprits behind climate change and global warming. While farts aren’t the only way cows are expelling methane, it is, at least, accurate to say that cow farts play a part in our planet’s climate growing hotter.

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Bonus Facts:

  • In 2010, the United Nations proposed a “global levy on livestock methane emissions,” or as the press dubbed it, “the fart tax.” This didn’t pass… but it is something that has continued to be discussed.
  • According to the Food & Agriculture Organization of the United Nations, livestock also cause phosphorus and nitrogen over contamination. This contributes to biodiversity loss in marine ecosystems, most dangerously at the moment in the South China Sea.
  • In the early to mid-20th century, dairy farming started becoming big business in America, England, Australia, Argentina, and New Zealand.  The number of cows in the world first doubled, then tripled. In order to feed this massive influx of cows that natural growing grass and flowers could no longer handle, pastures were reseeded with perennial ryegrass. This grass lacks the nutrients and is difficult digest, which causes even more methane gas to be expelled from cows.
  • Feeding cows maize silage and fermenting corn shuckings can mean a thirty three percent decrease in methane gas emissions.

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  1. James April 17, 2014 at 7:07 am - Reply

    If the population of cattle has increased so significantly in recent years and thus the amount of methane gas produced, why hasn’t the mean temperature of the earth increased in over 17 years? Your ending paragraphs that suppose that man-made global warming (aka AGM) is fact are in error. AGM is a theory much in doubt and your claims to the contrary show that this site is no more based in truth than or The Onion.

    • Daven Hiskey
      Daven Hiskey April 17, 2014 at 2:36 pm - Reply

      @James: “why hasn’t the mean temperature of the earth increased in over 17 years” It has.

      • FriedFish April 28, 2014 at 9:53 am - Reply

        You are using Wikipedia as your source? THAT’S funny. You should’ve busted out the hockey stick graph or some East Anglia emails to really cement your position.

        • Daven Hiskey
          Daven Hiskey April 28, 2014 at 3:23 pm - Reply

          @FriedFish: Wikipedia is nearly as accurate as Encyclopedia Britannica. Would you say the same about it, arguable one of the most accurate general knowledge compilations in human history? The important thing with Wikipedia is simply to check their sources and, as with any source, never trust a single one implicitly. Nobody bats a thousand. For example, I’m no etymologist, but have found numerous errors in even the likes of the OED over the years studying the origins of words and phrases, but it doesn’t change the fact that they are a phenomenally accurate source on the whole, perhaps the best in human history when it comes to language. So bottom line, attack the information on its merits (or lack thereof), not the source. Everybody’s inaccurate sometimes- it’s impossible not to be as the state of human knowledge progresses. And even chain emails occasionally have a kernel of truth.
          But if you still don’t like that answer, the above linked graph is courtesy of data from a NASA news release, and the lengthy references backing what is said/shown in the preceding link are here.

          • FriedFish April 29, 2014 at 5:58 am -

            Follow the money on that one. If you want to use a NASA reference; good.

            “A prominent scientist and former NASA researcher has added his voice to those who challenge the “scientific fact” that manmade carbon emissions are causing global warming.

            Dr. Leslie Woodcock is a professor emeritus of chemical thermodynamics at the University of Manchester in England, with a Ph.D. from the University of London, and served as a senior research consultant at the Wright-Patterson Air Force Laboratory in Ohio.

            In an interview with Britain’s Yorkshire Evening Post, Woodcock declared: “The theory of ‘manmade climate change’ is an unsubstantiated hypothesis.”

            Climate change is called the seasons; spring, summer, fall and winter. Happens every year.

  2. Ms Kew April 26, 2014 at 10:47 pm - Reply

    1.3 – 1.5 Billion cows worldwide – and you expect me to believe that these animals produce more methane than the estimated 30 – 50 billion bison that roamed the Americas prior to the arrival of Europeans?

    • Daven Hiskey
      Daven Hiskey April 26, 2014 at 11:56 pm - Reply

      @Ms Kew: Kudos to you for correctly calling them “bison” rather than buffalo, which they are not, contrary to popular belief. :-) But your estimates are a bit high there. At their peak, it’s estimated there were about 100 million American Bison which actually happened after the Europeans arrived. Evidence suggests that the bison population in the Americas was kept in check thanks to the Native Americans. Once the vast majority of the natives rapidly died out from European diseases, the bison population exploded and, indeed, they became one of the most numerous wild mammals on Earth for a very brief time, but nowhere near 30-50 billion.

  3. Ralph May 4, 2014 at 1:43 pm - Reply

    Beano for Bovine?

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