Who contributes most to global warming - cows or humans?

Answer 1

Brief Answer:

Yes, scientists agree that methane, a powerful greenhouse gas, is belched out by cattle and other ruminant animals, enough to make a significant, but not the main, contribution to global warming.

In detail:

The question is asking whether cows--and cattle--are responsible for climate change or as stated above, global warming. Much public discourse, harsh criticism and even fear-mongering has fostered the belief by the media and the general public that cows are indeed responsible for global warming, especially when you realize that there are millions of these animals around the world. No doubt there is evidence to back up such allegations, such as the fact that cows, being ruminants, belch out methane gas--a by-product of rumen fermentation--every minute of every hour, 24 hours a day, 365 days a year. However, science has also provided us facts that cows are not the ones to blame here. How much methane does a cow produce per day? Such is one question that is often asked by the average person, and such a question is not as easy to answer as one might expect. "How is methane measured from a cow?" is also a question subject to debate and discussion. This question, or this answer, rather, does not ask nor should answer these questions, but rather attempt to settle the debate as to whether cows really do contribute to climate change--or is it just a load of hot, smelly air?

Methane gas, being one of several gaseous chemical compounds attributed to and contriving of the concern for global warming, is the main source of concern for this particular question. Atmospheric methane gas is more potent and unstable than carbon dioxide (less so than nitrous oxide), and thus is part of the concern for "greenhouse gas emissions" which have been attributed to the "greenhouse" effect of the Earth's atmosphere--consequently coined as "global warming." It is also known as "natural" gas--the stuff we like to bring in to our homes through miles upon miles of gas pipes to heat our homes and cook our food--and is denoted by chemists by the formula CH4. It is also the very gas that is produced as one of several by-products by the natural process of rumen fermentation in the cow.

Cows have a much different digestive system than we do. Compared to us humans, whom are termed "monogastrics," cows are ruminants, or animals with a multi-chambered stomach designed to digest coarse plant matter and regurgitated half-eaten plants to rechew during resting periods. They have four chambers to their stomach--the reticulum, the rumen, the omasum and the abomasum. The first three are merely extensions of the esophagus, whereas the latter is the true stomach. Hence, cows are often also called "fore-gut (or fore-stomach) fermentors." The rumen is the largest compartment of the ruminant fore-stomachs, and is responsible for the fermentation, breakdown and digestion of the coarse plant material--such as grass, forbs and the occasional tree leaf or green branch--once it reaches this chamber.

Common misconceptions state that the rumen "stores" plant matter until the cow regurgitates it to rechew it during her recumbant or resting state. As a matter of fact, the fermentation process that happens in the rumen is already happening when a cow swallows a sward of grass or mouthful of hay whole. Tiny microbes "attack" this material and begin producing enzymes and organic chemicals to begin the fermentation process and obtain the necessary nutrients for themselves and ultimately the cow herself.

Another common misconception is that this process is the "decomposition" or "composting" of plant matter. Though the processes of fermentation and decomposition are the same (by use of bacteria, protozoa and fungi to break down organic matter), the difference is the nature of the substance that is created--or even the by-products released--by fermentation versus decomposition are different. If the substance created is deemed harmful or toxic to animal or human, it is said to have been "decomposed." If the substance is beneficial, it has been "fermented." Since the substances that are created in the rumen are highly beneficial to the point of being necessary to the requirements of the cow and even, indirectly, to the human in the form of meat and milk, the term "fermented" is far more relevant to this topic--or any topic regarding ruminant nutrition--than "decomposition" or "composting."

The partly fermented digesta is regurgitated in the form of a bolus and rechewed to better encourage the break down of the fibrous material. This has been long known as "chewing the cud" or rumination. (NOTE: The previously deleted answer mentioned that the re-mastication of this forage is "...to prepare the material for digestion." This is false. This step of ruminant digestion is simply to help further break down partly-digested forage material, never to "ready" nor "prepare" such material for digestion.)

The entire process of rumen fermentation is the critical element to the question of whether cows contribute to global warming. When plants are fermented, gaseous compounds (i.e., methane), ammonia and organic acids are released as by-products from the biochemical process of fermentation. Three main organic acids are produced: Proprionic acid, Butyric acid, and Acetic acid. All of these are regarded as Volatile Fatty Acids or VFAs. These are sources of energy, as is methane. The amount of acetic versus proprionic acid produced (often denoted by bovine nutritionists as proprionic acid:acetic acid ratio or proprionate:acetate) determines the amount of methane produced. The more acetate produced, the more methane is produced. Inversely, the more proprionate produced, the less methane. The latter is associated with high-concentrate diets and cattle fed ionophores to encourage proprionate production. The former: via high-forage or pasture-based diets.

Methane is the gaseous by-product of rumen fermentation, and is regarded by all ruminant nutritionists as an unusable source of energy. It is primarily released from the rumen through belching or eructation--colloquially called "burping." (VFAs, on the other hand, are not released via eructation but used as an energy source by the rumen microflora and the cow when they enter the liver.) A cow will eructate once every minute. How much methane the average cow releases per minute is inconceivably difficult to measure, as mentioned above. This is because it depends on the individual cow, her genetics, the feed she is fed, breeding, age, physiological restraints, environmental restraints, the list piles up.

Yet another common misconception is that bovine flatulence is the cause for the concerns of global warming. What is not known by the general public is that flatulence contributes to a minute portion of the release of methane gas--even nitrous oxide--compared with the constant belching associated with rumen fermentation. Though the author of this answer has no significant studies to back what you would call her "claims" up, it is estimated that 90% of the methane gas released from a cow comes from the mouth, not the anus. But when it comes to the fecal matter that is excreted several times in a day, that's an entirely different story.

Yes, cow feces do contain methane gas as well. When produced en masse in confined feeding operations or CAFOs, such as in feedlots or commercial dairy operations, then taken and spread out onto fields to encourage better crop production, much methane gas is released into the atmosphere. Even other animals that are raised in CAFOs have this same "environmental" issue--hogs and poultry being the main contenders--when their feces are collected and "harvested" for the same purpose. Yet, such feces are being more used purposely as an energy source to power homes and even the entire farm's operations. Several dairy farms have found the practicality of converting waste from their cows into a usuable source of electricity via combustion, and thus have been able to reduce their electricity bills--even eliminate them all together. Still, many farms do not have the resources to do this, and still continue to collect and use the manure as fertilizer for their fields. Of course, we are limiting ourselves purposely to the intensive confinement operations because such practices are limited to such operations, not extensive, pasture-type ones.

When the discussion of the production of methane, nitrous oxide and carbon dioxide diverts to a pasture setting, we begin to see a marked difference. On the pasture, the feces of grazing animals stays where it was deposited and, by the powers that be through the process of decomposition, this manure is incorporated into the soil and reused and recycled by the plants for additional nutrients--just as Nature intended. Pastures and permanent fields see a greater rate of carbon sequestration than confined feeding operations could ever hope to achieve. Pastures and rangelands become "carbon sinks" instead of "carbon sources" because of the plant community's ability to take carbon and nitrogen, in its many gaseous forms (including carbon dioxide, nitrous oxide and methane) and put it back into the soil. The grazing of cattle, among other grazing animals, assist in this natural "cleaning" of the atmosphere and release of essential oxygen. Only someone with no level of understanding would argue the fact that grasslands and plant comminuties of rangelands are benefited by the grazing of large ruminants such as the domestic bovine.

So, do cows really contribute to global warming? From what has been mentioned so far, it can be assertained that it is entirely possible. But what is gleaned from such a question is the assumption that cows are the primary contributors of global warming. This is where the line must be drawn and what many anti-animal-agricultural and environmental-extremists cross in their efforts to do anything to prove themselves right. This answer--nor the author--is about to cross that line and provide a bunch of warped, misconstrued, twisted and misinterpreted facts, figures and statistics to show how cows are "signficiant" contributors "...to air pollution and subsequently global warming." It is not uncommon to even misinterpret evidence supplied by the Food and Animal Organization (which is a part of the United Nations) in their book Livestock's Long Shadowand come to dastardly unfounded conclusions that support an equally dastard cause.

The facts, as presented below, indicate that cows and other livestock are not the primary contributors to global warming. As mentioned previously, the conclusion that thay contribute "significantly to air pollution and subsequently global warming" is unfounded. No doubt there are millions, possibly billions of these animals around, but wasn't it the same for similar ruminant animals, such as the bison? Millions of bison once roamed the Great Plains of North America and even parts of Europe before they were hunted and shot nearly to extinction. Nobody ever had cause for concern of how much methane they belched and flatulated every minute of every day. (Global warming was unheard of back then!) There still are many other ruminant animals around that "pass gas" and belch out their methane gas, from the wild to the domesticated.

Getting off the soap box, it should be recognized that cows are animals too, just like us humans, like dogs and cats and bunnies and frogs and deer are. No way are they machines or factories or anything that is manufactured or man-made that spout out vast amounts of air pollution like much of the coal factories do. They still are a product of Mother Nature, just modified a bit by the human hand. Figure this out now: Compare the city to the country. Cities are often full of smog and other pollutants that can be a cause for concern for citizens with respiratory issues--"air-quality" advisories often must be submitted when smog or even smoke from distant forest fires blanket a densely-populated urban area. You don't have that problem out in the country where cows are commonly raised. Sure you're going to get a good whiff of some stinky air (the stuff you say "pee-yew!!" to) coming off a farm that's spreading manure or when the air currents shift so that you're down-wind from a large feedlot operation, but that's nothing compared to the gross air pollution seen in many metropolitan areas.

When you get down to the facts and the statistics, cows aren't the animals or "products" of anthropomorphic activities that are the cause of concern. According to the FAO's Livestock's Long Shadow, the summary table (Table 3-15 found on page 113) shows the amount of greenhouse gas emissions that are emitted by livestock and anthropomorphic activities. According to that table, cows (or livestock in general), contribute to only 37% in methane alone. Humans, however, are responsible for the other 63% of methane production, which is a much larger fraction than that emitted by other animals on Earth. Livestock only contribute to 11.5% of total greenhouse gas emissions, and with the LULUCF factor (denoted as Land Use, Land Use Change and Forestry), livestock are said to emit a total of 18%. (Note that most of the LULUCF factors are brought about by human activity, not livestock.) Humans, by comparison, contribute to 88.5% of total emissions.

To conclude this lengthy answer, no doubt cows do contribute to global warming. Efforts by the livestock industry are and have been long underway to find ways to mitigate and reduce the production of methane from cattle, from breeding programs to feeding alternatives to studies in the intricate biochemistry analyses involved in ruminant nutrition and digestion. However, it should be also noted that cows are not the main sources of concern for global warming, hence not the primary contributors nor a significant source for air pollution and greenhouse gas emissions compared to the two-legged, yappy, opposable-thumbed, big-brained mammals that occupy 97% of the terrestrial portion of this planet. WE are the ones that are largely responsible for the production of methane and other gaseous chemical compounds that enter the Earth's atmosphere. (Natural changes, such as earthquakes, volcanic eruptions, gaseous releases from swamps, lakes and bogs, oceanic releases from earthquakes and underwater volcanoes and others are also responsible for their inputs of greenhouse gas emissions.) We are creating our own problems, but many are just too proud or irresponsible to admit it, and choose to find a scape-goat, like the cow, to blame instead. That is a sad thing to realize indeed.

Answer 2

Cows produce great amounts of so called 'green-house' gasses (mostly methane) which create a thermal layer above our planet. This thermal layer keeps the heat (from the sun rays, UV and infrared light) closer to the surface causing global warming.

Answer 3

No. The main cause of global warming is the burning of fossil fuels in business and travel.

Ruminant animals, like cows, contribute methane from their burps, and methane is a serious greenhouse gas causing global warming.

Answer 4

Cattle are ruminants (Biblically speaking they "cheweth the cud") like sheep, goats, camels, and buffalo. The bacteria in their guts (the rumen specifically) make methane from the digestion of the cellulose. The cattle flatulence contains the methane and they release it to the atmosphere. Methane is a Greenhouse Gas 21 times more potent than carbon dioxide.

So how much methane do ruminants produce? Estimates range as high as 65 to 85 Tg (65 to 85 million tonnes) a year of the total world emission of methane - 400 to 600 Tg (400 to 600 million tonnes) a year - comes from this source. That's more than 10% of the total.

Answer 5

Cattle eructations (belches) actually produce much larger volumes of methane (CH4) gas than does flatulence. Although methane is a potent greenhouse gas, by volume it is dwarfed by the human emission of carbon dioxide (CO2) from the combustion of fossil fuel.

Answer 6

When cattle release gas (belch, fart) they produce methane gas which contributes to global warming.

The digestive system of cattle is very different from humans and is very complex.

Cattle have multiple stomachs and the first one temporarily"stores" the vegetable materials the cow eats. At later times, the cow regurgitates the rough cut materials in order to fully chew [long referred to as "chewing its CUD] it to prepare the material for digestion.

The stored materials begin to anaerobically decompose which results in the generation of METHANE gas [what we call "natural " gas, and use to cook and heat our homes, IS methane, chemical formula CH4].

As a result of all that gas generation, cows do a whole lot of BELCHING, releasing TONS of methane into Earth's atmosphere every hour, 24 hours per day.

Additionally, cattle also "pass" a lot of methane gas at the other end too!

Methane, is one of several gaseous chemical compounds, which when in Earth's ATMOSPHERE contributes greatly to the "greenhouse" effect, and thus, to GLOBAL WARMING.

When we consider the millions, possibly billions of cattle on the Earth, their contribution to global warming is very substantial.

A:
Other than feeding the people who create green house gases, cattle do little to affect greenhouse gases. No, their farts do not cause it. I own a ranch and has never seen a cow fart. They eat grasses which absorb greenhoouse gasses, but American lumber companies kill more plants in half a day than a herd of 250 cattle do in their life time.

So in a simple answer, almost nothing. Nada thing.

Answer 7

Yes, and so do other ruminant animals such as elk, buffalo, bison, deer, sheep, goats, antelope and caribou. Cattle are naturally inclined to emit methane through belching and releasing the waste products of fermentation in their rumen, as are the other ruminants listed. Cattle are also a valuable resource for sustainable agriculture and ranching practices, because they are more adapted to the fragmented landscape of grasslands and ranges than bison are, and because they are built and adapted to a grass-dominated diet like the bison are and have been, thus fill an ecological gap that has been created due to the disappearance of the large bison, antelope, elk and deer herds that once roamed the landscape over 200 years ago. Because of that, cattle, when managed properly through managed or controlled grazing practices suitable to the area, outdo their flaws of being methane-belchers through contributing to increased soil water and nutrient retention, carbon sequestration, wildlife habitat and healthy riparian habitat. They can also be used to manage invasive species and encourage increase of biomass and native plant propagation.

As such, it is not the cows themselves that contribute to "global warming," but how they are raised. Because many cattle are raised intensively in feedlots or barns, the manure that is accumulated must be dealt with. Manure, particularly liquid manure that mainly comes from conventional intensive dairy operations, accounts for a significant portion of the greenhouse gas emissions from livestock production, and such emissions come from storage, transportation and movement from storage facility to open fields. Much carbon is also released from the growing, raising, and harvesting crops for the confined animals instead of letting them harvest on their own, or harvesting less during times of need (winter, or drought).

Humans are also responsible for the production, transportation and processing of food and other items. Electricity production and fuel consumption take up a large part of this. According to the EPA, 32 and 28 percent of greenhouse gas missions come from electricity production and transportation, respectively. Only 10 percent comes from agriculture. (EPA, 2012) As far as methane is concerned, livestock only account for around 2 to 4 percent of total greenhouse gas emissions.

When questioning about cows and other ruminants contributing to global warming, consider this: There has been no change in methane levels since the 1950s, and the number of cows that are around today are less than the number of other ruminant animals, like those listed above, that were present 200 and earlier years ago. Like cows, these animals also belch a lot of methane, but there were no noticeable affects of climate change like we're seeing today. Thus, ruminants may contribute to global warming or climate change, but their contributions are puny potatoes compared to the problems we humans have developed with our addiction to fossil fuels, inorganic and unsustainable crop production, and others.

Answer 8

Humans, by far. According to a study done by the United Nation's Food and Agriculture Organization (FAO), cows (or any other livestock) only contribute to 18% of total greenhouse gases--and that's including the LULUCF (land use, land use change and forestry) factor. Take away that factor, and they only contribute to 11.5% of total greenhouse gas emissions. Humans, on the other hand, contribute to a whopping 88.5% of the Earth's greenhouse gas emissions.

Even though cows have a 37% contribution in total methane production, humans are responsible for the other 63%. Livestock also only contribute to 0.5% of all carbon emissions.

To find and work out such calculations as made above, see the link below to Livestock's Long Shadow, Table 3-15 on pg. 113.