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Tag: Meat

It’s time to stop comparing meat emissions to flying

By Frank Mitloehner

Millions of people grapple with the effect their lifestyle choices have on climate change, often leading them to draw comparisons between the greenhouse gas (GHG) emissions of their activities. But the discussion around emissions is full of nuances, and while we often search for easy analogies to paint a full picture of human-related climate impacts, they can create more confusion than clarity.

Case in point: I’ve recently come across several articles (here and here) comparing beef emissions with aviation emissions. They’re disappointing on many fronts. For starters, whenever we say a hamburger dumps more greenhouse gases (GHGs) in the atmosphere than a trip on an airplane, we’re reinforcing a misunderstanding of the true GHG emissions of aviation. What’s more, we do it in a way that’s colorful, memorable and easy to latch on to.

I can appreciate how having a sound bite is tempting and even useful like the recent Bloomberg assertion “… that the humble hamburger is a bigger contributor to the warming of the planet than the jumbo jet,” for example. The problem is, it’s not as simple as all that. Animal agriculture’s impact is overstated when speaking to an American audience, and aviation’s effect is understated when speaking to any audience.

U.S. livestock farmers have – and continue to – reduce GHGs

Globally, animal agriculture accounts for 14.5 percent of GHG emissions, the number that tends to be used to support the claim that eating meat is a bigger planetary enemy than the combustion of the fossil fuels used in aviation. But in the United States, isn’t it more helpful to look at U.S. animal agriculture statistics, especially when they’re vastly different from the global picture?

Here in the U.S., animal agriculture makes up a far smaller percentage of total GHG emissions than worldwide: 3.9 percent, according to the U.S. Environmental Protection Agency (EPA). Granted, the lower U.S. percentage is due in some part to the fact that the United States is highly industrialized and wealthy, and we are major users of energy, fossil fuels and transportation. So as those percentages swell, animal agriculture takes up a smaller piece of the pie.

Even so, our farmers are the most efficient in the world. Case in point: In Mexico, it takes up to five cows to produce the same amount of milk as one U.S. cow, and in India, it takes up to 20. These statistics point to the United States having the lowest GHG emissions per unit of milk of any country in the world. It’s a similar story for other ruminant and non-ruminant animals that produce meat in the United States. In fact, emissions from all U.S. livestock species are much lower than those in Brazil, China, India and countries in the European Union, among others.

Americans fly more – much more – than people in any other country

Consistent with using a global number for animal agriculture is the tendency to do the same thing with the GHG emissions of air travel, and that likewise distorts the picture for the United States. Whereas the global animal agriculture figure is inflated for a U.S. audience, the global aviation figure downplays the role air travel plays in the United States’ GHG emissions. 

That’s because Americans fly much more than people in other countries, including China, the United Kingdom, Germany and Japan, other top consumers of air travel. According to Bureau of Transportation Statistics, there were 1 billion passengers on U.S. airlines and foreign airlines serving the U.S. in 2019, a record and yet another year-over-year increase since the global recession of 2008-2009.

Aviation is two to three times more damaging to the environment than is often reported 

In our hamburger-airplane example, aviation is assigned a GHG emissions number of 2 percent, giving most readers reason to have a clear conscience when boarding a plane. But that number doesn’t capture a plane’s full emissions footprint.

A 2 percent “GHG emissions” figure for aviation accounts only for the amount of carbon dioxide (CO2) air travels puts in the atmosphere. It ignores, the other GHGs that come from planes (for example, nitrous gases, water vapor, soot, particles and sulphates).

Emissions from flying

Graphic credit:

In addition, the 2 percent number is a tailpipe assessment, meaning what is being measured are the direct CO2 emissions from the jet fuel that is combusted in the planes’ turbines. The figure fails to consider things such as the manufacture of materials for parts used in the aircraft, the transportation of materials and parts to factories where planes are made, wear and tear on roads and runways, and many more.

Life-cycle assessments and tailpipe emissions are GHGs’ apples and oranges

When we look at our metaphorical burger, we’re taking into account pretty much every GHG that is emitted by the activities and processes required to get the proverbial burger on a dinner table. Called a life-cycle assessment (LCA), it provides a more accurate and total picture of GHG emissions than does a direct (tailpipe) assessment.

In the same example, air travel gets a huge break by being subjected only to a measurement of its (direct (i.e. tailpipe) emissions. To make a fair comparison, the same system of quantification must be used for both the burger and the airplane ride, and ideally, a life-cycle assessment would provide the figures. The thing is, we don’t have life-cycle assessment numbers for planes, or other parts of the transportation sector.

Direct emissions vs. life-cycle emissions

Graphic credit: Thompson Reuters Foundation News.

Methane is a short-lived GHG; carbon dioxide might be forever 

When we talk about the GHG emissions of livestock or the carbon footprint of meat, methane is often at the heart of the matter. Ruminant animals such as cows emit methane. As far as global warming potential, methane is a powerful GHG, with about 28 times the warming potential of carbon dioxide over a period of 100 years. 

But methane doesn’t hang around for a century; it’s a short-lived GHG. In about a decade’s time, it’s converted to water vapor and carbon dioxide, which is part of the cycle whereby plants take CO2 out of the atmosphere and convert it into feed via photosynthesis. Animals eat the non-human edible vegetation and upcycle it to meat and dairy products that provide efficient sources of protein and other essential nutrients to humans. It’s a cyclical process, also referred to as the biogenic carbon cycle, that’s been around as long as life itself.

Given the advances American farmers have made in animal agriculture, today we are producing as much food as we did 50 years ago from cattle herds that are far smaller. All told, the U.S. herd is contributing less methane to the environment as a result.

On the other hand, our voracious appetite for fossil fuels has resulted in an enormous glut of carbon dioxide in the atmosphere. According to the EPA’s GHG inventory, CO2 accounted for 82 percent of GHGs in 2017, with industry, transportation and electricity contributing nearly 80 percent of the total. It’s so much more emissions than oceans, rainforests and plants can absorb, by conservative accounts, it will hang over the planet for a thousand years. Realistically, it could be forever.

The comparison between livestock and aviation has so many nuances, the chances for getting it wrong are high. And when we do get it wrong, we diminish the impact of major polluters. Can we afford to take such a gamble when the information might become the basis for public policy decisions we so desperately need?

As the saying goes, when pigs fly.

Frank Mitloehner is a Professor and Air Quality Specialist. Director, CLEAR Center. Department of Animal Science, University of California, Davis. You can follow him on Twitter at @GHGGuru.

The “Cowspiracy” Conspiracy: Anti-Animal Agriculture Movie Producers Change Their Story

Something remarkable happened recently: The producers of the movie “Cowspiracy”, a documentary produced by Leonardo DiCaprio, which makes wildly inaccurate claims about the role of animal agriculture in climate change, publicly backed away from the main tenet of the movie and what may well be the biggest gee-whiz stat in the 2014 documentary.


In an effort to present animal agriculture as the most fearful threat to our environment, the World Watch Institute and producers Kip Andersen and Keegan Kuhn cherry-picked an inflated number from a single, flawed source. Armed with the faulty data, they made the claim that animal agriculture is responsible for a staggering 51 percent of greenhouse gas (GHG) emissions worldwide, more than any other source, including transportation.

I am afraid “someone whipped data until they confessed”, which does not make them right after all.


As a professor and air quality specialist at the University of California – Davis, and the former chairman of LEAP, a global United Nations Food and Agriculture Organization (FAO) partnership project to benchmark the environmental footprint of livestock production, I was dismayed by “Cowspiracy’s” claim. Not just has LEAP commented on Conspiracy earlier, I’ve been working tirelessly to set the record straight about animal agriculture in general and “Cowspiracy” in particular. My efforts are not simply for the satisfaction of being right; but rather, to help us focus on real, scientific-based facts that will lead to working toward a common, effective, well-informed solution to mitigate the serious problem of global warming.


I’m not alone, either. Anne Mottet and Henning Steinfeld, leading FAO livestock staff, recently published an article on the dangers of oversimplifying GHGs from livestock. Although they submit there is no life cycle estimate for global transportation, in the United States alone, “the life cycle of passenger transport would be about 1.5 times higher than the operational ones.”


These days, Andersen and Keegan are much closer to the truth, having tweeted and posted that 18 percent of GHGs is from global animal agriculture on their website,

Incidentally, the 18 percent figure is still not accurate, having come from the FAO study “Livestock’s Long Shadow,” which has since been revised by its authors to 14.5 percent (FAO “Tackling Climate Through Livestock,”), but at least it is far less misleading than 51 percent. Perhaps reluctant to dial back the statistic, they seemingly couldn’t resist stating that even at 18 percent, it is more than “the combined exhaust of all transportation,” using a life cycle (direct and indirect) assessment for animals and a mere tailpipe emission (direct only) for transportation, an assertion Mottet and Steinfeld debunked in their article noted above.

Even more disturbing is that the overly inflated 51 percent number is still being espoused, even in the infographic still on and elsewhere on the internet where people go for information. No wonder everyone is confused.


One of the latest to pick up on the cringe-worthy 51 percent is Beyond Meat, which showed the stat on its home page as recently as September 2018, seemingly to sway more people to purchase the company’s plant-based products that mimic meat.

Now, I’m not here to tell you what to buy or what to eat by any means, nor do I worry that others are happy to do one or both. What I take exception with is using false data for any purpose.


With that in mind, I fear that “Cowspiracy” is another example in a long list of vegan spokespeople who are more interested in furthering their agenda than in telling the truth. Given the size of the audience that “Cowspiracy” has played to on Netflix, I want to offer the facts to one that is just as large, if not more so. I’m hoping you agree.


Finally, when researching about this blog, I noticed that the same Leonardo DiCaprio who produced this film Cowspiracy, is also significant investor in Beyond Meat, the plant based company using the same flawed numbers. Some would say a logical consequence; other would call it a conflict of interest. Regardless, no reason why the one cannot learn from the other.


At the risk of sounding naïve, I believe people generally want to do the right thing. The problem is, we continue to bombard them with directives based on falsehoods. Whether intentionally or through misinformation, the outcome is the same. It keeps us from getting on the same page to work on a global solution to the problem of climate change.


-Frank Mitloehner (aka @GHGGuru)


Beef with meat tax and cancer claims

It seems we live in a time when people simply don’t know what to eat. Many of us want to do what’s right for our bodies and our planet, but we’re bombarded with conflicting messages or information that is just plain false.


On Nov. 7, 2018, news giant CNN, which touts itself as “the most trusted name in news,” reported a global meat tax could save 220,000 lives and cut health care bills by $41 billion each year. CNN’s report is based on a recent study from Oxford University.


“The numbers are based on evidence that links meat consumption to increased risk of heart disease, cancer, stroke and diabetes. Three years ago, the World Health Organization declared red meat such as beef, lamb and pork to be carcinogenic when eaten in processed forms, including sausages, bacon and beef jerky,” it said.


My life’s work centers on animal agriculture and air quality, and the goal of feeding a world population that will reach 10 billion in about three decade’s time. Information such as that put forth by CNN concerns me because meat’s connection to cancer has never been substantiated. Neither can one put the blame for heart disease, stroke and diabetes squarely on the shoulders of meat.


Peeling back the layers, today I want to take a half-step away from my day-to-day work to focus on the myth (perpetuated by many, including CNN yesterday) that eating meat, especially red meat and processed meat, can lead to cancer. My reason? We need – and will continue to need – animal protein to sustain human life. Without it, we simply can’t get enough essential nutrients for our global population. Buying into an unsubstantiated claim that red meat and processed meat lead to colorectal cancers (CRC) takes our eyes off the ball with nothing to be gained in return.


Partly to blame for the misconception is a 2015 study from the International Agency for Research on Cancer (IARC), part of the World Health Organization (WHO). The report tried to link meat with certain types of cancer, primarily CRC. This year, IARC released the full scientific basis of its finding, confirming just how weak the evidence linking meat and CRC is.


For instance, IARC claimed that 800 studies were used in its review, but in reality, nearly all were eliminated. Only 14 studies investigating red meat and 18 studies investigating processed meat were considered, and evidence showed deeply conflicting findings, not clear and convincing evidence. In the end, one has to wonder why it took IARC more than two years to present the evidence used to arrive at its 2015 conclusion, especially if that evidence was so bulletproof.

The message from IARC has been so misleading and has caused such confusion that its parent organization, WHO, came forward several years ago to deflate IARC’s claim and reassure the public that meat should be consumed in moderation as part of a healthy, balanced diet.


In addition, the U.S. National Cancer Institute (NCI) states in relation to colon cancer, “There is no reliable evidence that a diet started in adulthood that is low in fat and meat and high in fiber, fruits, and vegetables reduces the risk of CRC by a clinically important degree.” In fact, the NCI takes it one step further, saying it’s “not clear” if diet affects the risk of colon cancer at all.


Professors Gordon Guyatt and Benjamin Djulbegovic, two leaders in evidence-based medicine, recently pointed out the minimal relative risk of meat leading to CRC: 1.17. Compare that to smoking, which makes one’s chances of developing lung cancer nine to 25 times greater, or to the fact that when IARC tested 1,000 substances for cancer-causing properties, only one – a chemical found in yoga pants – was found not to cause cancer. Further muddying the waters is the fact that it’s not possible to test meat’s connection to cancer in a vacuum. Other factors can’t be isolated easily, if at all. To that point, Professors Guyatt and Djulbegovic are correct in pointing out that vegetarians tend to be more alert to good health in general. They are more likely to exercise and refrain from smoking, at the same time coming from a higher-than-normal socio-economic class, some or all of which could have a bearing on the development of cancer.

If only cancer could be linked to a single cause. Who wouldn’t wish for that? However, cancer is a very complex disease that simply can’t be traced to one factor, let alone one food source. Genetics, physical activity levels and lifestyle habits (e.g., tobacco and alcohol use) play a role.


Putting a so-called “sin tax” on meat would only make it more difficult for consumers to access a food product that is vitally important to human health and survival now and in the future. Adding insult to injury is the fact that its upside (or promise) is negligible at best. There is no credible, science-based evidence to prove it would reduce cancer.


-Frank Mitloehner (@GHGGuru)



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