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Tag: Flight Emissions

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.

No, Four Pounds of Beef Doesn’t Equal the Emissions of a Transatlantic Flight

Cattle graze on rangeland.


By Frank Mitloehner and Darren Hudson

A story in The New Yorker came out this week about Dr. Pat Brown, the founder of Impossible Foods. If readers scan the headline and subhead, they’ll get the gist of what author Tad Friend is trying to say: “Can a plant based burger help solve climate change? Eating meat creates huge environmental costs. Impossible Foods thinks it has a solution.”

That’s unfortunate. It might even be dangerous. In the article, Mr. Friend writes that Every four pounds of beef you eat contributes to as much global warming as flying from New York to London – the average American eats that much each month.

If only.

For the record, since it’s not noted in the article, Mr. Friend is citing from the work of Tim Searchinger of Princeton University and the World Resources Institute. It suggests all one needs to do to hop on a transatlantic flight with a clear conscience is to forego a few weeks’ worth of burgers. Professor Searchinger asserts that reforesting all grazing lands and giving up three-quarters of beef and dairy would reduce total global greenhouse gas emissions by 20 percent.

It’s yet another example of misleading data that is misinforming readers and even worse, perhaps affecting public policy in a way that is detrimental to us and our planet.

Since the story came out this week, we shudder to think how many people have bought into the 4-pounds-of-beef argument that is stated upfront, incidentally. So, let’s dissect that number and try to set the record straight.

Four pounds of beef in the United States DOES NOT equate to the greenhouse gas emissions (per passenger) of a flight from New York to London.

Per passenger, a one-way flight from NYC to London causes 1,980 lbs (898 kg) of COequivalent emissions (

U.S. beef produces 22 kg of COequivalent emissions per kg. Thus, 4 pounds of U.S. beef would result in approximately 40 kg of emissions, less than 1/20th of the emissions per passenger of the plane ride in question.

So how come that the New Yorker estimate is so far off reality? A premise in Professor Searchinger’s work is that beef yields 188 kg of CO2 equivalent per kg. But that’s his global number, and we’re talking to an audience of American readers. If you live and work in the United States and are in the market for a car, would you look at emissions from the global car-fleet average or from those in the United States? Of course, it’s the latter.

The most comprehensive cradle-to-grave (i.e. life-cycle) assessment for U.S. beef was recently conducted by a USDA Agricultural Research Service team led by Dr. Alan Rotz at Penn State. The team found that U.S. beef is responsible for 3.7 percent of total America’s greenhouse gas emissions.

Using a global number to represent U.S. animal agriculture is a disservice to American farmers – the most efficient in the world – and members of the American public who are making lifestyle choices based on the research they come across, whether it’s correct or not. It is also a disservice to Americans who expect that meaningful changes are being implemented to reduce climate pollutants. It is unquestioned by most experts, as well as by the Environmental Protection Agency, that fossil-fuel-intensive sectors, such as transportation, power and industry, emit approximately 80 percent of total U.S. GHG emissions. The plastic-straw-light-bulb-burger discussion that is frequently touted as a meaningful climate change solution seems to be a smokescreen to sidetrack from the major polluters.

Professor Searchinger, whose work is the foundation of the above mentioned assertion in The New Yorker article, has created a model of global marginal land use change and greenhouse gas emissions for beef. The core of his argument is that beef consumption anywhere will lead to global expansion of production and therefore puts pressure on, say, Brazilians to deforest in order to establish pasture. In a broad sense, supply must rise to meet demand. Taken a step further, he suggests if Americans stop reaching for beef as often as they do now, farmers and ranchers in the United States will turn to exporting more of their product, which will keep cattle producers in foreign countries from deforesting their homelands.

But Americans have already cut back on consumption, and companies have shifted to exports. In 1970, Americans consumed about 80 pounds of beef per person. Today? About 57 pounds. And in 1970, the U.S. exported less than 1 percent of its production but over 11 percent in 2018. Americans have long been doing their part according to this model. So, why is Brazil expanding its grazing area?

In short, they are different products serving different markets. Beef from Brazil is not the same as beef from the U.S., which specializes in producing well-marbled, grain-finished beef. Conversely, Brazilian beef exports tend to be grass-finished, leaner and in general lower-quality products. As a result, these two countries are producing beef for very different consumers – the U.S. is targeting higher-income countries for exports, such as Japan, South Korea and Taiwan, where demand growth is slower, whereas Brazilian beef is headed to lower-income consumers in countries such as China, Chile, Egypt and Iran, where demand growth is much faster. In short, any potential gains by U.S. consumption have been swamped by growing demand elsewhere.

Would increased U.S. beef exports eventually displace Brazilian beef exports in lower-income countries? Maybe, but it would take a considerable change in consumer choices and income in those countries. We have no evidence to indicate that would occur anytime soon, if at all. The predictions of the huge benefits of reducing U.S. beef consumption are, then, just based on unsupported assumptions.

Indeed, we live in a globalized world, but the beef market realities fly in the face of the globalized consumer model put forward by Professor Searchinger and the World Resources Institute. It’s just not that simple. Ultimately, a U.S. consumer eating less meat has not and will not displace consumption of Brazilian beef in Iran or China and therefore, decrease land expansion into the Amazon. That’s not how global beef markets work.

Solving the world’s climate change crisis is a weighty topic, and it is highly improbable (if not “impossible”) that an imitation beef burger is our savior. It is also a dangerous assertion, because it takes away focus from major polluters and our progress toward climate solutions.

Maybe – just maybe – American farmers and ranchers deserve some credit for efficiencies that for decades have decreased greenhouse gases while improving food production at unprecedented levels.

In short, for doing what the fossil fuel industry hasn’t figured out yet.

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.

Darren Hudson is a Professor & Combest Endowed Chair. Director, International Center for Agricultural Competitiveness. Department of Agricultural and Applied Economics. Texas Tech University, Lubbock, TX. You can follow him on Twitter at @CompetitiveAg.

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