We cannot eat our way out of climate change, says expert


Source: Dairy Farmers of Canada


  • Dr. Mitloehner brought up two key problems with the way cattle emissions have been portrayed:
  • One, that the way we measure greenhouse gasses (GHG) is not realistic;
  • And two, that methane should not be treated as having the same impact on climate change as carbon dioxide.

Dr. Frank Mitloehner, a leading professor and air quality specialist, has a real beef with all the finger-pointing around cattle emissions.

“The notion that a change of diet would have a drastic impact on climate is completely overblown, and in my opinion, quite dangerous,” said Dr. Mitloehner. “It takes our attention from where that 800-pound gorilla sits, and that’s square in the area of fossil fuels.”

The professor of animal science at the University of California, Davis recently spoke to delegates at a virtual edition of the BC Dairy Association’s annual Nutrition Forum on the intersection of food and climate change. He noted that, if a person were to switch from an omnivore to a vegan diet, studies show they would reduce their carbon footprint by around one tonne per year. But if they take just one trans-Atlantic flight during that time, they will not only cancel this reduction out completely, they will add another tonne of pollution into the air.

Reframing carbon emissions from cattle

Dr. Mitloehner brought up two key problems with the way cattle emissions have been portrayed: one, that the way we measure greenhouse gasses (GHG) is not realistic; and two, that methane should not be treated as having the same impact on climate change as carbon dioxide.

“Every time you’ve ever driven a car, or burned coal or gas,” says Dr. Mitloehner, “you’ve put out CO2 into the atmosphere and that gas is still there throughout your entire lifetime – and that of your parents, and that of your grandparents, and so on.” Methane, on the other hand, has an atmospheric lifetime of approximately one decade, very different from greenhouse gasses like carbon dioxide that are long-lived, with its half-life of 1,000 years.

When a cow belches out methane, not only is its emission made naturally of carbon from photosynthesis through the plants it consumes, this methane stays in the atmosphere for just 12 years before turning back into CO2 that can be used for photosynthesis, and another cow, again. “Without ruminant animals,” Dr. Mitloehner says, “we could not make use of grasses that grow on two-thirds of all agricultural land in the world.” This process is called the biogenic carbon cycle – emissions that come from natural sources.

But is this a good thing, considering the long half-life of carbon dioxide?

“The question is not [whether this is] a good or bad thing,” Dr. Mitloehner explains. “The question is, is the carbon from our livestock new and additional carbon added to the atmosphere, causing additional warming?”

The answer to that question is no.

Moving beyond carbon neutrality

A working group from Oxford University under Professor Myles Allen supports the idea that we are treating methane the wrong way and has proposed a new unit of measure to look at how short-lived emissions like methane affect the climate. The group claims that the current GHG measurement overestimates livestock-produced methane’s warming effect and ignores methane’s ability to induce cooling when emissions are reduced.

“Our goal should be climate neutrality,” Dr. Mitloehner says, “not carbon neutrality.”

Dr. Mitloehner calls the current GHG measuring system ‘the literal apples to oranges comparison,’ where foods are weighed against each other despite having unique nutritional profiles. Beef production may have the highest GHG emission per kilogram at almost 60 times that of vegetables or fruit, but Dr. Mitloehner stresses that this comparison is not realistic.

“A kilogram of beef is a very nutrient-rich food,” he explains. “A kilogram of apples does not contain an equal amount of essential nutrients.”

What’s more, the U.N.’s Intergovernmental Panel on Climate Change (IPCC) estimates that 70 to 80 percent of the environmental footprint of livestock occurs in developing or emerging countries. “These are not the numbers that apply to Canada or the United States; these are global averages,” Dr. Mitloehner explains, adding, “I have a real beef with that.”

The future of methane recycling

Agriculture and forestry accounted for 10.5 percent of all emissions in the U.S. in 2018, but they also created a reduction of 11.8 percent. This ability to be destroyed at almost the same rate it is emitted, along with its shorter lifespan, means that methane does not act like carbon dioxide and therefore should not be compared as a its equivalent.

“[These]are the only two sectors in society that have the capacity to actually provide a solution to a very important societal aspect,” says Dr. Mitloehner, “which is improving the climate.”

In California today, methane gas from some dairy cattle herds is being collected in covered lagoons and converted into renewable natural gas, creating the most “carbon-negative fuel type there is,” says Dr. Mitloehner. These innovative dairy producers have already reduced emissions by 25 percent.

While methane has sometimes been portrayed as ‘the dairy industry’s Achilles heel,’ according to Dr. Mitloehner, simply blaming animal agriculture for methane emissions also downplays the contribution of plant-based foods towards greenhouse gases. For instance, plant agriculture emissions accounted for 0.6 percent of U.S. greenhouse gas emissions in 2017, while animal agriculture emissions actually accounted for less – just 0.5 percent.

Recycling methane from dairy farms into renewable natural gas not only offers farmers an additional source of income, it is helping displace the diesel fuel used in transportation. If this practice continues, within five to 10 years most of the dairy industry in California will be climate neutral, “meaning [the industry] will not affect temperatures on our planet,” Dr. Mitloehner says. “And that is the path I’m on.”