Can Our Diets Impact the Planet? The GHG Guru Weighs In

April 20, 2021

More consumers are having conversations about meat, milk and eggs and the factors they weigh when making decisions about what ends up on their tables. One of those factors is the carbon footprint of today’s livestock, dairy and poultry farms and the potential impact on climate change. Can changing our diets impact the planet?

I’m certainly no authority on the topic but was fortunate to have a conversation with one of the foremost experts on environmental impacts of meat and milk production, Frank Mitloehner, Ph.D., professor and air quality specialist in the Department of Animal Science at the University of California, Davis. Dr. Mitloehner, who goes by the Twitter handle @GHGGuru, is also director of the Clarity and Leadership for Environmental Awareness and Research (CLEAR) Center at UC Davis.

During our conversation, he debunked myths, shared the science and detailed a way that animal agriculture can actually contribute to global cooling.

Dr. Dorman: Should consumers change their diets to impact the environment?

Dr. Mitloehner: There are detractors who will say livestock is the largest contributor to global greenhouse gas (GHG) emissions. That’s not just incorrect, it’s dangerous. It’s misleading the public to believe that what we put in our bodies matters more to the environment than everything else we do. That’s dangerous because we may then let our guard down on other ways we can have an impact.

Dr. Dorman: What are greenhouse gases?

Dr. Mitloehner: GHGs are gases in our atmosphere that, when hit by solar radiation, heat up and trap the heat from the sun. They are like a blanket over the atmosphere that keeps the earth warm. The more greenhouse gasses, the thicker the blanket. The problem is the blanket has become too thick and now too much heat from the sun is trapped in our atmosphere. That leads to global warming.

Dr. Dorman: What is animal agriculture’s environmental footprint?

Dr. Mitloehner: If you consider all sources of GHGs in the U.S., there are three sectors that stand out; transportation (including cars, trucks, planes, trains, ships), power production and the cement industry that makes concrete. These three combined emit 80 percent of all GHGs in the U.S. The dairy industry contributes two percent and the beef industry approximately three percent in the U.S..

Dr. Dorman: So how can consumers have an impact on the environment?

Dr. Mitloehner: I know we all want to do our part but the way we individually impact GHG emissions by, for example, washing our clothes in cold water, switching to energy efficient lightbulbs, or altering our diets is very small. Let’s say that as a meat eater you decide to go vegan for an entire year. You would save 0.8 tons of GHGs. Contrast that to one flight from the U.S. to Europe, which would produce 1.6 tons of GHGs. The vast majority of impact could be exerted by 30 companies in our country; they are making up the majority of total emissions.

Dr. Dorman: Methane from cattle seems to get a great deal of attention. We’ve likely all chuckled at the headlines about cow farts. Is it an issue?

Dr. Mitloehner: Again, cattle only contribute to about five percent of all U.S. GHG emissions and while they do produce methane, a majority of it actually comes from belching. Research conducted at UC Davis shows that adding essential oils, seaweed or new molecules to livestock feed can reduce such emissions anywhere from 10 to 80 percent. So it’s really significant and could be one of the main ways of reducing methane in the years to come.

Dr. Dorman: I’ve heard you talk about animal agriculture actually contributing to global cooling. Can you explain what you mean by that?

Dr. Mitloehner: Carbon dioxide (CO2), of which a majority comes from burning oil, gas and coal, stays in the atmosphere forever. However, methane only has a life span of 12 years since it’s broken down by a natural reaction in the atmosphere. Even though it’s roughly 30 times stronger than CO2, it doesn’t accumulate in the atmosphere like CO2. And if emissions are constant, a source can emit the same amount being removed in the atmosphere, creating balance. But no one ever factors that into the equation when calculating GHG impact on the climate. That means how we judge the warming impact of methane is incorrect. If we can reduce methane from cattle, such as by installing anaerobic digesters on farms to capture methane from manure, that can actually contribute to global cooling because less methane is emitted than is being removed from the atmosphere through the natural process I mentioned before. So, if we keep the cattle population steady, yet reduce methane emissions, we’re actually part of the solution – contributing to reduced GHG emissions. Visit this site for infographics that help illustrate the concept.

For those of us who want to play a part in protecting our planet, it’s important to cut through the clutter and consider the facts to better understand how we can truly make a difference. Dr. Mitloehner applauds all efforts, but weighing the benefits and tradeoffs can help us make decisions that align with our lifestyles and values.

To learn more about environmental impacts of animal agriculture, I encourage you to connect with Dr. Mitloehner on Twitter @GHGGuru, visit his blog or subscribe to CLEAR Center newsletter. More of his work can be found at and on Twitter at @UCDavisCLEAR.

And as always, I’d love to connect with you! Reach out at @AskDrDorman or by email at