Here at the LWR Innovation Center, we know a lot about manure. In fact, we consider ourselves to be manure experts! But we aren’t experts on greenhouse gases and we’re on a mission to really understand the role that cows play when it comes to emissions.

We’ve all heard that animal agriculture creates greenhouse gas emissions. Have you also heard that cows that they can be part of a climate solution? With so many different messages, I decided to reach out to a real expert to help us understand the relationship between cows, carbon, and the climate… and what better timing than to do it on Earth Day!

This year the world celebrated the 50th anniversary of Earth Day. The theme for 2020 is climate action and I am excited to share the exciting ways that animal agriculture can positively impact the future of humanity and the life-support systems that make our world habitable.

Animal science professor Frank Mitloehner reaches beyond academia to inform the public about animal agriculture’s influence on greenhouse gas emissions. (photo: UC Davis)

Dr. Frank Mitloehner, aka @ghgguru on Twitter, is a Professor and Air Quality Specialist in Cooperative Extension in the Department of Animal Science at the University of California, Davis. He is an expert for agricultural air quality, livestock housing and husbandry and conducts research that is directly relevant to understanding and mitigating of air emissions from livestock operations. His research includes the implications of these emissions for the health and safety of farm workers and neighboring communities. Dr. Mitloehner is also director of the new CLEAR Center at UC Davis, which is focused on research and science communication.

He shared some of his wisdom with me last week, and it’s my pleasure to share that insight with you here.

Jenkins: First, I can help but want to understand why cows, in particular have been targeted in such a negative way?

Dr. Mitloehner:

Animal agriculture has been targeted by different groups for a long time. They are trying to use the climate argument to get consumers to disassociate from animal sourced foods. Most of the real, legitimate concern is around methane, and in particular ruminant livestock methane that is more potent than other greenhouse gases. They want to convince us that by simply consuming less animal sourced foods, that we can make large changes to the climate.

Jenkins: What factors should be included in the greenhouse gases that are attributed to livestock production?

Dr. Mitloehner:

When it comes to greenhouse gases from animal agriculture the most important one is methane. The second is nitrous oxide which not as well known to people but it is actually much more potent than methane. Nitrous oxide is emitted when you fertilize fields with both chemical and manure fertilizers.

But let’s talk about methane because that is the point of contention. Methane is 28 times more potent as a greenhouse gas than CO2. There is no question that methane is a potent greenhouse gas. In addition to its potency, there are other important differences between methane on the one side and nitrous oxide and CO2 on the other side. Mainly and most importantly, CO2 and nitrous oxide are long lived climate pollutants with a lifespan of hundreds to a thousand years. Once a molecule of CO2 or Nitrous Oxide enters the air, they stay there pretty much forever.

Methane, on the other hand, only has a lifespan of only 10 years. Methane is produced, but it is also destroyed, and here is where most people fall short when accounting for methane: they only account for the production of this gas, but not for the destruction of this gas, and when you do this beef and dairy look really bad because when you only look at the one side of the accounting sheet and not the other side then you get the wrong picture.

Critics of animal agriculture fall short in a drastic way. What they should do is look at the real warming potential of methane, and not just how much methane is emitted and can be expressed as CO2 equivalent.

By simply using a factor of 28 to calculate the CO2 equivalent of methane some have assumed that methane is 28 times worse than CO2 but in fact that has zero relevance to the actual warming impact of methane. The warming impacts are not being expressed by the current unit that is being used.


Imagine this: Worldwide, there are 560 terragrams of methane produced. That is a high number, and people take that number and say “see how bad it is?!” but…. While it is a high number, the part of the story that isn’t being told is that while it’s produced at a rate of 560 terragrams it is destroyed at a rate of 550 terragrams. The global net methane is not 560 but in fact it is only 10.


Atmospheric chemists have known this for a long time but they haven’t been a part of the methane conversation. If they were, it would really be a game changer. By only using the production numbers, we have seen public policy effected in a very negative and non-scientific way. Methane is important but it is currently not being characterized appropriated.

Jenkins:  So what would happen if we could reduce methane?

Dr. Mitloehner:

If you keep methane constant by having constant cattle numbers without making any changes to manure management practices, or to reduce enteric emissions, the methane emitted by your cows will stay stagnant – constant – and will not add any additional new methane to the atmosphere because as those cattle emit methane, the same amount is being destroyed in the atmosphere. However, if you increase methane by adding new cows, then you drastically increase warming impact and we want to prevent that by all means.

Now, if you reduce methane from US animal agriculture by 10 to 20 percent you are actually pulling carbon out of the atmosphere, which leads to a net cooling effect, which results in global cooling which can counteract fossil fuel related warming impacts.

So by using a technology that reduces methane, that reduction correlates to a net cooling impact and that to me is so exciting and should be so exciting to companies such as yours.


Jenkins: Are there any methane solutions that you are particularly excited about?

Dr. Mitloehner:               

Methane is produced in anaerobic conditions… whether that’s the ruminant of the cow or in the manure lagoon on the dairy. In those environments you have a drastic increase of methanogens that produce methane gas. If you want to reduce that, there are different technologies that are under development from an enteric methane perspective, there is a drug called 3NOP that has been very well researched and is a good successful candidate for enteric methane reductions.

From a manure methane reduction perspective, anaerobic digesters certainly have a major role to play – now whether that always makes economic sense is a different question. In California we have reduced methane from manure by 25 percent over the last two years largely through the use of anaerobic digesters which is something the dairy industry should be very proud of.

There are also alternative manure management practices that are being supported financially here in California by the California Department of Food and Agriculture. Both anaerobic digesters and alternative manure management practices (including the LWR System) have received half a billion dollars of public funds over the last two years in California.  People are quantifying the impacts of these technology and the public sector is supporting them.

Jenkins: How important is manure treatment in the greenhouse gas equation? 

Dr. Mitloehner:               

There is no doubt hat the short-lived climate pollutants such as methane have the most immediate impact on climate. It is because they are short lived that when you reduce them, you will see an immediate impact on climate.

It would be a wonderful thing if we could all stop emitting CO2, but the fact remains that the CO2 we have been emitting will still be in the atmosphere in 1000 years. Now if you reduce methane, that reduction will impact the climate immediately. and that’s why it’s such a big deal!

Jenkins: What do you say to people who say we should just go meatless?

Dr. Mitloehner:               

I say that if someone feels better about eating a plant based diet than that’s their decision. Will it have a major impact on methane? The answer to that is no.

The demand for animal sourced foods is strong and it’s not being reduced at all through plant-based alternatives. The meat demand in the United States and Canada has been increasing while at the same time the demand for plant-based alternatives has also been increasing so we do not see that one is replacing the other.

Even if 10 or 20 percent of consumers switch over to a plant-based diet, that would have a minimal impact on our climate.

If all 320 million Americans stopped consuming all animal sourced foods, if everyone became vegan, the carbon footprint of the United States would be reduced by only 2.6 percent! If we all were to go meatless on Mondays, our carbon footprint would be reduced by 0.3 percent. (Nutritional and greenhouse gas impacts of removing animals from US agriculture)

Stay tuned for part 2 of our conversation where Dr. Mitloehner will fill us in on one of the the biggest misconceptions about methane, and what the future has in store! In the meantime, be sure to follow @ghgguru on Twitter, and check out the GHG Guru’s blog


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