Rethinking methane

Many livestock producers have suffered unfair blame when it comes to their environmental footprint, but Dr. Frank Mitloehner of UC Davis is determined to change that.

By Angela Lovell

At the Manitoba Beef Producers Annual General Meeting in February, Mitloehner explained how he, and other researchers, are changing the narrative on greenhouse gas (GHG) emissions from the beef and dairy sector, to one where producers are viewed as an asset in the fight against global warming, rather than a liability.

The narrative begins with dispelling the myths and highlighting the facts around methane production from cattle.

Methane is very different from CO₂

The fact is that cattle production does produce GHG emissions of carbon dioxide (CO₂), nitrous oxide (N₂O) and methane (CH₄), but it’s important to understand that these gases operate very differently in the atmosphere. CO₂ and N₂O both persist for a long time in the atmosphere (up to 1,000 years), but methane is destroyed by a process called hydroxyl oxidization within 12 years.

To relate the importance of this for cattle production, it’s necessary to understand the Biogenic Carbon cycle by which methane from livestock is produced and destroyed.

The Biogenic Carbon cycle (see link at end of article) begins with photosynthesis, where plants convert sunlight, water and carbon from the atmosphere into carbohydrates, such as cellulose or starch. A bovine eats this material, digests it through a process called enteric fermentation, and expels methane in its waste products. Carbon in the methane is converted, through hydroxyl oxidation, back into CO₂ which goes back into the atmosphere, but that carbon is recycled carbon, identical to the carbon that was in the atmosphere in the form of CO₂ that the original plants photosynthesized to begin the cycle.

“As long as herd sizes are stable, the amount of methane produced by your cattle, and the amount of methane destroyed by hydroxyl oxidation will be in balance,” Mitloehner said. “Constant cattle herds do not add additional carbon or methane to the atmosphere, and they do not cause additional warming to our climate.”

Carbon derived from fossil fuels (oil, gas, coal) is different because it’s a one-way process, said Mitloehner. “Fossil fuels were formed from decayed plant material that fossilized and accumulated in the ground over a very long period of time,” he said. “Over the last 70 years, we have extracted about half of that ancient carbon, and burned it in our cars, planes, trains, ships, power plants and so on. We put that carbon into the atmosphere mainly in the form of CO₂ and why we see CO₂ levels rising year after year, is because it’s not a short time cycle, but a very long, one-way street of fossil carbon from the ground into the atmosphere.”

Why animal agriculture gets a bad rap

The reason why animal agriculture has been vilified in terms of the impacts of methane on the climate has largely been due to a matrix called the GWP100, used for the past 30 years to calculate global warming potential of different GHGs. Generally, using this formula, methane (and N₂O) emissions are converted into CO₂e (equivalents) and, in the case of methane, is multiplied by a factor of 28. So, a ranch producing 100 tonnes of methane, is producing 2,800 tonnes of CO₂e.

This system is wrong, Mitloehner said, because it does not take into account that methane is both produced and destroyed, and is not cumulative in the atmosphere over a long period of time as CO₂ and N₂O are. Scientists have developed a new matrix, called the GWP* that does account for this difference, and gives a more accurate picture of methane’s climate impact.

Scientists compared three scenarios, increasing methane by 35 per cent over 30 years, maintaining the same amount of methane emissions over 30 years, and decreasing methane emissions by 35 per cent over 30 years, using both the GWP100 and GWP*.

The GWP100 predicts strong increases in CO₂e, translating into increased global warming, with all three scenarios, while the GWP* predicts that increasing methane by 35 per cent would indeed increase warming, but maintaining a stable level of methane would result in a slight decrease (around 10 per cent) in warming, and a reduction of 35 per cent of methane emissions would result in cooling.

Applied in the context of animal agriculture, the key message is that stable herds or flocks will not add to global warming, and that, in fact, if methane emissions from livestock production can be decreased, it will help to reduce global warming. So, it appears that beef production can be an important part of the climate solution. Beef production part of the climate solution “The Paris Climate Agreement is all about keeping global warming under one-and-a-half degrees,” said Mitloehner. “In most of the developed world we see that livestock herds are staying pretty stable and producing constant amounts of methane. If we have a constant CO₂ source and a constant methane source, the constant CO₂ source still leads to increased amounts of warming because it’s cumulative, but a constant methane source leads to no additional warming. And when you decrease the methane to net zero, you have an instantaneous decrease in warming.”

The same is not true of CO₂, which, if emissions were reduced to net zero (an unrealistic goal given that would basically require no burning of fossil fuels at all), CO₂ emissions would plateau, but global warming would continue to increase for a long time because of the massive amounts already in the atmosphere, that have already been accumulated due to the burning of fossil fuels over the past 120 years.

“Methane is not a super pollutant like CO₂,” Mitloehner said. “Methane is a super opportunity because if we, in animal agriculture, manage to reduce it, that has an instantaneous cooling effect, and that makes you a potential solution provider to overall climate issues.”

Reducing methane in livestock production

Is it possible to reduce methane emissions on livestock operations? Its’s already being done, said Mitloehner, giving examples from California, where there are substantial financial incentives available for livestock producers, including beef and dairy operations, to help reduce methane emissions by 40 per cent, by 2030. These Low Carbon Fuel Standard Credits more than offset the investment required to implement technology like anerobic digesters, lagoon covers and feed additives that all help reduce methane and other GHG emissions.

A very successful practice, that has been widely adopted by California’s dairy industry, is covering open lagoons, and converting the captured biogas into renewal natural gas (RNG), a carbon negative fuel source, that is used to fuel semi-trucks. (See link at the end for information). This one practice has already reduced methane emissions from the dairy sector by 25 per cent.

Research into feed additives has also identified five that work to reduce methane emissions anywhere from 10 to 50 per cent. One is already commercially available, and the others should be within the next four years.

Making animal agriculture more efficient is also going to be key, added Mitloehner, to meet the challenge of feeding 9.5 billion people by 2050, as populations, especially in southeast Asia and Africa continue to increase exponentially. These are also areas of the world where livestock production is less efficient, and produces higher GHG emissions compared to the developed world.

“The developing part of the world currently produce between 70 to 80 per cent of all GHG from the livestock sector globally,” said Mitloehner. “So, there are areas where there is significant room to grow to lower the environmental footprint of livestock through things like improved reproduction and genetics, better veterinary care, and more energy dense diets.”

A model for GHG reduction

Mitloehner sees what is being done in California as a model for North America and internationally, because it works. “There is no other form of GHG reduction or carbon sequestration that is as cost effective as reductions through animal agriculture, and in the years to come we will be viewed not as a liability in the climate arena, but as an asset,” he said. “Beef and dairy do produce GHG, but if you can manage to reduce them, you can be part of the solution. What I told you today is something you have probably never heard before, but you will hear it again because I and my colleagues are working to ensure the narrative gets set right. And all of you can help with that.”

Farmers must tell their story, especially when they have compelling facts and science to support that what they are doing on their farms and ranches is playing an important role in climate mitigation.

“Your strongest weapon, as a farmer is your authenticity, and consumers eating beef in Manitoba and Canada have a high respect for you,” he said. “You know more than anyone else how to produce beef, and you should be proud of what you do. If someone attacks you, don’t operate on that level, just tell your stories, what you do, how you do it, and that you have a legacy you are proud of. On that level you can engage any kind of discussion.”

LINKS:

Explanation of the Biogenic Carbon Cycle and cattle https://clear.ucdavis.edu/explainers/biogenic-carbon-cycle-and-cattle

Agriculture’s Contribution to Climate Change and Role in Mitigation Is Distinct From Predominantly Fossil CO2-Emitting Sectors https://www.frontiersin.org/articles/10.3389/ fsufs.2020.518039/full

UC Davis White Paper that Re-Examines Methane’s Role in Climate Change, and How the California Dairy Can Achieve Climate Neutrality https://clear.ucdavis. edu/news/methane-cowsand-climate-change-california-dairys-path-climate-neutrality