Clearing the air: Animal agriculture and greenhouse gases

Is the warming effect of all greenhouse gases (GHGs) the same? And could livestock producers actually be part of the climate solution? Let’s start with the basics.

Not all greenhouse gases are created equal

 First, it’s crucial to understand that multiple greenhouse gases contribute to the greenhouse effect, and each one impacts the environment differently.

Carbon dioxide (CO₂) is the most prominent GHG and is often considered synonymous with all greenhouse gases, but it’s not.

• How carbon dioxide is released: Through human activities like the burning of fossil fuels, land use changes and deforestation, and other natural processes.
• How long it remains: Centuries.
• How it’s removed: Carbon dioxide is removed from the atmosphere, or sequestered, when it’s absorbed by plants as part of the biogenic carbon cycle.

Methane (CH₄) is a potent greenhouse gas with a global warming potential that’s about 28 times greater than carbon dioxide over a 100-year period. Methane does not cause direct harm to human health or crop production, but its presence in the atmosphere can affect the amount of other greenhouse gases like tropospheric ozone, water vapor and carbon dioxide.

• How methane is released: Methane is released during the production and transport of coal, natural gas and oil. Methane is also released through decomposing plant matter, livestock and other agricultural practices.
• How long it remains:  About 12 years.
• How it’s removed: Methane is broken down in the air by a natural process called hydroxyl oxidation, during which atmospheric radicals take hydrogen away from methane and convert it to CO₂. That means as methane is produced, it’s also destroyed.

Nitrous oxide (N₂O) is an ozone-depleting gas that’s about 300 times more potent than carbon dioxide.

• How nitrous oxide is released: From bacteria in the soil, through modern agricultural practices like tilling, soil cultivation and livestock waste management, and through the use of nitrogen-rich fertilizers.
• How long it remains: About 110 years.
• How it’s removed: Nitrous oxide is absorbed by certain types of bacteria or destroyed by ultraviolet radiation or chemical reactions.

Taking the heat off of cattle

Now that we’re clear on the differences between the top greenhouse gases, where do cattle and farm systems come into play? This is a subject Dr. Frank Mitloehner, director of the CLEAR Center and a professor and air quality specialist at the University of California, Davis, is committed to clarifying.

It’s commonly said that livestock emissions represent anywhere from 14% to 50% of total GHG emissions. But according to Dr. Mitloehner, this does not reflect actual livestock emissions in developed countries like the United States, where the number is closer to just 4% of all U.S. emissions.

Beyond misconceptions like this is the fact that the general public is just not aware of how greenhouse gases like methane and carbon dioxide actually work — and their varying impacts on the planet.

Comparing cows to cars just doesn’t add up

Yes, methane is more potent than carbon dioxide. But the environmental differences between belching cows and gas-guzzling cars has become increasingly clear.

For example, as a short-lived “flow gas,” methane only lives in the atmosphere for about 12 years. This means the global warming potential of methane emissions is a small window of time. And after that time, methane is destroyed and absorbed by plants as CO₂, converted into cellulose and eaten by livestock. This is possible via hydroxyl oxidation, a powerful natural process by which methane is broken into CO₂ and becomes available to enter the biogenic carbon cycle.

In short, if a source of methane such as a herd of cattle stays constant for 12 years, its methane emissions will nearly equal what is destroyed. In other words, if herd sizes were to remain constant for a decade, the rate of methane emission would balance out with its natural removal from the atmosphere, thus making the warming impact neutral.

“What makes methane from animal agriculture a flow gas is that it’s not just produced — it’s destroyed and taken out of the atmosphere,” said Dr. Mitloehner.

On the other hand, carbon dioxide packs a longer-lasting punch. As the primary climate change culprit, CO₂ is a “stock gas” that culminates in impact over hundreds of thousands of years. So while methane is quickly removed from the atmosphere, CO₂ persists for centuries, adding greater warming impacts over time. This steady accumulation leads to exponential increases in warming, whereas when methane increases, the warming is linear.

Making animal agriculture a part of the climate solution

 It’s not a question whether animal agriculture plays a role in climate change. Of course it does. But in order to find the most innovative climate solutions, we have to look at the bigger picture. Casting livestock as the scapegoat for a problem that’s much larger than grazing cattle is not the answer. We must work together to shed light on the facts, debunk agriculture myths and improve sustainable farm management practices.

California is proof that the path to carbon neutral dairy production and sustainable animal farming practices is more than possible. By implementing solutions for animals raised on farms like dairy digesters, integrated nutrient management, cover crops and manure management systems, livestock producers can make small changes that can make a big difference in protecting our planet for generations to come. From the processing and transportation of animal products to emissions generated from feed production and processing, minimizing agriculture’s footprint will require a holistic approach that is rooted in science, truth and research.