Research overseen by Dr Frank Mitloehner, professor and air quality specialist in the Co-operative Extension in the Department of Animal Science at the University of California, and Dr Myles Allen from Oxford University has shown that livestock-related greenhouse gases are distinctively different from greenhouse gases associated with other sectors of society.
Dr Mitloehner explained the differences at the 2020 Alltech One digital experience and gave the example of Los Angeles and its population of 13 million painted an image of a concrete jungle, where Ireland portrays picturesque green countryside. But surprisingly Ireland has a greater carbon footprint than Los Angeles.
The unit used to describe greenhouse gases is carbon dioxide equivalents.
Los Angeles has emission equivalent to 50 million metric tons, where the country of Ireland emits 60 million metric tons. But it does not seem to make sense when you consider the fossil fuel usage in both places he said.
“You have to think about gases, such as methane, are not just emitted, they are also reduced. They are sequestered. And a place like Ireland, with all the grass, with all the hedges, and trees, and so on, with the soils in agriculture and forestry, it sucks out a lot of greenhouse gases,” Dr Mitloehner explained.
“So, while the world is always thinking of how much greenhouse gases are emitted by different sources, they often don’t consider that there are certain sectors of society such as forestry and agriculture that also serve as a sink for greenhouse gases.”
Comparing three greenhouse gases, carbon dioxide, methane and nitrous oxide, is often in relation to a Global Warming Potential, or GWP 100.
“For example, if there were 100 pounds of methane emissions, it gets multiplied by 28 which gives the carbon dioxide equivalence or 100 pounds of nitrous oxide emissions gets multiplied by 265 for the carbon dioxide equivalence.
“Carbon dioxide and nitrous oxide are referred to as long-lived climate pollutants, and methane on the other hand is a short-lived climate pollutant. When methane is put into the atmosphere a reaction occurs and some of the methane is converted to carbon dioxide again.
Another major difference between the three gases is the lifespan, carbon dioxide has a lifespan of 1000 years, nitrous oxide is not quite as long but still hundreds of years and methane has a half-life of 10 years. Meaning the methane that our cows and other livestock put out will be gone after 10 years.
“But we cannot disregard the impact from methane. While that methane is in the atmosphere, it is heat-trapping, it is a potent greenhouse gas,” he said.
“The question really is: do our livestock herds add to additional methane, meaning additional carbon in the atmosphere, leading to additional warming? The answer to that question is no.
“If we have constant herds or even decreasing herds, we are not adding additional methane hence not additional warming.”
If herd sizes were to rise there would be increasing amounts of methane but data regarding livestock in the United States demonstrates drastic reductions in numbers. In the 1970s they had 50 million more beef cattle than they do today and in the 1950s, they had 25 million dairy cattle, where they only have nine million today. This also leads to a decrease in the amount of carbon being put into the atmosphere.
Fossil carbon originates from fossil fuel, which comes from ancient forests and animals that were fossilised hundreds of millions of years ago and stored in the ground.
The human population extracts it and uses it as fuel, which takes carbon out of the atmosphere where it was trapped, burns it, and puts it back into the atmosphere.
“This is not a cycle but a one-way street because the amount of carbon dioxide that we put into the atmosphere by far overpowers the potential sinks that could take up carbon dioxide such as oceans, soils, or plants. And this is the main culprit of greenhouse gases in our atmosphere and the resulting warming,” Dr Mitloehner said.
“I have yet to see a climate scientist who would say that it’s the cows that are a primary culprit of warming. Most of them will agree that the primary culprit is the use of fossil fuels.”
Comparing the lifespan of the gases, carbon dioxide builds like interest, where methane, being short-lived, is a flow gas. It is taken out of the atmosphere even when more is being put in.
“But if we can decrease methane, we can actively take carbon out of the atmosphere. And that has a net cooling effect.
“If we find ways to reduce methane, then we counteract other sectors of societies that do contribute, and significantly so, to global warming, such as flying, driving, running air conditioners, and so on.
“So, if we were to reduce methane, we could induce global cooling. And I think that our livestock sector has the potential to do it. And we are already seeing examples where that happens.”
Dr Mitloehner and the team measure greenhouse gas emissions and the impacts of different mitigations through bovine bubbles.
They take devices out into commercial farms and measure emissions before and after the implementation of technologies to quantify the impact of different mitigation technologies to further reduce methane.
“So, can we get to that point where we reduce methane? That’s the question. And the answer is yes. We need to find true mitigation techniques and technologies that help us to make the livestock sector more efficient,” he said.
“Like the automobile sector learned to make their costs more efficient, more fuel efficient for example, to get us from A to B using half the amount of gas as our parents’ cars, or two thirds less than our grandparents’ cars. Because that reduced use of fuel directly translates into lesser emissions.
“And the same is true for livestock. If we produce more efficient livestock, that means we reduce the environmental footprint. And we do this in incredible ways.
In my opinion, that really needs to be quantified and needs to be publicised. It needs to be made very clear as to which role all farmers are already playing now, making very significant reductions to their environmental footprint.”
