Cow farts are not a major source of global warming
A lot of us want to do our part to stop climate change. We hear a lot of suggestions for what to do:
• Drive an electric car.
• Put solar panels on your roof.
• Stop eating meat.
I’ve written about car choices and rooftop solar. Today, I’m going to look at how important that last point is.
How much do our diets contribute to global warming? Do we all need to go vegan, to save the planet?
The science of biogenic methane
When cows burp or fart, they emit methane. Methane is a potent greenhouse gas that warms the planet about 100 times more than the same amount of carbon dioxide.
Methane doesn’t stay in the atmosphere for very long, though. It breaks down into carbon dioxide after about 12 years, on average. After that point, it traps the same amount of heat as carbon dioxide.
In the case of cows, we’re talking about biogenic methane. Cows eat grass and other plants. When those plants grow, they pull CO2 out of the atmosphere. After eating those plants, cows produce some methane. A decade later, that methane breaks down into CO2, which feeds more plants.
It’s a closed cycle. There’s never any increase in carbon dioxide.
It’s different than fossil fuels. When we dig up coal or drill for oil, we take carbon that’s been trapped underground and put it into the atmosphere. The more we burn, the more the planet heats up.
To be specific, the cows do cause some increase in temperature, because it takes a decades for the methane to break down into carbon dioxide.
That temperature increase is constant, though. It doesn’t build up.
Putting some numbers on it
There are about a billion cows in the world, with Brazil and India having the most:
A world with 1 billion cows in it is warmer than a world without any cows. But it doesn’t keep getting warmer over time, the way that a world with 1 billion cars in it does.
That should be kind of obvious, if you think about it.
A few hundred years ago, the United States had 30–60 million bison, roaming the plains. Early settlers shot most of those animals and then replaced them with about 90 million cows. If cow farts could cook the planet then the bison would have, over time.
How much warmer do one billion cows make the world?
Global emissions from cows are 73 million tons of methane.
Methane is about 100 times more potent than CO2, so that’s equivalent to 7.3 billion tons of CO2.
But it also decays over time. Only 12 years of emissions will build up.
So, the total effect is equal to 88 billion tons of CO2.
Fossil fuels emit about 40 billion tons of CO2 every year.
In other words, the total warming from cows is equal to 2.2 years of warming from fossil fuels.
Converted into a temperature rise, those billion cows raise world temperatures by about 0.1 degrees Celsius.
If you want to think of it as an annual contribution, the cows will raise world temperatures by 1/12th of that much in the first year, 2/12th’s by the second year, and so on. By the 12th year, the temperature increase hits 0.1 degrees. But after that, it won’t increase more, because the methane from the 1st year has already broken down. It has turned into CO2. Plants will absorb that CO2. Cows will eat those plants.
We could all stop eating beef, get rid of every cow, and it would drop temperatures by 0.1 degrees.
But that sacrifice would be meaningless if we keep burning fossil fuels. After 2 years we would have polluted enough CO2 to compensate for that.
On the other hand, if we stopped burning coal and gas, we could eat beef forever and the planet would never get more than 0.1 degrees warmer than it would be otherwise.
So, why do people worry about eating beef?
There might be some valid reasons to eat less meat. Some people are vegetarians because they worry about animal rights.
Clearing land to raise cattle can also be bad for wild animals living on that land. It’s harmful if Brazil clears the rainforest to raise more cattle. We need to set aside some land for national parks, to keep wild animals from going extinct.
But I think the concern about beef and global warming comes for a different place.
At times, environmentalism seems like a religious movement.
I’ve written before that climate apocalypticism resembles religious doomsday predictions. Both predict that our sins will bring about the end of the world.
Maybe there’s also some kind of religious zeal behind the concerns about eating beef.
People want you to take climate change seriously. They want you to make sacrifices to atone for it. They want you to drive less, travel less, buy less things, eat less meat. Some people don’t even want you to have children, to keep the future planet safe for the children you won’t have.
The truth is, I don’t want to give up a good life to stop climate change, and most other people don’t want to either. If you want to sell people on fixing climate change, maybe it’s better to not frame it that way.
The good news is that we don’t have to. We just need to replace the things that are truly unsustainable, like burning gasoline.
Instead of telling people that the world is ending because of their personal choices, we can give them better alternatives.
In a world with clean electricity and electric cars, we should be able to eat meat without destroying the planet.
That’s the kind of sustainable future I look forward to.
