You probably heard the story: Animal agriculture, especially of cows, causes global warming. Free range grass fed cows are worse offenders, because the roughage they eat makes their digestive system produce even more methane than grain and soy fed CAFO animals. At least, this has been a common narative that has been taken up by the main stream media.
In this blog post I want to look at these claims and paint a different picture that might have you rethink your food choices. I want to have a good look at methane, how it is intertwined into our food production, and how it actually contributes to global warming.
Lets start by looking at our suspect.
A methane molecule is made up out of one carbon atom and four hydrogen atoms. When you burn methane, or after a while when part of the atmosphere, oxidative processes will turn our CH4 methane molecule and two O2 oxygen molecules into a CO2 carbon-dyoxide molecule and two H20 water molecules. A methane molecule, when not burned will on average live for about eight years before this happens.
(image source Anne Marie Helmenstine)
It is important to note that CH4 is about 250 times as potent a greenhouse gas as CO2, so it would be fair to compare these 8 years our carbon atom spends as part of a methane molecule to be the equivalent of 2000 years from a global warming perspective.
Now we get at the important part. Cycle length. Let's tell a tale of four atoms.
- Carbon atom one, lets call her Alice, was exhaled as part of a CO2 molecule by a free range grass fed cow.
- Carbon atom two, lets call him Bob, was exhaled as part of a CO2 molecule by an environmentalist and vegan.
- Carbon atom three, lets call her Carol, was burped out as part of a CH4 molecule by a free range grass fed cow.
- Carbon atom four, lets call him Dave, was released as part as an accidental fart by an environmentalist vegan.
To understand which ones of these carbon atoms contributes (most) to global warming, we need to at the history as much as we need to look at the future of these carbon atoms.
The important thing to realize is that each of these carbon atoms was part of an atmospheric CO2 molecule, and is, or will be again. Carbon atom Alice was part of an atmospheric CO2 molecule just months ago, or maybe even just weeks or days ago. But lets say for reference that the cycle for Alice started 0.1 years ago and ended when she was exhaled by Betsie the cow.
I hope we can all agree that Alice isn't capable of contributing to global warming. She was in the atmosphere 0.1 years ago, and she is again now. She hasn't been away long enough to make a difference and now she is back.
But now for Carol, she too was part of an atmospheric CO2 molecule just 0.1 years ago, but now she is part of an CH4 molecule, and shell likely won't be part of a CO2 molecule again until about eight years from now. In those eight years, shell add as much to global warming as Alice will in 2000 years. You could say the effective cycle length of Carol is a whopping 2000.1 years. So far this is all in line with the narrative we've heard all so often. A narrative we can be sure our environmentalist vegan beliefs in with whole his heart.
But its not the whole story.
(image source Justine de Valicourt)
The story for Bob and Dave begins about 300,000,000 years ago, when Bob and Dave were both absorbed by an aquatic plant. After three hundered milion years under the ground, most of which as a methane molecule as part of natural gas, Bob and Dave where both given a temporary home in the petrochemical industry, where they first migrated from being part of a CH4 methane molecule to being part of a HCN Hydrogen Cyanide molecule. After that, they migrated again and became part of KCN Potasium cyanide molecules.
From Methane to Hydrogen Cyanide, from Hydrogen Cyanide to Potassium Cyanide, fro Potassium Cyanide to Potassium cyanate, and finaly, thanks to our old friend Friedrich Wöhler, to CH4N2O Urea. A nitrogen fertilizer. But in this case, one that contains 300,000,000 year old carbon atoms.
Both carbon atoms end up in produce eaten by our environmentalist vegan, and at the end of our story end up being respectively exhaled and released in a fart.
So lets look again at our four atoms, and look at their CO2->C02 cycle length.
- Carbon atom one, lets call her Alice, was exhaled as part of a CO2 molecule by a free range grass fed cow: 0.1 years
- Carbon atom two, lets call him Bob, was exhaled as part of a CO2 molecule by an environmentalist and vegan: 300,000,000.1 years
- Carbon atom three, lets call her Carol, was burped out as part of a CH4 molecule by a free range grass fed cow. 2,000.1 years
- Carbon atom four, lets call him Dave, was released as part as an accidental fart by an environmentalist vegan: ** 300,002,000.1 years**
So as it turns out four our four atoms, while the cow burp carbon atom is significantly worse for the climate than the cow breath atom, compared to the vegan environmentalists atoms, its contribution is absolutely negligible.
Note that the explanation above is very much a simplification of the petrochemical and biochemical processes involved, but the core cycle mechanism is valid. Global warming is caused by long cycle processes, not by short cycle processes, and while a 2000 year cycle equivalence for cow burps might sound long, its really nothing compared to the cycle length of hundreds of millions of years implied by the reintroduction of fossil carbon.