Cow Burps As a Metaphor for Life

Reduce, replace, repeat, refine

So, cow burps constitute roughly 4% of greenhouse emissions.

They burp methane, a potent greenhouse gas. This isn’t exactly a secret; you might have read about it; for instance, here’s a 2020 article from CNN. But if you’re like me, you filed it away under “things that are too weird to internalize and too what-the-heck-can-I-do to worry about”.

Despite what you might be thinking, most of the methane does emerge at the front end of the cow. The fancy term is “enteric methane”. “Enteric” means “relating to or occurring in the intestines”, and you needn’t thank me for making you think about cow intestines, I write this blog as a public service. But in any case the primary source here is actually the cow’s stomach, specifically the “the rumen, which supports the microbial populations able to break down cellulose” – the reason cows are able to digest things like grass. There’s an entire ecosystem of microbes in there; one source describes cows as “wetlands on four legs”. Another notes that “microorganisms known as archaea… use the hydrogen that is released by other microorganisms in the rumen to produce methane.”

Since this is the cow’s stomach, I don’t know why it’s called “enteric methane” and not “gastric methane”, but let’s just move on. One last note on the science: I gather that generating methane is not actually beneficial to the cow; it’s a waste of food energy. In fact there is some evidence that reducing enteric methane helps cows get more value out of their food.

So, cow stomachs are responsible for a significant portion of greenhouse emissions. What can we do about it?

Cows Are Not Wind Turbines

Here are a couple of wind turbines, one older, one modern. See if you can tell which is which.

Here’s the cow again, showing no signs of remorse for what it’s doing to the environment:

I’m not going to bother tracking down pictures of a 1950s cow and a 2020s cow; they haven’t changed the way wind turbines have. We’ve gotten used to technology evolving at a blistering pace; cows, not so much. “From 1961 to 2018, enteric methane emissions per unit of beef decreased in the United States by 36 percent” [source]. In the same period, the cost of wind power dropped by at least a factor of ten, and solar cells by several hundred! Notice how different these two graphs look.

Wait, 36% Is A Lot Actually

I just dismissed a 36% reduction in enteric methane emissions as basically representing stasis. In the world of climate tech, we’re used to technologies that improve by huge factors, so 36% seems uninteresting. But that rapid progress usually arises only in immature technologies, technologies that haven’t yet been optimized, and need huge improvements to become commercially relevant. A 36% efficiency gain in a mature, dominant technology (I guess cattle farming counts as a “technology"?) is huge.

The source which puts the improvement at 36% says it was “due in large part to improved breeding as well as management”. The basic idea seems to be that healthier, better-fed animals grow more efficiently. A cow that is just barely getting by spends most of its calories merely to survive. Modern US cattle get a lot of surplus calories, allowing them to put on weight rapidly. In the end, the growth-per-calorie ratio is a lot higher. No one was specifically attempting to reduce cow burps; the methane reduction was a side effect of optimizing beef-per-dollar.

Critically, many countries haven’t caught up to where the US was in 1961, let alone today. Here are a few passages from another source. Feel free to skip ahead; basically these quotes say that beef and dairy production in developing countries, representing most of the globe’s cattle, is anywhere from 2x to 30x less efficient than in the developed world.

…the most dramatic reductions occur in shifting from the least digestible feeds to moderately more digestible feeds. For example, according to one study, improvements from the least efficient to a medium efficient grazing system in Brazil, which still relies entirely on pasture, reduces methane emissions per kilogram of meat by more than half (Cardoso et al. 2016). In another study of actual Brazilian farms, methane emissions per kilogram of meat ranged by a factor of more than 5 and was strongly associated with cattle growth rates (D’Aurea et al. 2021).

…beef production in many countries has 10 to 30 times the emissions rate of
beef production in Europe, the United States, Canada and Japan. The FAO similarly
estimates that dairy production in India releases twice the emissions per liter of milk as in Europe, and in Africa five times European emissions (Gerber et al. 2010).

One study estimated that modest increases in use of high protein leaves from nitrogen-fixing shrubs and use of grains at a level of 0.5 kg/day would reduce emissions intensity of both dairy and beef production in sub-Saharan Africa and South Asia by more than 55% (Thornton & Herrero 2010).

As science fiction author William Gibson famously said, “The future is already here — it's just not very evenly distributed”. If we can distribute it a little bit better, we can dramatically reduce enteric methane emissions.

The Cleanest Cow is No Cow At All

There’s a lot of room to reduce emissions by propagating existing best practices. But that’s no small task; hundreds of millions of cattle are raised in circumstances that don’t support US-style industrial farming practices. And even good ol’ American cows burp quite a bit of methane.

Another way to reduce emissions from cattle is to have fewer cattle, i.e. consume less beef and dairy. And in fact this has been the trend in the United States; per-capita beef consumption peaked in the 1970s, at around 90 pounds per year, and has declined to the upper 50s. However, the trend bottomed out around 2015 and American beef consumption has risen slightly in the last few years. We can’t count on people simply eating less meat.

Fortunately, there are other paths to fewer cattle. Plant-based beef substitutes – Impossible Burger, et al – are still a small fraction of beef consumption, but growing rapidly. I had trouble finding a good figure for the market share of plant-based beef in this country, but it seems to be approaching 1%. (Circa 2020, the market share was about 1% by dollar value. Plant-based products are currently more expensive, so the per-pound market share is lower, but sales are growing rapidly and the 2020 figure is already out of date.) 1% is small, but also a substantial base for a category which is growing exponentially. Electric vehicles are on track to go from 1% to 10% worldwide market share in just six years.

Replacing beef with other meats such as pork or chicken also reduces emissions. The climate footprint of beef is something like 5x that of pork, and 10x that of chicken; in other words, pork and chicken have almost no climate impact in comparison to beef.

We Don’t Have To Get To Zero

In John Doerr Has a Plan, I talked about how the book Speed & Scale presents a plan for net-zero emissions in 2050. The plan only calls for agricultural methane emissions to come down 50%. (It assumes steeper reductions in other sectors, and balances the remaining emissions with direct removal of carbon dioxide from the atmosphere.) So we don’t need to eliminate enteric methane entirely; a 50% reduction is sufficient. This demonstrates the importance of a comprehensive plan: we can give ourselves some slack in the most difficult-to-decarbonize sectors.

Unfortunately, we’ll have to achieve this 50% reduction in the face of an increase in global consumption. Beef consumption in the US is well below the 1970s peak, but as incomes rise in the developing world, global consumption is projected to increase by perhaps 45% by 2050 (The Clean Cow report, page 7).

How does it all add up? Here’s one scenario for change between today and 2050:

• Global beef consumption increases 45%.

• 20% of that consumption consists of plant-based beef. (From today’s US market share, this would require growth of around 12% per year. Current growth rates are much higher, more like 100%.)

• In response to environmental campaigns, 10% of that consumption shifts to pork, chicken, or other non-ruminant animal meats.

• Methane emissions per pound of cattle are reduced 20% through a combination of new techniques (e.g. feed additives) and wider use of existing best practices. (Hopefully this is conservative; page 8 of The Clean Cow report suggests that potential reductions are closer to 50% if we pursue all available options.)

• 50% “catch-up” reduction in emissions per pound for the less-efficient producers in the global south. I’ll estimate that these regions constitute 80% of 2050 consumption.

On these assumptions, 2050 emissions would be 1.45 * (1 - 0.2 - 0.1) * 0.8 * (0.2 + 0.8 * 0.5) = 49% of today’s emissions, or slightly better than the Speed & Scale target for agricultural methane. In other words, the goal seems pretty achievable!

Disclaimer: these are fuzzy numbers. It’s a complicated subject, different sources provide varying estimates, and I couldn’t always find estimates for the exact figures I needed. Also I’ve glossed over the fact that pork, chicken, and plant-based beef do have some greenhouse impact, but this won’t throw things off too much, as their impact is much lower than cattle. I’m not trying to provide a precise analysis, just to show the general lay of the land.

I Promised You A Metaphor For Life

I exaggerated. The metaphor for life isn’t cow burps, it’s “all the world’s a stage”. But the challenge of enteric methane illustrates some widely applicable principles.

First, when you have to do a big thing (reduce emissions by 50%), look for ways to get there by doing several small things (20% market share for plant-based meats). For any category of greenhouse emissions, we can explore at least four avenues:

• Reduce usage of the offending product. (For cattle, this is the one avenue I didn’t model, on the assumption that it will be difficult to simply ask people to eat less meat.)

• Replace the product a greener product (e.g. plant-based meats, or chicken)

• Repeat existing best practices (healthy, well-fed, modern-breed cattle)

• Refine practices by introducing new techniques (e.g. feed additives to reduce enteric methane)

Second, make sure you’re planning to address the problem as it will exist in the future, not just as it exists today. Beef consumption is projected to increase 45% by 2050, so to reduce emissions by 50%, we need emissions per pound to shrink by 66%.

Third, gradual improvements are important. A 12% annual increase in market share of plant-based meat would have huge impact by 2050. The 36% decrease in enteric methane per pound of beef from 1961 to 2018 – that’s less than 1% per year! – is critical to putting us on track for 2050.

Fourth, always go for the easiest wins. Improvements come easier for wind turbines than for cattle, so we’ll aim to get more emission reductions from power generation than beef.

Finally, always do the math. Until you’ve modeled a problem, you don’t know how hard it is, or where the key challenges / opportunities lie.