🐄Bringing Intellectual Honesty To The Ruminant Methane Emissions Conversation

I recently read an Economist article that compared beef to coal, underscored cattle’s methane emissions, and suggested that people should become vegetarians or abandon beef.  The conclusion of the article stated:  “Doing without beef from live cattle is hard to imagine, but the same was true of coal 100 years ago.  Cultured meat could play an essential role in staving off a climate catastrophe.”  Articles like these lead many to believe that eating beef is bad, regardless of whether the meat comes from CAFOs or is regeneratively raised, and that cows and fossil fuels are equally accountable for global warming.  I believe such reasoning is fundamentally wrong, yet I fear many Americans (and in particular, millennials and Gen Z) fall for such incomplete narratives because they increasingly hear nothing else.   

Understanding our food system and its environmental impact is extremely important and incredibly complex.  As I’ve studied regenerative agriculture over the past year and learned more about indoor farming, cultured meat, and the explosion of plant-based products, I’ve tried to make sense of competing narratives and searched for balanced voices of reason.  I’ve sought out experts to better understand how methane operates and impacts global temperatures, how it has historically been measured and how it should be measured, and how it can be mitigated.  In early 2021, a close friend sent me a fantastic podcast with Frank Mitloehner, a brilliant professor in the Department of Animal Science at UC Davis.  I’ve become a huge fan of Frank Mitloehner because he provides a nuanced analysis of ruminant methane emissions driven by data and science.  While acknowledging the need to reduce ruminant methane emissions (and actively working to do so), Mitloehner persuasively argues that cows’ role in increasing global temperatures has been wildly exaggerated.    

I’ve been fascinated by what I’ve learned from scientists like Frank Mitloehner and Myles Allen and clear thinkers like Nicolette Hahn Niman.  Here are some of the key learnings that I believe are critical to honestly assess the impact of ruminant methane emissions on global warming.

Methane Behaves Fundamentally Differently Than Carbon Dioxide

As clearly explained in this excellent CLEAR Center article and accompanying Rethinking Methane video, biogenic methane (from cattle), which is derived from atmospheric carbon, is a short-lived flow gas that lasts in our atmosphere for about 12 years, whereas carbon dioxide is a stock gas that accumulates in our atmosphere for approximately 1,000 years.  The initial emission pulse of methane creates a warming effect.  Indeed, methane is a potent greenhouse gas with a warming potential more than 28 times that of carbon dioxide, and accordingly it is absolutely critical that we do not increase methane emissions.  However, given that methane is a flow gas, if its emission rate stabilizes, it will ultimately be destroyed at the same rate that it is produced and thus will not increase warming.  If methane emissions decrease, cooling will occur.  By stark contrast, every time you burn fossil fuels, the released CO2 tops off the cumulative CO2 stock that has been gathering for the past 1,000 years.  In other words, even if CO2 emissions decline, warming will continue because the previously released CO2 (over the past 1,000 years) remains in the atmosphere.        

In elucidating how biogenic methane recycles carbon, Mitloehner’s team explains:  “As part of the biogenic carbon cycle, plants absorb carbon dioxide, and through the process of photosynthesis, they harness the energy of the sun to produce carbohydrates such as cellulose.  Indigestible by humans . . . ruminant animals . . .  break it down in their rumens, taking the carbon that makes up the cellulose they consume and emitting a portion as methane, which is CH4 (note the carbon molecule).  After about 12 years, the methane is converted into carbon dioxide through hydroxyl oxidation. That carbon is the same carbon that was in the air prior to being consumed by an animal.  It is recycled carbon.

Beef Cattle’s Relatively Low Share of U.S. Direct Greenhouse Gas Emissions

In The Bogus Burger Blame, Mitloehner notes that animal agriculture is responsible for approximately 4% of U.S. direct greenhouse gas emissions, with beef cattle representing approximately 2.2% of such emissions.  (Crop cultivation accounts for approximately 5.5% of U.S. GHG emissions.)  Dwarfing such numbers, fossil fuel driven sectors account for the overwhelming majority of America’s GHG emissions.  CO2 accounts for 80% of U.S. GHG emissions and methane accounts for 10%.   

Through improved breeding, genetics, and nutrition, American livestock agriculture has become markedly more efficient over the past few decades.  Whereas 140 million head of cattle were required to meet U.S. demand in the 1970s, the current 94 million cattle inventory produces more meat and feeds more people.  Similarly, slightly over 9 million dairy cows produce 60% more milk today than 25 million dairy cows generated in 1950.  While cows are way more productive than they were 30-40 years ago and thus emit more methane on a per head basis, because the overall number of cows has drastically diminished, total cow methane emissions in the U.S. have declined.  

U.S. v. Global Methane Emissions

As noted by Nicolette Hahn Niman in Defending Beef: The Ecological and Nutritional Case for Meat (Revised & Expanded Edition), U.S. methane emissions have steadily and substantially declined by ~16% from 1990 to 2017.  Significantly, she notes that “there has been no parallel between US cattle numbers and US methane levels.”  Global methane emissions are rising, sparked by a greater than 50% increase in natural gas consumption over the past two decades.  On the cattle front, Nicolette Hahn Niman relays journalist Judith Schwartz’s argument from Cows Save The Planet that the lack of correlation between global methane levels and ruminant numbers casts doubt upon their actual contribution to atmospheric methane.  

Nevertheless, meat demand will continue to rise in the developing world, with beef demand in Asia expected to rise by 300% by 2050.  Importantly, the developing world isn’t nearly as efficient as the U.S. in producing beef and dairy.  For example, in India, which has the world’s largest cattle population but very low beef consumption, cows live longer and emit more methane over their lifetime.  Cows in tropical areas generate less milk and meat and accordingly require more time to get to market.  Mitloehner notes that “[i]f you have hundreds of millions of cattle to achieve a dismal amount of product, then that comes with a high environmental footprint.”  

GWP100 v. GWP*

According to Mitloehner and Myles Allen, GWP100 (the 100-year Global Warming Potential), the standard currently used to measure methane’s impact on warming, is fundamentally flawed because it treats methane as if it is a long-lived stock gas like carbon dioxide.  By failing to “distinguish the cumulative and non-cumulative nature of different gases,” GWP100 grossly misrepresents methane’s impact on global warming.  

To correct this glaring error, Dr. Allen created GWP*, which calculates the warming impact of short-lived flow gases by focusing on changes in their emission rates.  The key inquiry is whether the total emissions are increasing, decreasing, or stabilizing.  The below comparison between GWP100 and GWP* under different emission rates is illustrative.  When methane emissions are relatively stable (falling by 0.3% per year) or falling (by about 1% per year), GWP100 would still register considerable warming, whereas GWP* would reflect stable temperatures or cooling.  During a recent American Science Dairy Association presentation, Mitloehner stressed that a strong reduction of methane actively pulls carbon out of the atmosphere and therefore results in cooling.  On the flipside, in an article he published a couple days ago, Mitloehener reiterated that methane is a powerful greenhouse gas that must be reduced, and noted that GWP100 underestimates temperature increases when methane emissions increase.  

John Lynch, Dr. Allen’s colleague, emphasizes:  “Basing climate policies and emission trading systems on a metric that demonstrably fails to reflect the impact of different emissions on global temperature, while at the same time claiming these are designed to deliver a long-term temperature goal, risks undermining confidence in the entire strategy [of climate policy].”  By greatly overstating the global warming impact of ruminant methane, GWP100 and inaccurate media characterizations of biogenic methane have diverted attention away from fossil fuels.  Dr. Allen further notes that the “science is not controversial,” but many scientists, governments, and organizations are reluctant to confront the policy implications of abandoning the faulty GWP100 methodology.    

The Role of Regenerative Agriculture in Methane Reduction

In healthy soils that are part of vibrant regenerative ecosystems incorporating rotational grazing and avoiding agricultural chemicals and tillage, methanotrophic bacteria help consume methane expelled by ruminants.  As noted by Josh Tickell in Kiss The Ground, “the Earth has a number of methane-balancing mechanisms that include soil-based methanotrophic bacteria that absorb methane produced by grazing ruminants.”  Allen Williams further explains that there were hundreds of millions of grazing ruminants for several thousand years without a methane problem.  CAFOs, monocultures, pesticides, fungicides, herbicides, synthetic fertilizers, and tillage have degraded our soil and eliminated methanotrophs that digest methane.  Furthermore, because synthetic nitrogen fertilizer production (through fracking) generates many times as much methane as CAFOs, crops grown with such fertilizers are arguably a greater source of methane than CAFO beef.

Methane Mitigation In California Through Effective Regulation & State Programs

Because livestock in low and middle-income countries contribute 70% of ruminant emissions, it is critical that the developed world masters methane mitigation strategies that can be successfully exported to developing countries.  California’s dairy sector presents an excellent case study for effectively reducing methane emissions.  Significantly, California has enacted legislation to ensure that its GHG emissions are reduced to 40% below the 1990 levels by 2030.  Since its peak in 2008, the number of dairy cows in California has declined by over 7%, and its dairy industry has already achieved a 25% reduction in methane emissions since 2013.  

On top of lower methane emissions resulting from greater efficiency, methane can be further diminished through feed additives, anaerobic digesters, and alternative manure management (e.g., compost pack barns and solid separators).  California has an Alternative Manure Management Program and Dairy Digester Research & Development Program to spur methane reduction.  More than 213 dairy methane reduction projects have been incentivized with state funds, and such efforts are expected to achieve 2.2 million additional metric tons of GHG reduction each year.  With rising animal protein demand in the developing world, it is critical to follow states like California to mitigate methane through regulation, governmental programs, and innovation.    

Seaweed & 3-NOP

New findings from UC Davis, led by Dr. Ermias Kebreab, show that seaweed in cattle feed can reduce emissions from beef cattle by as much as 82%.  Over five months, Dr. Kebreab and his team added minimal amounts of red seaweed (asparagopsis taxiformis) to 21 beef cattle and found that they gained as much weight as their herdmates while burping out 82% less methane.  Taste tests indicated no differences in beef or milk flavor.  In response to claims that people should eat less meat to address climate change, Dr. Kebreab believes that we should instead focus on cattle nutrition because of the central role of livestock in our ecosystems.  As Dr. Kebreab explains, “Only a tiny fraction of the earth is fit for crop production.  Much more land is suitable only for grazing, so livestock plays a vital role in feeding the 10 billion people who will soon inhabit the planet.  Since much of livestock’s methane emissions come from the animal itself, nutrition plays a big role in finding solutions.”  Mitloehner further underscores that only one-third of agricultural land is arable, and ruminant agriculture is critical for thriving ecosystems, nutrition, and income in the other two-thirds.      

3-NOP (3-nitrooxypropanol), a potent methane inhibitor, has also been shown by various ruminant professionals (including Dr. Dipti Pitta and Dr. Alexander Hristov) to appreciably reduce ruminant methane emissions.

The more I dig, the more it appears that cows have been disproportionately blamed for methane emissions and that ruminant methane’s impact on global warming has been substantially exaggerated.  In addition to standardizing the use of GWP*, I believe we must spur regenerative livestock practices and eliminate CAFOs and liquefied manure storage lagoons, which are used for industrial pork, egg, and dairy facilities, but not cattle ranches or beef feedlots.  We cannot overwhelmingly point to all cows as methane culprits without considering how they are being raised and without honestly evaluating how much methane is produced by fossil fuels, rice farming, or synthetic fertilizers used for crops.  A regeneratively raised cow can actually be a carbon sink, so eating a hamburger from such a cow can be far healthier and better for the environment than eating most plant-based alternatives.  

I’ll leave you with a relevant excerpt from the most recent FS (Farnam Street) Sunday Brain Food newsletter.  “We tend to think that what we think is true. And because we think something is true, we ignore information that might tell us it’s not true.  Charles Darwin deliberately looked for thoughts that disagreed with his own.  He wrote, ‘whenever a published fact, a new observation or thought came across me, which was opposed to my general results, to make a memorandum of it without fail and at once; for I had found by experience that such facts and thoughts were far more apt to escape from memory than favorable ones.’  Darwin was out for truth, not to confirm his view of the world.”

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Further Deep Dive Recommendations

Is GWP* Really “Fuzzy Math?”  You Decide. (by Frank Mitloehner)

Pathway to Climate Neutrality for U.S. Beef and Dairy Cattle Production

Global Warming Potential* (GWP*): Understanding the Implications for Mitigating Methane Emissions in Agriculture

Demonstrating GWP*: A Means of Reporting Warming-Equivalent Emissions That Captures the Contrasting Impacts of Short- and Long-Lived Climate Pollutants

Farmers Unite for Global Statement on GWP* (Farm Gate Podcast)

Exposing Climate Threats From an Empire of Dying Wells

Sara Place on the Meet Your Herdmates Sodcast

Trends in the Anaerobic Digestion of Food Waste 

The Foods That Reverse Climate Change 

A $90 Million Plant to Produce Methane-Reducing Cattle Feed Using Seaweed is Being Built in South Australia

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