Background
Methane has gotten a lot of attention recently in relation to fighting climate change:
"The oil, gas and coal industries are the largest source of human-caused methane emissions. An Environmental Defense Fund study found that cutting methane emissions now could slow the near-term rate of global warming by as much as 30%."
While these facts may be true, it takes theory to explain facts, and unfortunately bad theory leads to bad decisions even if we get the facts right. A recent article in Politico provides an example in it's criticism of the Biden administration's failure to target methane emissions from livestock to combat climate change:
"This creative accounting and the administration’s policies belittle the livestock industry’s role in the methane emergency. While Biden and other U.S. officials are preaching the importance of slashing methane emissions to prevent catastrophic warming and imposing tough new methane regulations on fossil fuel companies, they are allowing super-polluting meat and dairy corporations to continue to emit massive amounts of the same greenhouse gas with impunity."
Are all methane sources equal?
Accounting for methane is key, but there is a lot of nuance to understand about methane in order to account for it appropriately so that we take the right course of action when it comes to policy and food choices.
Let's start with a bigger picture looking at total GHG emissions by source:
When we drill into agriculture and focus on beef in the U.S. we find that it accounts for about 4% of total emissions. But on a global scale, which matters most to climate change, overall, total GHG emissions related to U.S. beef consumption accounts for less than 1/2 of 1% (i.e. .5%) of global GHG emissions (EPA GHG Emissions Inventory, Rotz et al, 2018). When we talk about methane emissions associated with eating U.S. sourced beef in the U.S., we are talking about a very thin slice of total global warming potential.
When we zoom in on this slice of potential and focus on methane this is what we see according to the current administration's Methane Emissions Reduction Action Plan:
Enteric emissions account for all ruminant livestock emissions in the U.S. which would include both beef and dairy but that gives us a pretty good picture. Again, we have facts that are all true, but *how* should we interpret this? A naive interpretation would be to simply compare the pieces of the pie assuming that we can make apples to apples comparisons between each piece and choose a course of action based on the 'facts.' But this would be misleading without understanding the underlying biology and data generating mechanisms giving rise to this data.
The crude infographic that I put together below sheds some light on this (See this video for a better illustration or Dr. Frank Mitloehner's more detailed explanation of the biogenic carbon cycle here; see also Allen, M.R., Shine, K.P., Fuglestvedt, J.S. et al., 2018). At the highest level, methane emissions produced by beef cattle are constantly recycled. The ultimate source of methane starts in plants and is consumed by livestock and later removed from the atmosphere in the form of CO2 by plants again to repeat. This can be visualized by a tank with water going in and eventually draining out. In this context methane is a 'flow' gas.
Methane sourced from natural gas and petroleum behaves differently. When we extract, refine, and burn fossil fuels the methane associated with this is released into the atmosphere, but absent any sort of mitigation it ultimately converts to CO2 where it remains to have a long lasting warming effect. This can be visualized by a tank with water going in but never draining out.
In relation to the first tank representing enteric emissions from livestock, there are additional nuances. When we look at U.S. cattle inventories over the last 30 years what we see is that the rate of flow from the faucet has mostly been decreasing. We have not only been recycling the same methane in the atmosphere over and over the last few decades, but less of it. Thanks to advances in economic development, technological change, innovations in management, marketing, and pricing value in the beef industry (for just a few examples see here, here, here, here, and here), we've seen gains in beef production and quality. Additionally, in 2007 compared to 1977 we were able to produce the same amount of beef using roughly 30% fewer cattle and 30% less land. Feed and and water usage were down between 15-20% with a 16% lower carbon footprint (Capper, 2007). All of these factors have culminated in a healthier, more nutritious, higher quality product with a lower carbon footprint. We can't say the same about methane associated with fossil fuels and transportation which continues to flow at greater rates and doesn't get recycled.
Source: https://www.nass.usda.gov/Newsroom/2021/01-29-2021.php
So when you get in your car to go to your favorite restaurant, the associated methane and CO2 emissions that result represents new and long lasting emissions. For the most part the steak or burger on your plate doesn't directly add any new warming potential to the atmosphere that didn't already exist, nor has any steak or burger you may have eaten in the last 30 years based on this data!
Are all sources of beef equal?
Why focus on U.S. beef production and consumption in this discussion? Because in the Politico article and in many conversations like this, the context is often subtly switched between consumers of U.S. beef and consumption of beef sourced in other parts of the world as if they are substitutes. This change in context ignores important differences between technological capabilities and production practices but also differences in incomes, tastes, and preferences. A lot of the criticism of U.S. beef may actually be true in relation to beef produced and consumed in other parts of the world. We are not burning down rain forests in the U.S. in order to produce and consume beef, and the indirect connection between U.S. beef production and consumption and deforestation in other parts of the world is very weak due to the way global beef markets function. However, there are opportunities to make beef greener in other parts of the world that should not be ignored and should be researched further (see Mrode et al., 2019; Silva et al., 2018; Gates, 2017).
Should we just ignore the very potent warming potential represented by methane emissions associated with U.S. beef consumption just because it represents a thin slice of the global pie that is relevant to climate change? No, but we should put it in the proper perspective, and think of the overall global portfolio of choices we make in our diets and daily lives and not get anchored on facts divorced from the proper context so we can actually make impactful decisions.
Consumer fads and a climate friendly behavior change strategy
As discussed above, even if all U.S. consumers gave up beef tomorrow cold turkey, there is an upper limit on the impact we can have globally. Modest changes either reducing beef consumption or switching to alternative proteins would be even less impactful. However, we should still recognize that lots of small changes could add up to have a meaningful effect in the aggregate. Given the behavioral and nutritional challenges that make any meaningful reduction in beef consumption mostly impractical at a population level (and ignoring the elephant in the room that is transportation) it is an empirical question as to what other seemingly arbitrary lifestyle changes we could suggest to decrease our impact on climate - maybe that once a week trip to the grocer to buy in bulk instead of having the fleet of Amazon, UPS, and FedEx trucks down your street multiple times a week is one example. Other consumerist trends we've seen that could also be adding to our carbon footprint could involve the fads and infatuation with local, natural, and organic food consumption, and the notorious 'free-from' food marketing campaigns that tend to demonize climate saving technologies (see here, here, here, here, here, and here for related info).
Putting the lens of behavioral science on this, we need to think about the problem we are trying to solve or outcome we are trying to achieve (climate change mitigation) and consider the behavioral map that relates all of the target actions we could take to achieve this outcome. What role does science literacy and misinformation and disinformation play in the trends and food fads noted above that could lead to hesitancy to adopt climate saving technologies? Which solutions are technically correct but also the most impactful at scale from a behavior change perspective? Is a reduction in modern U.S. beef production or consumption the target behavior we should be trying to change compared to other options? Maybe for some people but I'm not convinced it is a global solution.
Getting the most nutritional bang for our climate buck
How do we know we are getting the most nutritional bang for our climate buck when thinking through this? In a 2010 Food and Nutrition Research article, authors introduce the Nutrient Density to Climate Impact (NDCI) index. Metrics like this could add some perspective. According to their work:
"the NDCI index was 0 for carbonated water, soft drink, and beer and below 0.1 for red wine and oat drink. The NDCI index was similar for orange juice (0.28) and soy drink (0.25). Due to a very high-nutrient density, the NDCI index for milk was substantially higher (0.54) than for the other beverages. Future discussion on how changes in food consumption patterns might help avert climate change need to take both GHG emission and nutrient density of foods and beverages into account."
Authors Drewnowski, Adam et al. apply this more nuanced approach to 34 different food categories including meat and dairy:
"Efforts to decrease global GHGEs while maintaining nutritionally adequate, affordable, and acceptable diets need to be guided by considerations of the ND and environmental impact of different foods and food groups. In a series of recent studies, the principal sustainability measure was carbon cost expressed in terms of GHGEs (8, 14, 15). Testing the relation between nutrient profile of foods and their carbon footprint can help identify those food groups that provide both calories and optimal nutrition at a low carbon cost."
Just as combining trips and carpooling might be effective ways to reduce your carbon footprint getting the most out of every mile driven and gallon of gas used, to be truly impactful regarding climate change, we should be trying to get the most out of every bite we take and ounce we drink.
Weighing efficiency and values
The previous discussion starts to sound a lot like a position related to optimization and efficiency which ultimately requires making value judgements that science and economics can't make.
As discussed in Heyne, Boettke, and Prychitco's text The Economic Way of Thinking:
"efficiency is essentially an evaluative term. It always has to do with the ratio fo the value of output to the value of input...in effect it depends on what people want done and how they value what they want done. It follows that the efficiency of any process can change with changes in valuations."
What I am getting at is that maybe people prefer to have sustenance from beef vs rice or other alternatives and we have to give weight to that in a policy framework. Physical and technical facts alone can never fully determine efficiency. That's what makes economics so powerful. Its the study of people's choices and how they are made compatible. It is way more than just the study of the technical allocation of resources because it forces us to consider each individual's preferences based on the knowledge of their specific circumstances of time and place.
Science and economics can't make value judgements for us, but we should strive get the facts right, and the stories we tell with the facts need to be true to the science behind them.
Additional and Related References:
HJ. L. Capper, The environmental impact of beef production in the United States: 1977 compared with 2007, Journal of Animal Science, Volume 89, Issue 12, December 2011, Pages 4249–4261, https://doi.org/10.2527/jas.2010-3784
Rafael De Oliveira Silva, Luis Gustavo Barioni, Giampaolo Queiroz Pellegrino, Dominic Moran, The role of agricultural intensification in Brazil's Nationally Determined Contribution on emissions mitigation, Agricultural Systems, Volume 161, 2018, Pages 102-112, ISSN 0308-521X, https://doi.org/10.1016/j.agsy.2018.01.003.
Mrode, R., Ojango, J., Okeyo, A. M., & Mwacharo, J. M. (2019). Genomic Selection and Use of Molecular Tools in Breeding Programs for Indigenous and Crossbred Cattle in Developing Countries: Current Status and Future Prospects. Frontiers in genetics, 9, 694. https://doi.org/10.3389/fgene.2018.00694
C. Alan Rotz et al. Environmental footprints of beef cattle production in the United States, Agricultural Systems (2018). DOI: 10.1016/j.agsy.2018.11.005
https://phys.org/news/2019-03-beef-resource-greenhouse-gas-emissions.html
What cowboys can teach us about feeding the world. Could a cattle ranch in Australia improve food security in Africa? Bill Gates. Gates Notes. July 18, 2017. https://www.gatesnotes.com/Development/What-Cowboys-Can-Teach-Us-About-Feeding-the-World?WT.mc_id=07_18_2017_10_AustralianCattle_BG-LI_&WT.tsrc=BGLI
Scarborough, P., & Rayner, M. (2010). Nutrient Density to Climate Impact index is an inappropriate system for ranking beverages in order of climate impact per nutritional value. Food & nutrition research, 54, 10.3402/fnr.v54i0.5681. https://doi.org/10.3402/fnr.v54i0.5681
Drewnowski, Adam et al. “Energy and nutrient density of foods in relation to their carbon footprint.” The American journal of clinical nutrition 101 1 (2015): 184-91 .
Allen, M.R., Shine, K.P., Fuglestvedt, J.S. et al. A solution to the misrepresentations of CO2-equivalent emissions of short-lived climate pollutants under ambitious mitigation. npj Clim Atmos Sci 1, 16 (2018) doi:10.1038/s41612-018-0026-8
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