Which is worse for climate change, feeding grass to cows or feeding corn to cows? Basically, this is the wrong question we should be asking, but in the process of answering it, we can see what the right question is.
In many respects, grass-fed beef is much better than sending cows to feedlots and feeding them corn. Feedlot systems take more energy to produce a given quantity of animal protein (Pimentel and Pimentel, 2008). Feedlots also are less humane than letting cows eat their natural food, which is grass. But unfortunately, climate change is not one of the areas in which grass-fed beef is superior to grain-fed beef. Cows emit methane and lots of it. Methane is about 25 times worse than carbon dioxide in terms of its global warming potential, and, as can be seen in the studies cited below, grass-fed beef emits a lot more methane than grain-fed beef.
Why is this? It’s because cattle are ruminant animals. They digest their food through a process known as “enteric fermentation,” which results in methane production as a by-product. There is nothing particularly controversial about this; it’s basic cow physiology. The ecological niche of cows (and all other ruminant animals, such as sheep, bison, goats, moose, and antelope) is precisely to be able to eat plants which are widely available (grass) but indigestible for a lot of animals, including humans. Cows do this by having four stomachs and a lot of bacteria in their stomach that help break down the cellulose in grass. One of the by-products of this bacterial break-down is methane, which is mostly emitted in “burping.” Feedlot beef, however, overcomes this process by feeding the cows corn or other grains rather than grass, at least during the “finishing” stage. It’s not good for the cows, because corn is not their natural food. However, they gain weight quickly, so they are brought to market a lot faster, and don’t have as much cellulose for the methane-producing bacteria to munch on. All this results in less methane being emitted.
“Livestock’s Long Shadow” (FAO, 2006) discusses this and various ways to deal with the problem. It reports (p. 113) that “extensive systems” (namely, grazing systems) contribute 8 times as much methane as “intensive systems” (namely, feedlots). The primary way that methane emissions can be minimized is through more efficient feeding (p. 119-121). But what is “more efficient feeding”? It means feeding cows a diet in which they gain weight faster. This is exactly what happens when you feed them grains, which is why feedlots are such a popular technique. We are short-circuiting the evolutionary niche of grass-eating that cows occupy in nature in order to facilitate more rapid weight gain.
Robert Goodland estimates that pasture-fed beef emits as much as three times the methane as does intensively-raised livestock (Goodland, 2010) . Gidon Eshel said that grass-fed cows emit four to five times as much methane as feedlot cows (Bendrick, 2009). This is somewhat offset by the fact that feedlot beef generates a lot of greenhouse gas emissions (GHGs) to grow all the corn that they eat. But the methane from grass-fed beef outweighs all of this. Science magazine quoted a talk by Nathan Pelletier of Dalhousie University in Halifax, Nova Scotia:
“We do see significant differences in the GHG intensities [of grass vs grain finishing]. It’s roughly on the order of 50 percent higher in grass-finished systems.” When an audience member questioned whether he had heard that right, that grass-fed cattle have a higher carbon footprint, Pelletier reiterated, “higher. Yes.” (Raloff, 2009)
Methane emissions are likely an even worse problem than the FAO reports. The actual figure of human GHG emissions attributable to livestock is not just 18% of all human-caused GHG emissions as the FAO reported — which would be bad enough — but more like 51%, because methane from livestock has been seriously undercounted and because land-use contributions to global warming have been largely disregarded (Goodland and Anhang, 2009). “Our article suggests that livestock’s shadow is not just long, but colossal” (Goodland, 2010, p. 50).
But there is some good news in these figures. Moving towards a plant-based vegan diet can drastically reduce greenhouse gas emissions and do it much more quickly and cheaply than alternatives. A mere 1% reduction in world meat consumption would have the same effect as $3 trillion in solar energy investments (Goodland, 2010, p. 51). While methane is 25 times worse than carbon dioxide, it also dissipates much faster in the atmosphere; its half-life is only 8 years, as opposed to at least 100 years for carbon dioxide. Reducing meat consumption would also greatly reduce pressure on the land; in the United States, 80 – 90% of all agricultural land is devoted to livestock production.
That is why Rajendra Pachauri, head of the Intergovernmental Panel on Climate Change, and who represented the IPCC when it shared the Nobel Peace Prize with Al Gore in 2007, said that “in terms of immediacy of action . . . reducing meat consumption clearly is the most attractive opportunity.” That is why Lord Stern, the former World Bank chief economist and author of the “Stern Review on the Economics of Climate Change” released by the British government in 2006, states that “Meat is a wasteful use of water and creates a lot of greenhouse gases. It puts enormous pressure on the world’s resources. A vegetarian diet is better” (Goodland, 2010).
In terms of the environment, both range-fed beef and factory-farmed beef both have serious disadvantages. The real question is not whether grass-fed or grain-fed beef is worse; it is why we are eating meat at all. The overlooked climate solution is no further away than our own plates: a plant-based vegan diet.
Bendrick, Lou. “Of cow burps, beef, and methane,” May 22, 2009. On Grist.org, accessed Feb. 12, 2011.
FAO (Food and Agriculture Organization of the United Nations). Livestock’s Long Shadow. Environmental Issues and Options. Rome, 2006.
Goodland, Robert, and Anhang, Jeff. “Livestock and Climate Change.” WorldWatch, November/December 2009.
Goodland, Robert. “The Overlooked Climate Solution,” Journal of Human Security, August 2010, 6(3): 50-60.
Pimentel, D. and Pimentel, M., editors. Food, Energy, and Society, Third Edition. Boca Raton: CRC Press, 2008.
Raloff, Janet. “The carbon footprints of raising livestock for food.” February 15, 2009.