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 Spring 2011

By David Kohn and Doug-Gurian Sherman

Although U.S. beef consumption has gradually declined in recent years, for many Americans beef is still what’s for dinner. But it comes at a cost: in addition to other environmental impacts, raising the nation’s beef cattle puts millions of tons of heat-trapping gases, mostly methane and nitrous oxide, into the atmosphere.

While reducing meat consumption can help reduce these impacts, smarter and more efficient pasture-based production systems can also make a difference. As UCS found in its new report,  Raising the Steaks: Global Warming and Pasture-Raised Beef Production in the United States, changing production practices could reduce beef’s climate impact by as much as 88 percent, and the impact from U.S. agriculture as a whole by as much as a third.

Cows Need Better Diets Too

Beef production is responsible for about 18 percent of U.S. emissions of methane, which has 23 times the warming effect of carbon dioxide. Most of this methane is generated by microbes within cows’ digestive tracts; on average, one cow burps between 176 and 242 pounds’ worth of methane a year.

Methane emissions from pasture-raised cattle could be reduced between 15 and 30 percent. UCS found, for example, that cattle fed a mixture of grasses and readily digestible legumes such as alfalfa often produce less methane than animals fed on grasses alone; they also grow faster and need less food. One particularly promising legume is a plant known as birdsfoot trefoil. Like all legumes, it adds nitrogen to the soil, which improves the productivity of pasture grasses. But unlike most other legumes, it contains chemicals known as condensed tannins, which appear to reduce methane production during digestion. Since all beef cattle spend at least part of their lives on pasture, adoption of such practices can reduce methane emissions from all beef production systems.

Livestock production also generates nitrous oxide, which has nearly 300 times the warming effect of carbon dioxide. This compound is produced from nitrogen in manure, legumes, and nitrogen-based fertilizers that are widely used in the United States and other developed countries. Farmers can reduce these emissions by optimizing fertilizer application and spreading their cattle out over all the available land, which spreads manure evenly on pastures and allows more of its nitrogen to be used by pasture plants rather than escaping in the form of nitrous oxide.

To Graze or Not to Graze?

Despite extensive research, one key question remains unresolved: do pasture operations or CAFOs (confined animal feeding operations) have a smaller climate footprint? Some studies have found that CAFO cattle, which fatten quickly due to their unnatural carbohydrate-rich diet of corn and other grains, produce less methane because they are slaughtered sooner than their pastured counterparts. However, UCS found that there is potential to improve the nutritional value of pasture crops, which could substantially reduce the advantage CAFOs currently show in both growth rate and methane emissions.

Smart pasture operations do have some current advantages over CAFOs. For example, compared with grain crops grown for CAFOs, well-managed pastures better protect soil from erosion. They generally sequester more carbon dioxide as well, which may offset a substantial portion of the total potential heat-trapping emissions from beef production. Pasture systems also offer a variety of non-climate-related benefits for both the environment and cows alike (see the sidebar below).

Global Change Begins at Home

Federal policies are needed to initiate a large-scale shift to the production practices described above. UCS recommends that the United States increase research into improving the productivity and nutritional value of pasture crops, as well as the ability of pasture plants to store carbon and use nitrogen more efficiently. We also recommend that the U.S. Department of Agriculture provide financial incentives and technical assistance to help and encourage farmers to adopt climate-friendly practices such as increasing the ratio of legumes in cattle diets and applying amounts of nitrogen fertilizer appropriate to crop needs.

A better burger would be no small achievement. Beef production generates about 160 million metric tons of heat-trapping emissions per year—equivalent to the annual emissions of 24 million cars and light trucks. While other U.S. sectors such as transportation generate much more, the United States accounts for so much of the world’s heat-trapping emissions—about a quarter of the total—that beef production nevertheless offers an important opportunity to help curb global warming.

These findings could have an even greater impact outside our borders. Livestock farming generates almost a fifth of the world’s heat-trapping emissions, according to a 2006 report by the United Nations. The world’s cattle population now stands at 1.5 billion, and will likely increase considerably over the next several decades as consumers in developing countries become wealthier and eat more meat. By implementing the steps outlined in our report, the United States could set an example for other countries to follow and lay the groundwork for healthier and more sustainable agriculture worldwide.

David Kohn is a former press secretary at UCS. Doug Gurian-Sherman is a senior analyst in the UCS Food and Environment Program.


The Grass Is Greener—in More Ways than One
Raising cows on pasture has benefits beyond lower global warming emissions.

Most cattle spend significant parts of their lives in crowded CAFOs, a production system that poses several environmental and public health risks. For example, CAFO cattle are routinely fed antibiotics to compensate for the filthy conditions and an unhealthy grain-heavy diet (cattle are not adapted to eat grains); this practice contributes to antibiotic resistance, making it more difficult to treat food-borne diseases in humans. In addition, growing grain crops for animal feed requires large amounts of pesticide and fertilizer that can pollute water supplies and harm marine life. Pollution also results from the massive amounts of manure generated in a relatively small area by CAFOs.

Pasture operations largely avoid these problems. Cows raised on their natural diet of forage rarely require antibiotics, helping to reduce the use of antibiotics (and the risk of antibiotic resistance). And cows spread out on pasture produce less concentrated manure than in CAFO feedlots, reducing the manure disposal problems that face CAFOs.


Learn more about the climate impact of beef production, and read the full report, Raising the Steaks: Global Warming and Pasture-Raised Beef Production in the United States