Is grass-fed beef better for the environment?

Illuminating answers to environmental questions.
Dec. 21 2010 10:44 AM

Pass on Grass

Is grass-fed beef better for the environment?

Cows grazing. Click image to expand.
Cows grazing

Grass-fed beef is all the rage these days. Everyone says it tastes better and is more humane for the cattle. But what about the environment? Is pasturing earth-friendly, or just cow-friendly?

No matter how you slice it, eating beef will never be the greenest thing you do in a day. Scientists at Japan's National Institute of Livestock and Grassland Science estimate that producing 1 kilogram of beef emits more greenhouse gas than driving 155 miles. Since the average American covers 32 miles to and from work, your 8-ounce steak dinner might contribute to global warming as much as your daily commute.

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Wouldn't it be nice if carnivores could minimize their environmental impact just by switching from one dead-cow product to another? Unfortunately, both grass-fed and corn-fed beef are terrible for the earth—but each in its own way.

First, a little background on how a calf becomes a meal. Whether destined for the high-dollar, natural-market butcher or for the convenient-mart freezer case, beef cattle must drink milk and eat grass during their youth. It's the period that cattlemen call "finishing"—the final two months to one year before slaughter—when their diets might diverge.

Under USDA regulations, cattle bearing the "grass-fed" label can eat only foods known as "forage" once they have been weaned. Forage includes grass, hay, brassicas (a group of plants that includes turnips, kale, and cabbage), and the leaves and tender stems of young trees and shrubs. The cattle must have access to pasture. Unless the beef is labeled organic, they may receive antibiotics and hormones, although most producers trying to capture the high-end market avoid these drugs.

As Michael Pollan has described over and over and over (and over) again, the feedlot life differs enormously from the idyllic, sun-drenched wonderland of the pasture. When conventional cows are ready for fattening, they typically move into a pen with 10 to 14 other animals. Each cow, measuring (PDF) around 5 feet long and 2 feet wide, gets a 16-by-16-foot space, on average. After a brief transition period, the rancher begins to introduce grain into the cow's diet. While corn-finished cattle don't eat only corn—they might also consume straw, alfalfa, soy, and fruit—the grain can make up as much as 90 percent (PDF) of their diet. A feed-truck dumps their rations in a trough three times daily, with a side of hormones and antibiotics.

From an environmental perspective, concentrated animal-feeding operations—CAFOs, as they're known in the industry—aren't great. Putting 1,000 pounds of weight on an animal in a few months requires a staggering amount of grain. During its finishing period, the average beef cow eats 2,800 pounds of corn. In fact, more of our grain crop goes to feeding animals than humans. Livestock, poultry, and (believe it or not) fish consume 80 percent of the corn grown in the United States, all of which requires lots of energy to grow and transport.

Nevertheless, some researchers argue that cattle fattened at a CAFO are better for the earth than their free-ranging cousins. Jude Capper, a professor of animal science at Washington State University, recently compared the energy input for the two kinds of beef. She found that grass-finished cattle require about two-and-a-half times as much energy to produce as grass-fed ones. A couple of big caveats: Capper co-authored the paper with an employee of Elanco, a company that supplies food and medicine to CAFOs. The paper has not been published in a peer-reviewed journal but was presented at an annual meeting of animal-science associations—of which Elanco happened to be a "Platinum Sponsor."

By Capper's estimation, cows that live shoulder-to-shoulder are just like humans crammed into urban spaces: Transporting food to the animals, and the animals to the slaughterhouse, requires less energy for CAFO-raised cattle. In addition, cows that are hopped up on hormones and eating calorie-dense grain grow two to three times faster, enabling ranchers to crank out more beef with fewer resources. And while finishing a 1,200-pound corn-fed cow requires three acres of land, finishing a grass-fed cow requires nine acres.

Not everyone buys these numbers. Ranchers with the American Grassfed Association insist that they use no synthetic fertilizers, contrary to Capper's assumptions. There are a host of other farmers  claiming  their operations are carbon-negative, and the USDA has  gotten behind them. Still, with so little rigorous research published, it's hard to tell which side is right. The numbers depend on a range of variables, such as how much fertilizer an individual rancher uses to grow grass, for which data simply aren't available.

There's also a disagreement on methane, the powerful greenhouse gas that cows belch (and excrete, but to a lesser extent). Capper believes that a corn diet and a shorter life span results in one-third the methane output of a grass-fed cow. Other researchers, however, have suggested that grass's ability to sequester carbon may compensate for the difference.

Even if Capper is correct on all counts, it isn't a TKO for the CAFOs. There's more to environmentalism than greenhouse gases. CAFOs produce 300 million tons of manure per year, twice the volume of human feces. Even if it were spread out, that would be a lot of bullshit. But it's particularly bad when concentrated on small patches of land. CAFOs usually capture their waste in lagoons before spraying it back onto the fields as fertilizer, but the storage units sometimes fail. Large volumes of manure can kill aquatic plant life, the base of the marine food chain. Massive dead zones from CAFO runoff exist in the Gulf of Mexico and the Chesapeake Bay. Based on some estimates, we spend more than $4 billion (PDF) annually trying to clean up CAFO manure runoff. In addition, the long-term, low-dose antibiotics CAFOs give livestock can lead to antibiotic-resistant bacteria, further undermining our dwindling supply of useful medicines.

May the Lantern make a humble suggestion? Stop eating so much beef. Whether grass- or corn-fed, it's pretty bad for the environment, and it's not that great for your body, either. If your palate simply can't resist grassy notes, get them from a nice sauvignon blanc. Locally produced with a natural cork, of course.

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Brian Palmer writes about science, medicine, and the environment for Slate and the Natural Resources Defense Council. Email him at explainerbrian@gmail.com. Follow him on Twitter.

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