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The Kindest CutWhich meat harms our planet the least?

By Nina Shen RastogiPosted Tuesday, April 28, 2009, at 6:54 AM ET

Is lamb bad for the environment?Green Lantern, you're always telling us how bad meat is for the environment. I'm willing to throw some more zucchini kebabs on my barbecue this summer, but are all meats equally awful? Or are there some that I can grill with a little less guilt?

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The Lantern loves her roasts and rib-eyes, too, but she's glad the message is starting to sink in: Meat is not sweet, ecologically speaking. According to an extensive U.N. report from 2006, the livestock industry not only uses more land than any other human activity; it's also one of the largest contributors to water pollution and a bigger source of greenhouse-gas emissions than all the world's trains, planes, and automobiles combined.

You can do a lot for the planet simply by cutting back your overall meat intake—food writer Michael Pollan recently suggested that if Americans went meatless one night a week, it would be equivalent to taking "30 to 40 million cars off the road for a year." When you do decide to eat meat, though, you can make a difference by making more responsible selections.

As a general rule, red meat—beef, lamb, goat, and bison—are the worst offenders. A recent report for Defra, the British government's environmental authority, compared common animal products across seven categories: use of energy, pesticides, land, and nonrenewable resources; and impacts on global warming, acidification, and eutrophication (a kind of water pollution in which excess nutrients lead to fish-killing algae blooms). Beef and lamb got the poorest marks of all meats in terms of energy usage, global warming, and eutrophication. Beef also used the most land, had the highest acidification impacts, and came close to the bottom in the remaining categories. Lamb did better, though—in fact, it scored the highest of all meats in terms of pesticide and nonrenewable resource usage. All in all, chicken and turkey were the greenest meats surveyed.

Cows, sheep, and other ruminants end up looking so bad in part because they eat a lot more, pound for pound, than their single-stomached brethren: That means more fertilizers, more pesticides, and more energy are required to grow their food. (The livestock industry as a whole consumes a whopping share of the world's crops—at least 80 percent of all soybeans and more than half of all corn.) One bright side: Ruminants' hardy stomachs can digest cellulose, which means they can graze on grassland other animals can't.

Cattle, at least, also produce more poop than other livestock. A typical cow might drop 22,000 pounds of patties a year; assuming a high yield of 625 pounds of edible meat and a slaughter age of 12 to 22 months, that's an estimated 35 to 65 pounds of manure incurred per pound of saleable beef. Hogs, by contrast, come in at around 13 to 18 pounds of manure per pound; chickens, around 2 to 4. (Actual numbers will be a little lower, since baby animals poop less than their parents.)* Animal manure doesn't just stink—it also releases air-polluting ammonia, nitrous oxide, and methane and can threaten groundwater supplies. (Manure does make an excellent fertilizer, which offsets some of its negative impact. But large farms may end up with more waste than the land can absorb.) Plus, cows and sheep emit plenty of extra methane when they belch and fart. The U.N. report estimates that most of the methane produced by livestock—which accounts for some 37 percent of all anthropogenic methane emissions—comes from gassy ruminants.

What does that all add up to? According to a study published last year in the journal Environmental Science & Technology, the production of red meat generates, on average, four times more greenhouse-gas emissions than an equivalent amount of chicken or fish, and turns out more carbon-dioxide equivalent than any other food group. Red meat is so resource-intensive, in fact, that if we all cut our consumption of it by one-quarter, the reduction in greenhouse gases would be the same as shifting to a 100 percent locally sourced diet.

The authors of that study included pork in their red meat figures. By and large, though, pig meat is greener than beef, mutton, or other ruminant meats. For one thing, pigs don't expel methane from their digestive tracts throughout the day. They also reproduce more efficiently: While a cow or sheep may give birth to a single offspring a year, a sow typically has 20 to 30, meaning fewer resources are expended on breeding stock. Finally, pigs take a lot less time—and therefore less feed—to reach their market weight. It takes about five to six pounds of feed to produce a pound of edible pork; you'd need about twice as much to produce a pound of beef.

Poultry and eggs come out best of all. Chickens breed furiously—a single bird can produce hundreds of chicks annually—and are highly efficient weight gainers. A recent independent life cycle analysis on U.S. poultry found that producing a calorie of chicken protein required about 5.6 calories of fossil fuels, compared with reported figures of about 14 calories for pork and 20 to 40 for beef. Still, as the most widely eaten meat in America, chicken farming has a major impact on the environment. The poultry-broiler industry consumed some 240 billion megajoules of energy in 2005, or the equivalent of 42 million barrels of crude oil. That's more than the entire country of Sri Lanka consumed the same year—all to keep us well-stocked with wings and drumsticks.

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