Broccoli and cauliflower from istock.
Oh, those ruminants and the methane they produce. But pork and poultry are on a par with green vegetables when it comes to climate impact by calorie.
Hens in "colony cages,‚Äù which fulfill a California law that requires farmers to provide generous living conditions for chickens, at JS West and Companies‚Äô Dwight Bell Ranch in Atwater, Calif., Feb. 13, 2014. Lawmakers in California are demanding of out-of-state farmers who sell eggs in California adhere to the same law, setting off a feud over interstate commerce that has spilled over into the farmyard at large. (Peter DaSilva/The New York Times)
Eat meat or veggies? It's a tough call
- Article by: Tamar Haspel
- Special to the Washington Post
- March 29, 2014 - 4:44 PM
The argument that a vegetarian diet is more planet-friendly than a carnivorous one is straightforward: If we feed plants to animals, and then eat the animals, we use more resources and produce more greenhouse gases than if we simply eat the plants. As with most arguments about our food supply, though, it’s not that simple. Although beef is always climatically costly, pork or chicken can be a better choice than broccoli, calorie for calorie.
Much of the focus on the climate impact of meat has been on cattle, and with good reason. Any way you slice it, beef has the highest environmental cost of just about any food going, and the cow’s digestive system is to blame. Ruminants — cows, sheep, goats — have a four-chambered stomach that digests plants by fermentation. A byproduct of that fermentation is methane, a greenhouse gas with some 20 times the heat-trapping ability of carbon. One cow’s annual output of methane is equivalent to the emissions generated by a car burning 235 gallons of gasoline.
Methane isn’t the only strike against ruminants. Cows can have one calf per year, which means the carbon cost of every cow destined for beef includes the cost of maintaining an adult for a year.
Then there’s feed conversion. It takes six pounds of feed to make one pound of beef, but only 3.5 pounds for pork and two pounds for chicken.
It’s clear that the ruminants do more damage than one-stomached barnyard animals.
Comparing cows with pigs, and meat with plants, is often done using data from the Environmental Working Group, which produced a report in 2011 that detailed the environmental cost of meat. The report ranks foods according to the amount of emissions generated in the course of production. Ruminants are the worst offenders, with lamb generating 39 kilograms of carbon dioxide (or its equivalent) for each kilogram of meat, and beef generating 27. Then come pork (12), turkey (11) and chicken (7). Plants are lower.
But there’s another way to look at the same information. If you stop eating beef, you can’t replace a kilogram of it, which has 2,280 calories, with a kilogram of broccoli, at 340 calories. You have to replace it with 6.7 kilograms of broccoli.
When you reorder the chart to look at climate impact by calorie, the landscape looks different. The ruminants still top the chart, but low-calorie crops like broccoli don’t do so well. Although beef still looks bad and beans still look good, pork and poultry are on a par with green vegetables, which means that a beef-and-leaf paleo diet is the worst choice going, environmentally speaking.
The claim that vegetarianism is kinder to the planet also fails to consider a couple of kinds of meat that aren’t on the Environmental Working Group’s chart. Deer and Canada geese do active damage in the areas where they’re overpopulated, and wild pigs leave destruction wherever they go.
Most people, though, are most likely to get their food from the farm, and it’s important to note that, although the chart attaches one number to each kind of food, farming styles vary widely and not all pork chops — or tomatoes, or eggs — are created equal. Unfortunately, it’s all but impossible for us consumers to figure out the climate impact of the particular specimens on our dinner table, whether they’re animal or vegetable.
When it comes to meat, trying to eat responsibly presents a genuine conundrum: What’s best for the planet is often what’s worst for the animal. The efficiencies of modern conventional livestock farming do indeed decrease greenhouse gases, but they also require the confinement and high density that draw the ire of animal welfare advocates.
There are other arguments, on both sides — so many that it’s easy to make the case for whichever kind of agriculture you’re inclined to support.
© 2016 Star Tribune