Columnist, Food

A rib-eye steak at the Musso and Frank Grill in Los Angeles. (Melina Mara/The Washington Post)

I think it’s safe to say we all want to save the planet, and a good chunk of what’s written about food systems is about how to do it.

Estimates vary, but something in the neighborhood of 30 percent of total greenhouse-gas emissions are pegged to food. If you’re a farmer and you’re trying to do your part to reduce that, you have a lot of choices: planting cover crops, reducing tillage, using state-of-the-art tools to apply fertilizer only where you need it. If you’re an eater, it’s harder to make a dent.

If you’re looking for advice on how to make climate-friendly food choices, you’ll find there’s plenty of it. Unfortunately, most of it is either wrong or self-evident. (Though you will occasionally stumble on a thoroughly researched, tightly reasoned piece of advice about, for example, why you ought to eat more oats.) In the “wrong” category is the advice to buy local or organic. Sometimes those are better climate choices and sometimes they’re not, and it’s all but impossible to know which is which. In the “self-evident” category is waste, and how you should try to generate less of it, both in food and packaging.

What’s left is one piece of advice that is about as true as food advice gets: Eat less meat. Beef, particularly, is a carbon Sasquatch, mostly because the digestive systems of cattle (and all ruminant animals) release methane, a powerful greenhouse gas.

Replacing one 5-ounce steak a week with the caloric equivalent of beans, such as chickpeas, offers the same climate benefits as not using 38 gallons of gas. (Juanmonino/Getty Images/iStock)

Unless you’ve just crawled out from under a Hummer, you’ve heard the eat-less-meat advice and you’ve probably even heard that beef is the biggest offender. There’s plenty of evidence bolstering that position, and the latest came in the form of a detailed analysis of the impact of various foods and production systems from the University of Minnesota. The lead author, PhD student Michael Clark, looked at categories of foods, organic vs. conventional production, and several measures of environmental impact.

Once I got over feeling like an underachiever — because, really, what had I accomplished at his age? — I dug into his data. He helped. In fact, he worked with me to do a detailed analysis of the greenhouse-gas implications of a weekly five-ounce steak. We’re not taking any radical step like going vegan here, just eliminating one weekly beef meal.

We looked just at greenhouse gases, even though there are many other factors at play (several of which are included in Clark’s paper). There’s water use, land use and pollution, all of which affect the environmental impact of what we eat. There’s also animal welfare, impact on rural communities and worker conditions, all of which matter in other ways. We’re looking at one thing: the greenhouse gases you’re responsible for every time you decide what’s for dinner.

Here’s the upshot: If you trade in steak for beans once a week for a year, you will keep the equivalent of 331 kilograms of carbon dioxide (CO2) out of the atmosphere.

How much is 331 kg of CO2? It doesn’t help much to know that it’s 730 pounds, because then you just visualize things that weigh 730 pounds — three football players, a smallish camel — populating the atmosphere. It’s much more useful to compare it to the CO2 savings from other common climate-saving measures.

Giving up beef once a week in favor of beans, over the course of a year, is the equivalent of not burning 38 gallons of gas, or of trading in 12 incandescent bulbs for LED. That 331 kg is equal to about 5 percent of the average household’s electricity use. If you plant a tree (which I strongly suggest you do), it will remove that 331 kg in, oh, 83 years.

Let’s face it, though. Beans might be a tough sell. What if you trade in your steak for chicken or pork? That’s a win, too, although not as big a win. The impact of beef (334 kg for that weekly steak) dwarfs that of beans (3 kg for a weekly serving), but it’s also larger than that of chicken (64 kg) and pork (68 kg). But, whatever you do, don’t trade your beef for lamb; your impact will more than double. Realistically, if you cut back on beef, you’ll probably replace it with a combination of foods — pork and beans, perhaps — and the heavier you go on the legumes and grains, the better you do.

But this isn’t the end of the story. Clark’s analysis didn’t include the potential that grazing cattle have to rebuild soils and actually lock carbon away (called sequestration) in the process. I checked in with Jason Rowntree, an associate professor at Michigan State University who’s researching just that. Last time I spoke with him, a couple of years back, he was in the midst of a grazing experiment. Now he has preliminary results showing more than 3 metric tons of carbon sequestered annually per hectare, which would, he wrote me by email, “at minimum [produce] carbon-neutral beef but most likely a beef product that has a negative carbon-footprint.” (He also cautioned that these numbers haven’t yet been peer-reviewed.)

A grass-fed steer with a carbon-negative footprint that turns food humans can’t eat into something barbecue-ready is, climatically speaking, a free lunch. But that lunch may be hard to find at your local grocery store, because you have no way to determine whether any particular steak, even if it’s labeled “grass-fed,” came from a rancher who’s managing for carbon sequestration.

I asked Carrie Balkcom, executive director of the American Grassfed Association, whether carbon footprints were on most ranchers’ radar. “We try not to be invasive into people’s production methods,” she said, but they do survey their membership and know that 93 percent say they’re doing some kind of managed grazing. Some are even measuring soil carbon.

Me, I’d love to see a certified “carbon-negative” label, but that probably won’t be showing up in the meat case any time soon.

While carbon-negative beef is possible, it might not be common. And its benefits may run out after a while. Most soil scientists I’ve spoken with say they believe the soil’s ability to lock carbon away is finite. Once you hit that ceiling, you’re stuck grazing cattle to keep it locked away, but with no additional carbon sequestered to compensate for the methane the cattle produce.

Rowntree cautions against trying to figure out just how long that would take. “Nature is complex,” he wrote me in an email. “We try to linearize nature’s responses and that leads to placing ceilings on what can happen with management.” But he adds, “It is naive to believe that with changing landscapes, the carbon sequestered is permanent. It is stored in soil as energy and it will be cashed out as well.”

Beef has climate impacts because of the methane gas cattle emit. But grazing cattle on grass can help. (Daniel Acker/Bloomberg News)

Grass feeding does more than sequester carbon, Rowntree points out. It can restore degraded land, something that can have benefits for future uses and generations. It also does what has made cattle a mainstay of human civilization. It converts grass to milk and beef by letting cattle do what cattle do best: graze.

Should you eat less meat? Yeah. And waste less food. Use less packaging. Eat oats! But, of course, it’s never quite that simple, and we’ll all do better if the people who raise our food have a reliable way to tell us about it, and the people who buy it to pay attention.

Also, change your lightbulbs already.