No meal is more emblematic of American cuisine than the hamburger. No dish is found on more menus, grills and laps, and summer hasn’t even hit yet. But as beloved as the burger is, it comes at a steep environmental cost. Beef contributes as much as 17 percent of the world’s greenhouse gas emissions, and to the surprise of many, multiple studies have shown grass-fed beef to have a higher carbon footprint than beef coming out of feedlots.
A new Michigan State University study, however, offers a ray of hope to America’s climate-concerned burger eaters. Raised the right way, grass-fed beef could be a part of a carbon-neutral—or even carbon-negative—diet, according to the study, led by professors Paige Stanley and Jason Rowntree and published in the journal Agricultural Systems.
The study sought to explore claims, long argued by advocates of holistic management, that cattle managed intensively can be viable stewards of prairies and grasslands, mimicking the activity of the herds of buffalo and elk that once roamed these lands.
From deep taproots to spongy humus to clouds of insects above perennial grasses, a healthy prairie is an ecological force to be reckoned with on par with the carbon-sequestration potential of jungles, these advocates argue. Ruminant herds hold the ecosystem together by ranging around the land, depositing nutrient-rich manure and then moving on, so foraged plants can grow back and sequester more carbon in the soil.
Given these benefits, how did previous studies overstate the environmental impact of grass-fed livestock? The Michigan team zeroed in on two shortcomings. Previous studies consistently underestimated the impact of erosion in fields where corn and other cattle feed is grown. These farms are losing topsoil, which represents a loss of the earth’s capacity to absorb carbon from the atmosphere. Adding in those losses, the researchers found feedlot-grown beef was worse ecologically than previously estimated.
More significantly, the team argued, previous analyses underestimated the amount of carbon that can be sequestered from a properly managed grassland, and how quickly cattle can grow to marketable size on healthy pasture. In short, previous research on grass-fed beef reflected unhealthy grazing practices, skewing the greenhouse gas estimates, argued the MSU team.
In contrast, the new study monitored the carbon sequestration rates over a four-year period on a 30 year-old Michigan pasture stocked with 2.7 cows per hectare (about one animal per acre). “Rotation frequency focused on preventing overgrazing and assuring forage recovery, allowing appropriate regrowth before being grazed again,” the study says.
The experimental system, dubbed adaptive multi-paddock grazing, resulted in animals that were ready for slaughter 150 days earlier than previous studies assumed. At this earlier date, each animal was an average of 99 kilograms (219 pounds) heavier than their counterparts in previous estimates. In other words, the lighter stocking rates led cows to gain weight faster because the entire system was more efficient.
The pastured animals released about twice as much methane as the feedlot animals, confirming the results of previous studies. (Methane is a potent greenhouse gas). Presumably the greater emissions arise because cow stomachs must work harder to digest the diverse fibers of healthy grassland, compared with corn. But these emissions were more than offset by the carbon sequestered in a well-managed pasture, since grasslands fertilized by the cows grew back faster and sucked carbon out of the air. After four years, the study estimated, the production of these grass-fed cattle resulted in a net removal of carbon from the atmosphere—compared with a net contribution from the feedlot system.
That might cheer eaters of grass-fed beef, but it comes with two important caveats. One, the grass-fed system produces only half as much beef on the same amount of land as the feedlot model, including the land it takes to grow livestock feed. Secondly, the rate of carbon sequestration measured after four years isn’t likely to hold indefinitely; as the pasture reaches its optimal state, the rate of carbon absorption may slow.
The grass-fed cattle in the MSU study were also slaughtered in December, which happens to be an advantageous timeline for any grass-fed beef rancher facing a long, cold winter. When green forage stops growing, ranchers have to supply hay to their cattle, and it’s a struggle for the animals to maintain their weight. Thanks to their fat reserves from the previous summer, grass-fed animals make it through the winter, but as those reserves drain off, meat quality suffers. The rancher has a smaller amount of lower-quality product to sell.
Processing the animals all at once in December avoids that problem, but the meat must be frozen until it’s used. Feedlot beef, by contrast, can be supplied year-round, on demand, and those animals are as fat in January as they are in July. If it has to be a fresh market, grass-fed beef simply can’t hang.
So the study, while tossing a meaty bone to climate-conscious, grass-fed beef lovers, raises an issue for the bigger burger-eating population. They would have to accept a diet lighter on beef, simply because the land could not support as many animals. And they would have to be satisfied with a frozen product, rather than a fresh one.
As a hunter, I can see firsthand how meat ages in the freezer, from the day it dropped to a year later, when we see the bottom of the freezer. A well packaged piece of frozen meat won’t lose a step for a long time.
Steak needs to thaw overnight, but burger is ready to go at a moment’s notice. So if you like burger and can handle frozen meat, it could give some breathing room to small ranchers turning greenhouse gases into grass-fed beef and lush pasture. And that, friends, is how you rule the grill this summer.