His concerns come more than a year after the company pledged to move toward sustainability; its web site promises to never stop "working toward improving our environmental performance ... And reaping 'double green' benefits around the world."
Langert's comments bring up pointed questions. McDonald's defines "double green" as plans and actions that ultimately benefit society and business growth, but how easy is it to make a business sustainable -- particularly fast food businesses that rely heavily on beef -- and what does beef sustainability even mean?
Interest in sustainability has skyrocketed among major players in the food service industry in recent years, mirroring conversations in the broader green and food communities about the agriculture industry's role in serious environmental challenges.
Bryan Weech, director of livestock agriculture for World Wildlife Fund, told The Huffington Post that "there is no one, universally accepted definition" for beef sustainability. Weech also represents the WWF on the Global Roundtable for Sustainable Beef, one of several groups working toward a definition.
Sustainability is impossible to define by a simple set of facts and figures, he said. Determining what is and isn't sustainable depends on the region.
Myriad things must be considered: impact on protected wildlife, biodiversity, soil and land quality, water resources usage and quality, deforestation, land use and management, social responsibility, nutritional security and community and financial viability.
"There is not a silver bullet," he warns. "There's not a blueprint or a map that says you do A, B, C and D and you're sustainable. It's more complex than that."
Dr. Jude Capper, an adjunct professor of animal sciences at Washington State University, agrees. Moving toward sustainability is easier said than done, she says.
"There is no doubt that for every restaurant or airline or car company, this is the kind of trendy issue at the moment," Capper explains, though she admits being impressed by recent comments by McDonald's Langert.
In 2011, McDonald's said it accepted the "responsibility that comes with our global presence" and would require, over time, that all agricultural raw materials be supplied only from sustainably managed lands. A year and a half later, however, Langert acknowledged that the definition of beef sustainability remained elusive:
Can we say we’re buying any sustainable beef today? No, we can’t. Could we be buying sustainable beef? We might be. What I mean by that is that there are no standards, measures, accountability and traceability to make those claims today.
"I thought that was pretty honest," Capper mused, noting that we live "in a world where there are other companies saying '[this is] the answer.'"
Capper also applauded Walmart's recent beef sustainability efforts; pledges unveiled in 2010 included a global commitment to help small- and medium-sized farms expand their business, earn more from their products and reduce the environmental impact of farming.
But even the most well-meaning plans by large-scale companies to move toward beef sustainability can go awry, simply because of the number of factors involved.
"Perhaps we need to define it first on the national basis and look at the 10 most system-wide improvements that could be made," Capper suggested. "Then on a regional basis, we say what things are doable or not achievable in Montana versus Texas versus northeast Texas versus northwest Texas."
Capper says basic improvements that could be implemented globally are straightforward ones, like attending to sick animals and providing nutritionally adequate feed. Also important is using land efficiently, which could be helped by simply increasing the number of calves in a herd. More animals healthily housed in less space, essentially.
"[I]n the States at the moment only about 90 percent of cows have a live calf every year," said Capper. "If we were to go to Argentina, that number goes down to 50 to 60 percent every year. If on a global basis, every cow had a calf every year, that would make a huge improvement."
Marilyn Noble, the communications director for the American Grassfed Association, says that raising cows on grass helps one aspect of the sustainability question -- producing healthy cows and nutritional beef. (Capper disagrees, saying if cows are managed properly, they work equally well on grass and grain-fed systems.)
Noble isn't alone in suggesting that grass-fed beef is more sustainable. She also brings up an important point about outfits aiming to piggyback on the sustainability trend. Lack of a single definition for sustainable beef opens the floodgates for supposedly green products, which may not deserve some of the claims they're making.
"You can call it green-washing, you can call it food fraud," Noble said. "That hurts people who are trying to do it right."
Noble offers praise for companies like Chipotle, which offers grass-fed meat at some of its restaurants, but questioned if such a thing would be possible for global companies.
"I think that would be really hard the way the system exists now for grass-fed producers to supply McDonald's," she says, though she allowed that there are other models that could be considered sustainable.
Weech believes that we're still a ways from defining beef sustainability, but conversations like these are important ones. "None of these are the total answer," he said, "but they're a starting place to begin this work."