Bob Langert worked in logistics for McDonald's in the late 1980s when he was asked to take on a "temporary" six-month assignment to get chlorofluorocarbons out of the company's clamshell packages.

Twenty years later, Bob has worked with WWF and Conservation International on marine stewardship and sustainable beef, spent a decade with Temple Grandin dealing with animal welfare issues, visited chicken farms and slaughterhouses, picked tomatoes with migrant workers in Florida, lectured on sustainability in China and taken a nine-day raft trip down the Amazon River with his pals at Greenpeace.

"I never, ever imagined this," Bob said. "To have the good fortune to do this work, and make a difference in the world is beyond my expectations."

I interviewed Bob, who is vice president for corporate social responsibility, at McDonald's, last week at the State of Green Business Forum in Chicago. We talked about what he'd learned about working with NGOs, his accomplishments, frustrations and whether selling hamburgers can be "green."

Here are a few highlights:

A pioneering partnership: Langert's work with packaging led to a partnership with the Environmental Defense Fund, which ruffled feathers in the corporate world and the environmental community.

"Fred Krupp [EDF's chief] was a visionary back then," Bob said. "It was not politically correct to work with big companies."

EDF's crew did a shift working in a McDonald's, and proceeded to help with dozens of initiatives -- from trimming the size of straws to using recycled paper in napkins.

Recalled Bob: "We didn't spend one penny more. We saved millions and millions of pounds of packaging and costs."

The future of fish: McDonald's joined with the WWF to develop guidelines for the companies that supply its fish. What's the business case, I asked, for investing corporate time and money in sustainable fisheries?

"Assured supply," Langert replied. "The guy in charge of buying fish for McDonald's, he was really concerned with being able to buy fish 10 or 20 years from now….The No. 1 job of everyone in supply chain at McDonald's is to make sure we have stuff on the menu tomorrow."

This kind of long-term thinking -- so rare in big public companies -- is a key to sustainability.

Picking tomatoes: When McDonald's was urged to support efforts by migrant workers in Florida to win better wages, Langert worked side by side with the pickers. "I couldn't keep up with people half my size," he remembered. "Females doing the work all day long in the sun and you see the living conditions which are not good at all." Just last month, the workers hashed out an agreement that should bring them higher pay.

Bears and the Amazon: When Greenpeace protesters dressed as chickens picketed a McDonald's in London, accusing the company of destroying the Amazon, Langert's first job was to calm down his colleagues.

He recalled saying: "Let's not get all in a tizzy about their tactics. Greenpeace doesn't have an advertising budget, so they had to use McDonald's to get the word out. Let's look at the issue." The allegation was that tropical forest was being cut down to grow soy to feed chickens in Europe that became McNuggets.

When he asked trusted partners at Conservation International and WWF about the charge, he decided Greenpeace had a point. He approached the group and, before long, McDonald's, Greenpeace and big suppliers like Cargill had agreed to stop buying soy from deforested land.

The raft trip came later. "We spent nine days -- four of us from McDonald's, four of us from Greenpeace, to get the lay of the land. I gave up a Chicago Bears Superbowl game to go so that tells you where my passion is. Anyone who knows me knows that besides my family and my faith, it's the Chicago Bears."

Langert's to-do list: He'd like to find new ways to engage consumers in McDonald's sustainability work. The company serves about 64 million people a day.

He also wants to do more to reduce the environmental impact of the company's 33,000 stores, most of which are owned and operated by others. "Energy's a big issue for us," he said. New initiatives are on the way, he hinted.

The problem with burgers: Because beef has such a big environmental footprint, I asked Bob how he could reconcile the company's desire to grow -- and sell more beef -- with its environmental ethic. I told him that my rabbi, Fred Dobb, has said that one of the easiest things people can do to help the planet is to eat less beef, and asked if McDonald's would try to wean its customers away from Big Macs.

"I'd like to talk with your rabbi," Bob replied. He acknowledged the beef production has a big footprint, but said that "at the end of the day, we're going to give people what they want. We're going to do it in a good, responsible, clean, safe way. We've tried veggie burgers. They hardly sell at all. The day we can sell 500 a week in a restaurant, they'll be on our menu forever and ever. I don't have angst. You've got to face the realities of the world. And the reality of the world is that people eat protein from livestock and meat. Nothing wrong with that from my moral compass. I respect others that have a different moral compass. It's our job as a company to make things better, though. We're starting on that path–working with WWF on sustainable beef. That's the next step."

Certainly McDonald's offers choices to those who would prefer to avoid beef. Hey, the company even gave out pedometers and yoga CDs a few years ago to encourage people to be more active. But…given the climate crisis and the obesity crisis, maybe the next step ought to be to encourage those 64 million customers to make choices that are healthier for themselves and for the planet.