As executive director of the Environmental Defense Fund, the advocacy group that made its name fighting to ban DDT, Fred Krupp knew he had gone out on a limb when he teamed up with the McDonald's Corporation to tackle the fast-food company's solid-waste problem. Then last October, Krupp received a call from EDF scientist Dr. Richard Denison, warning that McDonald's was about to announce a major recommitment to the polystyrene clamshells that kept their Big Macs and other hot food warm. Suddenly Krupp feared the limb might break. Immediately he picked up the telephone and called the president of McDonald's U.S.A., Ed Rensi. "I said, 'Ed, use the alternatives that are available. Before you go ahead, please take a second look.' "

In a testament to one of the more unusual alliances in recent environmental history, Rensi listened. A week later McDonald's sounded the death knell for the 25-year-old clamshell, the ubiquitous plastic foam box that had become a symbol of throwaway society. This month McDonald's will complete the conversion to thin, paper-based wrappings in all 8,500 domestic restaurants. "McDonald's is one of the most visible producers of waste in America," says Denison, head of the three-person EDF task force that has worked with McDonald's for more than a year. "By giving up polystyrene, the company is assigning a value to the environment that's comparable to those they place on service and cleanliness."

Not everyone has cheered McDonald's decision—or the EDF's part in it. Forbes magazine complained, "McDonald's caves in [to environmentalists]." In February the National Polystyrene Recycling Company, an industry consortium that stands to lose millions of dollars in business, mounted a multimillion-dollar national ad campaign claiming that the McDonald's switch amounted to trading environmental apples for oranges because coated paper with food waste attached wasn't recyclable. "It's pure disinformation," says Krupp, noting that two of the three wraps have proved to be biodegradable. "What they're not telling you is that, even though all materials pollute, some truly are better for the environment than others. And this paper will take up 70 percent less space in America's landfills."

A decade ago Krupp's willingness to cooperate with corporate America rather than simply confront it would have been considered heresy by many environmentalists. Today he is the point man in an EDF strategy called Third Wave Environmentalism, in which science and economics are used to persuade business that environmentally oriented decisions can be good for the bottom line. "Fred is comfortable discussing environmental issues in cost-benefit terms," says Denis Hayes, organizer of the 1970 and 1990 Earth Days and director of Green Seal Inc., a new group that is certifying environmentally sound products. "He is effective because he understands that the business world is more responsive to consumers than to regulators."

Krupp, 37, learned that lesson as a boy in Verona, N.J. His father's business involved processing waste rags, which were later made into roofing materials. His mother, a high school history teacher, encouraged Fred to pursue his love of both science and politics. Krupp attended Yale, where as a combined science's major, he was inspired by Prof. Charles Walker to find solutions to environmental problems. He went on to law school at the University of Michigan, then returned to New Haven, where he founded his own law practice and a group called Connecticut Fund for the Environment. There he also met Laurie Devitt, the public health nutritionist he married in 1982.

CFE's 1979 $1.5 million lawsuit against the Upjohn Corporation for discharging toxic chemicals into Connecticut's Quinnipiac River at North Haven caught the attention of the EDF board, which was looking for a new director. Although only 30, Krupp was offered the prestigious job and accepted on the spot. "I thought if I waited, they might come to their senses."

The EDF's choice paid off. Since assuming the $125,000-a-year position in 1984, Krupp has increased the nonprofit organization's budget from $3 million to $17 million and boosted membership from 35,000 to over 200,000. The EDF's environmentally friendly Park Avenue headquarters in Manhattan is home to 55 employees, including a cadre of scientists, lawyers and economists who work on issues from global warming to innovative ways to reduce the nation's acid rain problem. (The EDF's acid rain plan was eventually adopted in its entirety last November as part of the amendments to the 1970 Clean Air Act.)

Krupp is optimistic about the impact of the final report that the EDF and McDonald's will issue this month about the company's solid-waste reduction plans. Already McDonald's has initiated a pilot program in Portland, Maine, to compost its food and paper waste. "Imagine, a fast-food chain composting!" says Krupp enthusiastically. "It proves that McDonald's recognizes the future is green. Now all we have to do is help convince the rest of corporate America."