Wal-Mart's CEO, Lee Scott, says he wants to turn the world's largest retailer into the greenest. The company is so big, so powerful, it could force an army of suppliers to clean up their acts too.

As part of this commitment, Wal-Mart has invited America's most famous environmentalist, Al Gore, to show his movie, "An Inconvenient Truth."

Wal-Mart is embarking on a far-reaching plan to adopt business practices that are better for the environment. Scott states that the world will learn that "there need not be any conflict between the environment and the economy."

"To me," he says, "there can't be anything good about putting all these chemicals in the air. There can't be anything good about the smog you see in cities. There can't be anything good about putting chemicals in these rivers in Third World countries so that somebody can buy an item for less money in a developed country. Those things are just inherently wrong, whether you are an environmentalist or not."

In a speech broadcast to all of Wal-Mart's facilities last November, Scott set several ambitious goals: Increase the efficiency of its vehicle fleet by 25% over the next three years, and double efficiency in ten years. Eliminate 30% of the energy used in stores. Reduce solid waste from U.S. stores by 25% in three years.

Wal-Mart says it will invest $500 million in sustainability projects, and the company has done a lot more than draw up targets. It has quickly become, for instance, the biggest seller of organic milk and the biggest buyer of organic cotton in the world. It is working with suppliers to figure out ways to cut down on packaging and energy costs. It has opened two "green" supercenters.

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