Executives from the nation's biggest organic and natural foods grocery chain, Whole Foods, and low-price supercenter Wal-Mart discussed their efforts to go green and offer more sustainable products during the LOHAS (Lifestyles of Health and Sustainability) Forum in Boulder, Rocky Mountain News reports.

The two might seem an unlikely pairing for a panel discussing their respective approaches to reducing their environmental impact. But in the past two years, Wal-Mart has stepped up efforts to become a more sustainable company. CEO Leo Scott has pledged publicly that, one day, the world's largest retailer will be powered completely by renewable energy and produce no waste.

In 2005, Wal-Mart opened one of its first experimental “green” stores in Aurora to evaluate energy- and waste-saving techniques such as installing solar panels and wind turbines, and reusing old cooking and motor oil to help heat stores.

“Wal-Mart is not a green company. We are by no means where we want to be,” Wal-Mart's Rand Waddoups told the audience. “But the exciting part is that we at least see that there's a lot more that we can do. And that's my job -- to make sure that we're doing as much as we can.”

Waddoups worked in Bentonville, Ark.-based Wal-Mart's corporate offices for eight years heading the company's purchasing of salty snacks before he became head of the retailer's sustainable efforts. Wal-Mart began focusing on the environment after Hurricane Katrina in 2005, when the retailer marshaled a relief effort to aid victims, Waddoups said.

The company has since worked with the Rocky Mountain Institute and former Sierra Club president Adam Werbach to decrease its energy consumption, among other measures, and asked its more than 60,000 suppliers to comply with a “sustainability scorecard.”

“For me at the time as well as for Wal-Mart, we both had a bit of a wake-up call,” Waddoups said. “The realization that doing business as the largest company in the world isn't just about making money.”

Wal-Mart's environmental awakening has come with consequences for Whole Foods, which has had sustainable agriculture as a key mission since the company was founded 28 years ago. Wal-Mart is now the biggest purchaser of organic milk and cotton.

That has forced Whole Foods to differentiate itself in new ways of offering the highest-quality products possible, such as creating a Whole Trade certification, which is in addition to Fair Trade and Rainforest Alliance approvals, said Michael Besancon, Southwest regional president for Whole Foods.

“There's no way in the world that we'd win a price battle with Wal-Mart,” he said. “I'm relatively smarter than that.”