Wal-Mart is successful and success often comes with criticism, especially from activist groups, but when it comes to going green, even huge success stories like Wal-Mart need some guidance, so they've been getting help from eco-friendly organizations including Greenpeace, World Wildlife International and Conservation International as they develop a broad strategy to improve sustainability efforts.

“We’re not looking for the same old answers,” said Nancy Nagle, director of development, “We’ve got to let go of some of our old, preconceived notions and look for input, not just for ourselves, but to pass along to our suppliers.”

Nagel described Wal-Mart’s three-pronged sustainability strategy; being supplied by 100% renewable energy, creating zero waste, and selling products that conserve resources and sustain the environment.

Nagel conceded that these are lofty goals but they are intent on forging ahead even if the technology to do some things isn't available. The zero waste for emissions, for instance, may not come to fruition any time soon.

“We know we’re not going to get to zero, but we have an initial goal of reducing store emissions by 25 percent in seven years and to make our fleet 25 percent more efficient in three years, and we think that can realistically be accomplished,” she said.

Nagel also said they had to face challenges that were raised because of competitive issues in going green, such as the marketing concerns raised by a detergent manufacturer whose reformulation resulted in smaller packaging, possibly reducing its appearance on the shelf when compared against competitors larger packages.

As a solution, Wal-Mart changed aspects of its shelving where detergents are displayed.

“We wanted to encourage them to do this, so we gave a guarantee that they would get the same amount of space on the shelf as they had before,” Nagel said. “We didn’t want to penalize them for being efficient.”

While Wal-Mart’s size may make it a prime target for eco-criticism, Nagel said the retailer’s enormity is perhaps its best asset for prompting large-scale change.

“Because of our size, we can help create the critical mass to make this commitment,” she said.