There is much debate on the efforts of Wal-Mart's attempt to "green" itself.

First there is good news:

"Wal-Mart, the nation’s largest retailer, announced on Thursday that it would cut some 20 million metric tons of greenhouse gas emissions from its supply chain by the end of 2015 — the equivalent of removing more than 3.8 million cars from the road for a year."

and the mixed news:

"One of the significant consequences of Wal-Mart's rise and radical reshaping of the global economy has been a steep decline in the life span of many products. We wear out clothing, toasters, DVD players, and even furniture at a pretty rapid clip these days. It's part of the reason Americans are now creating twice as much trash as we did twenty years ago."

http://www.grist.org/article/putting-wal-marts-green-moves-in-context