Wal-Mart Stores Inc. plans to cut 20 million metric tons of greenhouse gas emissions from the life-cycle of its profits by the end of 2015, the retail behemoth said Thursday.

The number represents 1 1/2 times the massive company’s estimated carbon growth over the next five years, or the equivalent of the emissions produced by 3.8-million cars over one year, Chief Executive Mike Duke said in a webcast presentation from the company's Bentonville, Ark. corporate headquarters.

Wal-Mart previously announced an ultimate goal of relying solely on renewable energy to run all its operations while producing no waste. The mega-retailer completed three solar installations in Southern California last month.

“We have the capacity to do more,” he said. “We have the opportunity to lead. … It’s a very sizable goal, as we often do at Wal-Mart.”

The greening process will occur as raw materials are sourced and as goods are manufactured and transported, and even as customers handle and dispose of the products, Duke said. The company will focus first on product categories most associated with carbon.

The goal could even spark a “race, a treasure hunt” among suppliers to find competitive ways to cut emissions, said Fred Krupp, president of the Environmental Defense Fund , which is partnering with Wal-Mart to reach the sustainability goal.

“Wal-Mart is looking at the big picture,” Krupp said during the webcast.

Clear Carbon Inc. will check that Wal-Mart and its suppliers use proper methodology to produce complete and accurate calculations of reduced emissions, and Pricewaterhouse Coopers will confirm the procedures using consulting standards.

-- Tiffany Hsu

Photo: A Wal-Mart trucker at the Rosemead store. Credit: Robert Gauthier/Los Angeles Times