BENTONVILLE, ARK. — Walmart Stores, Inc. plans to eliminate 20 million tonnes of greenhouse gas emissions from its global supply chain by the end of 2015.

“Energy efficiency and carbon reduction are central issues in the world today,” said Mike Duke, president and chief executive officer. “We’ve been working to make a difference in these areas, both in our own footprint and our supply chain. We know that we have an opportunity to do more and the capacity to do more.”

The world’s largest retailer has collaborated with the Environmental Defense Fund to develop an approach that looks at the supply chain on a global scale. Other advisers to the effort include PricewaterhouseCoopers, ClearCarbon, Inc., the Carbon Disclosure Project and the Applied Sustainability Center at the University of Arkansas. The parties will identify projects, quantify reductions, engage suppliers and ensure proper procedures are followed.

“Like everything we do at Walmart, this commitment ends up coming down to our customers,” Mr. Duke said. “Reducing carbon in the life cycle of our products will often mean reducing energy use. That will mean greater efficiency, and with the rising cost of energy, lower costs, making our business stronger and more competitive. And, as we help our suppliers reduce their energy use, costs and carbon footprint, we’ll be helping our customers do the same thing.”

The program has three components — selection of product categories with the highest embedded carbon; action in terms of reducing greenhouse gas emissions from a product either in the sourcing of raw materials, manufacturing, transportation, customer use or end-of-life disposal; and assessment to account for reductions.

Walmart did not immediately identify which product categories featured the highest embedded carbon, but it did say reduction efforts would run the gamut and include methods of sourcing raw materials, manufacturing, transportation, customer use or end-of-life disposal.