Walmart wants to eliminate 20 million metric tons of greenhouse gas emissions from its global supply chain by the end of 2015.

The target figure represents 1.5 times the retailer’s estimated global carbon footprint growth over the next five years and is the equivalent of taking more than 3.8 million cars off the road for a year.

“Energy efficiency and carbon reduction are central issues in the world today,” said Walmart president and chief executive Mike Duke.

“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.”