Wal-Mart is going green.

The retail giant, which is also the nation’s largest grocery seller, is beginning to switch from petroleum-based to corn-based plastic packaging.

The first substitution, starting Nov. 1, involves 114 million clear-plastic clamshell containers used annually by the retailer for cut fruit, herbs, strawberries and brussel sprouts, Wal-Mart executive Matt Kistler said Wednesday.

“With this change to packaging made from corn, we will save the equivalent of 800,000 gallons of gasoline and reduce more than 11 million pounds of greenhouse gas emissions,” said Kistler, vice president for product development and private brands for the company’s Sam’s Club division.

Wal-Mart spokeswoman Tara Stewart said the company will feature the packaging in its 3,779 Wal-Mart, Sam’s Club and Neighborhood Market stores in the United States.