Over the past decade, Walmart has attempted to transform its image from a big-box purveyor of bargain goods sold by low-paid workers to a vanguard of corporate environmentalism, with solar-paneled stores regularly feted by the Davos set .

But for a retail behemoth whose business model still depends heavily on pollution, Walmarts green policies are more akin to a face-lift than surgical reconstruction, according to workers and advocates calling on the company to add an environmentalist to its board of directors.

Walmart is really good with the PR stunts about how sustainable they are, said Mary Pat Tifft, a 29-year employee at a Walmart in Kenosha, Wisconsin. But I have grandchildren, and Id like to leave them a healthy Earth and Id like their children to have a healthy Earth, too.

Tifft, 62, is a member of OUR Walmart, the nonprofit workers group that advocates for higher pay and better corporate policies at the notoriously union-averse retailer. Over a year ago, the group purchased about 40 shares, putting it comfortably above the $2,000 baseline required for a shareholder to submit a resolution. Now, OUR Walmart has proposed putting an environmental expert on the board to ensure that the companys lofty promises to shrink its carbon footprint and pollution output amount to more than just talk.

But the Bentonville, Arkansas-based firm says that Rob Walton, patriarch of the companys billionaire founding family, already provides environmental safeguards. Walton serves on the board of directors of Conservation International, a nonprofit to which the Walton Family Foundation has given millions in what critics call a years-long greenwashing campaign. He also holds the title of co-chair of the Arizona State University Global Institute of Sustainability, to which the family foundation gave $27.5 million in 2012.