Walmart’s green PR machine has been running on overdrive lately. Over the past few weeks, the world’s largest retailer has announced six new solar installations in Colorado, unveiled its fifth annual Global Responsibility Report, and promoted a live webcast of its Global Sustainability Milestone Meeting. Walmart Chair Rob Walton donated $27.5 million to Arizona State University’s Global Institute of Sustainability, and both he and the company’s top marketing guy, Duncan Mac Naughton, spoke at the Fortune Brainstorm Green conference.

Why the gush of the green hype? Maybe to distract us from not-so-flattering news, like a recent Consumer Reports survey that ranked Walmart as the second-to-worst supermarket chain in the U.S.? Or to keep us from noticing the company’s evasions about whether it sells genetically engineered sweet corn or ground beef made with pink slime?

There are lots of hard questions to be asked about Walmart’s commitment to sustainability — and very few of them are answered in the company’s new Global Responsibility Report.