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.

This year's glossy, photo-rich report goes on for 126 pages about how great Walmart is to its employees, suppliers, the environment, and the communities in which it operates. The section on sustainability seems thorough at first glance — there are certainly lots of statistics and small details on this or that program. But if you try to really digest the content and compare it to reports from previous years, you begin to realize that much of the data is elusive. The same stats aren't reported consistently each year. The metrics shift; promises touted one year are glossed over the next.

More significant are the many fundamental problems with Walmart's business model that these reports do not address, or even mention. It's as though, by loading up on pretty pictures and keeping the figures and details narrow, Walmart hopes readers will miss the forest for the trees.

To help people better evaluate Walmart's claims of being a green leader, Food & Water Watch and the Institute for Local Self-Reliance have published the Top Ten Ways Walmart Fails on Sustainability. Here's a quick rundown: