What we do know is that Wal-Mart plans to ask all of its suppliers 15 questions about sustainable practices. Among them are questions about corporate greenhouse gas emissions, waste reduction targets, and water use. Top tier U.S. suppliers will be required to answer the questions by October 1, with international suppliers given a bit more leeway. So what will happen to these questions? That's still up in the air, but Matt Kistler, Wal-Mart's senior vice president for sustainability, hinted that the Index could be used to choose suppliers. "It will be a way of making a final decision beyond cost," he said. On the consumer side, so-called "nutrition labels" for sustainability won't be available for at least five years. Wal-Mart won't say if it plans on offering a rating system for sustainability-hunting shoppers, but the big box retailer is working on some sort of simple tool to help customers sift through supplier information. Wal-Mart isn't working on the Index of its over 100,000 suppliers alone, natch.