Wal-Mart ( WMT) is set to announce a sweeping new environmental initiative Thursday as it continues its push into a green new world.At one time decried for its big-box effrontery to the environment -- with its sprawling parking lots and bald consumerist ethos -- Wal-Mart has over the last few years made a considerable effort to transform itself into a green leader. The company will present its plan Thursday at its Arkansas headquarters in a presentation it's calling the "Sustainable Milestone Meeting." As reported, Wal-Mart plans to create a system that would track and detail, through a rating system, the relative environmental friendliness of the products it sells. Many feel that the company is attempting to keep out in front of probable new green-labeling regulations from the federal government. Also, some have raised the specter of the program's inevitably high cost. The retailer has some 100,000 suppliers and must contract with hordes of outside experts and consultants to research the impact of each product across its lifespan, from manufacture to garbage heap. Wal-Mart stock closed modestly higher Wednesday at $48.53, up 40 cents on lighter-than-average volume.