Motorola is billing its new W233 Renew, a cell phone whose case is made from recycled water bottles, as the world's first "green" phone. The phone (click on image at right for a closer look), announced at this year’s Consumer Electronics Show and available from T-Mobile in February for an undisclosed price, claims an eco-friendly talk time of up to 9 hours and a “zero-carbon footprint.”

To reach that claim involved what is known as a carbon credit. Such credits, as our colleagues at the Consumer Reports Home and Garden blog have covered, aim to allow companies or individuals to offset the carbon emissions generated by their product or their lifestyle by funding projects that reduce carbon emissions, a key contributor to environmental impact of products.

In this case, then, Motorola says it will pay Carbonfund.org, which sells carbon credits, an undisclosed sum for every Renew to offset the carbon dioxide used to manufacture, distribute, and operate the phone. Carbonfund.org, in turn, says it will use the money to fund projects that reduce carbon emissions, such as wind farms and methane-trapping programs.

Our colleagues at GreenerChoices.org, the environmental website for Consumers Union, the non-profit publisher of Consumer Reports, see credits as a small but potentially helpful way to cut carbon emissions. However, they also urge that before buying any product on the basis of a carbon-offset program, be sure to read the fine print, since there are no federal guidelines (Adobe Acrobat required) for specific carbon offsets.