Researchers at Carnegie Mellon University are urging companies to broaden their carbon footprint calculations. They report that many U.S. companies in a variety of industries do not account for the entire supply chain that results in final goods and services—overlooking up to 75 percent of the greenhouse gas emissions involved.

Most factories, it seems, assess only carbon dioxide released directly and not from materials processing or production of parts done by suppliers, which contributes significantly to the ultimate footprints. Similarly, most retailers analyze only their stores and not their merchandise supply lines.

The payoff of broadening their carbon footprint analysis, says Chris Hendrickson, co-director of Carnegie Mellon’s Green Design Institute, is that companies will find “new cost-effective ways to reduce greenhouse gas emissions.” By looking beyond their own walls, businesses will uncover more ways to reduce the burden of looming carbon taxation and high fuel prices. Identifying more energy-conscious manufacturers, for example, could reduce emissions for retailers more dramatically than simply decreasing electricity use in stores.