Not so clean: service industries emit greenhouse gases too.

In recent decades, a large part of the U.S. economy has shifted to providing services rather than manufacturing products. Despite the presumption that the change bodes well for the environment, service industries such as the retail trade are creating just as much planet-warming carbon dioxide as the manufacture and operation of motor vehicles do, a new analysis suggests.

Industrial ecologist Sangwon Suh of the University of Minnesota in St. Paul scrutinized the movement of energy, raw materials, and products through various sectors of the economy. In such an analysis, emissions "that happen behind the scenes can then be taken into account," he notes.

In aggregate, all the companies that provide services are directly responsible for less than 5 percent of U.S. greenhouse-gas emissions, says Suh. However, when researchers also account for emissions that are generated in supporting activities such as the manufacture of equipment and supplies for service industries, some of them don't look so green.

For example, the retail trade--everything from large department stores on New York City's Fifth Avenue to small shops on any town's Main Street-boosts greenhouse gases annually in amounts that warm Earth as much as 326.8 million tons of carbon dioxide would. That retail-trade estimate includes the emissions generated in the construction of stores, the manufacture of goods to be sold, and their shipment to the retailer or customer, Suh notes. The total represents 5.4 percent of the nation's planet-warming emissions.

Similarly, restaurants, bars, and similar establishments each year contribute 5.0 percent. For comparison, the manufacture and operation of motor vehicles is responsible for 5.1 percent. However, greenhouse-gas emission from inefficiencies during generation of electricity and construction of those facilities is a whopping 16.2 percent.

When the emissions from supply manufacture and transport are included, hospitals account for 4.4 percent of U.S. greenhouse-gas emissions, Suh estimates. Real estate services contribute 2.1 percent, which is more than that generated by air transportation. Doctors' and dentists' offices are responsible for just under 1 percent, slightly exceeding that generated by trucking and courier services.

Suh describes his analysis in the Nov. 1 Environmental Science & Technology.

"People have forgotten that services rely on a background of physical products," says Reid J. Lifset, an industrial ecologist at Yale University. The type of analysis that Suh has conducted is "straightforward yet often neglected," he notes.

Suh's analysis may better apportion the responsibility for greenhouse gas emissions among various industries, says Brad Allenby, an industrial ecologist at Arizona State University in Tempe. However, it doesn't account for reductions in greenhouse-gas emissions that may come from opportunities, such as telecommuting, that a service-based economy offers.

"It's often tempting to look at a product [or service] and claim it's green," says Lester B. Lave, an economist at Carnegie Mellon University in Pittsburgh. "But what looks good for you may not be good for the Earth overall."