SAN FRANCISCO - Homeowners on the hunt for sparkling solar panels are lured by ads filled with images of pristine landscapes and bright sunshine, and words about the technology's benefits for the environment - and the wallet.
What customers may not know is that there's a dirtier side.
While solar is a far less polluting energy source than coal or natural gas, many panel makers are grappling with a hazardous waste problem. Fueled partly by billions in government incentives, the industry is creating millions of solar panels each year and, in the process, millions of pounds of polluted sludge and contaminated water.
To dispose of the material, the companies must transport it by truck or rail far from their own plants to waste facilities hundreds and, in some cases, thousands of miles away. Arizona receives some of it.
The fossil fuels used to transport that waste, experts say, is not typically considered in calculating solar's carbon footprint, giving scientists and consumers who use the measurement to gauge a product's impact on global warming the impression that solar is cleaner than it is.
After installing a solar panel, "it would take one to three months of generating electricity to pay off the energy invested in driving those hazardous waste emissions out of state," said Dustin Mulvaney, a San Jose State University environmental studies professor who conducts carbon footprint analyses of solar, biofuel and natural gas production.
The waste from manufacturing has raised concerns within the industry, which fears that the problem, if left unchecked, could undermine solar's green image at a time when companies are facing stiff competition from each other and from low-cost panel manufacturers in China and elsewhere.
"We want to take the lessons learned from electronics and semiconductor industries (about pollution) and get ahead of some of these problems," said John Smirnow, vice president for trade and competitiveness at the nearly 500-member Solar Energy Industries Association.
The increase in solar hazardous waste is directly related to the industry's fast growth over the past five years. New companies often send hazardous waste out of their plants because they have not yet invested in on-site treatment equipment, which allows them to recycle some waste.
Nowhere is the waste issue more evident than in California, where landmark regulations approved in the 1970s require industrial plants like solar panel makers to report the amount of materials they produce, and where they send it.
The Associated Press compiled a list of 41 solar makers in the state. The state records show the 17 companies that reported waste and that had 44 manufacturing facilities in California, produced 46.5 million pounds of sludge and contaminated water from 2007 through the first half of 2011.
Roughly 97 percent of it was taken to hazardous waste facilities throughout the state, but more than 1.4 million pounds went to nine other states, including Utah, Nevada, Washington, New Mexico and Arizona.