As the world seeks cleaner power, solar energy capacity has increased sixfold in the past five years. Yet manufacturing all those solar panels, a Tuesday report shows, can have environmental downsides.

Fabricating the panels requires caustic chemicals such as sodium hydroxide and hydrofluoric acid, and the process uses water as well as electricity, the production of which emits greenhouse gases. It also creates waste. These problems could undercut solar's ability to fight climate change and reduce environmental toxics.

A new ranking of 37 solar manufacturers, the Solar Scorecard, shows that some companies are doing better than others. Chinese manufacturer Trina scored best, followed by California-based SunPower.

The annual scorecard was created by the Silicon Valley Toxics Coalition (SVTC), a San Francisco-based nonprofit that has tracked the environmental impact of the high-tech industry since 1982. It's the group's fifth scorecard, and it shows that the industry is becoming more—not less—opaque when it comes to the sustainability of its manufacturing practices.

The coalition hopes the scorecard will increase transparency in a burgeoning industry that tends to be more focused on survival and growth than on tackling the dirtier side of an otherwise clean energy source.

What is Solar Power?

Patchy Data on Chemicals, Emissions

The SVTC relies on companies' self-reported data for its scorecard, which looks at such things as emissions, chemical toxicity, water use, and recycling. The coalition says the market share of companies willing or able to share details about their operations is declining. It praises the third- and fourth-ranked companies, Yingli and SolarWorld respectively, for responding to the survey every year and for showing a continued commitment to sustainability.

Name-brand companies on the scorecard represent about 75 percent of the solar panel industry, but more generic players that care less about their environmental impact have been entering the market, said Sheila Davis, the coalition's executive director. Her group is concerned that as these discount competitors gain market share, fewer companies will make sustainability a priority.

Varying regulations and manufacturing practices make it difficult to get standardized data about the environmental footprint of photovoltaic panels. A study released in May by Northwestern University and Argonne National Laboratory found that the carbon footprint of a panel from China is twice that of one from Europe, because China has fewer environmental standards and more coal-fired power plants.

China has already seen a backlash. Panel manufacturer Jinko Solar, for example, has faced protests and legal action since one of its plants, in the eastern province of Zhejiang, was accused of dumping toxic waste into a nearby river.

Solar manufacturers in the United States are subject to both federal and state rules that dictate, for example, how and where they can dispose of toxic wastewater. In Europe recent regulations mandate the reduction and proper disposal of hazardous electronic waste.

Still, researchers say it's difficult to get quality data across solar panel markets. The numbers available on the environmental impact of solar panel manufacturing in China are "quite different from those in the U.S. or in Europe," said Fengqi You, assistant professor of engineering at Northwestern University and a co-author of the May study. "It is a very complicated problem."

The SVTC hopes that pushing for more transparency now will lead to better practices later. "It's a new industry," said Davis. If companies adopt sustainable practices early on, she said, "then maybe over the next 10 or 15 years-as these panels begin to come down, the first wave of them, and we're beginning to recycle them-the new panels that are on the market are zero waste."

Not Enough to Recycle Yet

Right now, solar panel recycling suffers from a chicken-or-egg problem: There aren't enough places to recycle old solar panels, and there aren't enough defunct solar panels to make recycling them economically attractive.

Ben Santarris, strategic affairs director for SolarWorld, said his company has made efforts to recycle panels, but the volume isn't there yet. "We have product that's still performing to standard from 1978, so we don't have a big stream," he said. "It is a problem, because on one hand there is an interest in getting ahead of a swelling stream of returning panels. On the other hand, there's not a big market for it right now."

Recycling is particularly important because of the materials used to make panels, said Dustin Mulvaney, an assistant professor of environmental studies at San José State University who serves as a scientific adviser to SVTC. "It would be difficult to find a PV module that does not use at least one rare or precious metal," he said, "because they all have at least silver, tellurium, or indium."

Because recycling is limited, Mulvaney said, those recoverable metals could go to waste: "Companies that are reporting on a quarterly basis, surviving on razor-thin margins—they're not thinking 20, 30 years down the road, where the scarcity issue might actually enter the conversation."

The silicon used to make the vast majority of today's photovoltaic cells is abundant, but a "silicon-based solar cell requires a lot of energy input in its manufacturing process," said Northwestern's You. The source of that energy, which is often coal, he added, determines how large the cell's carbon footprint is.

The SVTC said it's leading an effort to develop a first ever sustainability standard for solar panels, similar to the U.S. Green Building Council's Leadership in Energy and Environmental Design or LEED, within the next two years. That effort will get under way as new solar panel factories come online in the U.S. and elsewhere: Mission Solar just opened a plant in San Antonio, Texas, and SolarCity plans to open a five-billion-dollar factory in western New York.

It remains to be seen whether solar companies will face enough external pressure to drive significant change in a business that, from a power-generation standpoint, already has plenty of environmental credibility.

"Despite the efforts of the SVTC," said Santarris, "there still is not nearly the awareness there should be that solar panels are not all created equal from an environmental standpoint."

But there is optimism that as the industry matures, solar companies will adopt stronger sustainability measures. In just the five years since the SVTC began its scorecard survey, Mulvaney said, it has seen a change.

"When we started this, there was no information on environmental performance, aside from the fact that it saves us from the dirtier fuels," he said. "Now these companies are producing sustainability reports."

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