As the solar industry has grown from a tiny upstart to major industry, it's been taking steps to lighten its footprint beyond the clean electricity solar panels produce.
Unfortunately, there are toxic chemicals involved in solar manufacturing, and as the industry grows it's having a bigger problem with hazardous waste.
Although some companies have invested in on-site equipment that lets them recycle some waste, many haven't and are forced to ship it elsewhere.
Some companies can't dispose of it nearby and they end up transporting it by truck or rail to sites that can be hundreds or even thousands of miles away, reports Associated Press (AP).
Since fossil fuels are used to transport that waste, that negatively impacts the industry's overall carbon footprint.
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," Dustin Mulvaney told AP. He's a professor at San Jose State University who studies the carbon footprint of solar, biofuel and natural gas production.
Last year, the Solar Energy Industries Association (SEIA) issued a report on how the industry needs evolve to be more socially and environmentally responsible.
"We want to take the lessons learned from electronics and semiconductor industries (about pollution) and get ahead of some of these problems," John Smirnow, vice president for trade and competitiveness at SEIA, told AP.
In California, industrial plants - which include solar manufacturers - are required to report the hazardous waste they produce and where they send it. Out of 41 solar companies in the state, just 17 reported their waste, according to AP.
Those 17 companies, which together have 44 manufacturing sites in California, produced 46.5 million pounds of sludge and contaminated water from 2007 through the first half of 2011, says AP. 97% of that was disposed of in-state, but that still leaves over 1.4 million pounds that ended up in nine other states as far away as Arkansas and even Rhode Island.
There's no comparison between the hazardous waste produced by the solar industry and fossil fuel industries, however. Gas and coal-fired power plants create more than 10 times the amount, according to Mulvaney.
Although solar advocates see this as an issue, they point out that at least this waste goes approved facilities - it doesn't enter the air and water. In contrast, a coal plant sends all those chemicals straight into the air, which also pollutes the water and land.
The Silicon Valley Toxics Coalition wants to create a scorecard that ranks solar manufacturers on their reporting of waste, but only the 14 biggest companies (out of 114 total) responded.
"We find the overall industry response rate to our request for environmental information to be pretty dismal for an industry that is considered 'green,'" Executive Director Sheila Davis told AP.
And only seven of SEIA's 81 manufacturing members have responded to their call for greater environmental responsibility. SEIA attributes that to the tough time the industry has been having and that it's currently focused on simply surviving.
As You Sow released a report last year that showed many solar manufacturers are using best practices, such as reducing water use and reusing water. Several companies are using safer materials, relying on renewable energy to power energy-intensive processes, and recycling waste.