Racing Turtles

“the [solar] industry could readily eliminate many of the damaging side effects that do exist. …Although the overall track record for the industry is good, the countries that produce the most photovoltaics today typically do the worst job of protecting the environment and their workers. To understand exactly what the problems are, and how they might be addressed, it’s helpful to know a little something about how photovoltaic panels are made. While solar energy can be generated using a variety of technologies, the vast majority of solar cells today start as quartz, the most common form of silica (silicon dioxide), which is refined into elemental silicon. …The quartz is extracted from mines, putting the miners at risk of the lung disease silicosis. Refining turns quartz into metallurgical-grade silicon, a substance used mostly to harden steel and other metals. That happens in giant furnaces, and keeping them hot takes a lot of energy, a subject we’ll return to later. Fortunately, the levels of the resulting emissions—mostly carbon dioxide and sulfur dioxide—can’t do much harm to the people working at silicon refineries or to the immediate environment. The next step, however—turning metallurgical-grade silicon into a purer form called polysilicon—creates the very toxic compound silicon tetrachloride. The refinement process involves combining hydrochloric acid with metallurgical-grade silicon to turn it into what are called trichlorosilanes. The trichlorosilanes then react with added hydrogen, producing polysilicon along with liquid silicon tetrachloride—three or four tons of silicon tetrachloride for every ton of polysilicon. Most manufacturers recycle this waste to make more polysilicon. Capturing silicon from silicon tetrachloride requires less energy than obtaining it from raw silica, so recycling this waste can save manufacturers money. But the reprocessing equipment can cost tens of millions of dollars. So some operations have just thrown away the by-product. If exposed to water—and that’s hard to prevent if it’s casually dumped—the silicon tetrachloride releases hydrochloric acid, acidifying the soil and emitting harAd”

Solar panels glimmering in the sun are an icon of all that is green. But while generating electricity through photovoltaics is indeed better for the environment than burning fossil fuels, several incidents have linked the manufacture of these shining symbols of environmental virtue to a trail of chemical pollution. And it turns out that the time it takes to compensate for the energy used and the greenhouse gases emitted in photovoltaic panel production varies substantially by technology and geography.