Scientific American runs an article about efforts to clean up the industrial processes involved in mining silicon and manufacturing several kinds of solar cells: … In fact, most of their dirty side derived from the indirect emissions of the coal-burning power plants or other fossil fuels used to generate the electricity for PV manufacturing facilities.
These four types of solar cells pay back the energy involved in their manufacture in one to three years, according to an earlier analysis by the same team. And even the most energy-intensive to produce—monocrystalline silicate cells with the highest energy conversion efficiency of 14 percent—emit just 55 grams (1.9 ounces) of globe warming pollution per kilowatt-hour—a fraction of the near one kilogram (2.2 pounds) of greenhouse gases emitted by a coal-fired power plant per kilowatt-hour.
Even though thin-film solar PVs employ heavy metals such as cadmium recovered from mining slimes, the overall toxic emissions are “90 to 300 times lower than those from coal power plants,” the researchers write in Environmental Science & Technology….
Photo of pulverized silicon from German Wikipedia, Wikimedia Commons