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.

NPR: Solar Industry Grapples With Hazardous Wastes

According to scientists who conduct so-called "life cycle analysis" for solar, the transport of waste is not currently being factored into the carbon footprint score, which measures the amount of greenhouse gases produced when making a product.

NPR: Solar Industry Grapples With Hazardous Wastes