If you follow the debate over renewable energy, fossil fuels and nuclear, you probably know the biggest selling point that proponents of solar and wind preach about. It’s clean. Wind power, in particular, pushes the fact that nothing gets burned, no carbon is generated… it’s just giant, beautiful turbine blades spinning in the breeze and cranking out electricity for the masses.

But is it true? Well… mostly. But it turns out there’s one significant exception to that rule. Those giant turbine blades break or wear out over time and then they have to be replaced. And there’s almost nothing useful to be done with them so most wind up in landfills. (NPR)

While most of a turbine can be recycled or find a second life on another wind farm, researchers estimate the U.S. will have more than 720,000 tons of blade material to dispose of over the next 20 years, a figure that doesn’t include newer, taller, higher-capacity versions.

There aren’t many options to recycle or trash blades, and what options there are is expensive, partly because the U.S. wind industry is so young. It’s a waste problem that runs counter to what the industry is held up to be: a perfect solution for environmentalists looking to combat climate change, an attractive investment for companies such as Budweiser and Hormel Foods, and a job creator across the Midwest and Great Plains.

720,000 tons of turbine blades is a lot of material to dispose of. And because they have to be lightweight, yet strong, they’re made of a rather nasty combination of resins and fiberglass. Oh, and they’re still very heavy. And big. The blades range from 100 to 300 feet in length. Moving them requires special trucks and equipment to lift, load and unload them. That gets expensive pretty quickly.

Then there’s the problem of what to do with them. Since most wind farms are put out in rural areas, the township or county may have only a single landfill in operation, and generally not a large one. They don’t want their entire landfill taken up with a pile of these gigantic blades. Most utilities wind up having to cut the blades down to a more manageable size using special equipment. That adds more cost to the process and generates more resin and fiberglass dust.

NPR interviewed one guy in Texas who has started a company aiming to recycle the blades as much as possible. But that requires stripping all the resin off and then grinding them down into pellets that can then be used to make things like decking material. But the technology is still in its developmental stages and that’s an expensive process when all you’re producing is basically fiberglass pellets.

Is this enough to sink the wind energy industry? Certainly not. But it’s something for investors to consider and an issue that the industry will have to find a way to deal with going forward. And it’s also a good reminder that whenever someone tells you they’ve found a “clean” way to produce energy, be sure to look closely. No business is ever as clean as they make it out to be.