As it turns out, wind energy may not be as eco-friendly as the environmentalists let on. Not only are they 24/7 bird-killing machines, they are also now piling up in landfills because they cannot be recycled.

“The municipal landfill in Casper, Wyoming, is the final resting place of 870 blades whose days making renewable energy have come to end. The severed fragments look like bleached whale bones nestled against one another,” reports Bloomberg Green.

Even the disposing of a turbine blade expels tremendous energy, being that they have to be hauled away and must be sawed through with “a diamond-encrusted industrial saw to create three pieces small enough to be strapped to a tractor-trailer.”

“Tens of thousands of aging blades are coming down from steel towers around the world and most have nowhere to go but landfills,” continued Bloomberg. “In the U.S. alone, about 8,000 will be removed in each of the next four years. Europe, which has been dealing with the problem longer, has about 3,800 coming down annually through at least 2022, according to BloombergNEF. It’s going to get worse: Most were built more than a decade ago, when installations were less than a fifth of what they are now.”

The blades were built to “withstand hurricane-force winds” and cannot be “crushed, recycled, or repurposed.” In places that lack the land-space to hold such waste, the search for alternative materials is now underway. Bob Cappadona, the North American chief operating officer for Veolia Environnement SA, said the wind turbines will be in those landfills “forever.”

“The wind turbine blade will be there, ultimately, forever,” saidCappadona. “Most landfills are considered a dry tomb. The last thing we want to do is create even more environmental challenges.”

One solution has been provided by the European Union, which burns some windmill blades in kilns that “create cement or in power plants.” The drawback, however: “their energy content is weak and uneven and the burning fiberglass emits pollutants.”

“In a pilot project last year, Veolia tried grinding them to dust, looking for chemicals to extract. “We came up with some crazy ideas,” continued Cappadona. “We want to make it a sustainable business. There’s a lot of interest in this.”

Global Fiberglass Solutions has developed at least one method of pressing the blades into “pellets and fiberboards to be used for flooring and walls.” The company’s Chief Executive Officer Don Lilly told Bloomberg they are now able to “process 99.9% of a blade and handle about 6,000 to 7,000 blades a year per plant.”

“When we start to sell to more builders, we can take in a lot more of them. We’re just gearing up,” added Lilly.

Though there indeed might be a solution the windmill landfill problem, the death of birds is another story. According to Audubon, wind turbines “kill an estimated 140,000 to 328,000 birds each year in North America, making it the most threatening form of green energy.”

“One of the most notorious wind farms—Altamont Pass Wind Farm in northern California—is a lesson in how poor siting can hurt birds. The farm, which straddles a windswept mountain pass, is also in the midst of a major avian migration route, and has been responsible for tens of thousands of birds’ deaths since its inception in the 1960s.”

Though companies have implemented some methods to curtail the bird deaths, such as radar systems to detect incoming flocks, none of them have exactly been proven and do not account for individual birds, such as pelicans.