Thousands of aging wind turbines will eventually need to be decommissioned, but the disposal of this “green” technology could prove to be a dirty job for environmental regulators.

While not nearly as productive as coal, natural gas or nuclear, wind turbines can churn out power more efficiently than solar panels, making them a more viable option of the renewable energy sector. The European Union has stood out as a global leader in utilizing this technology, with wind already its second largest power source. Germany — the first European country to wholeheartedly embrace wind energy —  has spent over $200 billion on a sweeping initiative to transition itself away from fossil fuels and toward renewable energy.

Besides a host of problems that occur during a wind turbine’s lifetime — such as intermittent power production and the killing of thousands of large, rare birds — Germany is now dealing with a another pressing issue:  What is to be done with a wind turbine once it’s reached the end of its life cycle? There are over 28,000 onshore wind turbines in Germany. More than one-third of these aging turbines will need to be decommissioned by 2023.

Many in the general public consider wind energy technology to be a completely operable without environmental degradation. However, this is not the case.

The high-tech blades used in wind turbines contain exotic compounds that are laborious to recycle. These rotor blades use carbon fibers and glass, and give off toxic gases and dust — which means burning them is not an option. Additionally, the concrete bases used to uphold wind turbines can go as far as 30 meters deep into the ground, making them very difficult to fully remove.

“The operators of wind farms in Germany [are] beginning to have to ask themselves, ‘What do we do with the assets that come up to the lifetime?’” said Giles Dickson, a wind energy lobbyist in Europe. The problem isn’t just on the horizon, but something that has already been plaguing German regulators for years. The country was forced to deal with 54,000 tons of waste from rotor blades in 2014.

“It will probably be a challenge for technology. It will really be an issue over the next years and decades probably to get old turbines off the field, so I expect industry will find technologies to cope with it,” said Dr. Jan Tessmer, an energy expert, during an interview with Deutsche Welle.

While he agrees that the disposal of wind turbines is hurting its image as a green energy source, Tessmer is still optimistic, believing technological innovation can bring about a manageable solution.

“I actually think it is important that we find good technologies for recycling, because wind turbines are pioneers in green energy technologies, and it would be a pity if we also cannot find green and environmentally friendly technologies for recycling them. But as I said, I think it’s only a matter of time to develop them and I’m quite confident that the image of wind turbines can be kept as a green technology,” he explained.

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This article originally appeared in The Daily Caller