One source of clean energy is turning into a dirty problem for Europe.

The Continent's first wind farms, built three decades ago, now host many towers that are too old, too small and too inefficient to keep working.

That means dealing with heaps of waste created by green energy — particularly the high-tech blades made of exotic compounds that are difficult to recycle.

“We’re getting to the point now where the 20 years are either up or nearly up in many of the first wind farms,” said Giles Dickson, the head of Europe’s wind power lobby WindEurope. "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?'”

Thanks to the EU's push for renewables to account for at least 27 percent of the bloc's energy use by 2030, that question will loom ever larger over time. Wind is already the EU's second-largest power source, just behind natural gas. Last year, EU countries installed a record 15.7 gigawatts of new capacity, an increase of 20 percent compared with the previous year, according to a new report from WindEurope.

From year to year, more wind plants are being dismantled, and not every plant finds a secondary market” — German wind association BWE in a paper

All those new wind towers mean something has to be done with the old ones.

Denmark and Germany are forging the path: They were the first European countries to embrace wind power. Many other EU countries have since followed suit, meaning the challenge of decommissioning, recycling and scrapping old wind installations will grow.

In 2017, Denmark decommissioned 174 turbines with a total capacity of 98 megawatts while 220 new ones generating 373 megawatts were connected, according to the Danish energy agency. By mid-2017, Germany had a total of about 28,000 onshore wind towers, according to the country's wind lobby.

The number of towers being decommissioned could rise after generous government support programs for the first wave of wind farms end in 2020. Rising maintenance costs and lower power output increase arguments to take them out of service and replace them with newer, more effective turbines.

Under current rules, operators have an obligation to manage the decommissioning process in countries such as Germany and Denmark.

"You need to do a decommissioning plan when you set up your turbines," said Jonas Pagh Jensen of Siemens Gamesa Renewable Energy, which produces wind turbines and constructs wind farms. While that wasn't the case in the past everywhere, "today, everyone is highly regulated ... our customer is obliged to make a plan [for] what they intend to do in 20-25 years time when the turbine is expected to come down."

Winding down old turbines

One option is selling old assets to poorer countries.

Germany's wind industry says "there's a well-functioning market for old installations, with former Soviet Union countries and southeast Europe important buyers." There are also customers in Latin America and Asia.

But resale market options for outdated wind generating equipment could change thanks to rapid technological improvement and as more wind power is added. "From year to year, more wind plants are being dismantled, and not every plant finds a secondary market," German wind association BWE said in a paper last year.

A modern wind turbine produces 180 times the electricity at half the cost of one built 20 years ago, according to the New Zealand Wind Association. The turbines themselves have also changed. In the 1980s, a wind tower stood about 20 meters tall, its blades spanned about 17 meters, and it had a capacity of about 75 kilowatts of electricity. A modern tower can stretch more than 100 meters tall, with blades that span 126 meters and a capacity of 7.5 megawatts — enough to power about 3,000 households. One of the world's largest rotors has a diameter of 164 meters. Its 82-meter blades correspond to the wingspan of an A380 airplane and it produces some 9.5 megawatts of power.

A few years ago, investors bought up worn German wind facilities and relocated them to Poland. But noise complaints from people living close to those towers helped fuel a political push to dramatically toughen wind farm rules in 2016, essentially throttling new investments.

It doesn't often make sense for wind developers to cling to old turbines. Instead, they often rebuild existing wind farms, which already have appropriate permits, by replacing them with newer and more effective turbines. That means all of the old turbines, towers and foundations have to be dismantled.

That creates the dilemma of what to do with old installations — especially the rotor blades.

"We’ve been called several times, why blade recycling is a challenge for the industry, and I would say, it’s because it’s not yet recyclable,” said Pagh Jensen of Siemens Gamesa.

Dumping or recycling

Burying the blades in landfills is increasingly difficult thanks to toughening EU waste rules. Countries should resort to waste disposal, including landfills and incineration only as "the least preferred option." New rules agreed to last year are meant to boost recycling rates and reduce landfilling.

Europe's wind industry says it's unclear how a 10 percent landfill cap on municipal waste by 2030 will affect industrial and construction waste but concedes that disposing waste through landfills or incineration without energy recovery are the "least favored" waste treatment methods.

Everything, except for rotor blades, is very well recyclable" — Michael Schneider, spokesman for Remondis

That's forcing operators to try hard to recycle as much as possible.

Wind tower foundations are made of concrete and steel. Towers tend to be steel. The nacelle — the casing atop the tower — contains gears, the drive shaft, generator and transformer (containing oils and lubricants) made of a mix of steel, iron, copper and silica. In total, about 80 percent of the complete installation can be recycled, according to the German wind association.

The turbine blades, however, are another matter. They are designed to be both very light and very strong, able to withstand enormous forces without bending and breaking. To do that, blades are made from either reinforced carbon or glass fiber, combined with polyesters and thermoplastics.

That strength comes at a price — such materials aren't designed to be easily recycled.

"Everything, except for rotor blades, is very well recyclable," said Michael Schneider, a spokesman for Remondis, one of the world's biggest recycling service companies. "The blades are a wonderful example of what happens when everything is second to the dictate of lightness and flexibility."

In 2014, the most recent year for which data is available, Germany had to deal with 54,000 tons of waste from rotor blades.

Schneider says wind industry claims that blades can be recycled are simplistic. "They shred the stuff ... to eventually produce [refuse-derived] fuel for industrial processes, such as cement — that's the theory, but we know it's not that easy."

So burning the shredded blades is one option. Another is to cut, shred or mill the blades into powder and fibrous fractions and then use the material as fillers or reinforcements or fuel to burn waste.

But for both options, the blades first must be cut into smaller sections, and that generates potentially dangerous amounts of dust, the wind industry said.

Other ways of handling blade waste include incorporating them into other wind turbines or using them in construction projects such as playgrounds or bridges.

The scale of the problem is likely to grow. Today, there are about 77,000 onshore and offshore wind turbines in Europe, according to WindEurope, and 640 megawatts worth were decommissioned in 2017.

The wind industry insists it will be able to handle the resulting waste problem.

"There are solutions," said Pagh Jensen of Siemens Gamesa. "If you drive around, it’s not that blades are piling up.”

Yet.

"In an ideal world we would reuse everything and that is our aspiration.”

This article is part of a series on the circular economy, Getting Wasted.