As aging wind turbines across Europe near the end of their useful lives, the sector is grappling with recycling solutions to avoid filling landfills with the remains of obsolete machines.

While steel from the towers and nacelles is recyclable, turbine blades are filled with a composite material that cannot be easily broken down. According to industry group WindEurope, about 14,000 blades will be decommissioned across Europe by 2023.

Germany faces the most immediate end-of-life questions, with 4 GW of wind capacity set to fall out of the country's revenue support system by the beginning of 2021. "Since we are mostly talking about small turbines with 1.5 MW and less, the sum of turbines affected is quite significant," WindEurope spokesperson Christoph Zipf said in an email.

Onshore turbines installed two decades ago will be the first to come down, but the issue will eventually reach the offshore sector too.

"It's not that just because we produce clean energy it's justified that we have a dirty production," Philippe Kavafyan, CEO of turbine manufacturer MHI Vestas Offshore Wind A/S, said in an interview. Before turbine blades even leave the factory, they produce an amount of scrap that is not negligible, Kavafyan said. "The more you become mainstream, the more you need to think about how sustainable is your full [business] model."

From blade to cement

Turbine blades are made from reinforced fibers including glass, polymers such as polyester, balsa wood, metals and coatings. In parts of the U.S. with turbine fleets older than those in Europe, many blades are discarded as landfill waste, with specialist recycling facilities not widely available or affordable. Blades can also be incinerated, with obvious environmental implications.

European countries have differing approaches. In Germany, sending blades to landfill is illegal due to their composition, while in the Netherlands, landfilling takes place because the cost of recycling is too high.

To avoid landfilling or incineration, the sector is working on recycling strategies with waste management partners, with the most promising one being cement co-processing, already underway in Germany by specialist recyclers such as Neocomp GmbH. In this process, the scrap glass fiber is broken down and used as a component in producing cement mix.

Demand for recycling solutions is on the rise, and other options including chemical dissolution or pyrolysis are being trialed but are not yet at an economic scale. The sturdy blades can also be repurposed for public infrastructure such as seating, playgrounds, bike sheds or walkway bridges.

To reduce the lifecycle emissions of turbines, some companies are also eyeing alternative building materials. Turbine-maker Vestas Wind Systems A/S is targeting "zero-waste," fully recyclable turbine production by 2040 and will do so by optimizing materials used in the blades and hubs as well as by supporting more specialist recycling options.

To lower the carbon footprint from the steel production process behind its turbines, Swedish utility Vattenfall AB recently entered into a collaboration with wind engineering company Modvion AB to trial the use of wooden turbine towers. Roughly a quarter of emissions from turbine manufacturing come from the steel tower, and using wooden towers could also cut costs, Vattenfall said.

Lifetime extension

Despite new waste management options becoming available, most developers faced with an aging asset are expected to kick the recycling can down the road wherever possible. "In the coming years, we are mostly extending the lifecycle of existing turbines. However, as we move forward, we will continue analyzing recycling options for our removed blades," a spokesperson for Spanish utility Iberdrola SA said.

Most wind turbines have warranties for 20 years of operation, assuming they are exposed to maximum wind forces. For the majority of sites, that leaves years of headroom, said Keir Harman, director of asset optimization and management at DNV GL, a consultancy.

DNV GL's advisory arm also advises portfolio owners on lifetime extension and often finds that turbines can spin 10 years beyond their warranty. Apart from the usual maintenance, this is not necessarily a costly undertaking. Operators can simply adjust the settings of their machines to preserve the equipment and increase its life, Harman said in an interview.

Replacing older, smaller turbines with more powerful ones can boost the output of a wind farm or reduce its visual impact, but in many cases, the economics skew in favor of keeping turbines in the field, Harman said. For example, U.K.-listed investor Greencoat UK Wind PLC in 2019 changed its assumption around turbine lifespan from 25 to 30 years across its portfolio, which bumped up the asset value of the fund by over 5% without the need for large capital investments.

Some wind farms also face challenges in renewing their site permits, maybe due to a change in biodiversity considerations or local opposition. Germany, for example, could see a reduction in its turbine fleet as fewer areas are available for planning. "In some areas of the world, it doesn't really make sense to take a wind farm down," Harman said.

A 30-plus-year life expectancy may become more commonplace for new machines in the coming years. In an industry first, General Electric Co. received a 40-year lifetime certification from Germany's TÜV NORD AG for one of its onshore wind turbine models in 2019. As developers gather experience data and turbine technology advances, the concept of a 20-year useful life could be broken down, Harman said. "It makes sense from an environmental point of view."