Some of the first utility-scale wind farms were installed in the early 2000s. Because the design life of a wind turbine is about 20 years, these turbines are reaching the end of their useful lives. Thus, it is time to either decommission or repower them. When these wind power projects were first installed, end-of-life wasn’t really a top concern, but this topic is getting more attention now.
Increasingly, people are thinking more about the decommissioning phase of renewable energy projects, and are wondering if wind power is really as green as it seems. On this point, there is good news.
Wind turbines can be recycled, because the two primary materials are metal and cement, which are recyclable. However, wind turbines are getting bigger, so the volume of material inputs is increasing. It’s therefore critical to have adequate recycling infrastructure in place to process wind turbines.
What are wind turbines made of?
More than 80%t of the mass of wind turbines is made up of recyclable materials such as steel, iron, copper, and aluminum. Although it varies by model, wind turbines are 66%-79% steel, 11%-16% fiberglass, resin, or plastic, 5%-17% iron or cast iron, 1% copper, and 0-2% aluminum by weight, according to the National Renewable Energy Laboratory. Most metals are readily recyclable repeatedly and easy to make into new products.
What parts of a wind turbine are recyclable?
There are numerous parts to a wind turbine, and each has different recycling challenges and opportunities.
Wind turbine towers
Wind energy turbines typically consist of a tubular tower made of steel that supports other components, including the gearbox, generator, and blades. They are wider at the base and narrower higher up to save materials.
Because these towers are so tall, they are manufactured into long sections to make them easier to transport. Thus, wind turbine towers are generally assembled on-site from several pieces and are hollow inside to reduce their weight and conserve resources.
As the hub height of turbines increases, so does the length of the wind turbine towers. In fact, the height of land-based utility-scale wind turbines has increased 59% from 1998-1999 to 2020 in the United States. Now, the average hub height is about 90 meters, roughly the height of the Statue of Liberty. But, the average hub height for off-shore wind farms is even taller.
Lattice wind turbine towers are no longer commonly installed for utility-scale projects. One downside to lattice towers is that they encourage birds to nest in these structures, which is counterproductive in preventing bird collisions. There were also issues associated with long-term structural issues from these towers.
Because wind turbine towers are primarily made of steel, they are readily recycled in mills or foundries. The melting process involves very high temperatures of up to 3000 degrees Fahrenheit. Unlike plastic, steel is highly recyclable and can be melted and remelted repeatedly to make new products.
Unfortunately, this is a very energy-intensive process due to the heat involved. However, recycling steel conserves almost 74% of the energy used in the production from raw materials. Therefore, it is much better for the planet to use recycled steel compared to using virgin steel. In fact, the European Union steel industry has reduced carbon dioxide emissions by 26% since 1990, primarily by using more recycled content and improving energy efficiency.
The melted metal from wind turbine towers is made into slabs and then rolled into sheets for easier transport to manufacturing or processing centers. Recycled steel can be manufactured or welded into pipes, tools, construction beams, bikes, and even to make new wind turbine towers.
Wind turbine foundations
A foundation is vital to secure wind turbines to the ground. Considering the height and weight of wind turbines and their windy locations, a secure foundation is critical. In addition, the foundation might need to withstand earthquakes, hurricanes, blade strikes, or floods, depending on the location. Therefore the exact approach and requirements vary by a given project.
For example, constructing the land-based San Roman Wind Farm in Texas, United States, involved excavating the turbine site to a depth of 3 meters, building a reinforcing cage containing 68.5 tons of steel, pouring 510 cubic meters of cement, and then backfilling.
Cement is recyclable, even though it is not a very widely discussed topic. This saves space in landfills and can prevent the use of virgin materials. The recycled product can be used either as a filling material or to make new concrete. It typically involves using industrial crushing equipment to make the materials smaller.
Wind turbine gearboxes
In horizontal axis wind turbines, the gearbox is located behind the rotor and is housed in the nacelle. The gearbox is between the blades and the generator. Its purpose is to help transfer the energy from the rotation of the relatively slow wind turbine blades to the power-hungry generator.
Often, gearboxes are a weak link in the wind turbine because they can be noisy and prone to breakdowns. However, because most gearboxes consist of aluminum, brass, and steel, most of the components are readily recyclable. Like steel, aluminum and brass are also recyclable, and manufacturers can use the recycled materials over and over into new products. Also, recycling reduces the need for mining for virgin materials, preserving wildlife habitat and water quality.
Wind turbine generators
Also housed in the nacelle, the generator is located behind the gearbox. It converts the mechanical energy from the rotating blades into electricity and contains rare-earth magnets. Although many parts of the generator are recyclable, the implications of recycling rare-earth elements have not been well studied.
Wind turbine blades
Like the hub height of the tower, the blades are also increasing in length to increase energy production. Unfortunately, the blades are one of the least recyclable components of a wind energy turbine.
Because they are made of a fiberglass and composite material, they cannot be truly recycled into high-value goods. However, it is possible to recycle wind turbine blades into low-value construction materials and fillers. Typically, this is more expensive than sending blades to a landfill though, so many are piling up in landfills.
The wind energy industry is not unique in its challenge to find ways to minimize waste from composite materials. Numerous industries also struggle with this, including the marine, transportation, and construction sectors.
However, there are many ways to repurpose wind turbine blades for a variety of civil engineering projects. The Re-Wind Network is a collaboration between researchers in the United States, Ireland, and Northern Ireland that is exploring repurposing options for decommissioned wind turbine blades in a variety of civil engineering projects.
“We’re exploring the potential reuse of the blades across architecture and engineering,” said Larry Bank, a member of the Re-Wind team.“Developing such methods can have a positive effect on air quality and water quality by decreasing a major source of non-biodegradable waste.”
The Re-Wind Network even produces a catalog with products made from wind turbine blades, including electrical poles, cell phone towers, pedestrian bridges, bus shelters, and agricultural applications. The reuse of wind turbine blades is relatively new but growing in popularity and utility.
“One of the first things we looked at was cutting up these blades into pieces that could be given for free or for very low cost to individuals in economically deprived neighborhoods that could be using them for construction,” said Bank,
Can wind turbines be refurbished?
Although recycling is an important strategy in minimizing waste, source reduction and reuse are even more effective. Therefore, recycling is an excellent option when there are no opportunities to reduce or reuse materials. The primary options for aging wind farms are recycling components, repowering wind farms, or refurbishing turbines.
Repowering initiatives can extend the life of land-based wind farms by a decade or more and entail refurbishing or upgrading existing wind turbines as needed. This process can include increasing turbine rotor size or upgrading the gearbox, hub, main shaft, and bearing assembly. Repowering a wind farm can also increase asset performance by boosting annual wind energy production.
Another option is refurbishing wind turbines to give them another 20 years of clean energy production. This can entail regrinding the gearbox, rewinding the generator, painting turbine blades with specialty paint, and then installing them in new locations.
For example, Boythorpe Wind Energy specializes in refurbishing Vestas wind turbines and selling them for less than half of their original cost. This company is headquartered in Yorkshire, UK, and sells wind turbines ranging in size from 225 kW to 3 MW or more.
“Using refurbished wind turbines can be an excellent way to boost the return on investment of a wind farm by significantly reducing the project’s equipment costs,” says Edward Rivis, co-founder of Boythorpe Wind Energy. “This approach also gives farmer and land owners the extra peace of mind that their ‘recycled’ wind turbines have an extremely low carbon footprint.”
Why is wind turbine recycling important?
Transitioning to cleaner sources of energy is critical for combating climate change. Even if deploying wind energy doesn’t involve burning fossil fuels, it still has an environmental footprint. Therefore, it is critical to examine the entire lifecycle of a wind farm to conserve resources, protect wildlife habitat, and reduce greenhouse gas emissions. This will enable wind energy to reach its full environmental potential.
Although constructing wind farms in most countries involves conducting environmental assessments and obtaining permits, these primarily examine the impact of the wind farm on the immediate environment, including flora and fauna. For wind energy to be the greenest form of energy possible, it is critical to consider the entire lifecycle of wind turbines, from materials extraction through decommissioning.
A critical component is the recyclability and end-of-life uses of wind turbines. One reason this topic is so essential is because of the potential scale of the waste generated from utility-scale wind energy projects. Because decommissioned turbine blades are the hardest part to recycle, they are getting the most attention and concern.
For example, a study by the University of Cambridge estimated that 43 million tonnes of wind turbine blade waste will be generated by 2050. Of this waste, 40% would be from China, 25% from Europe, 16% from the United States, and 19% from the rest of the world.
Government policies can also help encourage recycling, repowering, and refurbishing wind farms. One way to do this is by banning wind turbine blades from landfills or incinerators. Thus, this would mandate reuse or recycling, benefiting the environment. In addition, tax incentives could make it more financially appealing to refurbish wind turbines or repower wind farms.
Do wind farms create more waste than coal power plants?
By comparison, wind farms create a very tiny fraction of the waste that coal-fired power plants make. In fact, coal power plants generate an estimated 200 times more waste than wind farms. Wind turbines last about 20 years and have about 10 tonnes of blade material per megawatt of wind energy capacity. Because wind power uses no fuel source and all the other components are readily recyclable, the blades are the primary waste from most decommissioned wind farms.
By contrast, burning coal produces ash. Unfortunately, coal ash contains contaminants including mercury, cadmium, and arsenic. Without adequate management, it can pollute waterways, groundwater, drinking water supplies, and the air. However, some coal ash is used in products, such as building materials.
Although it is important to mitigate waste from wind farms, it is already a very clean form of energy, both from a waste management and an emissions standpoint. As the wind power industry matures, it is useful to adopt sustainable practices that help protect human health and the environment, like refurbishing wind turbines and repurposing wind turbine blades.