Much recent media attention has been paid to the end-of-life for wind turbines and solar photovoltaic panels. A recent exposé by Bloomberg called into question the practice of burying discarded turbine blades, while the film Planet of the Humans—produced by documentary filmmaker and provocateur Michael Moore, and released via YouTube on the 50th anniversary of Earth Day—casts renewables as no better than fossil fuels when it comes to environmental degradation.
But what is the truth?
To get to the heart of the matter, we sat down with Mr. Derek Berry and Dr. Garvin Heath, from the U.S.-based National Renewable Energy Laboratory (NREL). Mr. Berry is an aeronautical engineer with more than 25 years’ experience in wind turbine blade design and manufacturing. His work in composites has been key to research NREL is conducting on recyclable wind blades. Dr. Heath is a senior scientist with a PhD. in energy and resources from the University of California with expertise in circular economy and a passion for responsible end-of-life practices for solar photovoltaic.
Let’s start with an overview of a wind turbine.
Wind turbines are composed of three primary parts: the tower, the nacelle (where the actual turbine is housed), and the blades.
Most of these parts are made from steel, concrete, or composites. The tower is typically steel, concrete, or a combination of the two. The nacelle and turbine are constructed from a blend of metals and composites, and the blades and nose cone are typically produced from composites.
For example, the blades: Wind turbine blades are made from fiberglass composites and adhesives which allows them to remain light and flexible at great lengths. The blades are remarkably effective and efficient. They are designed for a minimum 20-year lifespan, and today’s new blades can be used for closer to 30 years, particularly if they are maintained in the field to avoid cracking or delamination. At the end of their service life, blades can be repaired or refurbished, which can keep them going for more like 40 to 50 years, although older blades are shorter and not able to capture as much wind power as today’s longer blade designs.
NPR recently reported that up to 90% of a turbine—representing a considerable amount of steel, concrete, and other components—can be sold or recycled. The blades are the exception; can you tell us more?
That’s correct. Today, the steel, concrete, and many bolts that connect the component parts have an easier path to recycling or reuse than the composites.
Wind turbine blades, of virtually every size, are produced using thermoset resin systems. These resins are hard to break down; the bonds made by these composites are difficult to change chemically, which makes them more difficult to recycle. Hundreds of thousands of blades are already at the end of their life, and while some of these are being used for repower or secondary market purposes, the challenge of what to do with the rest is one of the biggest hurdles for the circularity of the technology.
The aim is for us to invent and develop new blades with better end-of-life outcomes. We’re asking, “what’s better than what we have today?” We want to create a similar pathway to circularity as the rest of the turbine components by making blades more readily, efficiently, and cost-effectively recycled or repurposed.
What happens to turbine blades at the end of their life, currently?
There are a few ways that blades are managed at end-of-life, a decision normally made by the owner or operator of the turbine.
The first is by shredding the blades to produce small size aggregate that can be used as a filler in other materials. For example, concrete or cement can be added to this composite material to produce things like manhole covers and park benches. However, this process is not always cost-effective.
The second is to landfill the blades. Landfilling is more cost-effective and is safe. The blades don’t leak anything hazardous, but it does require space, and there can be a negative perception about this practice, as shown in the recent media. Today, there are large tracts of land where blades are being stored while we work to develop more cost-effective and higher-grade solutions.
Finally, and this is rarer, blades can be destroyed with the application of heat through pyrolysis. Energy can be trapped from this process and the remaining char can be used in other applications.
What about solar photovoltaic panels—how are they different, or similar, to wind turbines?
Despite their size, wind turbine components are not as complex as solar PV, which makes end-of-life for panels an even more complicated issue. A photovoltaic panel is a sandwich structure, where very thin layers are adhered together in a package that is supposed to last 30 years in any harsh environmental conditions. That makes it very difficult to extract materials at end-of-life, especially trace materials.
Today, recycling for solar panels exists on a very small scale in Europe and the U.S., with the European market being more mature. Unfortunately, the majority of today’s recycling operations are not specific to photovoltaic; rather, PV is added as a new product line within the recycler’s current business model (typically focused on either metals recycling or glass), which is then adapted as best they can to PV.
There is only one facility in the world, in France, that is dedicated to recycling the dominant PV module technology, crystalline silicon, and only one company that will takeback and recycle the second-highest market share PV module technology, cadmium telluride (at ~5% of global market share). Without a dedicated recycling technology to PV, only certain materials are recovered, leaving the non-targeted materials to be landfilled.
Nearly every component of a solar PV panel can be recycled; theoretically, even an intact solar cell can be extracted and placed into a new module. It ultimately comes down to cost. Because of the low volumes of materials (compared to traditional recycled material streams) and an inability of the incumbent recycling operations to recover all valuable materials, there is a relatively high cost to recycling PV modules today, a barrier to wider adoption.
Voluntary recycling ranges in price from $20-$30 per module in the U.S., which adds significant expense to what has become one of our most affordable energy sources. And, unlike Europe, which has a policy requirement for PV recycling, there is no federal mandate in the U.S. (and, so far, only one state requires it). The resulting challenge is that there is not enough voluntary demand for these recycling processes, so there is little volume. Without economy of scale, no specialized recycling processes or technology investments have been seriously pursued. (Contrast this to Europe, where the policy requirement has helped to increase volumes and lower unit cost).
As a result, many final owners of PV modules feel that the only practical end-of-life today is for panels to be landfilled or stored until there are better solutions. This is an externality that is rarely considered in the price of the panel. But it’s also a cost that, if amortized over the lifetime of the panel, would only add pennies. The outstanding question is whether recycling should be built into the cost of panels in order to generate the capital needed to grow the market. This is a question that some U.S. states (like North Carolina, New Jersey, Minnesota, and Illinois) are considering through legislatively mandated study commissions or voluntary agency processes.
Unlike turbines, there are also components in panels that may be hazardous, like lead in silicon modules, cadmium in cadmium-telluride, and selenium in CIGS.
The sentiments captured by the recent media are that renewable technologies are less environmentally friendly because of these end-of-life issues. Can you comment?
Let’s start with greenhouse gas (GHG) emissions. Outside of the falling cost of renewables, their dramatically lower carbon footprint is the primary driver for their adoption. For example, inclusive of end-of-life, typical lifecycle GHGs of solar is about 50 grams of CO2 per kilowatt-hour (kWh); wind is even less at about 20 grams of CO2/kWh. But let’s compare that to coal at 1,000 grams of CO2/kWh and natural gas at 500 grams. From a lifecycle GHG perspective, wind and solar are the clear winners.
Renewables also take dramatically less water to produce. Today in the U.S., about 40% of our freshwater withdrawals are used at electricity generation units. Most of that is for cooling purposes in fossil and nuclear generation processes. This has an impact on water quality as well as the volume of water available for other needs. The average water footprint for wind per unit of energy produced (including construction, operation, and fuel supply) is only 1.3; for solar, that number raises to 140. But for coal, it’s 495 and for natural gas, 247*.
Wind, and solar in particular, are often criticized for their need for raw and rare materials. The truth is that we aren’t going to be able to meet our energy demands without using these materials—whether we’re pulling coal or natural gas out of the ground, or sourcing silicon and cadmium for solar panels. And solar panels are getting more efficient and innovative all the time.
The end-of-life impact of these technologies is relatively small. Blades in landfills might be an unpleasant image, but this practice isn’t dramatically harming the environment, particularly when compared to the overall lifecycle, the pollution and waste produced by other forms of energy generation. And the same is true for solar PV. For example, the lifecycle GHG contribution of disposing of or recycling a panel is usually less than 5% of its total lifecycle GHGs, which are already very low compared to incumbent technologies.
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That doesn’t mean we should let the renewables industry off the hook and accept end-of-life pollution. For any industry, a circular economy of materials should be a key objective. It’s critically important because there is always a finite amount of materials that can be obtained from the earth. We need to continue to become a more sustainable industry that reuses materials and controls for hazardous waste. And, if we can close the loop by recovering materials, the end-of-life phase for these technologies becomes net positive, when compared to disposal.
How should companies that are considering investing in renewables take what you’ve shared into account?
First, they shouldn’t be dissuaded. The overall environmental footprint of both wind and solar are significantly less than all other types of energy generation.
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Second, they can consider engaging on this issue at the policy or practice level. Europe is advancing frameworks for blade research and treatment for end-of-life that is driving advancement globally. By joining these efforts or calling for standards, companies can help support the laboratories, owners, and operators that are seeking solutions.
Third, corporate purchasers can help to drive the market for more sustainable solutions by specifying in their procurement more sustainable products. Prepayment for solar end-of-life costs can also take care of end-of-life for the module, legacy systems, and administrative costs. These expectations for standardization and pre-payment programs are growing, through initiatives like NSF 457, the Sustainability Leadership Standard for Photovoltaic Modules and Photovoltaic Inverters, which will become part of the U.S. Electronic Product Environmental Assessment Tool (EPEAT).
Even though we still face challenges in renewable technology end-of-life pathways, we are many years into research on innovative composites, new manufacturing materials, and PV module design that makes liberation of materials easier. More concerted efforts are needed, and corporate awareness of, and support for those efforts, is encouraged.
Interested in learning more? View our Skeptic’s Guide to Corporate Renewables.
*The source for these figures is a scientific paper published in 2015, The Consumptive Water Footprint of Electricity and Heat: A Global Assessment.