Development of wind turbine blade recycling baselines in the United States

Over the past several years, the wind energy industry has received scrutiny regarding wind turbine blade (WTB) recycling due to the landfilling of WTBs caused by a lack of industrially viable recycling solutions. The amount of WTBs that will need to be recycled is set to increase in the United States as the deployment of wind energy is expected to rapidly grow to meet the nation’s energy goals by 2035. While significant progress has been made worldwide, it is still unclear which WTB recycling solutions would be the most cost and energy effective within the United States for the existing fleet of wind turbines. To guide researchers and industry with a clear path forward, a range of options for WTB recycling in the United States are modeled through development of baseline scenarios and the use of formal life cycle assessment (LCA). Model data have been collected through literature review, industry engagement, and expert opinion regarding current end of life practices and considerations surrounding equipment, labor, and logistics. A detailed baseline for WTB decommissioning processes has been developed and used to assess alternative approaches, such as on-site shredding to compare the impacts on greenhouse gas (GHG) emissions. The developed LCA model and baseline scenarios for WTB recycling is used to assess the current WTB decommissioning practices in the United States along with emerging recycling pathways, including cement kiln co-processing and pyrolysis. Initial findings indicate that there are different approaches to decommissioning WTBs in the United States, each of which has unique implications for recycling. In light of this finding, additional results from the modeling will be used to better understand decommissioning practices and assist in making educated decisions on recycling pathways for the future. Throughout the analysis, focus was given to where international efforts might differ from the United States. WTB recycling is occurring worldwide, and different countries have different drivers for creating markets for recycled WTB materials. The contrasts and similarities between the United States and other countries offer insight to areas of opportunity that the United States could investigate and areas that can be readily transferred from existing solutions. By modeling and characterizing the current decommissioning practices and potential recycling solutions for the United States, a clearer vision will be created for pathways forward as to how to handle end of life WTBs to enable more efficient and cost-effective opportunities for material recovery from end-of-life WTBs.


Introduction
Due to anticipated population and GDP growth, global energy and electricity consumption is anticipated to grow by 50% by 2050 amounting to 45 trillion kWh [1].In the U.S. alone, electrification of heating and the transportation industries alone will cause around a 50% increase in electricity demand by 2050.Growing energy demand is significant where, in the US in 2019, a quarter of all greenhouse gas (GHG) emissions were from the burning of fossil fuels for electricity alone [2].
Climate scientists overwhelmingly agree that the burning of fossil fuels, producing GHGs, is significantly contributing to the growing environmental crisis associated with global warming [3].Even so, our global society is becoming ever more dependent on energy to meet basic human needs, such as health, food, mobility, and communication.To combat this phenomenon, there has been a tremendous global effort to utilize renewable energy sources -such as solar energy, geothermal energy, hydropower, wind energy, and many others -which can provide energy without simultaneously generating GHGs as with fossil fuels [4].Of these, wind energy is the largest source of renewable power in the U.S., is one of the fastest growing sources of renewable power (15% growth per year), is showing tremendous job growth, and is one of the most cost-effective sectors (0.01-0.02USD/kWh) [5,6].The United States already has over 85,000 wind turbines in 50 states and its offshore wind industry is projected to grow rapidly [7].
While wind turbines can generate electricity during their functional use without the use of GHG emitting fuels, they create an additional challenge at end of life.Wind turbines must be decommissioned after their 20-30-year life [8,9] and many reach their end of life sooner due to financial incentives, defects in manufacturing, and damage from operation in the field [10][11][12][13][14].With increasing climate concerns and need for sustainability, the industry is turning towards new technologies with net zero environmental impacts and developing circular economies of domestic materials.Today, a wind turbine is made up of the blades/rotor, nacelle and drivetrain, and tower.Most of the turbine is recyclable other than the blades/rotor, which include a mix of fiberglass, balsa wood, polymer resins, carbon fiber, and metals from the lightning protection system [9].Currently, in the U.S. wind turbine blades are most commonly landfilled after being decommissioned [8,15].According to a recent study by Cooperman et al. published in 2020, assuming a 20-year turbine lifetime, the cumulative blade waste in 2050 is approximately 2.2 million tons [8].Cooperman et al. reviewed several processes to recover energy and materials from wind blades, finding that none are at cost-parity with landfilling -the current cost of disposing of blades in large segments or through grinding was relatively low compared to life cycle cost of energy.Ultimately, step-changes were needed in terms of recycling technology, new blade material and design, in addition to policy to achieve true circular economy of wind blades.
There are several recycling technologies that have been developed which are capable of processing the materials within wind turbine blades.These include mechanical recycling [16][17][18], thermal or thermochemical recycling [19][20][21][22][23], chemical or solvent recycling [24][25][26], and enzymatic recycling [27][28][29].While these technologies all exist, not all are available at scales relevant for the wind energy industry.Further, there is yet to be a robust analysis of the benefits/limitations of each technology along with life cycle assessment (LCA) to compare the technologies side-by-side within the existing infrastructure available in the U.S. for plastics recycling.In previous work by Sproul et al. similar analysis was performed for future recycling technologies including chemical recycling and microwave pyrolysis, with little attention paid to the decommissioning pathway utilized.However, in this work, the team strives to establish a set of robust technical baselines for current end of life processing technologies for wind turbine blades in the U.S. available at scales capable of processing wind turbine blade waste including the decommissioning step within the analysis.Recycling technologies included within this analysis include landfilling, cement kiln co-processing, pyrolysis, and mechanical recycling all of which are available and can process wind turbine blade waste in the U.S. today.

Methods
Data in the results section of this work were collected through U.S. energy industry stakeholder engagement and interviews.Stakeholders throughout the supply chain were involved in this process.This included manufacturers, owner/operators, local stakeholders, policymakers, decommissioners, recyclers, repurposers, and others from both the distributed or "small" and utility wind industries.Stakeholders were engaged in regular meetings throughout the project to ensure analysis and results were in-line with industrial perspectives.Their thoughts and input were summarized in the narrative below.
Process model methods were developed using the procedure outlined by Sproul et al [30].The model system used in this study was a wind turbine in Texas, U.S. which had all the metal removed, was decommissioned (disassembled/cut/shredded) on-site, and then transported to the landfill, cement kiln, or recycler.Inputs to the model were collected from peer-reviewed literature in combination with the knowledge from industry discussions.Models were developed using several peer-reviewed publications [31][32][33][34][35] and input from industry partners.

Decommissioning
Wind turbine blades are designed for a 20 to 30-year lifecycle.A tremendous amount of research and development has gone into designing blades to maximize their lifetime.As such, the materials within them are highly engineered to minimize costs and maximize functional life.These materials can include a mix of fiberglass, balsa wood, thermoset resins (either epoxy, polyester, and/or vinyl ester), carbon fiber in the main structural member, foams, and metals from the lightning protection system.Owner/operators want blades that survive in the field for as long as possible and require as little maintenance as possible.As such, the market is competitively pushed to highly engineered materials with maximized lifetimes.Limiting the lifetime of functional use of these blades are weathering and wear/tear on blades seen during their functional use -especially in the blade tip Conversely, wind turbine owners and operators indicate that as new wind turbine technologies are developed it is more difficult to compete on the market with older machines having smaller blades.As such, manufacturers are rapidly designing longer blades and releasing them into the market to capitalize on this opportunity.To remain competitive in the market, and maximize profit, owners/operators must decommission older but still functional blades and replace them with new blades (known as re-powering) approximately every 7-9 years (after only 23-45% of the design life of the materials in the blade).Repowering can be Minotdailynews.comWindpowerengineering.com seen in Figure 1.Although blades removed through this method are likely still functional, owner/operators still see these materials as waste that need to be removed from their site.
Another source for premature blade decommissioning results from damage and failure of the blade.Common sources of blade failure include lightning strike, leading edge erosion, manufacturing defects, and damage during transportation.Although there is growing interest and significant development in advanced, non-destructive characterization methods for finding and repairing damage in blades, it is often difficult to spot in the field.For example, damage in the inside of the blade from lightning strikes can be impossible to detect using current technology without someone physically climbing onto the blade.As a result, damage is often missed by owner/operators until non-repairable failure occurs.Currently, lightning protection systems are being created which can detect damage in real time and some are being deployed along with drone-mounted damage detection devices.However, these systems have been found to have their own failure mechanisms and do not operate with perfect reliability in the field.
Another reason for blade decommissioning is that materials reach the end of their design life at which point they are often decommissioned, though in the U.S. some can remain up and non-functional for months to years before being brought down.This often occurs between 20-30 years after the blades are installed and when the materials are no longer useful in this application.
The typical decommissioning process flow for the U.S. is displayed in Figure 2. As the further processing (left to right in Figure 2) occurs the recycling pathway options begin to decrease.The highest value recovery of the blade is for direct re-use in another turbine for sustainable energy generation.Industry partners indicate this is not often done for utility scale blades in the U.S. but is more common in the distributed or small wind industry.Additionally, wind blades at end of life can be repurposed into semi-structural or structural applications, such as bridges.However, most re-purposing efforts are not industrialized processes at this time and the structures would need to be recycled at the end of the repurposed life, which may be made more complex by the newly designed/built structure.
In the U.S., end of life blades are most commonly landfilled [8,15].However, in some cases they are shredded/ground into small particles which can be used as feedstock for concrete aggregate, cement production (most common), or as filler for oriented strand board panel alternatives.[36] It is difficult to estimate volumes for the different applications provided in this analysis, but industrial partners also suggest that most of the material at end of life is currently being landfilled at this time.Decommissioners indicated there have been recyclers who have agreed to recycle material but went out of business before successfully recycling all of the material in their possession.
Although often overlooked, decommissioning is an important step in the end-of-life management of wind turbine blades in relationship to the downstream material application.As shown in Figure 2, decommissioning significantly impacts the method through which the materials can be re-used or recycled impacting the recycled value of the blade materials.For example, re-powered blades at year 7-9 of their life could be valuable for 10-20 more years in service, though likely not in their original location.It could be possible to re-use those blades in a different location if it is cost competitive to do so and logistically possible to relocate them.However, due to the present lack of knowledge about the number of blades on the second hand market and where they are at any given time, and lack of predictability of this stream, it is not clear if such reuse strategies will be adopted in the U.S. market.

Decommissioning Analysis
Using data gathered through literature review and consultation with industry experts, an LCA was performed to compare the greenhouse gas emissions of different recycling approaches [30].Within that LCA, decommissioning, size reduction, and transportation of a 48.7m long wind turbine blade were considered.To compliment that work, decommissioning and transportation scenarios were developed in this paper to compare different methods of size reduction and transportation by truck.The primary considerations of these scenarios were the method of size reduction (on-site versus at the recycling facility), the packing efficiency of down sized material onto the truck relative to its available payload, and the transportation distance.
In six of the scenarios the method of downsizing material is limited to cutting material into 10-meter segments.In the remaining two scenarios, the same cutting operation occurs, but the material is then fed into an on-site mobile shredder.The way in which a blade is cut or shredded directly impacts how efficiently it can be loaded onto a truck for transportation.The scenarios developed in this LCA include consideration of four different packing efficiencies on the truck based on a range of values from expert opinion.The first three packing efficiencies are 25%, 50%, and 75% relative to the available payload.These efficiencies represent how much of the truck's 16,000 kg mass payload can be filled by blade mass.A low efficiency of 25% represents a scenario in which the blade segments cannot be packed efficiently and the volumetric constraints of the blade limit how much blade material is loaded on the truck.A higher efficiency of 75% represents a scenario in which blades are cut and stacked in an efficient manner on the truck, reducing the volumetric constraints and increasing the amount of mass that can be loaded on the truck.For shredding, a 100% efficiency is used to represent the likely scenario in which material can be condensed and will take up the full mass payload of the truck.
Once material is loaded on a truck, the final consideration is the distance of transportation.The current challenge in evaluating transport distance is that few blade recycling locations exist within the U.S. Therefore, there are no historical distances that can be used to gauge the impacts of transporting the blades.As a result, two generic transportation distances were considered in these scenarios to represent a likely upper and lower bound.The first distance of 200km represents a nearby end-of-life destination, more likely associated with landfill or cement co-processing.The second distance of 1000km represents transportation to a theoretical dedicated wind turbine blade recycling facility.While this distance remains uncertain, the 1000km scenario is in line with current distances of transport to some pilot scale facilities.
Figure 3 shows the greenhouse gas emissions of the size reduction and transportation scenarios considered.Across all scenarios truck transportation has the largest share of greenhouse gas emissions.Consequently, the packing efficiency and transportation distance have a significant impact on greenhouse gas emissions.However, this impact is far more pronounced for longer distances on an absolute scale.This means that on-site shredding has the most potential to meaningfully reduce greenhouse gas emissions if recycling facilities are located further away.Evaluating these emissions in IOP Publishing doi:10.1088/1757-899X/1293/1/0120186 combination with economic considerations would help identify the trade-offs between different size reduction approaches and identify an optimal solution for a given location.

Current Industrialized End of Life Strategies in the U.S. for Processing Wind Turbine Blades
A robust analysis of the state-of-the-art end of life strategies for wind turbine blades within the last 5 years is available in previous literature [37][38][39][40][41].For this work, we are summarizing the key processes below for purposes of the analysis performed.It is important to note that recyclers are financially motivated in this process and many of the technologies to recover wind turbine blades are low margin, high volume, meaning throughput of material is the limiting factor.Maximizing throughput of systems and therefore product generation is critical to enabling the recycling pathway.

Landfill.
Landfilling is the most common pathway for end-of-life blades due to the low cost in the U.S. (35-75 USD/ton) [42,43].However, this method sets the cost target for other recycling technologies.Because blades are so large and so tough, they can be challenging to shred.Further, maintenance of a shredder is expensive.Thus, often they are sliced into smaller pieces and then buried without further size reduction (minimizing costs and logistics).

Mechanical
Recycling.Mechanical recycling is the process through which material is downsized using industrial equipment to feedstock which can be reprocessed as-is using different recycling technologies.For mechanical recycling, wind turbine blades present a unique challenge given their size during functional use.Because of this, they require several steps to become small enough to be remanufactured.This process traditionally uses heavy machinery with large saws and then manual labor to cut the blade into parts small enough to go into an industrial-scale shredder system [8,9,38,44].This material is then ground up into granulate which is small enough to then be remanufactured using several recycling technologies.Costs of shredding, labor hours, and maintenance are the limitation to this process, as shredders are expensive to maintain and cutting large fiber reinforced composites is difficult.There are several companies in the U.S. employing this technology at pilot scale.This includes GreenTex Solutions, LLC who uses granulate mixtures as filler for new composite pieces including flooring and counter tops [36].RiversEdge has a similar technology where they are making 4'x8' panels filled with chopped wind turbine blades for lower cost boards for the marine industry [45].

Cement Kiln Co-Processing.
In this process, wind turbine blades are used simultaneously as feedstock and fuel for cement clinker production.The blades must be shredded down to an adequate size to feed into the cement kiln.Inside the kiln, the organic components within the blend are burned and used as fuel to partially power the process.Although it is not yet clear from an academic standpoint whether cement kiln co-processing should truly be considered recycling, the European Composites Industry Association considers cement kiln as an option because of the e-glass component being fully recycled into the cement product (~50% of the blade waste) [46].This process is often limited by the cost of shredding and other downsizing processes, as large scale shredders and size reduction technologies are expensive to maintain and use.The partnership between General Electric and Veolia in the U.S. is the best-known example of cement kiln co-processing of wind turbine blade waste.Estimates showed one 7-ton blade in the U.S. offsets 5 tons of coal and resulted in a 27% and 13% reduction in CO2 emissions and water consumption, respectively [47].However, it is uncertain what the maximum weight percent of end of life blade in the cement kiln co-processing fuel mixture can be before causing negative composition changes in the resulting clinker.Furthermore, as carbon fibers are more readily utilized in wind turbine blades cement kiln co-processing as an end of life wind turbine blade recycling pathway may become more difficult as fuel mixtures containing carbon fiber are often rejected.

Pyrolysis.
Pyrolysis is a thermal decomposition process performed in an inert gas atmosphere (in the absence of oxygen) above 600°C [48][49][50].During pyrolysis the polymer matrix and other constituent materials in the blade can be removed from the fiber reinforcement, to generate bio-oil, gas, and char which are recovered separately from the fiber [51].The fibers recovered from this process, unlike in cement kiln, can be re-compounded back into new polymer composites for downcycling into other highvolume applications, such as automotive plastics.Carbon Rivers' (based in Knoxville, TN) G2G technology is a well-known example of this approach who is capable of recovering chopped glass fiber and already has industrially available products for new applications.Another example currently being installed in the U.S. is thermolysis [52].Both technologies are similar and have been demonstrated for use for recovery of materials from wind turbine blades at pilot scale.

Existing Recycling Technology Analysis
In addition to size reduction and transportation, the overall results of the LCA can be compared across existing approaches [30].Figure 4 displays the baseline net greenhouse gas emissions of landfilling, mechanical recycling, cement co-processing, and pyrolysis.In the landfill baseline, blades are cut into segments, loaded onto a truck at 57% packing efficiency, and transported 100km to a sanitary landfill.In cement co-processing the blades are shredded on-site, loaded at 100% efficiency, and transported 200km to a cement plant.In mechanical recycling and pyrolysis blades are also shredded on-site and packed at 100% efficiency, but then are transported 500km to a dedicated recycling facility.The transportation distances for each approach were selected to capture the likely differences between endof-life destinations in the U.S. In this approach it is estimated that landfilling locations are abundant, requiring minimal transportation distance, while cement plants and theoretical recycling locations would on average be located further away.Given that there are currently limited cement co-processing locations and no full-scale recycling locations in the U.S., the distances selected are hypothetical and are based on a conservative estimate of potential future locations.The baseline size reduction and transportation estimates result in variations in greenhouse gas emissions which could be important for low emissions approaches such as landfill and mechanical recycling.However, these emissions are relatively small compared to the recycling emissions for cement co-processing and pyrolysis.
The recycling emissions shown in Figure 4 are the result of converting wind turbine blade materials into recycled products.For cement co-processing the recycled material is cement clinker, while in mechanical and pyrolysis the primary recycled material is recovered fiberglass.In addition to the primary recycled product, both mechanical recycling and pyrolysis produce additional co-products.For mechanical this co-product is powder from grinding, while in pyrolysis co-products include powder and oil.Substitution credits are given for the recycled materials of each process with a negative emission.The results of adding these substitution credits and the positive process emissions are the net greenhouse gas emissions, shown by the diamond markers.Comparing the net greenhouse gas emissions across processes highlights some key findings.First, the simplicity of mechanical recycling makes it the only process with the potential for net negative emissions.However, this finding comes with the caveat that the markets and corresponding value for mechanically recycled fibers and powders remains uncertain.Further research is needed to understand these markets and update the credit accordingly.Another finding from the baseline comparison is that cement co-processing and pyrolysis both result in higher net greenhouse gas emissions than landfilling.In both cement co-processing and pyrolysis, the major contributor to greenhouse gas emissions is thermal energy consumption.Within cement co-processing this thermal energy comes from incinerating the organic blade material, which results in direct carbon dioxide emissions.In pyrolysis this thermal energy is largely supplied by natural gas, which also results in carbon dioxide emissions at the point of combustion.Reducing thermal energy demand or changing to alternative sources of thermal energy could help reduce the emissions of pyrolysis.However, cement co-processing is limited by the origin of the organic content in the blade.As a result, lifetime emissions of the materials including cement coprocessing are unlikely to be significantly reduced unless the organic material of future blades is sourced from bio-based resources.

Discussion
Presently, the majority of wind turbine blade waste being generated in the U.S. is being landfilled.Owners and operators have indicated the reason for this is because they are motivated to choose the cheapest option which in the current U.S. market is landfilling material at a cost of 35-75 USD/ton, which varies based on location.Until costs of recycling are less than that of landfilling, there will be little incentive for owner-operators to choose to pay more to recycle materials.Several manufacturers, notably TPI Composites and GE Vernova, have indicated they are now working with owners to ensure their products do not end up going to landfill.It is not clear at this time if this will be a long-term solution to minimize blade waste going to landfill or merely a stepwise solution.In addition, because new blades are commonly decommissioned prior to the designed lifetime, more towers are being repowered than previous analysis indicated [8] resulting in more blade waste going to landfill in the U.S. Until manufacturers are incentivized to design blades for the known re-powering lifecycle, or designs become so optimized that there is little financial incentive to repower, there will be more end-of-life blade material to handle than is representative of the energy production of the design life.
Another major challenge facing this industry is that disassemblers/decommissioners are not incentivized to prepare the material for the most optimized recycling pathway.Disassembling a wind turbine is an engineering challenge involving many steps.Participants in this study indicate the businesses who do this are incentivized to get the material ready to be recycled as quickly as possible.The goal is to recover as much metal as possible for recycling separate from the non-recyclable streams, while maximizing packing density of those streams which cannot be recycled (including wind turbine blades).Because so many recyclers have promised to recycle these materials and then went out of business, at least one such company interviewed indicate they are reluctant to pursue other recycling technologies for blades until they are properly vetted by industry partners.This step has been engineered so that a full turbine can be taken down in just a few days.Until this portion of the supply chain for end-of-life materials is fully understood, and cost structures for recycling pathways are well developed, this portion will not be efficiently designed with the end of life of the blade in mind and will continue to be done as quickly as possible with metal recovery in mind.
From the recyclers' perspective the reason they are not recycling more material is that although the technologies have been proven at pilot scale, several of them are not available at production capacity.Currently, companies interviewed indicate promising recycling technologies have been funded by U.S. Federal agencies through demonstrations at the pilot scale and therefore to technology readiness level (TRL) 7-8.However, beyond demonstrations these recyclers cannot scale up their technology without private investment to industrially relevant scales (i.e., 100 MT/yr, etc.) for large scale recycling industries such as wind turbine blades.However, private investors will not invest in scaling-up processes without contracts being in place by customers (tier 1-2 suppliers, chemical manufacturers, original equipment manufacturers (OEMs)) for those industries.These customers will not put contracts in place without the recycler being able to process material at the scale relevant to industry.Right now, small business recyclers in the U.S. are caught in the middle of this.If it was possible to enable high-impact, high-likelihood of success companies to reach industrially relevant scale beyond pilot, this would significantly de-risk the adoption of that technology nationwide by enabling contracts to be put in place and therefore prompting private investment.As it stands, recycling approaches which are being employed are using technologies that are already available at industrially relevant scale without further investment (cement kiln, landfill, etc.) which may limit the adoption of new recycling technologies in the U.S. market.
In addition, participants indicated that more robust analysis of the cost and functional performance of recycled materials from commercially available recycling technologies is needed in the U.S. from reputable, non-biased sources.As it stands for the recycling industry in general, partners have indicated the demand for recycled materials (most importantly demand for recycling material for the automotive industry) is significantly higher than the current production rates available for them in the U.S. and it is unlikely the volume of material from recycled wind turbine blades alone will be enough to meet the demand for recycled glass fiber.It will likely require pulling similar materials from other waste streams (i.e.marine, vehicle, and aerospace scrap/waste) into the recycling stream in order to meet demand.This lends itself to a consistency, cost, and performance question which is limiting the adoption of these materials to higher performing applications.As the cost, performance, and consistency/quality of the materials recovered from recyclers become better understood it is likely there will be significantly more industrial pull for the recycled materials.Further, it is likely this will enable further optimization of the cost of recyclate and therefore more widespread adoption of the materials.

Conclusions
The unique analysis in this paper suggests that optimizing packing density in the truck is critical during the decommissioning phase, and that transportation over long distances is the driver for carbon intensity leading up to recycling facilities.It is likely that there will exist fewer companies doing plastic recycling than landfilling in the U.S. for quite some time, and thus these materials may need to be transported greater distances than otherwise to be re-processed.However, in the meantime developing techniques to reach 100% packing efficiency (i.e.shredding, maximizing stacking, etc.) can reduce carbon intensity of the blade decommissioning and transportation process by over 50% alone and should be considered.The results of this analysis suggest as well the promise of mechanical recycling as a decarbonization pathway for composite materials.However, the limitation of this analysis is largely that the value and performance of recovered materials are not currently well understood.Further research is needed to unpack the cost structures associated with the existing recycling infrastructure in the U.S. and determine the consistency and functional performance of the recovered materials.

Acknowledgments
This research has been funded by the U.S. Department of Energy Wind Energy Technologies Office through the Wind Technology Recycling Assessment project.Oak Ridge National Laboratory is operated by UT-Battelle, LLC.under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy.Sandia National Laboratories is a multi mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525.This paper describes objective technical results and analysis.Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government.The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes.

Figure 1 :•
Figure 1: Causes for wind turbine blade decommissioning as provided by industrial partners in the U.S. Figures from Wind-energie.de,Dailyenergyinsider.com,Wind-watch.org,Windpowerengineering.com, and Minotdailynews.com

Figure 3 :
Figure 3: Greenhouse gas emissions from eight different downsizing and transportation scenarios.

Figure 4 :
Figure 4: Greenhouse gas emissions of end-of-life approaches for wind turbine blades in the U.S [30].