Scrapyard challenge4 September 2020
Wind power is a vanguard technology for a greener future, but with most blades being made out of composite materials, the majority of turbines are not fully recyclable. Will Moffitt talks to Dr Lawrence Bank, principal investigator for engineering at Re-Wind, about the association’s mission to find ingenious ways of reusing turbines, and Richard Cochrane, professor of renewable energy at Exeter University, about building fully recyclable blades for the future.
In the arid dirt lands of Casper, Wyoming, lies a mass grave, where neat rows of pearly white fragments glint like dinosaur bones in the blazing midday sun. On the crest of the looming horizon overlooked by snow-capped peaks, their kin gaze back at them, slowly spinning over the pumpjacks scattered across the plains below.
To an uninitiated observer this municipal landfill site in the midst of the burnt out landscape could be straight out of a Cormac McCarthy novel. In fact, it is the final resting place for thousands of turbines that are hauled to Casper from three wind farms across the north-western reaches of the continental US. It is here that these gargantuan structures – which can measure up to 100m long and weigh 300t – are disposed of at the end of their lives, hewn into three parts by a diamond-encrusted saw before burial. Once a booming oil town, Casper now has one of the highest potentials for wind power generation in the US. Ironically, though, it has found a more profitable calling as one of the few go-to sites for turbine destruction, a business that generates about $675,000 annually for the town.
It’s a wasteful process, but someone has to do it; after all, it simply isn’t possible to recycle the entire turbine.
While around 85% of its components – including steel, copper wire, electronics and gearing – can be reused, most blades are built either from carbon fibre or, if they’re older models, glass fibre. Both materials are notoriously difficult to recycle. Size is another concern. “One of the biggest problems with recycling turbine blades is that they are gigantic structures,” explains Dr Lawrence Bank, principal investigator for engineering at Re-Wind. “Most of them are 60m long and the newest blades are about 100m, [so] you have to come up with solutions that manage this massive size and the material at the same time.”
No size fits all
Bank, an engineer by trade, knows more than most about the difficulties of blade recycling. After growing frustrated with the lack of alternatives to landfill and incineration, he set up Re-Wind in 2018 with a small team of like-minded researchers to devise more sophisticated ways of reusing turbine components in buildings, infrastructure, landscapes and public art.
As most turbines raised during the energy surge of the 1990s are now well past their sell-by date, Re-wind’s primary mission becomes more important with each passing year. According to research by the University of Cambridge, the total waste generated from wind turbine blades alone will reach about 43 million tonnes by 2050. Meanwhile, the rules surrounding the disposal of these components are also tightening. In the EU for example, new laws governing the landfilling of non-biodegradable plastics mean that conventional destruction methods for blades will no longer be permitted in a decade’s time.
In the US, despite a small clientele of owners and energy companies willing to pay to transport these structures to landfill sites like Casper, many local municipal sites are turning down the offer of service. “If you’re in a small town you don’t want your 20-year landfill getting filled up with wind blades. There’s simply not enough space locally to dump these big, empty things,” Bank explains. The fact landfills place a charge on the weight of each object, and that these blades are essentially hollow tubes, is yet another snag in the plan.
One way of recycling turbine blades is through pyrolysis, a chemical industrial process in which the components are chopped and melted down in an oven, leaving behind fibres that can be used for glues, paints and concrete. Industry body Wind Europe is particularly supportive of this approach, partnering with the European Chemical Industry Council (ECIC) and the European Composites Industry Association (EUCIA) to agree on a more extensive recycling plan.
Bank is less convinced. He believes that using supplemental fuels in areas such as cement production will be too expensive to orchestrate on a mass scale.
“A kiln does 500 to 1,000t of material a day, so it’s just a tremendous amount of material that goes into cement production,” Bank says. “If you are going to change the process to incorporate supplemental fuels, [that will] cost about €1,000 per tonne of material.”
The notion that pyrolysis is waste-free is also not entirely true. Given that blades are 60% glass and fibreglass, they do not burn particularly well, leaving large quantities of ash. There’s also a debate about just how eco-friendly these methods are in comparison to traditional forms of cement production, particularly in a sector renowned for its green credentials. Wind Europe argues that if recycled composite materials make up 75% of the cement’s raw materials, a 16% reduction in CO2 output can be achieved. Again, Bank is not so sure.
“All of the research is internal to the companies that are doing this,” he says. “There is very little academic research on this topic, so you can sort of say what you want at this time. It hasn’t been seriously investigated in terms of what the impacts are on the cement production.”
Of course, these large unwieldy structures can be put to greater use as far as local communities are concerned. In Rotterdam, for instance, turbine blades have been instrumental in the construction of a 1,200m2 children’s playground; in the Dutch city of Terneuzen, they’ve been used to make outdoor seats. Meanwhile, a company in the state of Washington has transformed fibreglass composites into small pellets that can be turned into injectable plastics, or waterproof boards for construction purposes.
That’s where Re-Wind comes in. The international group is based primarily in Cork – but incorporates expertise from City University of New York, Georgia Institute of Technology and Queen’s University Belfast – and seeks to develop a methodology for reusing turbine components at a national and local level, for energy and waste management, wind energy company executives, wind turbine manufacturers, installers and community members. “We’ve had a lot of interest, not just from industry and private companies, but particularly the OEMs [original equipment manufacturers] that make the blades and some of the energy companies that need to dispose of them,” Bank explains.
Now, after three years of diligent research, the organisation is moving to commercialise some of its ideas. These include plans to build a bridge in Cork using composite blades as support structures, converting rail lines into greenways, a potential power line project in the US and hollowing out composite blade structures into sheds, water tanks and feeding troughs for farm animals.
As these varied proposals demonstrate, the durable and flexible properties of fibreglass blades make them ideally suited to multiple roles, but rehabilitating these ailing patients back into the public service can be tricky. Not only is transportation a significant challenge given their weight and size, but a lack of design information can also make things difficult.
“OEMs do not provide geometric or structural drawings of their blades, but if you want to reuse them as a structural engineer and architect you have to understand their geometry, which is very complex because these blades twist, bend and change their shape continuously,” Bank explains. Luckily, Re-Wind can harness the insights of data-driven structural modelling, using light detection and ranging – or Lidar – scanning to calculate the material and geometric properties of turbines, thus enabling teams of structural engineers to redesign them to build all kinds of unique structures.
While organisations such as Re-Wind are unearthing ingenious ways of repurposing ageing turbines, others are searching for ways to build them with more recyclable materials from the off.
“One interesting strand of research is what we can do with the existing machines, [but] our work has been looking at the design implications of new materials,” says Richard Cochrane, professor of renewable energy at Exeter University. “If we’re switching to a resin that is recyclable, does it have an effect on turbine performance?” As it turns out, it does, but not too much. According to Cochrane’s research, while turbines made from more recyclable resins require more material to maintain the same strength as existing fibreglass blades, there is only a minimal compromise on design.
“You need more material to get the same strength. And because they are slightly heavier, the loading was higher, so you needed to gain more carbon fibre to cope with the loads,” Cochrane says. “But actually, some of the latest developments in recyclable epoxies are absolutely on a level with existing materials.”
A niche band of organisations have been researching the practical implications of using eco-friendly resins for some time, not least Vanderbilt University, where researchers have been experimenting with a self-curing resin called elium that reduces energy demand in the manufacturing process. More importantly, the durable material, made from composite thermo-plastics, enables fibreglass blades to be recycled as they are crushed into tiny parts, before being melted into a material with identical properties as the virgin resin. For Cochrane, while price remains a significant factor – eco-friendly resins are expensive to mass produce – more research is required into how these materials would cope in live conditions.
“As the turbines get bigger, gravitational loading becomes more significant and the other element is fatigue. So, to extend the longevity of the machines, can they cope with all these cycles?” Cochrane asks. “They also have to deal with the one in a 100-year storm that might hit, so there are numerous design cases that need to be analysed.”
Further work is now required to ensure that recyclable resins can create blades big and durable enough to sate manufacturers’ ambitions. To meet global energy needs, a more eco-friendly and sustainable way of recycling turbines must be uncovered before this waste problem begins to erode wind power’s image as a vanguard technology for planning a greener future.
As piles of bleached fragments build up, the clock is ticking for a solution. Otherwise, these pieces of plastic will be popping up a hundred years from now, as obsolete as the dinosaur bones once found strewn across the sprawling Wyoming prairies. Future generations raking through the debris will ask a question the wind industry should already be contemplating: why did a sector with vast resources and expertise fail to solve this very obvious problem?
Turbines to be decommissioned in the next five years in Europe.
Tonnes of turbine blade material that the US will have to dispose of over the next 20 years.
The total global waste, in million tonnes, that will be generated from wind turbine blades alone by 2050.
University of Cambridge