Renewing renewables

There is an old classical expression, “Medice, cura te ipsum”, or “Physician heal thyself.”  It’s generally interpreted as a criticism of hypocrisy - to attend to one's own defects before addressing those in others. When it comes to sustainable, renewable energy the maxim applies to recycling, especially wind farms. A green solution for worn out wind turbines is the subject of much research and debate.
The EU wants renewables to make up 27% of the total energy share by 2030. By this date, the installed capacity for photovoltaics will be 2,500 gigawatts, 180 GW for offshore wind and 1,600 for onshore wind. That will be a lot of panels and currently around 95% of their parts are recyclable. It’s expected that end of life management will prove a significant part of the value chain and a robust secondary market will develop for components and materials.

End of life blades

The modern windmill, which has its origins in 9th century BC Persia, isn’t quite so straightforward. Tens of thousands of aging blades are now coming down from their steel towers all over the world as the first generation of wind turbines near the end of their lives. Almost a quarter of a million windmills worldwide will need to be replaced by 2030. The rotor blades are made of valuable composite materials that are difficult to recover at the end of their energy generating life. New generation rotor blades made of glass or carbon fibre composite material have average lifespans of between 10 and 35 years.

The world’s largest turbine, the GE Haliade-X, has blades four times the norm 20 years ago and which measure 107 metres and together weigh 160 tonnes. These giants can produce 12 megawatts at full tilt. Larger onshore turbines are able to access faster wind speeds which occur higher in the sky.
Wind power boasts of being carbon-free and indeed isn’t bad when it comes to decommissioning. Around 85% of turbine components including the steel, rare-earth elements, copper, wire electronics and gear systems can be recycled or re-used after maintenance. 

Recycling of fiberglass  composite is possible though complex. It can be burned for its stored energy, but this is inefficient and emits unpleasant pollutants. Pyrolysis can also be used: after the blades are chopped up, pyrolysis breaks up the fiberglass in inert atmospheric ovens at 450-700 C. The process can recover materials for use in glues, paints and concrete but remains very expensive because it requires significant amounts of energy.

A dirty little secret

However, recycling of the more highly valued carbon fibre composite is currently impossible. Little wonder it’s headlined ‘the wonder material with a dirty secret.’  In many EU countries landfill of carbon composites is now prohibited. Thus, many rotor blades at the end of their wind turbine life are currently shredded and incinerated. In the US, more than 30,000 blades will be removed in the next four years, while Europe has about 3,800 coming down annually through at least 2022. At current growth rates, by 2034, there will be about 225,000 tonnes of rotor blade composite material produced annually, worldwide.

Over in Casper, Wyoming, there is an enormous wind turbine graveyard for up to 1,000 blades - each is cut into three, stacked and buried. Although the materials being buried are relatively inert and don’t leech into the water table this solution is not sustainable at all. This is why companies around the world are searching for novel, more sustainable approaches to deal with the tens of thousands of blades that have reached the end of their lives. 

For instance, one new solution has been devised by Don Lilly, the CEO of Global Fiberglass Solutions, in Bellevue, Washington. Lilly’s company crushes blades and transforms their fiberglass composites into small pellets, which he has named EcoPoly. These pellets can then be fashioned into injectable plastics or highly waterproof boards for use in construction. The company started producing samples at a plant in Sweetwater, Texas, near North America’s largest concentration of wind farms. “We can process 99.9% of a blade and handle about 6,000 to 7,000 a year,” says Lilly. 
The problem is not going to go away since a constantly growing number of wind turbines is coming to their end of life. Hence, it is becoming increasingly important to find a second or even third and fourth application for the blades. Some unconventional uses have been found already.

In Rotterdam, a children’s playground including slides, tunnels and ramps has been made from 5 old blades. Meanwhile, in the Danish city of Aalborg, Cesare Peeren, a Dutch architect, wants to turn two 55- metres blades into a bridge. Waste rotor blades are easy to find in Almere, Holland’s number one wind-energy region. Stacked in a Stonehenge like manner two 30- metre blades have been used to create a large bus shelter. The city, aptly, runs a number of pure electric buses.

"Progress with any new innovation is rarely linear," says Amir Sharifi, Managing Director in charge of Energy Transition at Ardian Infrastructure in Paris with a deep knowledge of the global energy market. "Green energy is the future and there will be a huge cost to the Earth and all of us who live on it if we lose sight of the carbon reduction agenda. The industry needs to take a holistic approach on value creation for renewable assets and consider all options when assets reach end of life, including repowering, revamping and recycling. Circular economy goes hand in hand with long-term value creation.”

Carbon fibre is where the future lies

Carbon fibre may be relatively exotic and costly, but it is where the future lies. Carbon fibre has about two times the strength-to-weight ratio of glass fibre, and more than three times that of titanium and aluminium alloys. It also has five times the stiffness-to-weight ratio of glass fibre, which helps it withstand the high aerodynamic forces that act on wind turbine blades.
However, when it comes to recycling, the key problem is that carbon fibre cannot simply be melted down and reformed like aluminium. Carbon fibre composites get their strength from long, precisely aligned carbon fibres, fixed within a glue-like polymer that is cured at high temperatures and pressures. Once cured, most of these tough polymers will not melt and have to be burned off or chemically dissolved to reclaim the valuable fibres.

Carbon fibre is recycled by over a dozen companies around the world, but the price tells it all - recycled fibre costs around $15 per kilos whereas virgin material goes for $24-30 per kilo despite taking ten times the energy to produce. With current methods nobody can be absolutely sure how the recycled product will perform - if it were to fail in a turbine blade the results would be disastrous. The race is now on to produce used carbon fibre that does the same job as steel when it is re-used.   
A final problem is Rare Earth Elements (REEs). The magnets in wind turbine generators are a mix of iron, boron (a mineral that is naturally present in the environment) and REEs, which improve their performance. Recycling such alloys is challenging given the time, technological complexity, chemicals and energy needed to dissociate alloy components.  Yet, there is a strong business case for reusing and recycling REEs. 

As technology advances, the development of standardized circular design models to facilitate the extraction and re-use of wind turbine magnets will become cost-efficient and have the advantage of future-proofing the supply chain. So far, such initiatives are rare, but wind turbine manufacturer Goldwind has developed a program to smelt old magnets to make new ones. As only around 1% of all REEs are currently recycled from used products, there is much room for improvement.
As the wind energy sector continues its exponential rise, it is increasingly important that turbine life cycle remains front and centre of the industry. Further development and industrialisation of alternative technologies like pyrolysis will provide the sector with additional answers for turbine blades reaching their end-of-life, and will enable the industry to deliver zero-waste turbines as we head towards a true circular economy.