From intense UV radiation and extreme temperatures to wind gusts and lightning strikes, wind turbine blades are engineered to withstand some of the harshest conditions. But that durability becomes a problem at the end of their lives, because the blades are also difficult to break down and recycle.
Reporting November 6 in the Cell Press journal Chem Circularity, researchers found a way to give discarded wind turbine blades a second life. By subjecting the blades to a brief burst of intense heat, they transformed the waste into silicon carbide and graphene, two valuable materials for manufacturing. The method could cut up to 83%–92% greenhouse gas emissions compared to conventional recycling strategies while also turning a profit.
"Wind turbines typically have a service life of around 20 years," says senior author and chemical and environmental engineer Bing Deng of Tsinghua University, China. "As aging turbines are decommissioned, especially in China, where wind power has expanded rapidly, much of the waste has ended up in landfills. It's a waste of resources."
The team's method takes advantage of the blades' own chemical makeup. Wind turbine blades are usually made from silica-containing fiberglass and carbon-rich polymer resin. Using a technique called flash Joule heating, the researchers heated the waste to about 2000°C (3632°F) in seconds. At this temperature, carbon can react with silica to form silicon carbide, a hard, heat-resistant material. Meanwhile, carbon can also reorganize into graphene, a material known for its strength and ability to conduct heat and electricity.
The researchers found that adding the broken-down blades to other materials made the materials more useful in several contexts, including for new wind turbines. Just 0.3% by weight of the recovered materials made resin stiffer and stronger and improved its resistance to deformation by 27% under tension and 9% when bent. At 0.1% concentration by weight, the materials increased the resin's thermal diffusivity by 41%, allowing heat to spread through more quickly.
"The mixture of silicon carbide and graphene can be incorporated back into resins for new wind turbine blades, improving their mechanical and thermal properties," says Deng.
Beyond creating valuable new materials, the process could offer a cleaner and more economical alternative to conventional recycling techniques such as pyrolysis, which uses heat to break down polymers into oil and gas, and chemical dissolution, which uses solvents to separate resin from glass fibers. The new method could cut greenhouse gas emissions by about 83% and 92% compared with pyrolysis and chemical dissolution, respectively.
"With conventional recycling methods, you have to spend money to process the waste. But our method could actually turn a profit of about $80 per ton because the recovered silicon carbide and graphene are valuable," says lead author and environmental engineer Hao Bi of Tsinghua University. "By comparison, pyrolysis costs about $460 per ton, while chemical dissolution costs about $1,800 per ton."
The team is working on ways to scale up their process and is hoping to collaborate with partners in the industry. Their method could also be adapted to process other durable materials used in aerospace, automotive manufacturing, electronics packaging, and construction.
"This is more than recycling. It's upcycling," says Deng. "We're turning something that has little value into something that's worth much more."
