Compostable turbine blades made from mushroom roots could solve waste problem

Concerns are growing, both inside the wind industry and out, about the impending waste problem of old turbine blades, but a researcher in the US is working on a new solution: compostable blades.  

Using bamboo, agricultural waste biomass and mycelium, the underground network of threads that grow fungi, polymer composites professor Valeria La Saponara at the the UC Davis Department of Mechanical and Aerospace Engineering is working on a blade strong enough to handle the force of a commercial turbine.  

A prototype will soon be tested on a small 1 kilowatt (kW) turbine with a goal of seeing whether they can withstand 85-mile-per-hour winds, with a goal of building up to a 10 kW turbine.

“The blade you see [above] is 60 cm long and was the very first prototype of this 400 W turbine. We are keeping it for demo purposes, and we have been working on the second generation, a 1 kW turbine,” La Saponara told RenewEconomy.

“We have the turbine, the aerodynamic modeling, and a number of prismatic mycelium samples (enough for one blade). The blades will be 1 metre long. Our academic year is close to completion and we will be ready to build soon afterwards.”

Image: UC Davis. Valeria La Saponara points to the internal structure of a wind turbine blade made from compostable materials, like bamboo and mycelioum.

Structural testing on the rotor will ideally start around the first week of July, with the first data point being the speed that the blade can withstand without shattering (800 RPM is the nominal speed of the commercial 1 kW turbine).

If all goes well, the team could have the turbine with all the mycelium/bamboo blades up and running by end of August 2023, La Saponara says.

“We want to do structural testing to find out how fast a rotation we can have, how much power we can generate,” she said in a university news release. 

“Once we have the proof of concept for 1 kilowatts, which is a reasonable amount of power, then we can start working with companies for the commercialisation of this concept for distributed energy applications.”

La Saponara says it takes two weeks to grow the mycelium samples to the point in which they are dense and strong, and then they need to dry — the process is a bit quicker in summer.

Blade technology is super-sized

Wind turbines are now sky-scaper sized with the largest blade ever made now just over 88 metres long. These must withstand enormous forces to bear their own weight at high wind speeds. 

Currently, blades are made from fibreglass, epoxy resins and balsa wood, which creates a not-very-recyclable combination but one that can withstand those forces while delivering the optimal amount of energy. 

Separating the cured resin from the other materials is the hard part, and is expensive to do. 

The demand for balsa wood is also a cause of increased logging and deforestation in the Ecuadorean Amazon rainforest, where 95 per cent of the world’s balsa wood comes from. One solution to date has been switching to polyethylene terephthalate (PET) plastic, but this comes with more waste challenges. 

In Australia, some 15,000 tonnes of old blades are expected to be decommissioned by 2034, as 31 of Australia’s 110 wind farms begin to near the end of their productive lives. 

Solutions are happening

Between 85-94 per cent of a turbine can be recycled, as the foundation, tower, parts of the gearbox and generator are reused.

But a Clean Energy Council report Winding Up: Decommissioning, Recycling and Waste Management of Australian Wind Turbines found the biggest barrier to recycling wind turbines is the blades, for which there are limited waste options. 

Based on the current ramp up in wind power in Australia, the country can expect to see about 10,000 tonnes of waste a year from blades, rising to 20,000 tonnes in 2030 and 300,000 tonnes by 2050, if no solutions are found, said Professor Peter Majewski from the University of South Australia Future Industries Institute in a study last year. 

He called for legislated recycling targets so development approvals for new wind projects are predicted on having end-of-life recycling plans in place.

Already, some European countries have banned wind turbines from landfills which is causing the industry to hastily look for viable alternatives.

In 2021, Siemens Gamesa made what it called the world’s first fully recyclable blade for commercial use, which used a new form of resin whose chemical structure makes it easier to separate from the other components by melting it in a mildly acidic solution. 

It tested the blades at RWE’s Kaskasi project in Germany before launched an onshore version in late 2022. Siemens Gamesa says it plans for all blades it makes to be recyclable by 2030. 

In Denmark, a startup called Continuum is planning to build six blade recycling factories across Europe and Turkey that will handle a minimum of 36,000 tonnes of end-of-life turbine blades each year, and will be powered by 100 per cent green energy.

Last year, Swedish power company Vattenfall committed to recycling all dismantled wind turbine blades by 2030, and announced they were lining up a range of partnerships that could see turbine blades turned into everything from skis and snowboards to construction materials for solar farms.

Similarly, in August 2022, scientists at Michigan State University announced that they had found a way to recycle wind turbine blades into gummy bears, nappies, and other everyday items.

And in the US a University of Tennessee spinout is currently ramping up a facility that can recycle all of the fibreglass in turbine blades to take in 50,000 tonnes a year.