Analysis: one way to deal with the estimated 200,000 tonnes of blade waste per year is to use them for other products like bridges

By Peter Deeney, UCC and Kieran Ruane, MTU

Believe it or not, wind turbine blades don't last forever. They have a life expectancy of about 25 years as they are exposed to sunlight, rain, wind and occasionally lightening. The nature of the loading the blades receive in service can also cause material fatigue. When they are no longer useful on a wind turbine, they are very difficult to recycle, so what can we do with them?

Three wind turbine blades were used in Cork to make a pedestrian "Blade Bridge". These 14m long blades came off a decommissioned Nordex 250kW turbine which was first used in 1994. While the first blade was tested to destruction, the other two replaced the steel girders usually placed either side of a typical small bridge. This bridge was built and installed on the Midleton to Youghal Greenway.

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From The Verge, report on the blade bridge on the Midleton to Youghal greenway

There are thousands of blades to be decommissioned in Ireland in the next few years. The amounts of blade material have been estimated at 12,000 tonnes between 2026 and 2030 and 14,000 tonnes between 2031 and 2035. It is difficult to recycle this material because they are made of many components which are quite difficult to separate.

There is metal at the root where the blade is attached to the hub and metal along the length working as a lightening conductor. There is balsa wood acting as a very light filler and there are coatings and paint. The main difficulty is the glass fibre reinforced polymer; it is made to be strong and stable, and to avoid decomposition, which makes it awkward to recycle.

There are several ways to recycle glass fibre reinforced polymer but these methods cost more to carry out than the recovered materials are worth. For example, the polymer can be heated in an oxygen-free environment to separate the resin which holds the fibres together, leaving the glass fibres. This produces an oil from the resin which can be used as a fuel. The issue is that it is expensive to do this and the glass fibres after this process are less strong and more expensive than new glass fibres. Similar results can be obtained using solvents, which have the same problems.

Prep work on the recycled wind turbine blades for the blade bridge

While many researchers are working on improving these methods, there are some workable solutions already in use, such as placing the crushed blades in a cement kiln to replace some of the material used to make cement. This is a very low value product which can be described as down-cycling rather than re-cycling, and there are practical limits to the amount of material which can be dealt with in this way. A higher value product would be preferable.

The most imaginative and most useful way to deal with old turbine blades is to use them to make new products, including electricity poles, parking shelters for bicycles, furniture, sound deflectors along roads, roofs for houses and bridges. The Cork Blade Bridge is the second one in the world and was designed by Kieran Ruane who is part of the Re-Wind Network. It's 4m wide and 5.5m long and can be used by maintenance and emergency vehicles as well as pedestrians and cyclists.

Blade bridges offer light workable bridges, which would be useful for farms and landowners as well as for councils. Using old turbine blades also offers jobs to those very parts of Ireland along the Atlantic coast which need more manufacturing jobs.

Putting the blade bridge into place on the greenway

The advantages to the environment are many, principally avoidance of landfill, and avoidance of using new materials such as steel. The glass fibre reinforced polymer is very strong and will last for years when subjected to static or slowly applied loads, it is the same sort of material which is used to make boats, airplanes and Formula 1 cars. Decommissioned turbine blades have significant reserves of static strength which is what makes them highly reusable after their first life generating power.

Whoever develops methods to cut and work with these blades has a huge potential market. It is estimated there will be 200,000 tonnes of blade waste per year by 2033, a situation which will continue for at least 25 years until more recyclable blades are the norm. Remember that offshore wind blades are getting bigger and will need bigger ideas. Ireland can lead the way on this.

The circular economy solution is to make the wind turbine blades which are easier to recycle. There are two methods which are leading the way towards that aim at present, (i) making the resin soluble in specific solvents and (ii) making the blades from thermosetting resin, so that by applying heat they can be melted and reformed. The second has the advantage that large blades could be assembled on site rather than having to be transported long distances.

The Re-Wind Network is funded by Cork County Council, Science Foundation Ireland, InvestNI/Department for the Economy and the National Science Foundation.

Dr Peter Deeney is a Principal Investigator and Senior Postdoctoral researcher in the Environmental Research Institute at UCC. Kieran Ruane is a lecturer in the Department of Civil, Structural and Environmental Engineering at MTU.

The views expressed here are those of the author and do not represent or reflect the views of RTÉ