For a sector that is a major player in the sustainable energy industry, how sustainable is wind energy? Wind energy is considered as one of the most sustainable sources of energy, generating electricity with lower carbon emissions than fossil-fuel powered generation techniques. However, it cannot be effectively sustainable due to the environmental impact of not dealing with the anthropogenic wastes responsibly. Although wind turbines have a recyclability rate of around 80% to 85%, making turbines completely recyclable at the end of their lifetime is crucial to increase the environmental benefits and move towards a circular economy.
To improve the performance of the turbines, the modern wind turbine blades are built from composite materials like carbon fiber or glass fiber, which allows them to be lightweight, longer, and stronger. On the other hand, these composites are toxic and cannot be recycled. The blades can only be cascaded, which is to produce products of lesser quality. The mass of the blades is relatively lower compared to the total mass of the turbine, but the other components like the tower, generator, gearbox, and foundations are for the most part made of steel and are recyclable, unlike the composite blades. A 5MW turbine, having three blades, has around 51 tonnes of unrecyclable composites as part of the blade mass. The previous generation wind turbines, installed around 20 years ago, are now coming to the end of their operational lifetime and are to be decommissioned in the coming five years.
In order to maximize energy production and lower the cost of generation of electricity, the size of the wind turbines has increased over the years. The power increases with the increasing height of the turbines due to the availability of higher wind speeds. The power can be increased by four times by doubling the diameter of the rotor. The Haliade-X, the world’s largest wind turbine, installed at the port of Maasvlakte-Rotterdam has blades that are 107m long and a blade sweep area of more than five football pitches. Due to the trend towards larger turbines, the mass of the blades increases and hence have to be made of lighter and stronger materials such as carbon fiber composites. In this decade, as the wind turbines keep getting bigger, the waste produced from composite material blades would go up to millions of tonnes per year.
Currently, the composite blades are usually sent to pile up in the landfills or are burnt in kilns for energy generation before sending the scrap to landfills. However, the energy content in the composites is very low and pollutants are emitted when incinerated. In some cement industries, the composite materials are shredded and used as filler reinforcements. Another measure in the downcycling of the blades is pyrolysis, where fibers are broken apart to be used in industries that produce glues, paints, syngas, and fertilizers. The problem with this method is that a significant amount of heat is required to activate the process. In some Dutch cities, decommissioned blades have been turned into recreational parks, playgrounds, or benches. With the increase in the number and size of the turbines, these measures of dealing with the composite wastes are not sustainable or sufficient.
Alternatively, the blades can be made out of wood-carbon composites or bio-composites that contain lesser plastic materials. They can be incinerated with lower emissions or reused in blade manufacturing. Although they lead to less composite waste than conventional blades, the blades will still not be entirely recyclable. From the 1880s, when wind turbines were invented, to the 1980s, the turbines were built largely out of materials like wood, metal, stone, and brick. Although these turbines were smaller and less efficient, they were completely recyclable and non-toxic. By sacrificing the performance and size, a lot can be gained in terms of sustainability if the blades are made completely out of wood.
It is true that at present, the wind industry produces far less composite waste compared to the construction sector, the electrical sector, and the transportation sector. Nevertheless, considering the current developments and rapid growth in the demand for wind power as the world moves towards sustainable energy sources, the composite wastes from the blades would increase significantly. As finding measures to dispose of the blades from older turbines in an environment-friendly way has become challenging and largely unyielding, it would be environmentally viable and not burdensome if the development of reliable and recyclable materials is integrated into the design of the next generation of turbines.
About the Author
Rohit Thota
Sustainable Energy Technology student
Being a student of SET, he aims to give readers an outlook on the climate crisis from a technical as well as a general perspective. He likes to write about entities that are contributing to a cleaner future and is a big fan of wind turbines.
References
Jensen, J.P. & Skelton, K., 2018. ‘Wind turbine blade recycling: Experiences, challenges and possibilities in a circular economy’
Kris De Decker, 2019. ‘How to Make Wind Power Sustainable Again.’
Jensen, Jonas Pagh, 2019. ‘Evaluating the environmental impacts of recycling wind turbines.’
Padraig Belton, 2020. ‘What happens to all the old wind turbines?’
K. Kalkanis, 2019. ‘Wind turbine blade composite materials - End of life treatment methods’