It’s hard to imagine our lives without (electrical) energy. Since the dawn of mankind, the search for sources and methods to generate energy has been a priority. Major milestones include the domestication of fire, the use of water power for mechanical work, or more recently, the discovery of nuclear fusion for energy generation. But this energy hasn’t always been sustainably generated. The exploitation of fossil resources, irreversible destruction of ecosystems and harmful emissions are only some of the negative traces that our energy usage’s enormous ecological footprint leaves behind.
TODAY ON A GLOBAL SCALE THE NUMBER ONE SOURCE OF GREENHOUSE GASES RELATES TO THE GENERATION OF ELECTRICITY, HEAT AND OTHER FORMS OF ENERGY WITH A SHARE OF 35 %. ¹
In recent years, the search for clean energy has been leaning towards renewables. Although the use of wind, water, sun and agricultural feedstock is hardly novel, their commercial use for the generation of electricity is rather recent. In 1980, the world’s first wind farm was connected to the electricity supply in the United States, which heralded a new era in the energy sector. Since then, many more farms have been constructed — both onshore and, since 1991, offshore with Denmark as a pioneer. After the introduction of wind energy, the industry has revealed ecological and economic benefits such as energy security, economic development (e.g. job creation) and price stability. According to Sandbag and Agora Energiewende ², 12% of the EU electricity demand is currently met by wind energy.
Wind energy is crucial to countering climate change in a targeted and decisive manner. International treaties by the United Nations Framework Convention on Climate Change (UNFCCC), such as the Kyoto Protocol in 1997 and the Paris Agreement of 2016, repeatedly stressed the importance of this energy source in efforts of climate protection and it is often referred to in (trans-)national climate objectives and energy policy goals.
Even as the exploration of these alternatives to fossil and nuclear energy carries on, the transition towards a clean energy supply is still not complete. Wind energy provides solutions, but also challenges.
1) The manufacturing, assembly, installation, and maintenance pose significant consequences for the environment, as they are energy-intensive processes that emit greenhouse gases and generate a significant amount of material waste.
2) The involvement and release of hazardous solvents during the manufacturing process are another concern.
3) Material waste is the most pressing challenge. Wind turbines are multi-material assemblies combining a number of different materials in significant volumes. Certain parts of the turbine — especially metal parts from the tower or the nacelle — are recovered at end-of-life with high-quality output and few material losses. However, other parts — such as the turbine blades — are more problematic.
In reference to the last challenge, turbine blades are mostly made of (glass and/or carbon) fibre reinforced polymers. These advanced materials provide the opportunity to substantially reduce the weight of blades — an essential prerequisite in the constant endeavour to increase their dimensions, and thus performance, to meet market demands. The largest wind turbine (15MW) now under construction is expected to have more than 150 tonnes of composite materials ³.
However, the recycling of this high-performance multi-material is challenging, since it is currently based on a thermosetting matrix. Thermosets are cured into a solid form after applying heat or activating the process through a curing agent — an irreversible process since the polymer is three-dimensionally crosslinked without the ability to be returned to its original uncured form.
Recycling approaches, therefore, require significant cycle times, and energy consumption, while the output product has significantly downgraded properties, resulting in downcycling rather than recycling.
Thus, blade waste management is still considered the industry’s blind spot, which is also evident in the lack of attention given to it in Life Cycle Analyses (LCA). LCAs of wind turbine manufacturer and operator Vestas show that about 85% of the materials used in their turbines are recycled. The missing 15% are mainly related to composite materials ⁴. Blade waste therefore usually ends up at landfill or incineration sites — options that are heavily criticised as they are the least preferred in the waste management hierarchy.
ON A GLOBAL SCALE, IT IS EXPECTED THAT BY 2050 THE WIND ENERGY SECTOR WILL ANNUALLY PRODUCE 2.9 MILLION TONNES OF COMPOSITE WASTE WITH A TOTAL CUMULATIVE WASTE OF 43 MILLION TONNES.⁵
Europe, as one of the leading regions in wind energy, will have to deal with a substantial part of this waste. Several factors such as a limited lifetime, premature material failure, replacement of outdated technologies as well as material from production scrap, constantly add to the existing waste inventory.
As highlighted at WindEurope’s Conference and Exhibition in Bilbao last month, the wind energy sector is highly engaged in identifying opportunities throughout the turbine’s lifetime to address the challenge of blade waste. These include:
- Repowering turbines
- Reusing components to extend a turbine’s lifetime through different measures
- Considerate decommissioning and waste management strategies
These first two options are used to delay the inevitable decommissioning and waste management for as long as possible. As an alternative to landfilling and incineration, waste management strategies currently include the recycling and recovery routes for composite waste. These involve quite advanced methods and processes — following mechanical, thermal, chemical or electrical approaches — all at different stages of market maturity and all facing individual challenges. There are as many reasons for these challenges as there are approaches used among EU recyclers and researchers themselves.
Some examples of these challenges:
- The different processes produce a variety of output materials from resin- and fibre-rich powders or clinker cement to chemicals and fibres with different degradation rates of material properties. Among European recyclers using similar processes, varying process parameters (e.g. throughput rates, temperature, pressure) or the input material’s state (e.g. damaged or fragmented blades) can lead to different results. These inconsistencies challenge the reintroduction of the material in the market.
- Europe’s current recycling capacity is sufficient for the more favoured carbon fibre composites, as already mature technologies (e.g. pyrolysis) absorb a large part of the current waste supply. Other, very promising technologies are therefore unable to be tested at a viable scale and enter the market. The main challenge in terms of capacity is therefore related to the much larger volume of glass fibre-reinforced composites with the low economic value of recyclates. Until now, the industry has failed to develop viable business cases for the recycling of this waste stream.
- Meanwhile, the economic viability of recycling is, for many processes, still uncertain. Costs related to the recycling process need to be significantly lower than the costs of virgin material production. There is currently no relevant business case for glass fibre recycling, apart from the co-processing in cement kilns. The added recycling costs result in a higher price for recycled glass fibres than the currently very low virgin fibre market price — a significant barrier to commercialisation for promising technologies. Therefore, most activities concentrate on composites with carbon fibre reinforcement.
- Another challenge is the unpredictability of the future quantities of the waste streams fuelled by shifts towards more carbon fibre use, hybrid structures or life-extension options. The uncertainty of continuous waste and therefore a secondary raw material stream is discouraging companies to invest time and resources into exploring applications for the recovered materials.
- The lack of consistent regulations at both national and EU levels is considered one of the main barriers to the development of an adequate recycling landscape. The current gate fees and landfill taxes in most member states are not high enough to be a driver for change. Furthermore, the lack of harmonised waste classification for composites across the EU poses challenges for both operators and recyclers, as responsibilities are unclear.
The prerequisite for the use of recyclates in mass applications is a reliable and consistent supply of secondary raw materials. This requires standards for virgin and recycled FRP materials and the harmonisation of regulations (waste legislation) and definitions across Europe. Further action would be the industry-wide introduction of material passports for wind turbines. Close collaboration between the wind and recycling industry stakeholders, national and European policymakers, and standardisation bodies will accelerate the transition to material circularity substantially.
Market barriers, such as the disadvantageous gap between the prices of virgin and recycled fibres, can be addressed through the introduction of legislation that favour recycled materials over virgin ones. This, in turn, will allow recyclers and secondary raw material supplier to create viable business cases.
Furthermore, the options for synergies between original equipment manufacturers, recyclers, material suppliers and end-users need to be explored more intensively. This will not only support the further optimisation of the processes in the context of the entire value chain but also the development of viable second-life opportunities for the blade material.
Therefore, exploring and developing recycling technologies is just one of many steps in facilitating the transition to circular material flows. Recycling is currently enjoying the spotlight, as the innovative, preventative measures, which are more desirable waste management strategies, are still at low maturity levels.
From all perspectives along the value chain and the life cycle, several methods, novel materials and processing technologies are evolving to facilitate the transition towards circular material flows. Their impact on the composite recycling industry is yet to be analysed and understood.
Read the study on Wind Energy in Europe conducted by Bax & Company on behalf of CEFIC (The European Chemical Industry Council).