The Technical University Bergakademie Freiberg, SGL TECHNOLOGIES, the Saxon Textile Research Institute, and TENOWO, to name but a few exhibitors, will be available at COMPOSITES EUROPE as experts on the topic of composites recycling. Furthermore, experts at the Composites Forum will discuss the basics, trends and innovations in this field on Thursday. The major challenges related to recycling will also be centre stage here.
40,000 tons of blade waste
By accounts of the German Wind Energy Association BWE, the challenge with blades of onshore wind energy turbines is to reclaim the composites contained in the turbine blades. After all, the blades contain not only reinforcement fibres, polymer matrices, the sandwich core and coating but also metals for lightning conduction or as heating elements for de-icing.
CFRP is substantially lighter but also markedly more expensive and therefore only used for particularly critical blade sections especially in large-scale turbines – and especially for offshore applications. For onshore applications, however turbine blades are made almost exclusively of GFP. Experts say that just under 500,000 tons of turbine blades have been built that way in Germany over the past 26 years. Considering the service life, newly installed wattage every year as well as the increase in weight by re-powered system they forecast around 40,000 tons of waste produced by turbine blades per year.
Cement made from used turbine blades
A 100% reuse ratio for up to 60,000 tons of GRP annually is offered by the “Composite Recycling” developed in Germany in 2011. This allows an efficient energetic and material use of the GFP contained in the turbine blades as an alternative to fossil fuels and is used in cement factories since these have high energy requirements. The ashes produced by incineration that account for some 50% of the total turbine blade mass, contain a very high amount of minerals. These are also used as a raw material substitute for cement production without any changes in quality.
The re-use of CFRP is more difficult. In a survey conducted by VDI Themenradar Automobil in early 2015, 27.6% of respondents felt that composites would only assert themselves once the recycling issue was solved. In contrast to this, only 13.8% were convinced that recyclability had no influence on the prospects of success. So far, no processes have been developed for re-use on an industrial scale. Alongside mechanical comminution, the pyrolytic separation of fibre and matrix is a central process used to obtain carbon fibres of various qualities and lengths.
New business models thanks to recycled carbon fibre
According to the “Composites Market Report 2017”, the strongly growing production output of carbon composites entails ever bigger waste streams containing carbon fibres – a fact that also holds new potential. The special composition of composites requires new recycling strategies, on the one hand. On the other, there is a chance of profitable business models for recycled carbon fibre (rCF) considering the high energy and resource consumption in new fibre production even though waste quantities are still low when compared with metals, plastics, or paper.
At present, dry cutting waste or uncured and out-of-date prepreg materials account for the by far biggest share in composite waste streams. An operational recycling economy is about to emerge here. Dry cutting waste is processed into non-wovens using textile processing methods. Even for prepreg waste, which predominantly originates from aviation and is of a correspondingly high quality, there is an initial process variation of pyrolysis/partial oxidation used on a commercial scale now to reclaim the fibres.
According to the Market Report, the balance will in future shift towards waste streams wetted with resin since the relevant components are still in use today. This development is also driven by lower-waste cutting processes. Furthermore, the calls for sustainable product solutions and material systems as well as for closing material cycles in view of both ecological (CO2 footprint) and social aspects (circular economy) will continue driving the CFRP recycling market.