Thousands of wind turbines across Germany are close to reaching the end of their contractually stipulated service life. Turbines that cannot operate economically must be dismantled, with obsolete turbines being disposed of. Many parts of a dismantled turbine are easy to recycle in a simple and very efficient manner, producing valuable recycled products. Concrete foundations and gravel from the substructure can be used in road construction; steel and other non-ferrous metals and electronic components are sorted according to type and recycled. To date, one of the biggest problems has been shredding and processing the huge rotor blades which are made from glass fibre reinforced plastic (GRP). Recycling specialists, Eurecum based in Lutherstadt Eisleben (Saxony-Anhalt), has recently developed a process for recycling them. The rotor blades are efficiently cut up on site, transported to a recycling centre and shredded into industrially valuable GRP granulate.

Fast, efficient cutting

The disposal procedure begins at the location of the disused wind turbine. A powerful material handler, like those used by recycling and demolition companies to handle material at their depots, is used to crush the dismantled rotor blades. In spring 2020, Eurecum took possession of a new Cat MH3024 (24t) material handler supplied by Zeppelin Baumaschinen GmbH through the company’s Erfurt branch. The material handler was delivered with an appropriately sized cutter attachment - a hydraulically driven Kemroc KDS 50 diamond saw (rated output power 135kW) with a 1,200mm diameter diamond cutting wheel. This attachment can also be fitted with a 1,000mm diameter diamond cutting wheel. In extensive preliminary tests, this combination of carrier and attachment provided optimal performance. The Zeppelin branch in Erfurt also determined the parameters such as rotation speed and cooling for the best results in terms of cutting speed, minimum noise and dust and wear of the diamond wheel for the customer. Eurecum also purchased a fully hydraulic quick coupler on the dipper stick to achieve rapid changes between the KDS diamond saw attachment and a grab as well as helping to keep process time to a minimum.

The KDS range of diamond saws from Kemroc were designed to cut concrete, steel, reinforced concrete, natural stone and aluminium, being particularly good at cutting glass fibre reinforced plastics as used for wind turbine rotor blades. High rotation speeds and a large selection of cutting wheels open a wide range of applications where these attachments can be extremely effective. In practice, in one day an operator with this combination of material handler and diamond saw can cut three 40m long rotor blades of a typical 20MW turbine, each weighing around 8t, in lengths suitable for transportation. Actual cutting time is around 5h. Jets spray water onto the diamond wheel trapping the dust which is collected in fleece mats placed under the rotor blade. The fleece mats are collected and disposed of in the correct manner. “Composite material GRP is not inherently hazardous to the environment; it is also used in boat building for example,” explained Eurecum managing director Alexander von Neuhoff. “But nevertheless, our method effectively prevents any dust from escaping into the environment.”

Recycling at a high level

By cutting GRP rotor blades into three or four relatively large sections on site, the environmental impact of recycling is kept to a minimum. Using a material handler with grapple, the sections are loaded onto trucks with so called ‘walking floor’ trailers and transported to the nearest Eurecum processing plant or to one of its partner recycling companies. At the Eurecum plant in Lutherstadt Eisleben, these sections are cut into sizes suitable for shredding in a twin shaft shredder down to the size of sheets of paper. This material is then passed through a single shaft knife rotor with secondary screening capability where it is reduced to a free flowing material with a grain size of 18mm. The next step is to separate out any iron and non-ferrous metals. The end product is a clean, fine grained mixture of glass fibres and plastic. There is an existing demand for this material as a substitute fuel in the cement industry, and also an increasing demand for this material at a higher level of recycling where it is used to produce recycled plastic parts.

Even before the Eurecum process was established, the recycling industry had ways to recycle rotor blades from wind turbines. However, according to the Alexander von Neuhoff, the volumes were not there to develop a process on an industrial scale. This is no longer the case and a solution had to be found that could handle the growing number of decommissioned rotor blades. “With our new recycling concept, which we offer throughout Germany, Eurecum can not only shred rotor blades in a highly efficient manner, but we can also produce material that can be reused which adds value to the recycled product. Our timing is perfect and with the planned shutdown or repowering of plants, we expect to be recycling between 2,000t to 3,000t per year,” explained Eurecum managing director Alexander von Neuhoff.