Because these parts are made of composites such as glass-reinforced plastic (GRP) and fibre-reinforced plastic (FRP), conventional methods of disposal, for example incinerating them or grinding them down into small particles for landfill, pose environmental and health hazards. Incinerating GRP leaves behind inorganic glass fragments, which can damage flue and chimney filters at combined heat and power plants. These processes can also be time-consuming and expensive. Fragmenting blades into small parts exposes operators to risks of breathing in high levels of tiny particulates and solvents, while shears and mobile crushers used to break down the blades suffer heavy wear and tear.
Disposal routes for other turbine components and materials are well established. Concrete towers can be broken up and the rubble reused for foundations. Good prices are paid for scrap steel, copper and aluminium, all of which are in high demand.
Work is now under way to find an economically viable and environmentally friendly solution for blade and nacelle disposal: turn them into clinker, a core component of cement. The idea was born in Germany, prompted by a ban in 2005 on landfilling large fibre-composite material components with their high levels of organic substances.
A conversation about the issue between chemist Erwin Schmidl, who heads up Geocycle, the waste management unit of global cement, aggregate and concrete producer Holcim, and a contact from a German turbine supplier, led to a research project to develop the process. The aim was to produce cement that would not only use fragments of disused rotor blade, but that could also be used to build new wind turbine foundations. Holcim is finding other markets for the cement in conventional construction industries.
A feasibility study on the recyclability of fibre-composite materials was carried out by Bremen University's Environment and Biotechnology Institute and fk-wind, the Research and Coordination Agency for Wind Power at Bremerhaven University. This established that an average of ten kilograms of rotor-blade material is required for every kilowatt of installed power of a wind turbine, which must then be recycled or disposed of 16 to 20 years later. Germany would account for almost a third of the 50,000 tonnes of waste rotor blades accumulating in Europe by 2020. Globally, there could be in excess of 200,000 waste blades and nacelle composite material a year by 2034, the academics predicted. As well as decommissioned blades, the wind industry also gets through a steady supply of blades for testing purposes. Small numbers that malfunction or are damaged during operation or production and cannot be fixed also add to the waste stream.
Using disused blades in cement production has several advantages. It helps save on the fuel used in production, as the resin in the blades has a high calorific value, meaning that less additional fuel is needed to achieve the high temperatures required. One tonne of resin replaces more than 500 kilograms of coal. Silica - a component of fibreglass - substitutes part of the natural sand that otherwise would need to be added for the cement to achieve the right chemical composition. And the high temperatures of the kilns leave no toxic residue.
The process was tested in a week-long trial in 2009, with 120 tonnes of composite materials supplied by a large turbine maker in Germany. Holcim worked with certified specialist disposal firm Zajons Logistik und Entsorgungsgesellschaft at Holcim's cement plant in Lagerdorf, Schleswig Holstein. Afterward, Zajons continued working on the crushing technique for the blades. The company has built a EUR5 million plant in Melbeck, 50 kilometres from Hamburg, to process the broken blades and nacelle housings, as well as fibre-composite waste from other industries. This is set to begin commercial operation in November and the material will supply the Lagerdorf plant.
Schmidl predicts that, in 2010-2011, Holcim will process 1,000 tonnes of composites sourced from the wind industry in Germany alone, and by 2015 anticipates that the company will be processing waste from nearby countries such as Denmark and the Netherlands.
To ensure enough material to make the process economically viable, Schmidl's team has been building partnerships with various businesses in the wind industry supply chain. These include wind farm owners, turbine suppliers who will remove old turbines and third-party contractors who dismantle turbines.
Once the blades are taken down, a special wire saw, similar to a hedge cutter, is used to slice the blades into manageable ten-metre pieces and transport them for further processing. Special shredders cut the components down to lengths of less than 50 millimetres and the fragments are blended. The fine dust generated during the crushing process is bound together to minimise dust emissions. If the initiative goes well, implementation on a global scale is feasible, as there will be enough demand for the cement from a construction industry that will see post-recession growth. The global nature of the wind industry will ensure a supply of material, from Brazil to China, as more and more wind farms and turbines are constructed and old blades are taken out of action. Schmidl has been making regular presentations about the process to his colleagues around the world - a sign of the potential to expand use of the process globally.
PAYBACK TIME LIFE-CYCLE ANALYSIS IN THE WIND INDUSTRY
The environmental impact of methods to dispose of turbine components, including Holcim's solution (main story), can be measured by life-cycle analysis (LCA) programmes. LCA data on wind turbines has been analysed in German and EU-wide studies over the past decade. Turbine giant Vestas has been carrying out LCAs of some of its machines since 1999 and has used the results to reduce the environmental impact of newer models.
LCAs can be used to establish the "energetic payback" period of a wind plant - the length of time a plant needs to operate to produce the equivalent amount of energy used in the production, transport, construction, operation and recycling of turbines and components.
According to the Research and Coordination Agency for Wind Power at Bremerhaven University in Germany, energetic payback is calculated as cumulated energy expenditure divided by the monthly or annual energy output. For most turbines tested, payback can occur in as little as six months for onshore and even quicker offshore.
Scientists from two universities in the German state of Bremen have examined the issues of disposal and recycling of waste by other industries in Europe, including the automotive and electrical sectors.
It concludes that turbine producers will eventually be accountable and responsible for waste as manufacturers in these other industries already are - and advocates that the industry joins certification systems such as the green fibre-reinforced plastics (FRP) recycling label before legal regulations force them to do so.