Innovation in technology has enabled us to execute some pretty amazing feats. We’ve built a skyscraper that is over half a mile high, a car that does 0 to 628mph in 50 seconds, and a passenger aircraft that flies faster than the speed of sound. For years, the focus in engineering has been on making products that are stronger, faster, better.
But as the world becomes more environmentally aware, we have begun to use this knowledge and skill to create new products and systems that are designed not only for function, but also to reduce our negative impact on the planet. We’ve found ways to generate renewable energy, power cars with electricity, and design efficient buildings that reduce our global demand for heating and cooling. These achievements have only been made possible because we’ve developed new materials, designs, and processes – but as we do, the outdated components of the past are discarded and replaced.
Too often, it’s only when they reach the end of their lives that it becomes clear what waste management difficulties they pose. Take wind turbines, for example.
Blades of glass
Wind turbines are an example of a ‘sustainable’ technology where the lifecycle is highly visible. The first wind turbines were erected over three decades ago. Our materials and technical manufacturing ability have progressed so much since then that it is no longer economically or environmentally viable to keep these old designs in operation.
Modern wind turbine blades are much longer (up to 127 metres!) and much more efficient. Turbines built with these new blades can produce roughly 180 times more energy at less than half the cost per kWh than the legacy systems. In fact, it takes just six months for a modern turbine to displace the energy and emissions needed to manufacture it. It’s difficult to argue against doing anything but replacing these old designs, especially when you consider that there are limited geographical locations at which wind turbines can be installed.
That leaves us with the issue of the old turbines. Much of a turbine (approximately 95%) is made from straightforwardly recyclable materials. The remaining “unrecyclable” 5% is primarily made up of the blades, which are made from multiple materials that are permanently adhered and bolted together. With the existing designs and our current recycling technologies, we’re unlikely to be able to achieve true circularity for turbines.
The primary material used in blade manufacture is glass fibre reinforced polymer (FRP) composite. A composite is a combination of two or more materials that, when combined, exhibit superior properties to either material on its own. FRP composites are made from a polymeric resin matrix with reinforcing fibres. The resins used to make wind turbine blades are thermosetting polymers. These harden through a chemical reaction that causes irreversible crosslinks to form in the polymer chains. Many of the plastics we are more familiar with, such as PET or polypropylene are thermoplastics, which can be melted down and reformed into new products at their end of life. Thermosets don’t have this property, which makes them very difficult to recycle. Reinforcing them with hundreds of thousands of extremely long fibres increases this challenge further. In fact, currently, there are no commercial-scale recycling technologies capable of reclaiming fibres and resin from waste glass composites.
Winds of change
But composites aren’t used for their recyclability. They are used because they are able to meet performance and weight design requirements. They are used because they are able to withstand thermal, chemical, and environmental degradation. And wind turbines aren’t designed to be decommissioned. They are designed to generate green electricity as efficiently as possible for their 20- to 30-year life span. They are high-performance systems with relatively long lifecycles. They’re designed for function, not for end-of-life.
As we remove and replace wind turbines installed in the 1980s and 1990s, the scale of the problem is becoming increasingly apparent. The sheer size of the blades and the complexities of their assemblies have left us unable to effectively dismantle and process the legacy parts. Wind turbine blade “graveyards” have appeared across the globe and are being used to store these vast structures while we await new technologies capable of reclaiming their inherent value. WindEurope estimates that 14,000 wind turbine blades will need to be recycled by 2023. That’s approximately 50,000 tonnes of mixed blade waste, equivalent to all the waste collected annually by a typical UK local authority.
If we predict that technological progress over the next thirty years will match, or even exceed, the past thirty, we should expect that today’s new blades will also be outperformed by future designs. They too will become obsolete in 20 or 30 years’ time, need decommissioning and require waste management plans. If this is the trajectory of the industry, surely we should somehow be accounting for the inevitable end-of-life?
Taking apart the issue
While co-processing GRP waste in cement kilns is one low value option, there are a few instances of turbine blades being reused in novel applications. For example, there is a children’s park in the Netherlands that has been built using decommissioned blades. There are also academic projects that seem to be making headway in the field of recycling. But non-disposal options remain limited, and low-volume, leaving us a long way from circularity.
Designing for disassembly could help to alleviate some of the future waste processing pressures. The first step to effective recycling is enabling separation of materials. Breaking blades down into their constituent parts would make it easier to identify any reusable components and recycle any others. On-site disassembly of large blade structures could also reduce logistics complexities, removing the need to transport full blade assemblies over long distances.
Design for disassembly could yield benefits beyond the wind energy industry. Being able to dismantle to repair, reconfigure, or recycle could provide a wide range of engineering applications with environmental and functional benefits. In some sectors, pioneering projects and companies have already begun to implement the concept. Take, for example, the R128 house in Stuttgart. The R128 house was built in 2000 and is a modular system designed to be disassembled and reconfigured to meet the changing needs of a household. It makes use of pre-fabricated elements to reduce on-site build time and eliminates permanent joining methods that could inhibit component and material recyclability.
While the R128 house is an example of a product that has been designed for disassembly but without compromising function, for some applications, this optimisation may not be possible. Improving end of life management may require wind turbine designs that are slightly heavier, slightly slower, slightly less-efficient.
Whether or not enabling better waste management is worth the possible compromises needs to be determined through a proper full life cycle assessment in each case to find the optimum balance between ‘in-use’ and ‘end of life’ considerations. For products such as wind turbines to be integrated within a more circular economy, and conform to the environmental policies, circular economy action plans, and resource efficiency targets being introduced worldwide, these analyses will need to feed back into design requirements and practice. Our continuing innovation cannot any longer take place without consideration of what can, and should, be done with novel materials and components once we’re finished with them.
Featured image: Bjorn Iuell (CC BY-NC-ND 2.0), via Flickr.