As an aircraft reaches the end of its life, its parts or even full airframes need to be valorized to meet circular economy principles. This concerns especially the dismantling and recycling of aircraft. The final edition of our Sustainability Snapshots series investigates circular dismantling and recycling of aircraft, and what SUSTAINair will bring to the table to advance this vital solution for circular aviation.
Current situation in the aviation & aerospace industries
Historically, circular dismantling and recycling did not receive a lot of attention in aviation and aerospace industries. Aircraft recycling used to be an almost non-existing, polluting industry, and many aircraft were mainly rusting and decaying in so-called aircraft graveyards. Furthermore, it was considered to be more economically attractive to just dump aircraft in these graveyards, rather than to invest in their meticulous dismantling and recycling. The pictures of huge aircraft graveyards storing thousands of planes in the American desert illustrated this past practice very well.
But in the last decade, aviation and aerospace industries have started to leverage the enormous economic and environmental potential of dismantling and recycling aircraft and its parts, such as the airframe, fuselage or engine. And while there are still gaps in the sectors’ approaches to recycling and dismantling – e.g. aircraft still not being designed with disassembly in mind, a lack of uniform EU regulation on aircraft decommissioning, or valuable materials from aircraft still landing unvalorized on landfills across the globe – the direction taken by the entire value chain is aligning with circular economy principles.
Nowadays, advances in circular dismantling and recycling have already led to specialized companies being able to recycle over 90% of an aircraft’ parts, which equals to some 800-100 parts in an average commercial airplane. Considering that the International Civil Aviation Organization (ICAO) recommends more and more circular strategies in its current approach to aircraft decommissioning management, and associations like the Aircraft Fleet Recycling Association (AFRA) are gaining traction and leading by example through rigid processes and rules in regard to recycling and final demolition of aircraft, the industry pathway is locked in on moving towards circular aviation in these areas. This is also crucial, as in the next two decades, at least 15,000 aircraft are expected to reach retirement – especially in China, where aircraft giants like Airbus are already investing massively in recycling infrastructure to capitalize on these developments.
Circular dismantling & recycling of aircraft parts and airframes
But what does circular dismantling and recycling of aircraft parts, especially the airframe, actually entail? What happens now when an aircraft reaches the end of its life? And how are aircraft currently dismantled and recycled in practice? As concerns the first question, the issues at stake in aircraft dismantling and recycling don’t only concern aviation and aerospace industries, but also many other key industries. For example, current commercial planes like the Airbus A350 and the Boeing 757 are arriving at the end-of-life stage, and are made from still non-recyclable polymer composites. Finding a solution to properly recycle polymer composites – which are becoming more and more important in aerospace engineering – would also benefit the wind turbines industry, where 10% of its non-recyclable materials are composite components. Additionally, the automobile industry would benefit from better dismantling and recycling of aluminium alloys from aircraft, as such alloys can e.g. find a second life in cars. Recycled and recovered aerospace-grade materials also find their ways into other industries and sectors, such as beverage cans, housing or fashion. While other areas benefit from circular dismantling and recycling of aircraft, aerospace companies could even enable direct recycling within the industry, which would not only increase the value of the materials, but also decrease requirements for new raw materials, thereby improving the sector’s environmental footprint.
The second question addresses the processes taking place at the retirement stage of an aircraft. When a plane has reached the end of its lifecycle, its owner usually first considers the trade-off between direct resale and dismantling & recycling. The aircraft owner will also divide the aircraft parts into reusable and non-reusable. The parts are then subsequently reused or dismantled and recycled. Dismantled parts and raw materials remain the property of the initial aircraft owner. Specialized aircraft end-of-life companies also store reusable spare parts for aircraft owners, maintaining them as necessary. If the owner so requests, these specialized companies can also act as a broker to maximise revenue from recovered parts and the natural resources they may contain. Removed aircraft parts are also placed in inventory, recertified and returned to the market in different conditions: as removed, overhauled, serviceable and repaired. Nowadays, highly valued parts such as engines, avionics, flight control systems, engine control systems, thrust reversers, hydraulic systems, landing gear, safety equipment, wheels, brakes, pumps and electric motors are components often being reused in other aircraft.
Finally, the third question deals with the practicalities of how specialized companies such as the Dutch SUSTAINair partner AELS actually dismantle and recycle an aircraft and its parts. When a retired aircraft arrives at the facilities of such a specialized company, it is first cleaned of hazardous substances such as oil, fuel and chemical oxygen generators. Technicians then disassemble all reusable parts. For example, the engines find a second life, the evacuation slides can be reused and a landing gear is also reusable. Some parts are also given a completely new purpose, such as airplane seats in the interiors of travel organizations. The aircraft skeleton that remains goes through a shredder in parts, so that the remaining usable raw materials can be separated. Metal scrap e.g. is typically shredded and separated using techniques such as density separation (air stream), Eddy current separation and magnetic separation. As these separating processes are currently not entirely effective, recovered metals are still often of reduced quality compared to the virgin metal. This is especially so in the recovery of precious and rare earth metals from avionics and other electrical equipment of the retired aircraft.
How SUSTAINair advances circular dismantling & recycling
In its research on circular dismantling and recycling, SUSTAINair will concentrate on several aspects. This will firstly include a rivet removal demonstrator using robotics and water jet cutting to improve the recovery of high-quality aluminium recycling materials. The main aim of this demonstrator is to show that automated dismantling of aircraft parts at their end of life, such as the fuselage, as well as the separation of materials, is both economically viable and feasible. As concerns recycling, SUSTAINair will both address recycling and upcycling as follows:
- The impact of Structural Health Monitoring sensors on recycling
- Near-net shape metallic process development / additive manufacturing of metallic components
- Inhouse recycling from cast housing production scrap
- Inter-recycling of wrought (solid form) / cast (liquid form) alloys
- Upcycling of thermoset prepreg production waste material
- Upcycling of thermoplastic production waste
- Characterization of new recyclate materials
- Life Cycle Assessment in compliance with the ISO14040:2006 standard
The expected outcomes are new up- and recycling technologies to reduce the Buy-to-Fly (BTF) ratio, saving substantial amounts of virgin material and with it associated costs. Additionally, the project aims to cut down on waste-streams in manufacturing by enabling inhouse reuse of scrap i.e. runner from casting, used Additive Manufacturing powder, uncured thermoset remainder of prepregs and thermoplastic short fibre feedstock.
Moreover, SUSTAINair seeks to achieve up to 75% cost reduction versus current 1st life composite materials, a 10-20% weight decrease, as well as up to 100% recyclability versus negative effects from downcycling, pyrolysis or landfill of thermoset fibre-reinforced plastics.
SUSTAINair incorporates two key enabling technologies for the recycling of aerospace-grade materials. The first concerns hybrid recycled laminate materials, enabling highly efficient variable thickness. The processes investigated in SUSTAINair should produce a novel hybrid thermoplastic upcycled material. This will be a homogeneous, laminate material from chopped/shredded recycled materials in combination with carbon fibre-reinforced plastics face layers of virgin Uni-Directional or fabric materials. The resulting highly efficient processes and applications with variable thickness and great specific strength and stiffness properties aim to achieve at least double the flexural strength compared to state-of-the-art recycling options.
The second includes the improvement of processing conditions in Laser Powder Bed Fusion (LPBF) and powder recycling strategies for enhanced titanium powder life cycles. For this, the project will develop and integrate process improvements for the inert gas handling and impurity monitoring in the LPBF process. This is one of the techniques used for metal 3D printing, next to laser-directed energy deposition (L-DED), and will also be used by SUSTAINair. This is expected to improve reusability of titanium powder and increase BTF ratio, by using it 6 times, versus the current one time use in the aviation and aerospace industries.