Out of the skies

What happens to old aircraft after they come in to land for the last time? Lydia Heida reports on the booming business of recycling the materials they contain.

By Lydia Heida

Not only does the UK have more aircraft recycling companies than any other European country, but new, innovative firms are working on the last technical problems to recycle the remaining 20% of aircraft that otherwise goes to landfill.

“Eighteen years ago, when I started this business, there weren’t half as many planes coming out as there are now,” says Mark Gregory, managing director of Air Salvage International (ASI), based at Cotswold Airport in Gloucestershire. “This was the first aircraft recycling company in the UK, and it is probably the biggest in Europe as the company recycles 50 to 65 aircraft a year.”

The British aircraft recycling industry has taken the lead in Europe as the country now counts more than 10 companies specialising in this area, from established businesses such as ASI, ECube Solutions and GJD Services to newcomers KLM UK Engineering, ARRCAM and Sycamore.

All aim to get their piece of the pie as globally 12,000 commercial aircraft – worth $1.3 trillion – are to be retired over the next 20 years, according to the Aircraft Fleet Recycling Association, which was founded in 2006 to develop a best practice guide for aircraft recycling. Rising fuel costs are leading to the renewal of fleets with lighter and more fuel-efficient models.

Reuse of parts

The value of an end-of-life aircraft can vary immensely. For example, a Boeing 747 could be worth between $5 million and $20 million. This depends mainly on the condition of the engines, avionics and landing gear.

Once removed from the old plane, they are refurbished and either returned to the owner of the aircraft who uses them for its own fleet or sold on the secondhand market.

“Over 90% of the value of an old aircraft comes from the reuse of parts,” says Arjan Meijer, managing director of KLM UK Engineering, which recycles Boeing 737s, BAE l46s, Fokkers and Airbus A320s at Norwich Airport. The engines are by far the most wanted commodity. “Properly working engines of a wide body can easily generate over $4 million, depending on the type.”

The current model for aircraft recycling is becoming problematic as the renewal of the fleet results in a surplus of parts.

Most of the weight of an old aircraft makes the least money, less than 10%. After stripping the aircraft of all its valuable parts, the aluminium shell is scrapped. This counts for 60% of the weight of a plane: a DC-10 contains about 75 tonnes of aluminium worth a mere $75,000.

Now, the current model for aircraft recycling is becoming problematic. The renewal of the fleet results in a surplus of parts, for example from early Boeing 737 Classics, for which demand is rapidly decreasing.

“That market is dead,” says Peter O’Carroll, managing director of ARRCAM, based at Bruntingthorpe Airfield in Leicestershire.

Recycling rates

To improve the business model, technological challenges need to be tackled, such as the recycling of the complex plastics from the interior, the proper separation of aluminium alloys, and the recycling of carbon fibre.

This is also important to increase the current recycling rate of aircraft, which lies around 80-85%, to 95% or higher, to stay in tune with the directives for vehicle recycling. Currently, the vast majority of materials that make up aircraft cabin interiors are sent to landfill.

To help solve this problem, SD Aviation opened a facility for recycling aircraft interiors last January. Located in Buckinghamshire, it is the first of its kind in Europe.

“Everything within that cabin we can recycle, from carpets, seats, luggage compartments, toilets to galleys,” says Aaron Day, managing director of SD Aviation, who has secured $10 million worth of new business this year.

“The biggest challenge has been the side-walls, galleys, ceiling and the floor that is made out of Nomex board.” This is a flame-resistant meta-aramid polymer, which is used to create honeycomb structures.

“We can melt that material down and the liquid we gain from that can be put into concrete or a sort of Lego brick to construct alternative accommodation for refugee camps and homes in Third World countries.

Aluminium alloys

“The only thing we are still struggling with is the back of certain seats. These are made of composite materials. At present, this is being tested in a lab to verify exact material content, how we can break it down and what it can be used for,” adds Day.

Other parts of the seats, such as the leather, are turned into bags and wallets, while the aluminium frames are destined for the more conventional metal recycler.

Nowadays, some 15 different aluminium alloys are used to make a plane, which can include copper, zinc, manganese, magnesium and traces of silicon, iron, titanium and chromium.

Some 15 different aluminium alloys are used to make a plane and proper separation could lead to a steep increase in the scrap value.

For example, a more corrosion-resistant aluminium alloy is used for the lower part of wings or fuselage. When an airframe is scrapped, these high-grade alloys end up on a huge pile and their worth is destroyed.

Proper separation of aluminium alloys could lead to a steep increase in the scrap value. X-ray fluorescence handheld devices are already used to determine the composition of different alloys, but this is a time-consuming and expensive method. Industry experts estimate that automated identification and sorting systems will become available in the next three years.

Carbon fibre

Last year, the European research project AiMeRe Clean Sky was set up to optimise dismantling, sorting and processing of high-grade metal alloys of aircraft so these can be used again, while retaining their original properties. Partners in this project are ENVISA, a French company specialising in environmental issues of aviation, and Bartin Recycling, a subsidiary of waste management company Veolia.

Aeroengine manufacturer Rolls-Royce is already recycling almost half of a used aircraft engine, such as titanium alloys, rhenium alloys, nickel-based super alloys and some high-cobalt steels. The recovered materials can be used again to make new engines.

The drive for fuel-efficient aeroplanes will increase the use of carbon fibre to replace aluminium, both for the interior and the shell, as it is lighter. The most renowned example is the recently launched Boeing 787 Dreamliner, made from 50% carbon fibre by weight.

Although the first retirements of these aircraft lie far away in the future, already Boeing 777s and Airbus A320s are being retired that have a composite element of up to 20% by weight. In 2003, the world’s first commercial-scale recycling facility for carbon fibre, named ELG Carbon Fibre, opened in the West Midlands.


The company has capacity to convert 2,000 tonnes of waste into milled and chopped fibre for the automotive and electronic industries as the recycled material can’t be used for aviation any more.

Recycling makes sound business as it takes 5% of the energy to produce recycled fibre as virgin fibre, which is very expensive. “There are many grades of virgin carbon fibre, with the price ranging from £15,000 to £40,000 per tonne,” says Frazer Barnes, managing director of ELG Carbon Fibre.

‘It takes 5% of the energy to produce recycled fibre compared to virgin fibre, but there are many challenges in the recycling process.’

A patented pyrolysis system is used for recycling, whereby heat resolves the resin from the shredded fibres, rendering a kind of fluffy fibre. “There are many challenges in the recycling of carbon fibre,” says Barnes. “It took us three years to optimise this technology.

“If you over-treat the material, you lose the mechanical properties such as stiffness and strength. By fine control of the condition within the furnace in terms of temperature, atmosphere and the way we feed the materials through, degradation of the fibres is minimised.”

Current trends

Aircraft manufacturing companies are also investing in research on recycling composites. One such project, EXHUME, kicked off last year involving the universities of Manchester, Exeter, Birmingham and Cranfield, as well as Innovate UK and Airbus. The project has a budget of £1.4 million.

In 2011, Boeing dedicated an annual £625,000 for at least the next three years to Nottingham University’s composites recycling research. Both are partners in the Affordable Recycled Carbon Fibre project.

Project leader Professor Steve Pickering says: “This project has two themes. First, to take short recovered fibres and look at ways to align those to produce a higher quality end product. Second, to use supercritical propanol to recover the fibres and the polymer resin. Such a process will lead to less degradation of the fibres, and the recovered aromatic compounds could be used in other chemical products.”

These research projects are set up at the right time, as results will become necessary only after 15 to 20 years, when aircraft with a higher percentage of carbon fibre will reach the end of their lives.

“In the future, aircraft recycling will be a very different ball game,” says Arjan Meijer of KLM UK Engineering. “It is in the nature of our business to be 20 years behind current trends in the material use of aircraft.”

Published: December 2014 in Professional Engineering Magazine.

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