Aircraft recycling
Aircraft recycling is the process of scrapping and disassembling retired aircraft, and re-purposing their parts as spare parts or scrap. Airplanes are made of around 800 to 1000 parts that can be recycled, with the majority of them made from metal alloys and composite materials. The two most common metal alloys are aluminum and titanium and the main composite material is carbon fiber.
Airplanes are disassembled at aircraft-recycling centers where non-metal components with no recycle value are discarded, major components are dismantled and metal alloy components are sorted based on their composition. The metal alloys are then remelted together to form a single homogenous alloy from scraps. It is estimated that roughly 400-450 airplanes are disassembled and recycled annually which drives the $2 billion aircraft parts market.
The main challenge in aircraft recycling is ensuring that the amount of metal impurities within recycled aircraft material is low so that they can be reused in other airplanes. Some major limitations in aircraft recycling include cost, impurities in alloys, hazardous materials, and the quality of recycled components. Parts that cannot be directly recycled can be reused or upcycled into artwork, clothing, and furniture.
Background
In the twentieth century, most aircraft were not recycled; old planes were abandoned in landfills. In the early 2000s, Airbus and Boeing, two of the largest airplane manufacturing companies developed systematic recycling processes to deal with their retired planes and parts as an alternative to moving them to landfills.In 2005, Airbus launched the project "Process for Advanced Management of End-of-Life of Aircraft" known as PAMELA, which demonstrated that 85% of an aircraft's weight can be recycled or reused. Airbus partnered with the waste management company, Suez-Sita and set-up a recycling facility at the Tarbes Airport. The project was tested on the Airbus A300 and was successfully completed when 61 tonnes of the original plane weight were recycled 32 months later in 2007. The project also created a standard for how to safely and responsibly deal with end-of-life airplanes that consisted of a three-step approach: decommissioning, disassembly and dismantling.
In 2006, Boeing founded the Aircraft Fleet Recycling Association, known as AFRA, to set up industry-wide guidelines for the dismantling and recycling of airplanes. The company joined forces with 10 others including Rolls-Royce, Europe Aviation, and Air Salvage International to create an industry code of conduct and collection of best practices. Together they formed a network of AFRA authorized recycling centers across the globe to deal with end-of-life planes in an environmentally friendly manner. AFRA has since grown, and as of 2022 consisted of 80 members which include stakeholders in all aspects of the aircraft recycling process from manufacturers to materials recyclers.
In 2013, Southwest Airlines created a recycling and community initiative, "Repurpose with Purpose," to upcycle the leather seat covers from their planes and provide economic opportunities for various vulnerable groups. The airline partnered with non-profit organizations that work with veterans, the disabled and victims of trafficking to turn the used leather into products such as soccer balls, shoes and jewelry. Since starting the program, over 900,000 pounds of leather have been recycled.
It is estimated that by 2040, about 44% of planes currently in the global fleet will retire from service; this will include over 13,000 commercial, military and private aircraft. In addition to an increase in recycled parts available from recent recycling efforts, blockchain technology has led to new ways in which recycled parts can be bought and sold. In 2019, Honeywell Aerospace introduced an online marketplace for aerospace parts called GoDirect Trade that uses blockchain to authenticate and trace the history of parts. The market for aircraft parts was valued at $5.4 billion in 2018 and is expected to grow to $7.7 billion by 2026.
However, during the COVID-19 pandemic, there was a decrease in the number of planes being scrapped and sent to junkyards. In 2020, 440 commercial jetliners were scrapped, which was a 15% decline from 2019. In 2021, the number continued to decrease another 30% from 2020. Additionally, the price of used planes decreased; before the pandemic, a used aircraft could be sold for $7–8 million, the price has since dropped to about $2 million. The decreased demand for used airplanes has resulted in lower prices.
Raw materials
Retired aircraft have on average 800 to 1000 components that can be repurposed through recycling. The major aircraft materials to be recycled are metal alloys and composite materials.Aluminum alloys
are used in aircraft structures, accounting for 80% of the aircraft's total weight. They are commonly used in the fuselage, wing, and supporting structure of aircraft because they are resistant to corrosion and have a good strength to weight ratio.Aluminum that is used in aircraft is commonly mixed with copper, lithium, magnesium, manganese, silicon, silver, and zinc to form alloys. The composition ratio of each alloy is adjusted according to its intended use in order to meet specifications.
Aluminum alloys have the most expensive manufacturing cost for aircraft because their manufacturing process is energy-intensive. In order to obtain the aluminum to form the alloy, a smelting process must take place. Aluminum is extracted from bauxite, aluminum's main ore, through electrolysis, which requires a lot of energy; 211 MJ of energy are required to produce one kilogram of aluminum with electrolysis.
Recycling aluminum is cheaper than manufacturing the alloy because it requires only remelting the used scrap. The remelting process is achieved at a lower temperature than electrolysis and therefore the process requires less energy, which lowers the cost.
The recycled aluminum alloys can be used in aircraft parts such as stiffeners and flaps, where a growth in fatigue stress and fracture toughness are not critical to the component's integrity. The alloys can also be used for non-aircraft applications, such as truck bodies, rivets, auto bumpers, and castings.
Titanium alloys
s are commonly used in the aircraft industry because they are strong and highly resistant to corrosion and heat. In comparison to aluminum, titanium is heavier but stronger, so less of it is required to form structural components, which reduces the overall weight and diminishes the in-flight energy consumption.Despite its natural abundance, titanium supply is limited when compared to other metals. The smelting process for titanium uses more energy than that of aluminum, consuming 361 MJ of energy for every kilogram of titanium produced.
The recycling of titanium utilizes the scraps from the manufacturing process. These scraps are cleaned to remove oxygen and iron impurities and then remelted.
Composite materials
s are used to lower the weight of aircraft because they are lighter than traditional metal materials such as aluminum. They also have high fatigue strength and good corrosion and fire resistance. In order to decrease the weight of aircraft, manufacturers incorporate more composite materials to the structure. The lighter weight leads to improved fuel economy, which in turn reduces operational costs for airlines.A major component of composite materials is carbon fiber. If the carbon fiber is recycled, it does not lose its mechanical properties, which can be potentially used for the following applications: structural, acoustic and thermal insulation, and air and liquid filtration. Recycled carbon fibers are valued at up to $50 per pound of material.
The recycling of composite materials is more challenging than metal alloys because the industry has yet to develop methods to reuse the individual components that make up the material. A large portion of the composite materials become waste as aircraft are retired and disassembled.
Recycling process
The recycling process must ensure that there are low amounts of metal impurities within recycled aircraft components. As recycled components need to meet required specifications when implemented into other aircraft, recycled components must be organized properly to secure successful processing. First, an aircraft is transported to an aircraft-recycling center where it is disassembled. Desert conditions are ideal for storage because low humidity is required to maintain the condition of the aircraft. The aircraft is drained of fuel, washed to remove corrosive salt, and lubricated.Explosive devices from the evacuation slides are removed, air ducts are sealed, and a protective layer of paint is applied. Non-metal components with no recycling value are discarded and the major areas of the aircraft are dismantled. Alloy components are organized based on their metallurgical composition, and then integrated as desired into alloying new metals.
Alloying involves the gathering of scrap metal with different properties to be re-melted together to make a single homogenous alloy. The majority of alloys used in aircraft are either 2xxx or 7xxx series steels. When secondary alloying elements are found in excess of 10% within a steel alloy, the properties of the steel are especially valuable for recycling into aircraft use. Oftentimes, different alloys are implemented into different components of the aircraft which allows for clearer steel separation.
Components such as landing gears, tail sections, flaps, wings, and fuselages are composed primarily of either 2xxx or 7xxx series steels, and are separated upon aircraft deconstruction. Seats can be worth up to $5000 and an aircraft landing gear can be sold for upwards of $1M. Cables, batteries and other electronic waste are fed into the conventional recycling chains. As plastic interior components often contain flame retardant chemicals, they are not recyclable. Even though recycled metal does not fulfill very high alloy specifications for properties such as toughness, recycled component metal can still be integrated into melting stock: a stock of different metals which are then melted together.
Before recycled metal is introduced into metal stocks for alloying, additional processing is sometimes required for contaminant removal. Elemental residue is a major concern when considering the recycling of aircraft steel because it cannot safely be introduced into repurposed steels. Though plastics have often not been recyclable due to flame retardant chemical use, new methods are being developed to recycle these plastics effectively. Allred and Salas conducted research in 2005 on a catalytic conversion process at low temperatures to convert rubber, thermosets, and thermoplastics into usable hydrocarbon byproducts. This process was shown to reduce hazardous substance presence by 80%. Other inorganic residues such as heavy metals and oxides can be re-melted to eliminate their toxicity. For large metal components that constitute the body of the aircraft, shredding is required before the resulting metal scraps can be introduced into melting stock.
Carbon fibers are among the most common non-metal materials recycled from aircraft. Recycled carbon fibers do not experience any mechanical degradation and can consequently be reinforced into plastics, polymers, or glass to form composite materials. Recycled fiber can be cut to specified lengths before being integrated into these materials: providing a large amount of flexibility in meeting reuse specifications.
An airliner can be dismantled in 1,500-2,000 parts in 30–60 days including engines, landing gear, auxiliary power units and components but it can be parked a year or two to maximize the part harvesting.
A metal aircraft can be recycled for up to 85-90% by mass, and can be maintained for composite airframes as the industry adapts with a growing carbon fiber market.