The aviation industry is a significant contributor to global carbon emissions through its extensive use of kerosene. Offering high energy at a low weight, and at relatively low cost, kerosene is difficult to replace with more sustainable types of fuel. Meanwhile, strict safety regulations and legal restrictions cause tonnes of unused kerosene to be disposed of.

In this article, the second in a series of articles on aircraft recycling, Aethos explores the possibilities and challenges offered by the residual fuel left in decommissioned aircraft. What are the obstacles preventing the reuse of kerosene in other aircraft, and can they be overcome?

How residual fuel is handled – ideally

As a rule, kerosene is only ever put in an aircraft once. And with good reason. Taking kerosene out of a tank means risking contamination with water, microbes or debris from an aircraft’s fuel system. Hence, reusing it can cause significant engine damage and even failure: unacceptable in an industry where safety is crucial.

So what can dismantling companies do with residual fuel in retired aircraft? Ideally, the aircraft is defueled in a 100% contamination-free way, the kerosene is kept in a 100% clean container, it is safely transported to an airport, and reused in another aircraft.

How residual fuel is handled now

Because of safety concerns and legal restrictions, however, this is not what happens. Kerosene is not taxed when used in an aircraft for international flights: taking it out of the aircraft and off an airport usually means that taxes and levies are due. What is more, kerosene counts as a hazardous substance and can only be moved around by licensed companies, which makes transport costly.

As a result, aircraft dismantling services find other ways to dispose of kerosene. Either by selling it off to other industries, where it can be used for asphalt, or mixed with motor oil and used for heating homes for instance – or by sending it to a licensed hazardous waste disposal facility, where it is usually turned into energy by burning it. In both cases there are costs involved, and more or less strenuous safety regulations apply. Processing the kerosene as waste also releases carbon dioxide into the atmosphere.

Towards a solution

Meanwhile, failsafe ways to defuel and refuel aircraft and store kerosene are already available. CH-Aero, an aircraft weighing service based in The Netherlands and a friend of Aethos, has successfully used a defuel-and-refuel procedure for several years now.

As commercial director Michelle Arentz explains: “Clients regularly asked us if we could defuel an aircraft before weighing it, and take care of correctly processing the residual fuel. In 2020 we got in contact with Weltens Transport, a company specialized in international ADR (Agreement concerning the International Carriage of Dangerous Goods by Road) transport, which used an advanced, universally compatible de/refueling pump. Their trucks have a license for European roads, and can move tanks with a capacity of 36 tonnes of fuel. That got us thinking: can’t we store the fuel from an aircraft for the duration of the weighing procedure, and put it back after? That way we don’t have to throw it away, it saves the client money, and it’s more sustainable.”

CH-Aero takes many precautions to ensure safety. “All the tanks and trucks we use are thoroughly cleaned and sealed off before every new job, by an EFTCO-approved cleaning facility. Using an ECD (EFTCO Cleaning Document), also known as a ‘clean truck certificate’, means the client can track the whole process. This is important to clients: because the procedure is new, but mostly because the damage contaminated fuel can do to aircraft is considerable. Whenever there is the least suspicion of contamination, we dispose of the kerosene as waste.”

The missing piece: reusing fuel in a different aircraft

CH-Aero’s approach is promising. However, one hurdle that remains to be tackled for the aircraft dismantling industry is finding a way to reuse residual kerosene in another aircraft, at another location. Because CH-Aero reuses the fuel in the same aircraft at the same airport, they avoid introducing the kerosene into the economic sphere of the surrounding country. If a dismantling company were to transport kerosene to an airport for reuse, taxes and levies would automatically be due.

On the other hand, finding a solution for this problem could have big implications for the aviation industry as a whole. Currently, tonnes of residual fuel are disposed of whenever fuel tanks are cleaned, for instance. A safe, reliable, cost-effective way to reuse residual kerosene in other aircraft, at other locations would truly be a step forward in making the industry more sustainable.

This article was written with the help of Dutch aircraft weighing service CH-Aero, a friend of Aethos.

Aethos is a foundation committed to advancing recycling efforts in aviation. It supports research and innovation in the field of material recycling from retired aircraft and components that are beyond reuse and repurposing.