Sustainable aviation

NLR’s goal for 2030

In the future, NLR wants to make its own organisation even more sustainable, aiming to become climate-neutral by 2030 for both direct emissions (known as scope 1 emissions) and emissions released elsewhere when generating the electricity that NLR consumes (scope 2 emissions). One of the more visible areas where NLR generates direct emissions is when test flights are carried out with laboratory aircraft. It is worth noting that many of these test flights, for example in the context of European research, are actually carried out in the context of research projects aimed at developing technology and procedures to reduce emissions in the long term.

NLR Flight Operations

The NLR fleet consists of two aircraft: an all-electric propeller-driven Pipistrel Velis Electro (registration PH-NLX) and a Citation II powered by conventional jet engines (registration PH-LAB). PH-LAB is 50% owned by NLR and 50% by TU Delft. PH-NLX emits no CO₂ at all during its flights, whereas PH-LAB emits approximately two tons of CO₂ per flight hour. The CO₂ emissions from PH-LAB on NLR test flights amount to approximately 10% of all NLR’s CO₂ emissions.

Our aim: to fly using sustainable aviation fuel

NLR is gaining significant experience in electric flight through PH-NLX. When the electricity used to recharge an electric aircraft is generated sustainably, flying it is climate-neutral.

There are still limitations to electric aviation: the energy density of batteries (kWh per kg) is still much too low for electric propulsion to be a realistic alternative for medium-haul and long-haul flights. But with climate targets looming, the current generation of aircraft powered by jet engines will be able to use what is known as ‘sustainable aviation fuel’, or SAF for short. This term refers to sustainable fuel produced either from biomass (e.g. algae), waste (e.g. frying fat) or synthetically from CO₂ extracted from the air. Aircraft can refuel with SAF as if it were kerosene and, depending on the method chosen, the production of SAF can be virtually circular. No new fossil fuels have to be extracted. That is how SAF should benefit climate-neutral aviation in the future.

Availability of SAF is very limited at present. It is not currently available at Rotterdam The Hague Airport, the home base of the NLR aircraft. Physically refuelling with SAF is therefore not an option for the PH-LAB operation at this time. An alternative is to use ‘SAF book-and-claim’, in which quantities of SAF produced elsewhere are ‘claimed’ without them physically ending up in PH-LAB. This is a trading structure similar to ‘green electricity’. The option is now feasible but still very expensive. It is anticipated that the availability of SAF will improve over the coming years and that the price will fall as it does. With that in mind, NLR Flight Operations has expressed its aim of gradually switching to using SAF over the next seven years, preferably by physically refuelling with SAF or through a book-and-claim construction where that is not possible. By 2030, we want our operations to be made completely climate-neutral by flying on sustainable fuel.

Interim solution: CO₂ compensation

Because sufficient SAF is not yet available, we decided as a transitional measure to offset the CO₂ caused by flying PH-LAB. We are doing that through what are known as ‘CO₂ credits’ that are purchased from the Climate Neutral Group. We have chosen an initiative in the Netherlands where biogas plants are installed on arable farms, backed up by climate subsidies. Fermentation of slurry and other waste flows produces electricity that is fed into the national grid. The project is VCS certified and its CO₂ credits have been released via the National Carbon Market. On an annual basis, PH-LAB logs about 350 flight hours; together with TU Delft, we compensated 700 tons of CO₂ emissions for 2022 through this project.