Sustainable Aviation Fuel (SAF) 101

Sustainable aviation fuel could be the key to decarbonizing aviation in the short term. To understand why, we need to cover our SAF basics first. Here’s the rundown on what Sustainable Aviation Fuel (SAF)  is, what makes it sustainable, and what it takes to increase its use in the future.  

The challenge of decarbonizing aviation

Currently, the aviation industry is considered to be responsible for 2-3% of global manmade CO2 emissions. This number is expected to rise if steps are not taken to decarbonize this industry.

Solutions that work for road transport like electric or hydrogen engines are still years off from being available for aviation, especially long-haul flights. It takes a lot of energy to get a plane in the air and batteries and hydrogen are not as efficient in carrying energy as kerosene is. Quite some innovation is still needed to get more than 50 passengers from A to B.

This is where sustainable aviation fuel (SAF) comes in. SAF acts as a “drop-in fuel”. A drop-in fuel is a fuel that can be mixed with fossil kerosene and used without having to change existing infrastructure and equipment.

Because of this, SAF is widely recognized as one of the solutions to drastically reduce CO2 emissions in aviation from today onwards.

But, what is SAF?

In short, Sustainable Aviation Fuel is a substitute for fossil jet fuels, being produced from sustainable resources, instead of being refined from petroleum. 

These sustainable resources, called feedstocks, can be from biological origins such as waste oils, agricultural and forestry residues, or from non-biological origins, such as green hydrogen. Since the first commercial flight operated by KLM in 2011, more than 300,000 flights have flown on a mixture of SAF and fossil jet fuel.

There are several benefits when comparing SAF to fossil jet fuel. In its neat form, SAF has the potential to significantly carbon emissions depending on the combination of technology and feedstock.

In addition to this, SAF does not emit SOx and results in a significant reduction of fine particles. The latest research shows that it even reduces contrails, having a positive impact on the radiative forcing effects of aviation.

How is SAF made?

There is no “one” Sustainable Aviation Fuel. There are currently 8 different certified SAF technology production pathways. This means there are 8 different technologies capable of producing SAF that meet strict technical requirements to be used in commercial aircraft.

Both the technology and feedstock affect how sustainable the SAF will be. But, with so many case-specific combinations possible, how do we assure sustainability?

Truly sustainable aviation fuel

Sustainability is much more than just avoiding harmful impacts. A sustainable feedstock has to meet three requirements.

  • First, higher-value applications such as living, food production, and high conservation areas should not be displaced.
  • The side effects of the SAF must also be far less negative than the usage of fossil fuel.
  • Finally, food security, environment, and biodiversity cannot be sacrificed, and preferably, should even be enhanced.

Assuring sustainability is difficult. This is why SkyNRG takes a 3-tiered approach that emphasizes external accountability.

  • Firstly, by certifying our operations by the Roundtable of Sustainable Biomaterials (RSB), a worldwide multi-stakeholder initiative concerned with ensuring the sustainability of biomass production.
  • Second, by being structurally advised by an independent Sustainability Board.
  • And lastly, by tracking the latest developments and thinking through a global NGO network.

This way, we can assure that the SAF produced is socially and environmentally sustainable and traceable.

Looking at the future: Puzzling the SAF scarcity issue

Currently, SAF still makes up less than 0.1% of all aviation fuel used. To successfully decarbonize the aviation industry, this needs to increase drastically. This is why SkyNRG aims to replace fossil kerosene with SAFs, driven by sustainable practices throughout the supply chain.

There are positive signs that the SAF market is due to grow. New mandates, SAF-dedicated plants, and programs designed to help airlines pay for SAFs are all exciting developments on the horizon. Upcoming blend mandates will be the biggest driver in increasing SAF use. Currently, SAF production and use is limited, due to the fact that airlines can voluntarily choose to buy SAF or not. As SAF is more expensive, airlines do not generally buy SAF on a large scale. Thanks to recently-announced blending mandates, which put an obligation on the production and use of SAF, the sector is expected to further take off. 

This also encourages the development of SAF-dedicated plants. In the coming years, several SAF-dedicated plants will become operative. Some will focus on pre-established technology, like SkyNRG’s DSL-01 plant with HEFA technology, which utilizes waste oils as its feedstock, while others, like Synkero, will be exploring how to make SAF from the combination of CO(2) and green hydrogen.

Customer programs, such as SkyNRG’s Board Now program, help co-fund the price gap over fossil kerosene. As explained above, SAF is more expensive than fossil kerosene and therefore airlines will currently not buy SAF to completely replace its fossil kerosene. When corporates step in to pay a part of this price gap, to also reduce their own emissions from flying, SAF suddenly becomes much more attractive for the airlines. These corporate programs enable further uptake of SAF.

In conclusion: all hands on deck

SAF is not the only solution to decarbonizing the aviation industry, but it is a very important piece of the puzzle. Flying less, further developing electric aircraft, investing in the infrastructure for international high-speed trains, and capping fossil fuels are all still needed to reduce aviation’s carbon emissions and keep our planet as we know it today.  

Text adapted from a transcript on an Introduction to SAF, presented by Karlijn Arts.

September 30, 2021