The Two-Faces of Sustainable Aviation Fuel: The Only Way But Not Ready for Take-Off

Photo: Honeywell

LONDON – “If working apart we are a force powerful enough to destabilize our planet, surely working together we are powerful enough to save it,” Sir David Attenborough told the COP26 in Glasgow.

However, the climate summit found itself at the center of controversy since, according to WingX’s data, it brought 118 bizjets to Scotland, registering an increase in arrivals of 525 percent compared to the week before (WingX, 2021).

A preliminary assessment shows that the carbon emissions for COP26 were expected to reach the equivalent of 102,500 tonnes of carbon dioxide, of which the majority (60 percent) from international aviation (, 2021).                 

Aviation environmental sustainability is a two-faced topic. Despite the technological evolution of aircraft delivering some benefits, the operating principle of the propulsion apparatus has remained the same as seventy years ago.

Photo: Shell Aviation

In the automotive field, the internal combustion engine has evolved towards lower consumption and emissions, but the principle of operation hasn’t changed. The EV transition, on the other hand, constitutes a change of perspective that might also rescue aviation in terms of supply (see Scale Production).

In the post-pandemic scenario, all airlines claim to be committed to the Sustainable Aviation Fuel (SAF), produced from sustainable feedstocks (i.e., used cooking oil, household waste, forestry waste) and very similar in its chemistry to traditional fossil jet.

However, the commitment appears to be a choice of green marketing rather than genuine care to the environment.

Pasquarelli (2021) states that the pandemic has changed people’s relationships with brands.

Price is no longer the only factor taken into consideration when booking a trip, but other elements come into play such as the perception of eco-sustainability. Conversely, there are airlines that gave a different response to generalized cutting-cost policies.

United has signed an aircraft purchase agreement with Boom Supersonic for 15 Overture jets that would fly from 2029 using 100 percent SAF but, as discussed in a previous article, there are clear contradictions in that bombastic announcement.

Boom Supersonic’s aircraft will cut travel times in half and operate on up to 100% sustainable aviation fuel.

Although the SAF appears to be the only realistic solution in the short-medium term, its development is hindered by three significant barriers.


SAF is two to six times more expensive than traditional aircraft fuel Jet A1.

According to IHS Markit, an Amsterdam-New York flight with 63 percent SAF mixed with Jet A1 fuel would result in an increase in the cost of US$120 per seat (Brooks, 2021).

Today the desire of a passenger to spend more for a green trip collides with two main factors:

  1. The pandemic has generally reduced flight operations, temporarily wiping out long-haul and stimulating the short-haul market.
  2. It follows that the low-cost carriers, most of them operating on the short-haul, are in a favourable position. This type of airline cannot afford to increase costs exponentially, albeit for a just cause, since the choice would affect their business model.

Also, as IATA shows, the cost of fuel was 70 percent higher in November against the start of the year (IATA, 2021). Consequently, the use of SAF would entail a further increase in airlines operating costs.


The development of the SAF also smashes into the huge shift in technology that could become a change of pace in the 2040s.

For instance, in the ZEROe project, Airbus sees two primary uses for hydrogen: propulsion and synthetic fuels.

The introduction of the first zero-emission commercial aircraft is expected in 2035 (Airbus, 2021).

We don’t know if the challenging deadline set by Airbus is likely, but the forecast reduces the lifespan of SAF assets.

Besides the new propulsion developments, there is a substitute for the train which in a hyper-connected region, such as Europe, could become the recommended direction (in some cases mandatory) by states to travel on the short-haul with an arguable lower environmental impact.

Scale Production

The lack of commercial-scale refineries adds a burden on alternative fuels.

It should be noted that there is a growing demand for biodiesel/ethanol plants that could also produce SAF, as well as an increasing trend of EV cars that could leave room for the production of aviation alternative fuels.

However, there is limited availability of sustainable feedstocks, cooking oil, or forest waste mentioned above, which doesn’t allow large-scale production.

Moreover, it is important to highlight that the SAF supply chain is still a grey area.

An integrated model could be crucial for the definition of downstream activities.

In addition to an increase in efficiency, a coalition of companies could lead to an overall reduction in costs and an expansion of core competencies, increasing the break-even opportunities for the SAF.

The key issues listed above inevitably clash with the European Commission’s proposal to introduce a blending mandate for the SAF at least 5 percent of aviation fuels by 2030, 32 percent by 2040, and 63 percent by 2050.

The current use of SAF in the EU is estimated to be close to 0.05% of total jet fuel consumption. Furthermore, most of the SAF currently used is either imported from or tanked in third countries (European Commission, 2021).

Finally, the ambitious goals proposed by the EU aren’t compatible with the scarce incentives available today for all the players involved in the supply chain. From the producers of SAF, still small and risky capital costs overrun due to high production costs and the lack of demand.

To airlines that in the current scenario have to deal with a huge decrease in profits and injected state aid are used for the survival of the airline itself and not as incentives for SAF.


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