Is Sustainable Aviation Fuel the Solution for the Aviation industry?

In a recent report from Rethink Energy, lead analyst Bogdan Avramuta makes the point that depending on “sustainable aviation fuel” — that is, kerosene created from waste — will not achieve the aviation industry’s goals of decarbonization.

“The 2050 target set by the industry to itself is to halve its emission compared to 2005 levels.”

Sustainable aviation fuel (SAF) is a direct replacement for aviation fuel (Jet A). Think kerosene from rubbish. There are nine ways of making SAF, most involving using some form of carbon-rich material waste — municipal solid waste, agricultural or forestry waste, cooking oils, animal fat, sugar cane, sugar beet, and plants high in saturated fat like jatropha and camelina.

Sustainable aviation fuel from waste is a possible solution … in theory. “Reports that looked into the global potential for such biofuels point at about 30 EJ – 1 exa-joule = 1 million terajoules – worth of annual feedstock out of which 43% represents straw and 33% forest residue.

“Only around half of this (~15 EJ) would be needed to hit the 100 billion gallons target, but putting in place an industry which collects all of this, to then transport it to chemical plants and oil refineries, just has not happened so far. And without an actual plan in place this means no one is truly serious about going down this route.”

“Which means the Sustainable Aviation Fuel industry is just an excuse to keep doing what it is doing,” adds Peter White, senior analyst of Rethink Energy and founder of Rethink Research. Business as usual.

In the end, the planes running on SAF are still emitting the same amount of carbon dioxide. Given that both Airbus and Boeing have predicted that the number flights and the number of planes will double in the next 30 years, what is the answer? Could we turn to hydrogen or electric powered panes perhaps?

Rethink Energy sees 3 possible scenarios: 1. SAF, 2. More SAF, and 3. Hydrogen.

Remaining emissions

Remaining emissions.

The advantages of hydrogen are that “its mass energy density is three times higher than that for kerosene. The downside though is that its volumetric energy density is three times lower.”

How do you store the volume and manage the particular chemical attributes of hydrogen? Universal Hydrogen is aiming to have a pressurized tank available for use in commercial flights in coming years. Rethink Energy predicts that H2 cost will be down to $1.50 kg by 2030.

Due to the lower mass/energy density (around 0.936MJ/kg or 260Wh/kg), Rethink Energy expects that battery-powered flight will be limited to very small aircraft. Other commentators have nominated a niche role for small electric aircraft like Alice to be used on short city-to-city flights, a bit like an Uber for the family.

“There are two types of hydrogen powered airplanes that are currently being developed: hydrogen-electric (H2-El) and hydrogen internal combustion (H2-ICE). … If the hydrogen used is produced with 100% renewable energy, then the ‘well-to-wake’ emissions will truly be zero.”

Adapting existing engines and planes to run on hydrogen will mean that these technologies will make it to market more quickly.

The Alliance for Zero Emission Aviation (AZEA) launched in the EU — and including hydrogen pioneers like ZeroAvia and Universal Hydrogen; airline operators like EasyJet and WizzAir; engineering giants like Airbus, Rolls-Royce, GE, and even Pratt & Whitney — should speed the transition of the industry towards zero emission fuels. It is expected that the EU will introduce regulations to encourage this. A notable frontrunner is Denmark, which is getting ready for its first zero-emission commercial flight as early as 2025 — powered by hydrogen fuel cells spinning electric motors.

SAF in the fuel mix

Projections of fuel mix.

Rolls Royce, in partnership with Tecnam and Widerøe, expects to have a commercial aircraft in service by 2026. Airbus believes that hydrogen is the fuel of the future and joined the world’s largest clean hydrogen infrastructure investment fund in 2022.

The majority of flights are fewer than 2000 km. It is expected that these routes can be serviced by turboprop-powered aircraft flying on hydrogen. They might just be a little slower. We have the technology, but the question now is how fast it can be implemented.

“In a world dictated by stock prices, dividends and shareholder needs, the aviation industry needs to decide who it wants to please. It’s not too late to turn its back on the poor decisions made so far, but as things stand, the skies are about to fall on its head.”

The sky is falling for those who choose profit over planet.


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