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All you need to know about sustainable aviation fuels

What are SAFs – sustainable aviation fuels and are they really sustainable? Can they really reduce flight emissions? Find out now!
Written by Team Oncarbon
Climate footprint data for travel products
May 27, 2022

Corporate travellers in Europe comprise about 12% of customers but are responsible for 30% of emissions1 – which is why more and more companies see seek to reduce emissions resulting from business travel.

They do that through offsetting the emissions, using alternative transport for short distances, or purchasing sustainable aviation fuel (SAF) certificates. Sustainable aviation fuels have been one of the hottest trends in the aviation industry – but what exactly are they and how can they help in reducing emissions? In this article, we'll answer the most important questions.

Sustainable aviation fuels – what are they?

Sustainable Aviation Fuels (SAFa) are aviation fuels that are produced largely from renewable bio-feedstocks (think corn, rapeseed, or palm oil) or waste from other production processes (used cooking oils, food waste, or other bio-based solid waste). They also include synthetic fuels, or e-fuels, such as solar kerosene and green hydrogen, but the production amounts of these new types of fuels are still today very small. Chemically, these SAFs are close to identical to conventional fossil fuels.

Are sustainable fuels really sustainable?

"Sustainable" in the context of biofuels means that production of SAFs does not compete with food crops or water supplies, or is responsible for forest degradation. Some biofuels can help reduce greenhouse gas emissions but not all biofuels are sustainable. If biofuel is produced from unsustainably produced crops that lead to deforestation, it can cause great harm to the environment.

For syntetic fuels, they can be sustainable in a way that their production does not involve carbon. For example, hydrogen fuel is produced with electrolysis of water, and it is burned with oxygen. Solar kerosene is made from carbon dioxide and sunlight, and when burned, it generates only as much CO2 as was removed from the atmosphere in its production.

Obviously, the production process requires power in the form of electricity – so for e-fuels to be considered sustainable and environmentally neutral, they should utilise electricity generated from renewable sources.

What's the market size of SAFs?

Today, SAF’s share of the global aviation fuel market is still very small. In October 2021, it accounted for only 0.05% of total aviation fuel consumption in Europe2.

The European Union proposed to force fuel suppliers to include SAF in aviation fuel delivered to EU airports at a level of 2% SAF from 2025, 5% from 2030, and 63% by 2050. The United Kingdom announced before COP26 that it is aiming for a SAF share of 10 % by 2030, and in Norway it has been mandatory for airlines to use SAF in combination with other fuels since 2020.

According to experts3, the sustainable fuel industry is set to grow to $15.7 billion by the time the 2030s arrive.

How do SAFs certificates work?

The Sustainable Aviation Fuel Certificate (SAFc) system is a new accounting tool that allows a traveller to cover higher cost of the jet fuel. When you buy a certificate, a given amount of SAF is delivered to the airport nearest to its production plant. The certificate was created by Clean Skies for Tomorrow (CST), an initiative led by the World Economic Forum (WEF).

Some companies, such as Netflix, JPMorgan Chase, Deloitte, Microsoft, Boeing, Boston Consulting Group and Salesforce, already use the system.

Does SAF reduce CO2 emissions?

Research shows that fuels derived from biomass could reduce CO2 emissions by 20-98% compared to conventional jet fuel4 but it doesn't mean that SAFs do not generate emissions at all. Also, some environmental NGOs have cast doubt on the “80%” emissions reduction statistic, as this data often comes directly from fuel producers.

Even if CO2 emissions can theoretically be reduced down to zero, flying would still generate NOx and contrail cirrus that have twice as much climate impact than CO2 today. Also, e-fuels require huge amount of renewable energy.

The largest problems with SAFs is that they – as for now – can't be scaled up rapidly enough to meet climate targets. Many airlines rely on the future technology that is still far from becoming commercially available. According to the research group Stay Grounded, alternative fuels' potential to mitigate climate impact of aviation is less than 5% of its total impact in 20305.

Why are SAFs not widely used by airlines?

Today, many airlines operate their aircraft on SAF blended with conventional fuel as most plane engines do not allow using 100% of SAFs. The widespread production and the use of SAFs is also limited by cost and requires significant investment. Experts predict that growing demand and regulatory pressure will lead to more production and lower costs.

IATA (International Air Transport Association) estimates that more than 370,000 flights have used SAF since 2016, and more than 45 airlines now have experience using SAF. Some have invested in jump-starting SAF use, while others have promoted SAFs through test flights, research and exploring local options. Five airports also have regular SAF service: San Francisco, Los Angeles, Oslo, Bergen and Stockholm.

Which airlines are using sustainable aviation fuels?

Right now, over 45 airlines globally are exploring SAF options6. However, use of SAFs is still limited, with costs historically two to four times that of jet fuel—although recent steep increases in oil and gas prices are significantly reducing the gap.

The airlines that use SAFs include, among others:

Alaska Airlines. This airline was one of the pioneers in using sustainable aviation biofuels made from corn and forest residues. Alaska Airlines has set an ambitious goal of zero carbon emissions by 2040.

KLM. Since January 2022, the Dutch airline has added 0.5% aviation fuel to all flights departing from Amsterdam. KLM customers can also purchase an additional amount of sustainable fuel when booking.

United Airlines. In December 2021, United Airlines flew a jet carrying more than 100 passengers from Chicago to Washington, using 100% sustainable aviation fuel.

SAS. The airline offers passengers the option to pay a surcharge for biofuel. This can be done when booking the ticket or at any time before departure and aims to “give travelers the opportunity to reduce their climate impact.”

Is buying SAF certificate better than buying offsets?

Sustainable aviation fuels are for now the most viable alternative to fossil fuels – as electric and hydrogen-powered aircraft will likely be limited to smaller units and shorter ranges. To meet the goals of reaching net-zero by 2050, 65% of the emissions reductions must be achieved by replacing the jet fuel used today with sustainable aviation fuel. Especially because the number of air travelers is growing rapidly, and air travel is forecast to reach 10 billion passengers trips per year by 2050.

If you are thinking about reducing your corporate climate footprint, the truth is that buying SAFs certificates or offsets will not get us much closer. The solution is to either replace part of business travels by online meetings, or use alternative forms of transportation.

Another thing that can be done is to push airines to disclose flight emissions, and communicate the carbon footprint of each flight. This, in turn, will allow passegners to make informed decisions. Carbon footprint labeling of flights is possible through solutions like Oncarbon – a calculation and communication toolkit for the climate footprint of travel products. Book a demo here and check out how our solution works.

Appendix: Examples of sustainable aviation fuels

Hydrogen fuel. Compressed or liquefied hydrogen contains a lot of energy per unit mass – up to three times more than conventional jet fuel. Its only waste product is clean water. Hydrogen could reportedly power a commercial passenger jet on a flight of up to 3,000 kilometers by 2035.

Solar kerosene. Hydrocarbon fuel produced from carbon dioxide and sunlight. Swiss, the flag carrier of Switzerland, recently announced that it will be the first commercial airline to fly on solar kerosene starting in 2023. According to experts, solar kerosene can be described as carbon neutral because all the carbon in the fuel has been taken from the surrounding air, so no additional carbon is added to the atmosphere during the combustion process.

Synthetic Fischer-Tropsch paraffin kerosene. This biofuel is made from renewable biomass such as municipal solid waste, agricultural waste, wood and forestry residues. This means that waste from households and businesses can be used to produce jet fuel instead of ending up in a landfill. The blending limit today is 50%.

Alcohol to Jet Synthetic Paraffinic Kerosene. This biofuel is made from isobutanol, which is derived from feedstocks such as sugar, corn or wood. The alcohol is dehydrated to an olefinic gas, oligomerized, hydrogenated and fractionated. The blending limit is 30% for isobutanol and 50% for ethanol.

Hydroprocessed Esters and Fatty Acids (HEFA). This type biofuel is produced from oleaginous biomass from a wide array of vegetable oils and fats, for example algae, jatropha, and camelina. Camelina is an energy crop with high lipid oil content, often grown as a rotation crop with wheat. Jatropha produces seeds containing 30-40% lipid oil and can be grown in difficult soil conditions, including land that cannot be cultivated. Algae can be grown in polluted or salt water, deserts and other inhospitable areas. The blending limit is also up to 50%.

Hydroprocessed Fermented Sugars to Synthetic Isoparaffins. It is produced by the microbial conversion of sugars to hydrocarbons. The blending limit is up to 10%.

Synthetic jet fuel by catalytic hydrothermolysis. It is produced from triglyceride-based feedstocks such as vegetable oils, waste cooking oils, algae oils, soybean oil, jatropha oil, camelina oil, carinata oil, and tung oil. The blending limit is 50%.

Original cover picture: Bing Hui Yau/Unsplash


Team Oncarbon
We’re on the mission to show you that we need – and we can – travel more consciously. We bring closer to you the topics of carbon footprint, sustainable travel and aviation, and transparency in emissions reporting.