In order to reduce the CO2 emissions of flying from now on, there is basically only one solution: sustainable aviation fuel, or Sustainable Aviation Fuel, short SAF. So far, it has most often been obtained from biomass or old cooking oil or synthesized from the components carbon and hydrogen, i.e. composed. For it to be truly emissions neutral, raw materials and energy must come from renewable sources.
Europe, especially Germany, could play an important role in the industry. The world market leader comes from Finland, in Emsland the world’s first industrial plant for synthetic aviation fuel went into operation in 2021. The first plant on an industrial scale for the production of kerosene from solar energy is currently being built in Jülich near Cologne.
There is almost no alternative to sustainable kerosene
Even if aircraft manufacturers are researching alternative drives, medium and long-haul routes will not be able to do without “green kerosene” in the long term: “Almost all analysts come to the conclusion that SAF plays a key role in any future net zero scenario,” writes Dan Rutherford, Director of the International Council on Clean Transportation ICCT’s Aviation Program, in a blog post.
The reason: no other energy store has such a favorable combination of properties for flying. The energy density is of particular importance – related to weight and volume: A lithium-ion battery, which can store as much energy as the kerosene tank of a passenger aircraft, is many times larger and heavier than the aircraft itself. The same contains hydrogen Although it weighs about three times as much energy as kerosene, it takes up three times as much space – even when liquefied.
Emissions could be reduced ad hoc
In addition, alternative drives still have to be developed, while SAF can be mixed with conventional kerosene without any problems – theoretically in unlimited quantities, i.e. 100 percent SAF is possible. The fact that a few technical fine adjustments and approvals are still necessary is more of a formality.
In any case, the amount of SAF produced worldwide is so small that it is currently a purely theoretical scenario: 125 million liters in 2021 – under favorable conditions, this is enough to take a jumbo jet from Frankfurt or New York to Sydney and to fly back. Or to put it another way: In a normal (non-corona) year, this amount can keep global aviation in the sky for about three hours.
Market ramp-up only with political support?
Very few doubt that air traffic will sooner or later grow far beyond the pre-corona level of 2020. Nevertheless, aviation should become CO2-neutral by 2050, 65 percent of the savings should, according to the International Civil Aviation Organization (IATA) through sustainable fuel be achieved. The crux of the matter: So far, SAF is two to five times more expensive than fossil kerosene – depending on the production method and the current oil price.
Of course, the airlines will not voluntarily increase their costs any further, says expert Rutherford: “The small change that the airlines are currently spending on SAF is not enough to really expand the offer and build real markets. It’s about the image of the airlines.”
SAF production capacity needs to multiply
Therefore, IATA is asking governments to provide incentives to bring the SAF share to 2 percent by 2025. That’s exactly what she wants Commit EU civil airlines. The USA is planning tax deductions for the admixture.
Small change for the image: In order to support the Emsland plant, Lufthansa and Kuehne+Nagel have agreed to buy 25,000 liters of SAF annually – that’s a tight tank filling for this Airbus A320neo
According to IATA, this would require a production capacity of five billion liters per year by 2025. The chances of that happening are pretty good. According to the company, the market leader Neste from Finland could alone supply the amount consumed according to IATA 2021. Neste wants to be able to produce 1.9 billion liters of SAF by 2023 and 2.75 billion liters from 2026. The US market leader World Energy wants to expand its SAF capacity to 1.15 billion liters by 2024 and double it again by 2026.
Dominant technologies recycle waste
There are a number of certified methods for producing SAF. The so-called HEFA process dominates the market. According to the US producer SkyNRG, 95 percent of the world production is made in this way. Unlike bio-ethanol, for example, which requires sugar or corn to produce, no edible resources are used, according to the producers. Waste is therefore recycled as raw materials: primarily used frying oil. But also other waste oils and fats from agriculture, the food industry and other sectors. There is therefore no competition with the cultivation of food.
Neste site in the port of Rotterdam: From 2026, 1.5 billion liters of SAF are to be produced here, for example from used frying oil
According to the manufacturers, up to 80 percent fewer emissions are produced than with fossil kerosene over the entire life cycle – from the transport of the raw materials to their combustion in the engines. The final product is currently approved for incorporation of up to 50 percent on commercial flights.
Synthetic fuel before the breakthrough?
According to Neste, it is difficult to say how much SAF the waste available worldwide will cover. However, there is enough available to significantly increase SAF production in the coming years. In the medium term, however, it seems clear that other resources and thus other production methods will be needed to meet global demand. Two of them are just beginning to grow out of their infancy: synthetic and solar kerosene.
The non-profit organization offers CO2 compensation and operates the first “industrial” plant for the production of sustainable Synthes kerosene with an annual production of one ton, i.e. 125,000 liters of SAF
After the world’s first industrial plant for synthetic kerosene has been running in Emsland since 2021, the builder Ineratec now wants to take the next step and build a plant that is almost 40 times more powerful: In the Frankfurt Industriepark Höchst, Ineratec wants around 4.6 million liters from 2026 Produce SAF – around four percent of Germany’s kerosene requirement. Sustainable synthetic kerosene is composed of CO2 – from biogas plants, exhaust gases or the ambient air – and green hydrogen. The problem: The production costs huge amounts of renewable electricity.
Solar kerosene and other innovations
The Swiss company Synhelion wants to avoid this problem by SAF directly using solar energy generated. For this purpose, sunlight – as in a solar tower power plant – is reflected into the top of a tower via a large number of reflectors. There, a heat carrier absorbs the heat and passes it on to a reactor, which uses it to produce the same syngas from CO2 and water vapor that is also an intermediate product of synthesis SAF. The rest of the process is then comparable.
Parts of the sun-to-liquid technology for the production of solar kerosene were researched at the Jülich solar research center
In September, Synhelion started building the first industrial solar kerosene plant in Jülich near Cologne. The technology was developed in the research center there and tested in Spain. The technology is now to be optimized until it is ready for the market. According to Synhelion, however, commercial plants need sunnier locations. In 2025, the company wants to bring 500,000 liters of solar kerosene onto the market. In 2030 it should already be 875 million liters.
Alternative technologies needed
Neste is also already looking at alternative manufacturing processes, the company told DW. Algae, municipal waste and woody biomass are possible raw materials. These technologies are still in the early stages of research, but are considered very promising. The US Department of Energy claims to have calculated that more than 60 billion liters of SAF could be produced annually from US forest and agricultural waste alone.
After all, that would be 13 percent of global demand in 2050. IATA estimates that at 449 billion liters. That’s 100 times what it plans to use in 2025. One can therefore assume that not only one technology will win the race.
