The future of flight: How to make aviation fossil-free

Aviation means around 2.5 percent of global CO₂ emissions. And barring a deep dip in the curve during the COVID-19 pandemic, emissions are rising.

Aviation, along with other sectors such as shipping and steel, are considered especially difficult to decarbonize or reduce. But there are some promising developments, both in terms of technical advances and new regulatory frameworks.

“What we are seeing now is that fossil-free electricity can play a very important role in reducing emissions also in the difficult-to-reduce sectors, and we need to decarbonize these sectors as well, because a large part of the emissions come from those sectors. . ”says Mikael Nordlander, director of industrial decarbonization at Vattenfall.

To ensure that flights do not use fossil fuels, there are four main routes: hydrogen, biofuels, electrofuels and batteries.

The most available are biofuels; however, its emissions reduction capacity may vary depending on the raw material and how it is manufactured. Therefore, Vattenfall and his First movers coalition Partners have committed to supporting biofuels that reduce greenhouse gas emissions by 85 percent or more, compared to fossil-based kerosene.

Raw materials such as straw or used cooking oil, which do not compete with food production, are the most sustainable options. The problem: While biofuels can be part of a fuel mix and could work as part of the solution, there is simply not enough biomass that can be produced sustainably to replace fossil fuels.

Batteries

Another option is battery-electric flight. The Swedish island of Gotland, with an airport about 200 kilometers from the capital, Stockholm, wants to have the country's first regular electric flight connection as early as 2028. Also on that date, the Swedish Heart Aerospace plans to have its 30 seats ES-30 airplanes flying. Appropriately, it is supposed to have an all-electric range of 200km when first in operation.

However, that is the main limitation for battery-powered aircraft. They will work well on short-distance light flights, but for longer, heavier flights, other power sources are needed.

Hydrogen and electrofuels enter the scene.

Not yet commercially available as aviation fuels, they are considered primary options for long-haul flights in the future, possibly combined with biofuels when it comes to electrofuels.

There are several ways to produce hydrogen and even more ways to produce electrofuels. But basically, fossil-free hydrogen is produced by separating water through electrolysis using fossil-free electricity. The hydrogen can then be used in gas turbines or by letting fuel cells convert the chemical energy back into electricity.

Already in 1989, the Russian company Tupolev manufactured the first hydrogen aircraft that ran on gaseous hydrogen. But hydrogen can also be cooled to liquid form at -253°C or lower, so it takes up less space.

One of the main challenges of hydrogen is that new infrastructure is needed, both for airplanes and for storage facilities and service stations, etc. Vattenfall is working on a cooperation with aircraft maker Airbus and others on hydrogen infrastructure at airports in Sweden and Norway.

While hydrogen has a high energy density compared to its weight, it is low compared to volume, also in liquid form, meaning that the same amount of energy takes up more space than other fuels. Therefore, Airbus, for example, is considering storing hydrogen in huge wings as an option.

The process of developing and obtaining a new type of aircraft is quite long and hydrogen aircraft are not expected to take to our skies in the next decade. But if hydrogen is combined with captured carbon, liquid electrofuels are obtained.

The captured carbon could, for example, come from a district heating installation that runs on forest by-products such as logs, tops and branches, instead of being released into the air. The carbon released by the plane will be captured again over time by new growing trees. Furthermore, CO₂ captured when producing biogas or ethanol could be used.

Another option is direct air capture or CO suction.₂ directly from the air. Then the cycle closes almost immediately. But the lower the concentration of carbon dioxide, the more energy it takes to extract it and the higher the cost. The co₂ The level in the air is currently around 420 PPM, or 0.042 percent. Higher than ever and increasing, but still a very low percentage compared to the other processes.

The advantages of electrofuels are great. If you get the right recipe, you can mix it with traditional fossil-based kerosene biofuels. Or even run solely on electrofuels without making any changes to the aircraft or infrastructure. As with hydrogen, more can also be produced when renewable energy sources, such as wind and solar, produce more and prices are lower.

Electrofuels possible around 2030

“I believe that the first aircraft powered by electrofuels, at least in tests, will fly around 2030,” says Mikael Nordlander.

Electrofuels and other fossil-free alternatives also recently received a major regulatory boost, when the EU adopted the Refueling EU aviation initiative. The regulation requires a minimum proportion of “sustainable aviation fuels” (SAF), which includes certified biofuels, from 2025 and, from 2030, a minimum proportion of synthetic fuels or electrofuels. Both percentages increase progressively until 2050. Fuel suppliers will have to incorporate 2 percent of SAF in 2025, 6 percent in 2030 and 70 percent in 2050. From 2030, 1.2 percent of fuels They must also be synthetic, reaching 35 percent in 2050.

The EU is also Phase out Free emissions allowances for the aviation sector in the EU ETS emissions trading system by 2026.

However, all of these solutions cost more than fossil-based kerosene, and fuel costs represent about 20-30 percent of the total expenditure of airline companies.

But if the costs are distributed evenly among all passengers, as is the case under EU rules with minimum combinations, prices do not need to rise as much and will eventually fall, says Mikael Nordlander.

But above all, as it stands now, fossil fuels are heavily subsidized because they don't pay for the damage they cause, he says.

"There is studies that shows that about 1/5 of the global economy will be destroyed due to climate damage by 2050 if we continue as we are now. “Fossil fuels are not footing the bill.”