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Lentokone ja polttoainevana taivaalla.
Photo: Vesa Val, Unsplash

Reducing the carbon footprint of flying is not easy

There is still a long way to go before we have passenger planes powered by electricity or biofuels.
3 min
Tiina Lankinen

Europe’s skies are buzzing with transport and holiday planes, and air traffic is growing globally. However, climate-conscious travellers are increasingly concerned about the carbon footprint of flying. It is predicted that the global volume of passenger flights will double in the next 20 years to approximately 48,000 aircraft and 8 billion passengers annually. At the same time, carbon emissions will keep growing until more environmentally friendly means of powering air flight are developed. 

We already have electric and hybrid buses, but passenger planes running on biofuels remain a distant hope. 

Unfortunately, there are no easy solutions to reduce the carbon emissions of flying in the near future, says Stephen Wright, Industry Professor in aircraft technology at Tampere University. 

“Safety is a big issue when it comes to aviation fuels. If a car engine starts to splutter, it is unpleasant, but it just makes you travel slower. Engine failure in an aircraft may be fatal,” he says. 

According to Wright, it is not currently possible to use anything but Jet A1 fuel in passenger planes. This is because compared to fossil fuels, the freezing point of clean biofuels is higher and they may contain more water. The altitudes at which aeroplanes fly are extremely cold, meaning that biofuels can clot or form ice crystals. This clotting starves the engines of fuel, which can have disastrous consequences. 

“This fuel starvation event happened to a Boeing 777 plane landing at London Heathrow airport in January 2008. During the landing approach, both engines failed because of ice crystals. The accident happened even though Jet A1 fuel was used,” he explains. 

Biofuels are costly 

However, sustainable aviation fuels can already be used in some capacity. 

For example, Finnair offers passengers the opportunity to buy biodegradable fuel to replace some of the fossil fuel that powers their flights. The company uses SkyNRG fuel that is partly made from renewable waste oils, such as cooking oil. According to the SkyNRG website, the biodegradable aviation fuel meets the same safety and quality standards as conventional fuel. 

The renewable fuel is always used as a mixture with regular kerosene. According to Finnair, the renewable fuel usually makes up a few percent of the total fuel mix. 

Unfortunately, the high price and delivery problems associated with renewable fuels are an obstacle to their wider use. The aviation industry annually consumes the vast amount of fuel – 300 million tonnes – and it is hard to substitute such a large quantity with low-emission fuels.

In addition, water causes problems in the production of suitable aviation fuels. Even fossil fuels contain small amounts of water, causing microbes and fungi to grow. Airlines deal with the problem by using biocidal products because these unwanted microbes slowly corrode the fuel tanks. 

“Bio-derived fuels are usually based on materials that contain even more water, which means that this problem would also be greater when they are used,” Wright says. 

More biofuels could be used at airports 

Nevertheless, Wright sees the potential of biofuels in other ways than just powering aeroplanes. 

“Airlines could use them in land vehicles at the airports, which also consume a lot of fuel,” Wright states.  

The aviation industry is also conducting new experiments involving electricity. Small electric planes are already airborne, and larger hybrid planes are being developed. For example, Airbus has launched the Airbus E-Fax X project, which involves testing an old RJ 100 aircraft and replacing one of its four engines with an electric fan.  

“Airbus’s testing is exciting, and it is definitely part of the future of the aviation industry,” Wright argues. 

Offsetting flight guilt 

While waiting for new technologies, passengers can minimise their flight emissions. In addition to avoiding flying completely, they can reduce emissions by making suitable route choices, travelling lighter and favouring the latest aircraft models.  

Everyone can pay attention to the number of stopovers and the amount of luggage they take. Airlines also offer consumers opportunities to offset the CO2 emissions of flying through compensation schemes that can be selected as one is reserving flights. However, consumers should compare the emission compensation calculators and assess their promises critically, because different calculators calculate the emissions slightly differently and the compensation fees vary considerably. 

One can also compensate for CO2 emissions by buying carbon sinks. For example, donations to protect swamps can be made via the carbon emissions exchange of the Finnish Association for Nature Conservation. Alternatively, by supporting the Finnish Natural Heritage Foundation, one can help buy preserved forests. Friends of the Earth Finland also offers the opportunity to pay a flight compensation, and the proceeds are used for the association’s climate campaigns. 


Tips to reduce CO2 emissions when flying 

  • Avoid stopovers and take direct flights whenever possible.

  • Only take hand luggage.

  • Offset your emissions by donating, eg to the preservation of virgin forests.