German airline Lufthansa says it would consume half of Germany’s electricity if it were to switch to green fuels

German airline Lufthansa has tried to make a sustainability push in recent years— the introduction of “Green Fares” earlier this year is one example, wherein customers can opt for fares in which the carbon off-setting feature is already built in. The company also says it’s among the biggest buyers of sustainable aviation fuel (SAF), which are alternatives to traditional fossil fuels.

But while Lufthansa has tried to do its bit to adopt sustainable practices, the company’s chief has said that switching the airline to green fuels like e-kerosene could come at a big price—half of Germany’s electricity supply.

“We would need around half of Germany’s electricity to create enough of the fuels,” Lufthansa's Carsten Spohr said at an aviation conference Monday, Bloomberg reported. He added that while green fuels made using renewable energy sources would help Lufthansa decarbonize its fuel consumption, the likelihood of having enough electricity to produce such materials was low.

“I don’t think Mr. Habeck is going to give me that,” Spohr said at the Hamburg conference, referring to German energy minister Robert Habeck.

Industry search for alternatives

Comments from the chief of Germany’s biggest airline come as the aviation industry looks for alternatives to high carbon-emitting sources that have traditionally been used by airlines. SAFs offer a path to achieving this as they are biofuels manufactured with a lower carbon footprint. Green kerosene, or e-kerosene, is a type of SAF made from CO2 and water, but requires copious amounts of renewable electricity.

The high demand and need for copious amounts of energy have made SAFs expensive—aviation industry leaders have wrestled with the trade-off that transitioning to such fuel sources would create as it would hike the price of air travel for customers.

But studies have shown the potential impact that synthetic fuels like e-kerosene could have—in Europe alone, this type of fuel could save millions of tons of CO2 emissions by 2030.

Industry executives like Spohr have recognized that such fuel sources are the way forward to decarbonize aviation. But at the same time, he has pushed back against European Union quotas on SAFs that could mandate targets for airlines on their use of cleaner fuel options.

"From today's point of view, it won't work to have even the availability of the quantities that are demanded of us, not to mention the high costs that in the end the passenger will have to bear," Spohr said during a press briefing earlier this month, Reuters reported.

He has also emphasized how capacity is one of the key constraints when it comes to scaling up the use of greener fuel alternatives.

"If the Lufthansa Group were to use all the SAF currently available, it would only be able to fly for just under two weeks. A market ramp-up, higher availability and associated lower prices are urgently needed to enable greater use of SAF," a Lufthansa spokesperson told Fortune in an emailed statement.

Even still, Lufthansa is ahead of the curve when it comes to SAF use—globally, only about 0.1% of airlines’ fuel comes from SAFs, while that same ratio is about 0.2% for Lufthansa.

"The use of SAF is still at the beginning of market scaling, and the supply volumes available today and the share of SAF in the Lufthansa Group's total fuel consumption are correspondingly small," the spokesperson said. "The Lufthansa Group does everything in its power to reduce the environmental impact of flying."

This story was originally featured on Fortune.com

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