Germany’s biggest airline would consume half of the country’s entire electricity production to switch its fleet to green fuels like e-kerosene, according to Deutsche Lufthansa AG, underscoring the challenge in reducing emissions from air transport. 

While synthetic fuels manufactured using renewable energy provided the best future path to decarbonize aviation, there is unlikely to be sufficient green electricity in Germany to generate them, Lufthansa Chief Executive Officer Carsten Spohr on Monday.

“We would need around half of Germany’s electricity to create enough of the fuels,” Spohr said at an aviation conference in Hamburg. “I don’t think Mr. Habeck is going to give me that,” Spohr said, referring to Germany’s Economy and Energy Minister, Robert Habeck.

The aviation industry is working to create a market for a carbon-neutral version of the kerosene that powers most modern aircraft. Green kerosene is derived from water and actually pulls carbon dioxide out of the air during creation. The process, which requires huge amounts of electricity generated from renewable resources to ensure carbon neutrality, fractures water into oxygen and hydrogen, which is then combined with carbon.

So-called synthetic fuels are seen by aviation executives like Spohr as the only technically viable way for the time being to decarbonize air travel. While battery-electric vehicles work for road travel, cells lack the energy density for the foreseeable future to lift a commercial planeload of passengers and cargo into the sky.