As nations work toward achieving net-zero carbon economies, commercial aviation will be one of the most difficult sectors to decarbonize. Fossil fuel’s energy-density advantage is too tough to beat, the argument goes, and rather than try to confront that, it might make more sense to continue the use of petroleum in airliners and to aim at offsetting their emissions using some negative carbon emissions technology.
 
Nonetheless, plenty of research is underway on lower-carbon aircraft propulsion. Some early-adopter airlines routinely blend biofuels into their aviation fuel, for example, and in 2018 Boeing flew a commercial airliner on 100% biofuel for the first time. But biofuels have their own drawbacks: The growing, gathering, and conversion of crops to liquid fuels is carbon-intensive. And biofuels’ potential is limited by agricultural and other competing land uses.
 
Another option is hydrogen-powered flight. To be carbon-neutral, the hydrogen must be produced either with renewable energy or with natural gas equipped with carbon capture and storage. Both of the world’s major airliner manufacturers are looking at the lightest element as one option for reducing their customers’ carbon footprint. Amanda Simpson, vice president for research and technology at Airbus Americas, says Airbus will decide by 2025 whether the market can support hydrogen-fueled airliners. Assuming that it can, the company projects its first hydrogen airliners will enter service in 2035.

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