For the 115 people aboard a recent flight^footnote1 from Chicago O’Hare to Washington’s Reagan Airport, nothing seemed unusual about the journey. The Boeing 737 Max 8 departed and arrived on time, and though it wasn’t apparent to any of the passengers, the flight was a world-first: a commercial passenger flight powered by a mix of traditional jet fuel and a new energy source made from used frier oil, lawn clippings, wood chips and even old newspapers.

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