For now, biofuel producers are relying on used cooking oil, rendered animal fat, the jatropha plant, algae and other so-called feedstock, but experts say refineries do not have access to enough of those materials to produce the billions of gallons of aviation fuel needed to reach the net-zero goal.

The elderly became the butt of friendly banter to lighten the mood among people sitting on stones and under the shade of small jatropha trees to escape the searing heat.

“No amount of Jatropha or Brazil-nut fuel can make business jets look eco-friendly,” said aviation analyst Richard Aboulafia.

Her bare arms and legs were covered in colorful tattoos, but Clubb was shy and nervous when asked to show off her second-place winner, a Jatropha podagrica, aka a Buddha belly plant with a bulbous body and geranium-like leaves.

Compared to two competing plant sources, soybeans and jatropha, lipidcane would produce about 15 and 13 times as much jet fuel per unit of land, respectively.