Vegetable fuel is fast becoming a concrete reality. In New Zealand, a passenger plane has successfully completed a two-hour test flight partly powered by jatropha oil.
Air New Zealand hailed the flight as a "milestone" in the development of sustainable fuels that could lower aeroplane emissions and cut costs.
AdvertisementOne engine of the Boeing 747-400 was fueled by a 50-50 mixture of jatropha plant oil and standard A1 jet fuel.
A Virgin Atlantic test flight in February used fuel derived from a blend of Brazilian babassu nuts and coconuts.
The Jatropha plant is being promoted in many third world countries including India. If its use as a fuel source increases in the future, then farmers will have a great future, they are told.
Jatropha is a plant that can grow in marginal lands and common lands. Jatropha curcas grows almost anywhere, even on gravelly, sandy and saline soils. It can also thrive on the poorest stony soil and grow in the crevices of rocks.
When jatropha seeds are crushed, the resulting jatropha oil can be processed to produce a high-quality biodiesel that can be used in a standard diesel car, while the residue (press cake) can also be processed used as biomass feedstock to power electricity plants or used as fertilizer as it contains nitrogen, phosphorous and potassium.
The plant yields more than four times as much fuel per hectare as soybean, and more than ten times that of maize (corn). A hectare of jatropha produces 1,892 litres of fuel.
Researchers at Daimler Chrysler Research explored the use of jatropha oil for automotive use, concluding that although jatropha oil as fuel "has not yet reached optimal quality, ... it already fulfills the EU norm for biodiesel quality".
But this is the first time jatopha oil is being tried on an aeroplane.
In Auckland on Tuesday, a range of tests were completed both on the ground and during the flight, said Air New Zealand Chief Pilot David Morgan.
He said the oil from the plum-sized jatropha fruit performed "well through both the fuel system and engine".
Air New Zealand said it was the first time a second-generation biofuel had been used to partly power a passenger plane.
Air New Zealand Chief Executive Rob Fyfe said the completion of Tuesday's flight was "a milestone for the airline and commercial aviation".
Second-generation biofuels are said typically to use a wider range of plants and release fewer emissions than traditional biofuels such as ethanol.
The International Air Transport Association says it wants a 10th of aviation fuel to come from biofuels by 2017.
But critics apprehend turning over large tracts of land to biofuels could eventually affect food production, leaving the poorer sections worse off.